xref: /openbmc/linux/kernel/workqueue.c (revision 241bce1c)
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * kernel/workqueue.c - generic async execution with shared worker pool
4  *
5  * Copyright (C) 2002		Ingo Molnar
6  *
7  *   Derived from the taskqueue/keventd code by:
8  *     David Woodhouse <dwmw2@infradead.org>
9  *     Andrew Morton
10  *     Kai Petzke <wpp@marie.physik.tu-berlin.de>
11  *     Theodore Ts'o <tytso@mit.edu>
12  *
13  * Made to use alloc_percpu by Christoph Lameter.
14  *
15  * Copyright (C) 2010		SUSE Linux Products GmbH
16  * Copyright (C) 2010		Tejun Heo <tj@kernel.org>
17  *
18  * This is the generic async execution mechanism.  Work items as are
19  * executed in process context.  The worker pool is shared and
20  * automatically managed.  There are two worker pools for each CPU (one for
21  * normal work items and the other for high priority ones) and some extra
22  * pools for workqueues which are not bound to any specific CPU - the
23  * number of these backing pools is dynamic.
24  *
25  * Please read Documentation/core-api/workqueue.rst for details.
26  */
27 
28 #include <linux/export.h>
29 #include <linux/kernel.h>
30 #include <linux/sched.h>
31 #include <linux/init.h>
32 #include <linux/signal.h>
33 #include <linux/completion.h>
34 #include <linux/workqueue.h>
35 #include <linux/slab.h>
36 #include <linux/cpu.h>
37 #include <linux/notifier.h>
38 #include <linux/kthread.h>
39 #include <linux/hardirq.h>
40 #include <linux/mempolicy.h>
41 #include <linux/freezer.h>
42 #include <linux/debug_locks.h>
43 #include <linux/lockdep.h>
44 #include <linux/idr.h>
45 #include <linux/jhash.h>
46 #include <linux/hashtable.h>
47 #include <linux/rculist.h>
48 #include <linux/nodemask.h>
49 #include <linux/moduleparam.h>
50 #include <linux/uaccess.h>
51 #include <linux/sched/isolation.h>
52 #include <linux/sched/debug.h>
53 #include <linux/nmi.h>
54 #include <linux/kvm_para.h>
55 #include <linux/delay.h>
56 
57 #include "workqueue_internal.h"
58 
59 enum {
60 	/*
61 	 * worker_pool flags
62 	 *
63 	 * A bound pool is either associated or disassociated with its CPU.
64 	 * While associated (!DISASSOCIATED), all workers are bound to the
65 	 * CPU and none has %WORKER_UNBOUND set and concurrency management
66 	 * is in effect.
67 	 *
68 	 * While DISASSOCIATED, the cpu may be offline and all workers have
69 	 * %WORKER_UNBOUND set and concurrency management disabled, and may
70 	 * be executing on any CPU.  The pool behaves as an unbound one.
71 	 *
72 	 * Note that DISASSOCIATED should be flipped only while holding
73 	 * wq_pool_attach_mutex to avoid changing binding state while
74 	 * worker_attach_to_pool() is in progress.
75 	 */
76 	POOL_MANAGER_ACTIVE	= 1 << 0,	/* being managed */
77 	POOL_DISASSOCIATED	= 1 << 2,	/* cpu can't serve workers */
78 
79 	/* worker flags */
80 	WORKER_DIE		= 1 << 1,	/* die die die */
81 	WORKER_IDLE		= 1 << 2,	/* is idle */
82 	WORKER_PREP		= 1 << 3,	/* preparing to run works */
83 	WORKER_CPU_INTENSIVE	= 1 << 6,	/* cpu intensive */
84 	WORKER_UNBOUND		= 1 << 7,	/* worker is unbound */
85 	WORKER_REBOUND		= 1 << 8,	/* worker was rebound */
86 
87 	WORKER_NOT_RUNNING	= WORKER_PREP | WORKER_CPU_INTENSIVE |
88 				  WORKER_UNBOUND | WORKER_REBOUND,
89 
90 	NR_STD_WORKER_POOLS	= 2,		/* # standard pools per cpu */
91 
92 	UNBOUND_POOL_HASH_ORDER	= 6,		/* hashed by pool->attrs */
93 	BUSY_WORKER_HASH_ORDER	= 6,		/* 64 pointers */
94 
95 	MAX_IDLE_WORKERS_RATIO	= 4,		/* 1/4 of busy can be idle */
96 	IDLE_WORKER_TIMEOUT	= 300 * HZ,	/* keep idle ones for 5 mins */
97 
98 	MAYDAY_INITIAL_TIMEOUT  = HZ / 100 >= 2 ? HZ / 100 : 2,
99 						/* call for help after 10ms
100 						   (min two ticks) */
101 	MAYDAY_INTERVAL		= HZ / 10,	/* and then every 100ms */
102 	CREATE_COOLDOWN		= HZ,		/* time to breath after fail */
103 
104 	/*
105 	 * Rescue workers are used only on emergencies and shared by
106 	 * all cpus.  Give MIN_NICE.
107 	 */
108 	RESCUER_NICE_LEVEL	= MIN_NICE,
109 	HIGHPRI_NICE_LEVEL	= MIN_NICE,
110 
111 	WQ_NAME_LEN		= 24,
112 };
113 
114 /*
115  * Structure fields follow one of the following exclusion rules.
116  *
117  * I: Modifiable by initialization/destruction paths and read-only for
118  *    everyone else.
119  *
120  * P: Preemption protected.  Disabling preemption is enough and should
121  *    only be modified and accessed from the local cpu.
122  *
123  * L: pool->lock protected.  Access with pool->lock held.
124  *
125  * K: Only modified by worker while holding pool->lock. Can be safely read by
126  *    self, while holding pool->lock or from IRQ context if %current is the
127  *    kworker.
128  *
129  * S: Only modified by worker self.
130  *
131  * A: wq_pool_attach_mutex protected.
132  *
133  * PL: wq_pool_mutex protected.
134  *
135  * PR: wq_pool_mutex protected for writes.  RCU protected for reads.
136  *
137  * PW: wq_pool_mutex and wq->mutex protected for writes.  Either for reads.
138  *
139  * PWR: wq_pool_mutex and wq->mutex protected for writes.  Either or
140  *      RCU for reads.
141  *
142  * WQ: wq->mutex protected.
143  *
144  * WR: wq->mutex protected for writes.  RCU protected for reads.
145  *
146  * MD: wq_mayday_lock protected.
147  *
148  * WD: Used internally by the watchdog.
149  */
150 
151 /* struct worker is defined in workqueue_internal.h */
152 
153 struct worker_pool {
154 	raw_spinlock_t		lock;		/* the pool lock */
155 	int			cpu;		/* I: the associated cpu */
156 	int			node;		/* I: the associated node ID */
157 	int			id;		/* I: pool ID */
158 	unsigned int		flags;		/* L: flags */
159 
160 	unsigned long		watchdog_ts;	/* L: watchdog timestamp */
161 	bool			cpu_stall;	/* WD: stalled cpu bound pool */
162 
163 	/*
164 	 * The counter is incremented in a process context on the associated CPU
165 	 * w/ preemption disabled, and decremented or reset in the same context
166 	 * but w/ pool->lock held. The readers grab pool->lock and are
167 	 * guaranteed to see if the counter reached zero.
168 	 */
169 	int			nr_running;
170 
171 	struct list_head	worklist;	/* L: list of pending works */
172 
173 	int			nr_workers;	/* L: total number of workers */
174 	int			nr_idle;	/* L: currently idle workers */
175 
176 	struct list_head	idle_list;	/* L: list of idle workers */
177 	struct timer_list	idle_timer;	/* L: worker idle timeout */
178 	struct work_struct      idle_cull_work; /* L: worker idle cleanup */
179 
180 	struct timer_list	mayday_timer;	  /* L: SOS timer for workers */
181 
182 	/* a workers is either on busy_hash or idle_list, or the manager */
183 	DECLARE_HASHTABLE(busy_hash, BUSY_WORKER_HASH_ORDER);
184 						/* L: hash of busy workers */
185 
186 	struct worker		*manager;	/* L: purely informational */
187 	struct list_head	workers;	/* A: attached workers */
188 	struct list_head        dying_workers;  /* A: workers about to die */
189 	struct completion	*detach_completion; /* all workers detached */
190 
191 	struct ida		worker_ida;	/* worker IDs for task name */
192 
193 	struct workqueue_attrs	*attrs;		/* I: worker attributes */
194 	struct hlist_node	hash_node;	/* PL: unbound_pool_hash node */
195 	int			refcnt;		/* PL: refcnt for unbound pools */
196 
197 	/*
198 	 * Destruction of pool is RCU protected to allow dereferences
199 	 * from get_work_pool().
200 	 */
201 	struct rcu_head		rcu;
202 };
203 
204 /*
205  * Per-pool_workqueue statistics. These can be monitored using
206  * tools/workqueue/wq_monitor.py.
207  */
208 enum pool_workqueue_stats {
209 	PWQ_STAT_STARTED,	/* work items started execution */
210 	PWQ_STAT_COMPLETED,	/* work items completed execution */
211 	PWQ_STAT_CPU_TIME,	/* total CPU time consumed */
212 	PWQ_STAT_CPU_INTENSIVE,	/* wq_cpu_intensive_thresh_us violations */
213 	PWQ_STAT_CM_WAKEUP,	/* concurrency-management worker wakeups */
214 	PWQ_STAT_REPATRIATED,	/* unbound workers brought back into scope */
215 	PWQ_STAT_MAYDAY,	/* maydays to rescuer */
216 	PWQ_STAT_RESCUED,	/* linked work items executed by rescuer */
217 
218 	PWQ_NR_STATS,
219 };
220 
221 /*
222  * The per-pool workqueue.  While queued, the lower WORK_STRUCT_FLAG_BITS
223  * of work_struct->data are used for flags and the remaining high bits
224  * point to the pwq; thus, pwqs need to be aligned at two's power of the
225  * number of flag bits.
226  */
227 struct pool_workqueue {
228 	struct worker_pool	*pool;		/* I: the associated pool */
229 	struct workqueue_struct *wq;		/* I: the owning workqueue */
230 	int			work_color;	/* L: current color */
231 	int			flush_color;	/* L: flushing color */
232 	int			refcnt;		/* L: reference count */
233 	int			nr_in_flight[WORK_NR_COLORS];
234 						/* L: nr of in_flight works */
235 
236 	/*
237 	 * nr_active management and WORK_STRUCT_INACTIVE:
238 	 *
239 	 * When pwq->nr_active >= max_active, new work item is queued to
240 	 * pwq->inactive_works instead of pool->worklist and marked with
241 	 * WORK_STRUCT_INACTIVE.
242 	 *
243 	 * All work items marked with WORK_STRUCT_INACTIVE do not participate
244 	 * in pwq->nr_active and all work items in pwq->inactive_works are
245 	 * marked with WORK_STRUCT_INACTIVE.  But not all WORK_STRUCT_INACTIVE
246 	 * work items are in pwq->inactive_works.  Some of them are ready to
247 	 * run in pool->worklist or worker->scheduled.  Those work itmes are
248 	 * only struct wq_barrier which is used for flush_work() and should
249 	 * not participate in pwq->nr_active.  For non-barrier work item, it
250 	 * is marked with WORK_STRUCT_INACTIVE iff it is in pwq->inactive_works.
251 	 */
252 	int			nr_active;	/* L: nr of active works */
253 	int			max_active;	/* L: max active works */
254 	struct list_head	inactive_works;	/* L: inactive works */
255 	struct list_head	pwqs_node;	/* WR: node on wq->pwqs */
256 	struct list_head	mayday_node;	/* MD: node on wq->maydays */
257 
258 	u64			stats[PWQ_NR_STATS];
259 
260 	/*
261 	 * Release of unbound pwq is punted to a kthread_worker. See put_pwq()
262 	 * and pwq_release_workfn() for details. pool_workqueue itself is also
263 	 * RCU protected so that the first pwq can be determined without
264 	 * grabbing wq->mutex.
265 	 */
266 	struct kthread_work	release_work;
267 	struct rcu_head		rcu;
268 } __aligned(1 << WORK_STRUCT_FLAG_BITS);
269 
270 /*
271  * Structure used to wait for workqueue flush.
272  */
273 struct wq_flusher {
274 	struct list_head	list;		/* WQ: list of flushers */
275 	int			flush_color;	/* WQ: flush color waiting for */
276 	struct completion	done;		/* flush completion */
277 };
278 
279 struct wq_device;
280 
281 /*
282  * The externally visible workqueue.  It relays the issued work items to
283  * the appropriate worker_pool through its pool_workqueues.
284  */
285 struct workqueue_struct {
286 	struct list_head	pwqs;		/* WR: all pwqs of this wq */
287 	struct list_head	list;		/* PR: list of all workqueues */
288 
289 	struct mutex		mutex;		/* protects this wq */
290 	int			work_color;	/* WQ: current work color */
291 	int			flush_color;	/* WQ: current flush color */
292 	atomic_t		nr_pwqs_to_flush; /* flush in progress */
293 	struct wq_flusher	*first_flusher;	/* WQ: first flusher */
294 	struct list_head	flusher_queue;	/* WQ: flush waiters */
295 	struct list_head	flusher_overflow; /* WQ: flush overflow list */
296 
297 	struct list_head	maydays;	/* MD: pwqs requesting rescue */
298 	struct worker		*rescuer;	/* MD: rescue worker */
299 
300 	int			nr_drainers;	/* WQ: drain in progress */
301 	int			saved_max_active; /* WQ: saved pwq max_active */
302 
303 	struct workqueue_attrs	*unbound_attrs;	/* PW: only for unbound wqs */
304 	struct pool_workqueue	*dfl_pwq;	/* PW: only for unbound wqs */
305 
306 #ifdef CONFIG_SYSFS
307 	struct wq_device	*wq_dev;	/* I: for sysfs interface */
308 #endif
309 #ifdef CONFIG_LOCKDEP
310 	char			*lock_name;
311 	struct lock_class_key	key;
312 	struct lockdep_map	lockdep_map;
313 #endif
314 	char			name[WQ_NAME_LEN]; /* I: workqueue name */
315 
316 	/*
317 	 * Destruction of workqueue_struct is RCU protected to allow walking
318 	 * the workqueues list without grabbing wq_pool_mutex.
319 	 * This is used to dump all workqueues from sysrq.
320 	 */
321 	struct rcu_head		rcu;
322 
323 	/* hot fields used during command issue, aligned to cacheline */
324 	unsigned int		flags ____cacheline_aligned; /* WQ: WQ_* flags */
325 	struct pool_workqueue __percpu __rcu **cpu_pwq; /* I: per-cpu pwqs */
326 };
327 
328 static struct kmem_cache *pwq_cache;
329 
330 /*
331  * Each pod type describes how CPUs should be grouped for unbound workqueues.
332  * See the comment above workqueue_attrs->affn_scope.
333  */
334 struct wq_pod_type {
335 	int			nr_pods;	/* number of pods */
336 	cpumask_var_t		*pod_cpus;	/* pod -> cpus */
337 	int			*pod_node;	/* pod -> node */
338 	int			*cpu_pod;	/* cpu -> pod */
339 };
340 
341 static struct wq_pod_type wq_pod_types[WQ_AFFN_NR_TYPES];
342 static enum wq_affn_scope wq_affn_dfl = WQ_AFFN_CACHE;
343 
344 static const char *wq_affn_names[WQ_AFFN_NR_TYPES] = {
345 	[WQ_AFFN_DFL]			= "default",
346 	[WQ_AFFN_CPU]			= "cpu",
347 	[WQ_AFFN_SMT]			= "smt",
348 	[WQ_AFFN_CACHE]			= "cache",
349 	[WQ_AFFN_NUMA]			= "numa",
350 	[WQ_AFFN_SYSTEM]		= "system",
351 };
352 
353 /*
354  * Per-cpu work items which run for longer than the following threshold are
355  * automatically considered CPU intensive and excluded from concurrency
356  * management to prevent them from noticeably delaying other per-cpu work items.
357  * ULONG_MAX indicates that the user hasn't overridden it with a boot parameter.
358  * The actual value is initialized in wq_cpu_intensive_thresh_init().
359  */
360 static unsigned long wq_cpu_intensive_thresh_us = ULONG_MAX;
361 module_param_named(cpu_intensive_thresh_us, wq_cpu_intensive_thresh_us, ulong, 0644);
362 
363 /* see the comment above the definition of WQ_POWER_EFFICIENT */
364 static bool wq_power_efficient = IS_ENABLED(CONFIG_WQ_POWER_EFFICIENT_DEFAULT);
365 module_param_named(power_efficient, wq_power_efficient, bool, 0444);
366 
367 static bool wq_online;			/* can kworkers be created yet? */
368 
369 /* buf for wq_update_unbound_pod_attrs(), protected by CPU hotplug exclusion */
370 static struct workqueue_attrs *wq_update_pod_attrs_buf;
371 
372 static DEFINE_MUTEX(wq_pool_mutex);	/* protects pools and workqueues list */
373 static DEFINE_MUTEX(wq_pool_attach_mutex); /* protects worker attach/detach */
374 static DEFINE_RAW_SPINLOCK(wq_mayday_lock);	/* protects wq->maydays list */
375 /* wait for manager to go away */
376 static struct rcuwait manager_wait = __RCUWAIT_INITIALIZER(manager_wait);
377 
378 static LIST_HEAD(workqueues);		/* PR: list of all workqueues */
379 static bool workqueue_freezing;		/* PL: have wqs started freezing? */
380 
381 /* PL&A: allowable cpus for unbound wqs and work items */
382 static cpumask_var_t wq_unbound_cpumask;
383 
384 /* for further constrain wq_unbound_cpumask by cmdline parameter*/
385 static struct cpumask wq_cmdline_cpumask __initdata;
386 
387 /* CPU where unbound work was last round robin scheduled from this CPU */
388 static DEFINE_PER_CPU(int, wq_rr_cpu_last);
389 
390 /*
391  * Local execution of unbound work items is no longer guaranteed.  The
392  * following always forces round-robin CPU selection on unbound work items
393  * to uncover usages which depend on it.
394  */
395 #ifdef CONFIG_DEBUG_WQ_FORCE_RR_CPU
396 static bool wq_debug_force_rr_cpu = true;
397 #else
398 static bool wq_debug_force_rr_cpu = false;
399 #endif
400 module_param_named(debug_force_rr_cpu, wq_debug_force_rr_cpu, bool, 0644);
401 
402 /* the per-cpu worker pools */
403 static DEFINE_PER_CPU_SHARED_ALIGNED(struct worker_pool [NR_STD_WORKER_POOLS], cpu_worker_pools);
404 
405 static DEFINE_IDR(worker_pool_idr);	/* PR: idr of all pools */
406 
407 /* PL: hash of all unbound pools keyed by pool->attrs */
408 static DEFINE_HASHTABLE(unbound_pool_hash, UNBOUND_POOL_HASH_ORDER);
409 
410 /* I: attributes used when instantiating standard unbound pools on demand */
411 static struct workqueue_attrs *unbound_std_wq_attrs[NR_STD_WORKER_POOLS];
412 
413 /* I: attributes used when instantiating ordered pools on demand */
414 static struct workqueue_attrs *ordered_wq_attrs[NR_STD_WORKER_POOLS];
415 
416 /*
417  * I: kthread_worker to release pwq's. pwq release needs to be bounced to a
418  * process context while holding a pool lock. Bounce to a dedicated kthread
419  * worker to avoid A-A deadlocks.
420  */
421 static struct kthread_worker *pwq_release_worker;
422 
423 struct workqueue_struct *system_wq __read_mostly;
424 EXPORT_SYMBOL(system_wq);
425 struct workqueue_struct *system_highpri_wq __read_mostly;
426 EXPORT_SYMBOL_GPL(system_highpri_wq);
427 struct workqueue_struct *system_long_wq __read_mostly;
428 EXPORT_SYMBOL_GPL(system_long_wq);
429 struct workqueue_struct *system_unbound_wq __read_mostly;
430 EXPORT_SYMBOL_GPL(system_unbound_wq);
431 struct workqueue_struct *system_freezable_wq __read_mostly;
432 EXPORT_SYMBOL_GPL(system_freezable_wq);
433 struct workqueue_struct *system_power_efficient_wq __read_mostly;
434 EXPORT_SYMBOL_GPL(system_power_efficient_wq);
435 struct workqueue_struct *system_freezable_power_efficient_wq __read_mostly;
436 EXPORT_SYMBOL_GPL(system_freezable_power_efficient_wq);
437 
438 static int worker_thread(void *__worker);
439 static void workqueue_sysfs_unregister(struct workqueue_struct *wq);
440 static void show_pwq(struct pool_workqueue *pwq);
441 static void show_one_worker_pool(struct worker_pool *pool);
442 
443 #define CREATE_TRACE_POINTS
444 #include <trace/events/workqueue.h>
445 
446 #define assert_rcu_or_pool_mutex()					\
447 	RCU_LOCKDEP_WARN(!rcu_read_lock_held() &&			\
448 			 !lockdep_is_held(&wq_pool_mutex),		\
449 			 "RCU or wq_pool_mutex should be held")
450 
451 #define assert_rcu_or_wq_mutex_or_pool_mutex(wq)			\
452 	RCU_LOCKDEP_WARN(!rcu_read_lock_held() &&			\
453 			 !lockdep_is_held(&wq->mutex) &&		\
454 			 !lockdep_is_held(&wq_pool_mutex),		\
455 			 "RCU, wq->mutex or wq_pool_mutex should be held")
456 
457 #define for_each_cpu_worker_pool(pool, cpu)				\
458 	for ((pool) = &per_cpu(cpu_worker_pools, cpu)[0];		\
459 	     (pool) < &per_cpu(cpu_worker_pools, cpu)[NR_STD_WORKER_POOLS]; \
460 	     (pool)++)
461 
462 /**
463  * for_each_pool - iterate through all worker_pools in the system
464  * @pool: iteration cursor
465  * @pi: integer used for iteration
466  *
467  * This must be called either with wq_pool_mutex held or RCU read
468  * locked.  If the pool needs to be used beyond the locking in effect, the
469  * caller is responsible for guaranteeing that the pool stays online.
470  *
471  * The if/else clause exists only for the lockdep assertion and can be
472  * ignored.
473  */
474 #define for_each_pool(pool, pi)						\
475 	idr_for_each_entry(&worker_pool_idr, pool, pi)			\
476 		if (({ assert_rcu_or_pool_mutex(); false; })) { }	\
477 		else
478 
479 /**
480  * for_each_pool_worker - iterate through all workers of a worker_pool
481  * @worker: iteration cursor
482  * @pool: worker_pool to iterate workers of
483  *
484  * This must be called with wq_pool_attach_mutex.
485  *
486  * The if/else clause exists only for the lockdep assertion and can be
487  * ignored.
488  */
489 #define for_each_pool_worker(worker, pool)				\
490 	list_for_each_entry((worker), &(pool)->workers, node)		\
491 		if (({ lockdep_assert_held(&wq_pool_attach_mutex); false; })) { } \
492 		else
493 
494 /**
495  * for_each_pwq - iterate through all pool_workqueues of the specified workqueue
496  * @pwq: iteration cursor
497  * @wq: the target workqueue
498  *
499  * This must be called either with wq->mutex held or RCU read locked.
500  * If the pwq needs to be used beyond the locking in effect, the caller is
501  * responsible for guaranteeing that the pwq stays online.
502  *
503  * The if/else clause exists only for the lockdep assertion and can be
504  * ignored.
505  */
506 #define for_each_pwq(pwq, wq)						\
507 	list_for_each_entry_rcu((pwq), &(wq)->pwqs, pwqs_node,		\
508 				 lockdep_is_held(&(wq->mutex)))
509 
510 #ifdef CONFIG_DEBUG_OBJECTS_WORK
511 
512 static const struct debug_obj_descr work_debug_descr;
513 
work_debug_hint(void * addr)514 static void *work_debug_hint(void *addr)
515 {
516 	return ((struct work_struct *) addr)->func;
517 }
518 
work_is_static_object(void * addr)519 static bool work_is_static_object(void *addr)
520 {
521 	struct work_struct *work = addr;
522 
523 	return test_bit(WORK_STRUCT_STATIC_BIT, work_data_bits(work));
524 }
525 
526 /*
527  * fixup_init is called when:
528  * - an active object is initialized
529  */
work_fixup_init(void * addr,enum debug_obj_state state)530 static bool work_fixup_init(void *addr, enum debug_obj_state state)
531 {
532 	struct work_struct *work = addr;
533 
534 	switch (state) {
535 	case ODEBUG_STATE_ACTIVE:
536 		cancel_work_sync(work);
537 		debug_object_init(work, &work_debug_descr);
538 		return true;
539 	default:
540 		return false;
541 	}
542 }
543 
544 /*
545  * fixup_free is called when:
546  * - an active object is freed
547  */
work_fixup_free(void * addr,enum debug_obj_state state)548 static bool work_fixup_free(void *addr, enum debug_obj_state state)
549 {
550 	struct work_struct *work = addr;
551 
552 	switch (state) {
553 	case ODEBUG_STATE_ACTIVE:
554 		cancel_work_sync(work);
555 		debug_object_free(work, &work_debug_descr);
556 		return true;
557 	default:
558 		return false;
559 	}
560 }
561 
562 static const struct debug_obj_descr work_debug_descr = {
563 	.name		= "work_struct",
564 	.debug_hint	= work_debug_hint,
565 	.is_static_object = work_is_static_object,
566 	.fixup_init	= work_fixup_init,
567 	.fixup_free	= work_fixup_free,
568 };
569 
debug_work_activate(struct work_struct * work)570 static inline void debug_work_activate(struct work_struct *work)
571 {
572 	debug_object_activate(work, &work_debug_descr);
573 }
574 
debug_work_deactivate(struct work_struct * work)575 static inline void debug_work_deactivate(struct work_struct *work)
576 {
577 	debug_object_deactivate(work, &work_debug_descr);
578 }
579 
__init_work(struct work_struct * work,int onstack)580 void __init_work(struct work_struct *work, int onstack)
581 {
582 	if (onstack)
583 		debug_object_init_on_stack(work, &work_debug_descr);
584 	else
585 		debug_object_init(work, &work_debug_descr);
586 }
587 EXPORT_SYMBOL_GPL(__init_work);
588 
destroy_work_on_stack(struct work_struct * work)589 void destroy_work_on_stack(struct work_struct *work)
590 {
591 	debug_object_free(work, &work_debug_descr);
592 }
593 EXPORT_SYMBOL_GPL(destroy_work_on_stack);
594 
destroy_delayed_work_on_stack(struct delayed_work * work)595 void destroy_delayed_work_on_stack(struct delayed_work *work)
596 {
597 	destroy_timer_on_stack(&work->timer);
598 	debug_object_free(&work->work, &work_debug_descr);
599 }
600 EXPORT_SYMBOL_GPL(destroy_delayed_work_on_stack);
601 
602 #else
debug_work_activate(struct work_struct * work)603 static inline void debug_work_activate(struct work_struct *work) { }
debug_work_deactivate(struct work_struct * work)604 static inline void debug_work_deactivate(struct work_struct *work) { }
605 #endif
606 
607 /**
608  * worker_pool_assign_id - allocate ID and assign it to @pool
609  * @pool: the pool pointer of interest
610  *
611  * Returns 0 if ID in [0, WORK_OFFQ_POOL_NONE) is allocated and assigned
612  * successfully, -errno on failure.
613  */
worker_pool_assign_id(struct worker_pool * pool)614 static int worker_pool_assign_id(struct worker_pool *pool)
615 {
616 	int ret;
617 
618 	lockdep_assert_held(&wq_pool_mutex);
619 
620 	ret = idr_alloc(&worker_pool_idr, pool, 0, WORK_OFFQ_POOL_NONE,
621 			GFP_KERNEL);
622 	if (ret >= 0) {
623 		pool->id = ret;
624 		return 0;
625 	}
626 	return ret;
627 }
628 
work_color_to_flags(int color)629 static unsigned int work_color_to_flags(int color)
630 {
631 	return color << WORK_STRUCT_COLOR_SHIFT;
632 }
633 
get_work_color(unsigned long work_data)634 static int get_work_color(unsigned long work_data)
635 {
636 	return (work_data >> WORK_STRUCT_COLOR_SHIFT) &
637 		((1 << WORK_STRUCT_COLOR_BITS) - 1);
638 }
639 
work_next_color(int color)640 static int work_next_color(int color)
641 {
642 	return (color + 1) % WORK_NR_COLORS;
643 }
644 
645 /*
646  * While queued, %WORK_STRUCT_PWQ is set and non flag bits of a work's data
647  * contain the pointer to the queued pwq.  Once execution starts, the flag
648  * is cleared and the high bits contain OFFQ flags and pool ID.
649  *
650  * set_work_pwq(), set_work_pool_and_clear_pending(), mark_work_canceling()
651  * and clear_work_data() can be used to set the pwq, pool or clear
652  * work->data.  These functions should only be called while the work is
653  * owned - ie. while the PENDING bit is set.
654  *
655  * get_work_pool() and get_work_pwq() can be used to obtain the pool or pwq
656  * corresponding to a work.  Pool is available once the work has been
657  * queued anywhere after initialization until it is sync canceled.  pwq is
658  * available only while the work item is queued.
659  *
660  * %WORK_OFFQ_CANCELING is used to mark a work item which is being
661  * canceled.  While being canceled, a work item may have its PENDING set
662  * but stay off timer and worklist for arbitrarily long and nobody should
663  * try to steal the PENDING bit.
664  */
set_work_data(struct work_struct * work,unsigned long data,unsigned long flags)665 static inline void set_work_data(struct work_struct *work, unsigned long data,
666 				 unsigned long flags)
667 {
668 	WARN_ON_ONCE(!work_pending(work));
669 	atomic_long_set(&work->data, data | flags | work_static(work));
670 }
671 
set_work_pwq(struct work_struct * work,struct pool_workqueue * pwq,unsigned long extra_flags)672 static void set_work_pwq(struct work_struct *work, struct pool_workqueue *pwq,
673 			 unsigned long extra_flags)
674 {
675 	set_work_data(work, (unsigned long)pwq,
676 		      WORK_STRUCT_PENDING | WORK_STRUCT_PWQ | extra_flags);
677 }
678 
set_work_pool_and_keep_pending(struct work_struct * work,int pool_id)679 static void set_work_pool_and_keep_pending(struct work_struct *work,
680 					   int pool_id)
681 {
682 	set_work_data(work, (unsigned long)pool_id << WORK_OFFQ_POOL_SHIFT,
683 		      WORK_STRUCT_PENDING);
684 }
685 
set_work_pool_and_clear_pending(struct work_struct * work,int pool_id)686 static void set_work_pool_and_clear_pending(struct work_struct *work,
687 					    int pool_id)
688 {
689 	/*
690 	 * The following wmb is paired with the implied mb in
691 	 * test_and_set_bit(PENDING) and ensures all updates to @work made
692 	 * here are visible to and precede any updates by the next PENDING
693 	 * owner.
694 	 */
695 	smp_wmb();
696 	set_work_data(work, (unsigned long)pool_id << WORK_OFFQ_POOL_SHIFT, 0);
697 	/*
698 	 * The following mb guarantees that previous clear of a PENDING bit
699 	 * will not be reordered with any speculative LOADS or STORES from
700 	 * work->current_func, which is executed afterwards.  This possible
701 	 * reordering can lead to a missed execution on attempt to queue
702 	 * the same @work.  E.g. consider this case:
703 	 *
704 	 *   CPU#0                         CPU#1
705 	 *   ----------------------------  --------------------------------
706 	 *
707 	 * 1  STORE event_indicated
708 	 * 2  queue_work_on() {
709 	 * 3    test_and_set_bit(PENDING)
710 	 * 4 }                             set_..._and_clear_pending() {
711 	 * 5                                 set_work_data() # clear bit
712 	 * 6                                 smp_mb()
713 	 * 7                               work->current_func() {
714 	 * 8				      LOAD event_indicated
715 	 *				   }
716 	 *
717 	 * Without an explicit full barrier speculative LOAD on line 8 can
718 	 * be executed before CPU#0 does STORE on line 1.  If that happens,
719 	 * CPU#0 observes the PENDING bit is still set and new execution of
720 	 * a @work is not queued in a hope, that CPU#1 will eventually
721 	 * finish the queued @work.  Meanwhile CPU#1 does not see
722 	 * event_indicated is set, because speculative LOAD was executed
723 	 * before actual STORE.
724 	 */
725 	smp_mb();
726 }
727 
clear_work_data(struct work_struct * work)728 static void clear_work_data(struct work_struct *work)
729 {
730 	smp_wmb();	/* see set_work_pool_and_clear_pending() */
731 	set_work_data(work, WORK_STRUCT_NO_POOL, 0);
732 }
733 
work_struct_pwq(unsigned long data)734 static inline struct pool_workqueue *work_struct_pwq(unsigned long data)
735 {
736 	return (struct pool_workqueue *)(data & WORK_STRUCT_WQ_DATA_MASK);
737 }
738 
get_work_pwq(struct work_struct * work)739 static struct pool_workqueue *get_work_pwq(struct work_struct *work)
740 {
741 	unsigned long data = atomic_long_read(&work->data);
742 
743 	if (data & WORK_STRUCT_PWQ)
744 		return work_struct_pwq(data);
745 	else
746 		return NULL;
747 }
748 
749 /**
750  * get_work_pool - return the worker_pool a given work was associated with
751  * @work: the work item of interest
752  *
753  * Pools are created and destroyed under wq_pool_mutex, and allows read
754  * access under RCU read lock.  As such, this function should be
755  * called under wq_pool_mutex or inside of a rcu_read_lock() region.
756  *
757  * All fields of the returned pool are accessible as long as the above
758  * mentioned locking is in effect.  If the returned pool needs to be used
759  * beyond the critical section, the caller is responsible for ensuring the
760  * returned pool is and stays online.
761  *
762  * Return: The worker_pool @work was last associated with.  %NULL if none.
763  */
get_work_pool(struct work_struct * work)764 static struct worker_pool *get_work_pool(struct work_struct *work)
765 {
766 	unsigned long data = atomic_long_read(&work->data);
767 	int pool_id;
768 
769 	assert_rcu_or_pool_mutex();
770 
771 	if (data & WORK_STRUCT_PWQ)
772 		return work_struct_pwq(data)->pool;
773 
774 	pool_id = data >> WORK_OFFQ_POOL_SHIFT;
775 	if (pool_id == WORK_OFFQ_POOL_NONE)
776 		return NULL;
777 
778 	return idr_find(&worker_pool_idr, pool_id);
779 }
780 
781 /**
782  * get_work_pool_id - return the worker pool ID a given work is associated with
783  * @work: the work item of interest
784  *
785  * Return: The worker_pool ID @work was last associated with.
786  * %WORK_OFFQ_POOL_NONE if none.
787  */
get_work_pool_id(struct work_struct * work)788 static int get_work_pool_id(struct work_struct *work)
789 {
790 	unsigned long data = atomic_long_read(&work->data);
791 
792 	if (data & WORK_STRUCT_PWQ)
793 		return work_struct_pwq(data)->pool->id;
794 
795 	return data >> WORK_OFFQ_POOL_SHIFT;
796 }
797 
mark_work_canceling(struct work_struct * work)798 static void mark_work_canceling(struct work_struct *work)
799 {
800 	unsigned long pool_id = get_work_pool_id(work);
801 
802 	pool_id <<= WORK_OFFQ_POOL_SHIFT;
803 	set_work_data(work, pool_id | WORK_OFFQ_CANCELING, WORK_STRUCT_PENDING);
804 }
805 
work_is_canceling(struct work_struct * work)806 static bool work_is_canceling(struct work_struct *work)
807 {
808 	unsigned long data = atomic_long_read(&work->data);
809 
810 	return !(data & WORK_STRUCT_PWQ) && (data & WORK_OFFQ_CANCELING);
811 }
812 
813 /*
814  * Policy functions.  These define the policies on how the global worker
815  * pools are managed.  Unless noted otherwise, these functions assume that
816  * they're being called with pool->lock held.
817  */
818 
819 /*
820  * Need to wake up a worker?  Called from anything but currently
821  * running workers.
822  *
823  * Note that, because unbound workers never contribute to nr_running, this
824  * function will always return %true for unbound pools as long as the
825  * worklist isn't empty.
826  */
need_more_worker(struct worker_pool * pool)827 static bool need_more_worker(struct worker_pool *pool)
828 {
829 	return !list_empty(&pool->worklist) && !pool->nr_running;
830 }
831 
832 /* Can I start working?  Called from busy but !running workers. */
may_start_working(struct worker_pool * pool)833 static bool may_start_working(struct worker_pool *pool)
834 {
835 	return pool->nr_idle;
836 }
837 
838 /* Do I need to keep working?  Called from currently running workers. */
keep_working(struct worker_pool * pool)839 static bool keep_working(struct worker_pool *pool)
840 {
841 	return !list_empty(&pool->worklist) && (pool->nr_running <= 1);
842 }
843 
844 /* Do we need a new worker?  Called from manager. */
need_to_create_worker(struct worker_pool * pool)845 static bool need_to_create_worker(struct worker_pool *pool)
846 {
847 	return need_more_worker(pool) && !may_start_working(pool);
848 }
849 
850 /* Do we have too many workers and should some go away? */
too_many_workers(struct worker_pool * pool)851 static bool too_many_workers(struct worker_pool *pool)
852 {
853 	bool managing = pool->flags & POOL_MANAGER_ACTIVE;
854 	int nr_idle = pool->nr_idle + managing; /* manager is considered idle */
855 	int nr_busy = pool->nr_workers - nr_idle;
856 
857 	return nr_idle > 2 && (nr_idle - 2) * MAX_IDLE_WORKERS_RATIO >= nr_busy;
858 }
859 
860 /**
861  * worker_set_flags - set worker flags and adjust nr_running accordingly
862  * @worker: self
863  * @flags: flags to set
864  *
865  * Set @flags in @worker->flags and adjust nr_running accordingly.
866  */
worker_set_flags(struct worker * worker,unsigned int flags)867 static inline void worker_set_flags(struct worker *worker, unsigned int flags)
868 {
869 	struct worker_pool *pool = worker->pool;
870 
871 	lockdep_assert_held(&pool->lock);
872 
873 	/* If transitioning into NOT_RUNNING, adjust nr_running. */
874 	if ((flags & WORKER_NOT_RUNNING) &&
875 	    !(worker->flags & WORKER_NOT_RUNNING)) {
876 		pool->nr_running--;
877 	}
878 
879 	worker->flags |= flags;
880 }
881 
882 /**
883  * worker_clr_flags - clear worker flags and adjust nr_running accordingly
884  * @worker: self
885  * @flags: flags to clear
886  *
887  * Clear @flags in @worker->flags and adjust nr_running accordingly.
888  */
worker_clr_flags(struct worker * worker,unsigned int flags)889 static inline void worker_clr_flags(struct worker *worker, unsigned int flags)
890 {
891 	struct worker_pool *pool = worker->pool;
892 	unsigned int oflags = worker->flags;
893 
894 	lockdep_assert_held(&pool->lock);
895 
896 	worker->flags &= ~flags;
897 
898 	/*
899 	 * If transitioning out of NOT_RUNNING, increment nr_running.  Note
900 	 * that the nested NOT_RUNNING is not a noop.  NOT_RUNNING is mask
901 	 * of multiple flags, not a single flag.
902 	 */
903 	if ((flags & WORKER_NOT_RUNNING) && (oflags & WORKER_NOT_RUNNING))
904 		if (!(worker->flags & WORKER_NOT_RUNNING))
905 			pool->nr_running++;
906 }
907 
908 /* Return the first idle worker.  Called with pool->lock held. */
first_idle_worker(struct worker_pool * pool)909 static struct worker *first_idle_worker(struct worker_pool *pool)
910 {
911 	if (unlikely(list_empty(&pool->idle_list)))
912 		return NULL;
913 
914 	return list_first_entry(&pool->idle_list, struct worker, entry);
915 }
916 
917 /**
918  * worker_enter_idle - enter idle state
919  * @worker: worker which is entering idle state
920  *
921  * @worker is entering idle state.  Update stats and idle timer if
922  * necessary.
923  *
924  * LOCKING:
925  * raw_spin_lock_irq(pool->lock).
926  */
worker_enter_idle(struct worker * worker)927 static void worker_enter_idle(struct worker *worker)
928 {
929 	struct worker_pool *pool = worker->pool;
930 
931 	if (WARN_ON_ONCE(worker->flags & WORKER_IDLE) ||
932 	    WARN_ON_ONCE(!list_empty(&worker->entry) &&
933 			 (worker->hentry.next || worker->hentry.pprev)))
934 		return;
935 
936 	/* can't use worker_set_flags(), also called from create_worker() */
937 	worker->flags |= WORKER_IDLE;
938 	pool->nr_idle++;
939 	worker->last_active = jiffies;
940 
941 	/* idle_list is LIFO */
942 	list_add(&worker->entry, &pool->idle_list);
943 
944 	if (too_many_workers(pool) && !timer_pending(&pool->idle_timer))
945 		mod_timer(&pool->idle_timer, jiffies + IDLE_WORKER_TIMEOUT);
946 
947 	/* Sanity check nr_running. */
948 	WARN_ON_ONCE(pool->nr_workers == pool->nr_idle && pool->nr_running);
949 }
950 
951 /**
952  * worker_leave_idle - leave idle state
953  * @worker: worker which is leaving idle state
954  *
955  * @worker is leaving idle state.  Update stats.
956  *
957  * LOCKING:
958  * raw_spin_lock_irq(pool->lock).
959  */
worker_leave_idle(struct worker * worker)960 static void worker_leave_idle(struct worker *worker)
961 {
962 	struct worker_pool *pool = worker->pool;
963 
964 	if (WARN_ON_ONCE(!(worker->flags & WORKER_IDLE)))
965 		return;
966 	worker_clr_flags(worker, WORKER_IDLE);
967 	pool->nr_idle--;
968 	list_del_init(&worker->entry);
969 }
970 
971 /**
972  * find_worker_executing_work - find worker which is executing a work
973  * @pool: pool of interest
974  * @work: work to find worker for
975  *
976  * Find a worker which is executing @work on @pool by searching
977  * @pool->busy_hash which is keyed by the address of @work.  For a worker
978  * to match, its current execution should match the address of @work and
979  * its work function.  This is to avoid unwanted dependency between
980  * unrelated work executions through a work item being recycled while still
981  * being executed.
982  *
983  * This is a bit tricky.  A work item may be freed once its execution
984  * starts and nothing prevents the freed area from being recycled for
985  * another work item.  If the same work item address ends up being reused
986  * before the original execution finishes, workqueue will identify the
987  * recycled work item as currently executing and make it wait until the
988  * current execution finishes, introducing an unwanted dependency.
989  *
990  * This function checks the work item address and work function to avoid
991  * false positives.  Note that this isn't complete as one may construct a
992  * work function which can introduce dependency onto itself through a
993  * recycled work item.  Well, if somebody wants to shoot oneself in the
994  * foot that badly, there's only so much we can do, and if such deadlock
995  * actually occurs, it should be easy to locate the culprit work function.
996  *
997  * CONTEXT:
998  * raw_spin_lock_irq(pool->lock).
999  *
1000  * Return:
1001  * Pointer to worker which is executing @work if found, %NULL
1002  * otherwise.
1003  */
find_worker_executing_work(struct worker_pool * pool,struct work_struct * work)1004 static struct worker *find_worker_executing_work(struct worker_pool *pool,
1005 						 struct work_struct *work)
1006 {
1007 	struct worker *worker;
1008 
1009 	hash_for_each_possible(pool->busy_hash, worker, hentry,
1010 			       (unsigned long)work)
1011 		if (worker->current_work == work &&
1012 		    worker->current_func == work->func)
1013 			return worker;
1014 
1015 	return NULL;
1016 }
1017 
1018 /**
1019  * move_linked_works - move linked works to a list
1020  * @work: start of series of works to be scheduled
1021  * @head: target list to append @work to
1022  * @nextp: out parameter for nested worklist walking
1023  *
1024  * Schedule linked works starting from @work to @head. Work series to be
1025  * scheduled starts at @work and includes any consecutive work with
1026  * WORK_STRUCT_LINKED set in its predecessor. See assign_work() for details on
1027  * @nextp.
1028  *
1029  * CONTEXT:
1030  * raw_spin_lock_irq(pool->lock).
1031  */
move_linked_works(struct work_struct * work,struct list_head * head,struct work_struct ** nextp)1032 static void move_linked_works(struct work_struct *work, struct list_head *head,
1033 			      struct work_struct **nextp)
1034 {
1035 	struct work_struct *n;
1036 
1037 	/*
1038 	 * Linked worklist will always end before the end of the list,
1039 	 * use NULL for list head.
1040 	 */
1041 	list_for_each_entry_safe_from(work, n, NULL, entry) {
1042 		list_move_tail(&work->entry, head);
1043 		if (!(*work_data_bits(work) & WORK_STRUCT_LINKED))
1044 			break;
1045 	}
1046 
1047 	/*
1048 	 * If we're already inside safe list traversal and have moved
1049 	 * multiple works to the scheduled queue, the next position
1050 	 * needs to be updated.
1051 	 */
1052 	if (nextp)
1053 		*nextp = n;
1054 }
1055 
1056 /**
1057  * assign_work - assign a work item and its linked work items to a worker
1058  * @work: work to assign
1059  * @worker: worker to assign to
1060  * @nextp: out parameter for nested worklist walking
1061  *
1062  * Assign @work and its linked work items to @worker. If @work is already being
1063  * executed by another worker in the same pool, it'll be punted there.
1064  *
1065  * If @nextp is not NULL, it's updated to point to the next work of the last
1066  * scheduled work. This allows assign_work() to be nested inside
1067  * list_for_each_entry_safe().
1068  *
1069  * Returns %true if @work was successfully assigned to @worker. %false if @work
1070  * was punted to another worker already executing it.
1071  */
assign_work(struct work_struct * work,struct worker * worker,struct work_struct ** nextp)1072 static bool assign_work(struct work_struct *work, struct worker *worker,
1073 			struct work_struct **nextp)
1074 {
1075 	struct worker_pool *pool = worker->pool;
1076 	struct worker *collision;
1077 
1078 	lockdep_assert_held(&pool->lock);
1079 
1080 	/*
1081 	 * A single work shouldn't be executed concurrently by multiple workers.
1082 	 * __queue_work() ensures that @work doesn't jump to a different pool
1083 	 * while still running in the previous pool. Here, we should ensure that
1084 	 * @work is not executed concurrently by multiple workers from the same
1085 	 * pool. Check whether anyone is already processing the work. If so,
1086 	 * defer the work to the currently executing one.
1087 	 */
1088 	collision = find_worker_executing_work(pool, work);
1089 	if (unlikely(collision)) {
1090 		move_linked_works(work, &collision->scheduled, nextp);
1091 		return false;
1092 	}
1093 
1094 	move_linked_works(work, &worker->scheduled, nextp);
1095 	return true;
1096 }
1097 
1098 /**
1099  * kick_pool - wake up an idle worker if necessary
1100  * @pool: pool to kick
1101  *
1102  * @pool may have pending work items. Wake up worker if necessary. Returns
1103  * whether a worker was woken up.
1104  */
kick_pool(struct worker_pool * pool)1105 static bool kick_pool(struct worker_pool *pool)
1106 {
1107 	struct worker *worker = first_idle_worker(pool);
1108 	struct task_struct *p;
1109 
1110 	lockdep_assert_held(&pool->lock);
1111 
1112 	if (!need_more_worker(pool) || !worker)
1113 		return false;
1114 
1115 	p = worker->task;
1116 
1117 #ifdef CONFIG_SMP
1118 	/*
1119 	 * Idle @worker is about to execute @work and waking up provides an
1120 	 * opportunity to migrate @worker at a lower cost by setting the task's
1121 	 * wake_cpu field. Let's see if we want to move @worker to improve
1122 	 * execution locality.
1123 	 *
1124 	 * We're waking the worker that went idle the latest and there's some
1125 	 * chance that @worker is marked idle but hasn't gone off CPU yet. If
1126 	 * so, setting the wake_cpu won't do anything. As this is a best-effort
1127 	 * optimization and the race window is narrow, let's leave as-is for
1128 	 * now. If this becomes pronounced, we can skip over workers which are
1129 	 * still on cpu when picking an idle worker.
1130 	 *
1131 	 * If @pool has non-strict affinity, @worker might have ended up outside
1132 	 * its affinity scope. Repatriate.
1133 	 */
1134 	if (!pool->attrs->affn_strict &&
1135 	    !cpumask_test_cpu(p->wake_cpu, pool->attrs->__pod_cpumask)) {
1136 		struct work_struct *work = list_first_entry(&pool->worklist,
1137 						struct work_struct, entry);
1138 		int wake_cpu = cpumask_any_and_distribute(pool->attrs->__pod_cpumask,
1139 							  cpu_online_mask);
1140 		if (wake_cpu < nr_cpu_ids) {
1141 			p->wake_cpu = wake_cpu;
1142 			get_work_pwq(work)->stats[PWQ_STAT_REPATRIATED]++;
1143 		}
1144 	}
1145 #endif
1146 	wake_up_process(p);
1147 	return true;
1148 }
1149 
1150 #ifdef CONFIG_WQ_CPU_INTENSIVE_REPORT
1151 
1152 /*
1153  * Concurrency-managed per-cpu work items that hog CPU for longer than
1154  * wq_cpu_intensive_thresh_us trigger the automatic CPU_INTENSIVE mechanism,
1155  * which prevents them from stalling other concurrency-managed work items. If a
1156  * work function keeps triggering this mechanism, it's likely that the work item
1157  * should be using an unbound workqueue instead.
1158  *
1159  * wq_cpu_intensive_report() tracks work functions which trigger such conditions
1160  * and report them so that they can be examined and converted to use unbound
1161  * workqueues as appropriate. To avoid flooding the console, each violating work
1162  * function is tracked and reported with exponential backoff.
1163  */
1164 #define WCI_MAX_ENTS 128
1165 
1166 struct wci_ent {
1167 	work_func_t		func;
1168 	atomic64_t		cnt;
1169 	struct hlist_node	hash_node;
1170 };
1171 
1172 static struct wci_ent wci_ents[WCI_MAX_ENTS];
1173 static int wci_nr_ents;
1174 static DEFINE_RAW_SPINLOCK(wci_lock);
1175 static DEFINE_HASHTABLE(wci_hash, ilog2(WCI_MAX_ENTS));
1176 
wci_find_ent(work_func_t func)1177 static struct wci_ent *wci_find_ent(work_func_t func)
1178 {
1179 	struct wci_ent *ent;
1180 
1181 	hash_for_each_possible_rcu(wci_hash, ent, hash_node,
1182 				   (unsigned long)func) {
1183 		if (ent->func == func)
1184 			return ent;
1185 	}
1186 	return NULL;
1187 }
1188 
wq_cpu_intensive_report(work_func_t func)1189 static void wq_cpu_intensive_report(work_func_t func)
1190 {
1191 	struct wci_ent *ent;
1192 
1193 restart:
1194 	ent = wci_find_ent(func);
1195 	if (ent) {
1196 		u64 cnt;
1197 
1198 		/*
1199 		 * Start reporting from the fourth time and back off
1200 		 * exponentially.
1201 		 */
1202 		cnt = atomic64_inc_return_relaxed(&ent->cnt);
1203 		if (cnt >= 4 && is_power_of_2(cnt))
1204 			printk_deferred(KERN_WARNING "workqueue: %ps hogged CPU for >%luus %llu times, consider switching to WQ_UNBOUND\n",
1205 					ent->func, wq_cpu_intensive_thresh_us,
1206 					atomic64_read(&ent->cnt));
1207 		return;
1208 	}
1209 
1210 	/*
1211 	 * @func is a new violation. Allocate a new entry for it. If wcn_ents[]
1212 	 * is exhausted, something went really wrong and we probably made enough
1213 	 * noise already.
1214 	 */
1215 	if (wci_nr_ents >= WCI_MAX_ENTS)
1216 		return;
1217 
1218 	raw_spin_lock(&wci_lock);
1219 
1220 	if (wci_nr_ents >= WCI_MAX_ENTS) {
1221 		raw_spin_unlock(&wci_lock);
1222 		return;
1223 	}
1224 
1225 	if (wci_find_ent(func)) {
1226 		raw_spin_unlock(&wci_lock);
1227 		goto restart;
1228 	}
1229 
1230 	ent = &wci_ents[wci_nr_ents++];
1231 	ent->func = func;
1232 	atomic64_set(&ent->cnt, 1);
1233 	hash_add_rcu(wci_hash, &ent->hash_node, (unsigned long)func);
1234 
1235 	raw_spin_unlock(&wci_lock);
1236 }
1237 
1238 #else	/* CONFIG_WQ_CPU_INTENSIVE_REPORT */
wq_cpu_intensive_report(work_func_t func)1239 static void wq_cpu_intensive_report(work_func_t func) {}
1240 #endif	/* CONFIG_WQ_CPU_INTENSIVE_REPORT */
1241 
1242 /**
1243  * wq_worker_running - a worker is running again
1244  * @task: task waking up
1245  *
1246  * This function is called when a worker returns from schedule()
1247  */
wq_worker_running(struct task_struct * task)1248 void wq_worker_running(struct task_struct *task)
1249 {
1250 	struct worker *worker = kthread_data(task);
1251 
1252 	if (!READ_ONCE(worker->sleeping))
1253 		return;
1254 
1255 	/*
1256 	 * If preempted by unbind_workers() between the WORKER_NOT_RUNNING check
1257 	 * and the nr_running increment below, we may ruin the nr_running reset
1258 	 * and leave with an unexpected pool->nr_running == 1 on the newly unbound
1259 	 * pool. Protect against such race.
1260 	 */
1261 	preempt_disable();
1262 	if (!(worker->flags & WORKER_NOT_RUNNING))
1263 		worker->pool->nr_running++;
1264 	preempt_enable();
1265 
1266 	/*
1267 	 * CPU intensive auto-detection cares about how long a work item hogged
1268 	 * CPU without sleeping. Reset the starting timestamp on wakeup.
1269 	 */
1270 	worker->current_at = worker->task->se.sum_exec_runtime;
1271 
1272 	WRITE_ONCE(worker->sleeping, 0);
1273 }
1274 
1275 /**
1276  * wq_worker_sleeping - a worker is going to sleep
1277  * @task: task going to sleep
1278  *
1279  * This function is called from schedule() when a busy worker is
1280  * going to sleep.
1281  */
wq_worker_sleeping(struct task_struct * task)1282 void wq_worker_sleeping(struct task_struct *task)
1283 {
1284 	struct worker *worker = kthread_data(task);
1285 	struct worker_pool *pool;
1286 
1287 	/*
1288 	 * Rescuers, which may not have all the fields set up like normal
1289 	 * workers, also reach here, let's not access anything before
1290 	 * checking NOT_RUNNING.
1291 	 */
1292 	if (worker->flags & WORKER_NOT_RUNNING)
1293 		return;
1294 
1295 	pool = worker->pool;
1296 
1297 	/* Return if preempted before wq_worker_running() was reached */
1298 	if (READ_ONCE(worker->sleeping))
1299 		return;
1300 
1301 	WRITE_ONCE(worker->sleeping, 1);
1302 	raw_spin_lock_irq(&pool->lock);
1303 
1304 	/*
1305 	 * Recheck in case unbind_workers() preempted us. We don't
1306 	 * want to decrement nr_running after the worker is unbound
1307 	 * and nr_running has been reset.
1308 	 */
1309 	if (worker->flags & WORKER_NOT_RUNNING) {
1310 		raw_spin_unlock_irq(&pool->lock);
1311 		return;
1312 	}
1313 
1314 	pool->nr_running--;
1315 	if (kick_pool(pool))
1316 		worker->current_pwq->stats[PWQ_STAT_CM_WAKEUP]++;
1317 
1318 	raw_spin_unlock_irq(&pool->lock);
1319 }
1320 
1321 /**
1322  * wq_worker_tick - a scheduler tick occurred while a kworker is running
1323  * @task: task currently running
1324  *
1325  * Called from scheduler_tick(). We're in the IRQ context and the current
1326  * worker's fields which follow the 'K' locking rule can be accessed safely.
1327  */
wq_worker_tick(struct task_struct * task)1328 void wq_worker_tick(struct task_struct *task)
1329 {
1330 	struct worker *worker = kthread_data(task);
1331 	struct pool_workqueue *pwq = worker->current_pwq;
1332 	struct worker_pool *pool = worker->pool;
1333 
1334 	if (!pwq)
1335 		return;
1336 
1337 	pwq->stats[PWQ_STAT_CPU_TIME] += TICK_USEC;
1338 
1339 	if (!wq_cpu_intensive_thresh_us)
1340 		return;
1341 
1342 	/*
1343 	 * If the current worker is concurrency managed and hogged the CPU for
1344 	 * longer than wq_cpu_intensive_thresh_us, it's automatically marked
1345 	 * CPU_INTENSIVE to avoid stalling other concurrency-managed work items.
1346 	 *
1347 	 * Set @worker->sleeping means that @worker is in the process of
1348 	 * switching out voluntarily and won't be contributing to
1349 	 * @pool->nr_running until it wakes up. As wq_worker_sleeping() also
1350 	 * decrements ->nr_running, setting CPU_INTENSIVE here can lead to
1351 	 * double decrements. The task is releasing the CPU anyway. Let's skip.
1352 	 * We probably want to make this prettier in the future.
1353 	 */
1354 	if ((worker->flags & WORKER_NOT_RUNNING) || READ_ONCE(worker->sleeping) ||
1355 	    worker->task->se.sum_exec_runtime - worker->current_at <
1356 	    wq_cpu_intensive_thresh_us * NSEC_PER_USEC)
1357 		return;
1358 
1359 	raw_spin_lock(&pool->lock);
1360 
1361 	worker_set_flags(worker, WORKER_CPU_INTENSIVE);
1362 	wq_cpu_intensive_report(worker->current_func);
1363 	pwq->stats[PWQ_STAT_CPU_INTENSIVE]++;
1364 
1365 	if (kick_pool(pool))
1366 		pwq->stats[PWQ_STAT_CM_WAKEUP]++;
1367 
1368 	raw_spin_unlock(&pool->lock);
1369 }
1370 
1371 /**
1372  * wq_worker_last_func - retrieve worker's last work function
1373  * @task: Task to retrieve last work function of.
1374  *
1375  * Determine the last function a worker executed. This is called from
1376  * the scheduler to get a worker's last known identity.
1377  *
1378  * CONTEXT:
1379  * raw_spin_lock_irq(rq->lock)
1380  *
1381  * This function is called during schedule() when a kworker is going
1382  * to sleep. It's used by psi to identify aggregation workers during
1383  * dequeuing, to allow periodic aggregation to shut-off when that
1384  * worker is the last task in the system or cgroup to go to sleep.
1385  *
1386  * As this function doesn't involve any workqueue-related locking, it
1387  * only returns stable values when called from inside the scheduler's
1388  * queuing and dequeuing paths, when @task, which must be a kworker,
1389  * is guaranteed to not be processing any works.
1390  *
1391  * Return:
1392  * The last work function %current executed as a worker, NULL if it
1393  * hasn't executed any work yet.
1394  */
wq_worker_last_func(struct task_struct * task)1395 work_func_t wq_worker_last_func(struct task_struct *task)
1396 {
1397 	struct worker *worker = kthread_data(task);
1398 
1399 	return worker->last_func;
1400 }
1401 
1402 /**
1403  * get_pwq - get an extra reference on the specified pool_workqueue
1404  * @pwq: pool_workqueue to get
1405  *
1406  * Obtain an extra reference on @pwq.  The caller should guarantee that
1407  * @pwq has positive refcnt and be holding the matching pool->lock.
1408  */
get_pwq(struct pool_workqueue * pwq)1409 static void get_pwq(struct pool_workqueue *pwq)
1410 {
1411 	lockdep_assert_held(&pwq->pool->lock);
1412 	WARN_ON_ONCE(pwq->refcnt <= 0);
1413 	pwq->refcnt++;
1414 }
1415 
1416 /**
1417  * put_pwq - put a pool_workqueue reference
1418  * @pwq: pool_workqueue to put
1419  *
1420  * Drop a reference of @pwq.  If its refcnt reaches zero, schedule its
1421  * destruction.  The caller should be holding the matching pool->lock.
1422  */
put_pwq(struct pool_workqueue * pwq)1423 static void put_pwq(struct pool_workqueue *pwq)
1424 {
1425 	lockdep_assert_held(&pwq->pool->lock);
1426 	if (likely(--pwq->refcnt))
1427 		return;
1428 	/*
1429 	 * @pwq can't be released under pool->lock, bounce to a dedicated
1430 	 * kthread_worker to avoid A-A deadlocks.
1431 	 */
1432 	kthread_queue_work(pwq_release_worker, &pwq->release_work);
1433 }
1434 
1435 /**
1436  * put_pwq_unlocked - put_pwq() with surrounding pool lock/unlock
1437  * @pwq: pool_workqueue to put (can be %NULL)
1438  *
1439  * put_pwq() with locking.  This function also allows %NULL @pwq.
1440  */
put_pwq_unlocked(struct pool_workqueue * pwq)1441 static void put_pwq_unlocked(struct pool_workqueue *pwq)
1442 {
1443 	if (pwq) {
1444 		/*
1445 		 * As both pwqs and pools are RCU protected, the
1446 		 * following lock operations are safe.
1447 		 */
1448 		raw_spin_lock_irq(&pwq->pool->lock);
1449 		put_pwq(pwq);
1450 		raw_spin_unlock_irq(&pwq->pool->lock);
1451 	}
1452 }
1453 
pwq_activate_inactive_work(struct work_struct * work)1454 static void pwq_activate_inactive_work(struct work_struct *work)
1455 {
1456 	struct pool_workqueue *pwq = get_work_pwq(work);
1457 
1458 	trace_workqueue_activate_work(work);
1459 	if (list_empty(&pwq->pool->worklist))
1460 		pwq->pool->watchdog_ts = jiffies;
1461 	move_linked_works(work, &pwq->pool->worklist, NULL);
1462 	__clear_bit(WORK_STRUCT_INACTIVE_BIT, work_data_bits(work));
1463 	pwq->nr_active++;
1464 }
1465 
pwq_activate_first_inactive(struct pool_workqueue * pwq)1466 static void pwq_activate_first_inactive(struct pool_workqueue *pwq)
1467 {
1468 	struct work_struct *work = list_first_entry(&pwq->inactive_works,
1469 						    struct work_struct, entry);
1470 
1471 	pwq_activate_inactive_work(work);
1472 }
1473 
1474 /**
1475  * pwq_dec_nr_in_flight - decrement pwq's nr_in_flight
1476  * @pwq: pwq of interest
1477  * @work_data: work_data of work which left the queue
1478  *
1479  * A work either has completed or is removed from pending queue,
1480  * decrement nr_in_flight of its pwq and handle workqueue flushing.
1481  *
1482  * CONTEXT:
1483  * raw_spin_lock_irq(pool->lock).
1484  */
pwq_dec_nr_in_flight(struct pool_workqueue * pwq,unsigned long work_data)1485 static void pwq_dec_nr_in_flight(struct pool_workqueue *pwq, unsigned long work_data)
1486 {
1487 	int color = get_work_color(work_data);
1488 
1489 	if (!(work_data & WORK_STRUCT_INACTIVE)) {
1490 		pwq->nr_active--;
1491 		if (!list_empty(&pwq->inactive_works)) {
1492 			/* one down, submit an inactive one */
1493 			if (pwq->nr_active < pwq->max_active)
1494 				pwq_activate_first_inactive(pwq);
1495 		}
1496 	}
1497 
1498 	pwq->nr_in_flight[color]--;
1499 
1500 	/* is flush in progress and are we at the flushing tip? */
1501 	if (likely(pwq->flush_color != color))
1502 		goto out_put;
1503 
1504 	/* are there still in-flight works? */
1505 	if (pwq->nr_in_flight[color])
1506 		goto out_put;
1507 
1508 	/* this pwq is done, clear flush_color */
1509 	pwq->flush_color = -1;
1510 
1511 	/*
1512 	 * If this was the last pwq, wake up the first flusher.  It
1513 	 * will handle the rest.
1514 	 */
1515 	if (atomic_dec_and_test(&pwq->wq->nr_pwqs_to_flush))
1516 		complete(&pwq->wq->first_flusher->done);
1517 out_put:
1518 	put_pwq(pwq);
1519 }
1520 
1521 /**
1522  * try_to_grab_pending - steal work item from worklist and disable irq
1523  * @work: work item to steal
1524  * @is_dwork: @work is a delayed_work
1525  * @flags: place to store irq state
1526  *
1527  * Try to grab PENDING bit of @work.  This function can handle @work in any
1528  * stable state - idle, on timer or on worklist.
1529  *
1530  * Return:
1531  *
1532  *  ========	================================================================
1533  *  1		if @work was pending and we successfully stole PENDING
1534  *  0		if @work was idle and we claimed PENDING
1535  *  -EAGAIN	if PENDING couldn't be grabbed at the moment, safe to busy-retry
1536  *  -ENOENT	if someone else is canceling @work, this state may persist
1537  *		for arbitrarily long
1538  *  ========	================================================================
1539  *
1540  * Note:
1541  * On >= 0 return, the caller owns @work's PENDING bit.  To avoid getting
1542  * interrupted while holding PENDING and @work off queue, irq must be
1543  * disabled on entry.  This, combined with delayed_work->timer being
1544  * irqsafe, ensures that we return -EAGAIN for finite short period of time.
1545  *
1546  * On successful return, >= 0, irq is disabled and the caller is
1547  * responsible for releasing it using local_irq_restore(*@flags).
1548  *
1549  * This function is safe to call from any context including IRQ handler.
1550  */
try_to_grab_pending(struct work_struct * work,bool is_dwork,unsigned long * flags)1551 static int try_to_grab_pending(struct work_struct *work, bool is_dwork,
1552 			       unsigned long *flags)
1553 {
1554 	struct worker_pool *pool;
1555 	struct pool_workqueue *pwq;
1556 
1557 	local_irq_save(*flags);
1558 
1559 	/* try to steal the timer if it exists */
1560 	if (is_dwork) {
1561 		struct delayed_work *dwork = to_delayed_work(work);
1562 
1563 		/*
1564 		 * dwork->timer is irqsafe.  If del_timer() fails, it's
1565 		 * guaranteed that the timer is not queued anywhere and not
1566 		 * running on the local CPU.
1567 		 */
1568 		if (likely(del_timer(&dwork->timer)))
1569 			return 1;
1570 	}
1571 
1572 	/* try to claim PENDING the normal way */
1573 	if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work)))
1574 		return 0;
1575 
1576 	rcu_read_lock();
1577 	/*
1578 	 * The queueing is in progress, or it is already queued. Try to
1579 	 * steal it from ->worklist without clearing WORK_STRUCT_PENDING.
1580 	 */
1581 	pool = get_work_pool(work);
1582 	if (!pool)
1583 		goto fail;
1584 
1585 	raw_spin_lock(&pool->lock);
1586 	/*
1587 	 * work->data is guaranteed to point to pwq only while the work
1588 	 * item is queued on pwq->wq, and both updating work->data to point
1589 	 * to pwq on queueing and to pool on dequeueing are done under
1590 	 * pwq->pool->lock.  This in turn guarantees that, if work->data
1591 	 * points to pwq which is associated with a locked pool, the work
1592 	 * item is currently queued on that pool.
1593 	 */
1594 	pwq = get_work_pwq(work);
1595 	if (pwq && pwq->pool == pool) {
1596 		debug_work_deactivate(work);
1597 
1598 		/*
1599 		 * A cancelable inactive work item must be in the
1600 		 * pwq->inactive_works since a queued barrier can't be
1601 		 * canceled (see the comments in insert_wq_barrier()).
1602 		 *
1603 		 * An inactive work item cannot be grabbed directly because
1604 		 * it might have linked barrier work items which, if left
1605 		 * on the inactive_works list, will confuse pwq->nr_active
1606 		 * management later on and cause stall.  Make sure the work
1607 		 * item is activated before grabbing.
1608 		 */
1609 		if (*work_data_bits(work) & WORK_STRUCT_INACTIVE)
1610 			pwq_activate_inactive_work(work);
1611 
1612 		list_del_init(&work->entry);
1613 		pwq_dec_nr_in_flight(pwq, *work_data_bits(work));
1614 
1615 		/* work->data points to pwq iff queued, point to pool */
1616 		set_work_pool_and_keep_pending(work, pool->id);
1617 
1618 		raw_spin_unlock(&pool->lock);
1619 		rcu_read_unlock();
1620 		return 1;
1621 	}
1622 	raw_spin_unlock(&pool->lock);
1623 fail:
1624 	rcu_read_unlock();
1625 	local_irq_restore(*flags);
1626 	if (work_is_canceling(work))
1627 		return -ENOENT;
1628 	cpu_relax();
1629 	return -EAGAIN;
1630 }
1631 
1632 /**
1633  * insert_work - insert a work into a pool
1634  * @pwq: pwq @work belongs to
1635  * @work: work to insert
1636  * @head: insertion point
1637  * @extra_flags: extra WORK_STRUCT_* flags to set
1638  *
1639  * Insert @work which belongs to @pwq after @head.  @extra_flags is or'd to
1640  * work_struct flags.
1641  *
1642  * CONTEXT:
1643  * raw_spin_lock_irq(pool->lock).
1644  */
insert_work(struct pool_workqueue * pwq,struct work_struct * work,struct list_head * head,unsigned int extra_flags)1645 static void insert_work(struct pool_workqueue *pwq, struct work_struct *work,
1646 			struct list_head *head, unsigned int extra_flags)
1647 {
1648 	debug_work_activate(work);
1649 
1650 	/* record the work call stack in order to print it in KASAN reports */
1651 	kasan_record_aux_stack_noalloc(work);
1652 
1653 	/* we own @work, set data and link */
1654 	set_work_pwq(work, pwq, extra_flags);
1655 	list_add_tail(&work->entry, head);
1656 	get_pwq(pwq);
1657 }
1658 
1659 /*
1660  * Test whether @work is being queued from another work executing on the
1661  * same workqueue.
1662  */
is_chained_work(struct workqueue_struct * wq)1663 static bool is_chained_work(struct workqueue_struct *wq)
1664 {
1665 	struct worker *worker;
1666 
1667 	worker = current_wq_worker();
1668 	/*
1669 	 * Return %true iff I'm a worker executing a work item on @wq.  If
1670 	 * I'm @worker, it's safe to dereference it without locking.
1671 	 */
1672 	return worker && worker->current_pwq->wq == wq;
1673 }
1674 
1675 /*
1676  * When queueing an unbound work item to a wq, prefer local CPU if allowed
1677  * by wq_unbound_cpumask.  Otherwise, round robin among the allowed ones to
1678  * avoid perturbing sensitive tasks.
1679  */
wq_select_unbound_cpu(int cpu)1680 static int wq_select_unbound_cpu(int cpu)
1681 {
1682 	int new_cpu;
1683 
1684 	if (likely(!wq_debug_force_rr_cpu)) {
1685 		if (cpumask_test_cpu(cpu, wq_unbound_cpumask))
1686 			return cpu;
1687 	} else {
1688 		pr_warn_once("workqueue: round-robin CPU selection forced, expect performance impact\n");
1689 	}
1690 
1691 	new_cpu = __this_cpu_read(wq_rr_cpu_last);
1692 	new_cpu = cpumask_next_and(new_cpu, wq_unbound_cpumask, cpu_online_mask);
1693 	if (unlikely(new_cpu >= nr_cpu_ids)) {
1694 		new_cpu = cpumask_first_and(wq_unbound_cpumask, cpu_online_mask);
1695 		if (unlikely(new_cpu >= nr_cpu_ids))
1696 			return cpu;
1697 	}
1698 	__this_cpu_write(wq_rr_cpu_last, new_cpu);
1699 
1700 	return new_cpu;
1701 }
1702 
__queue_work(int cpu,struct workqueue_struct * wq,struct work_struct * work)1703 static void __queue_work(int cpu, struct workqueue_struct *wq,
1704 			 struct work_struct *work)
1705 {
1706 	struct pool_workqueue *pwq;
1707 	struct worker_pool *last_pool, *pool;
1708 	unsigned int work_flags;
1709 	unsigned int req_cpu = cpu;
1710 
1711 	/*
1712 	 * While a work item is PENDING && off queue, a task trying to
1713 	 * steal the PENDING will busy-loop waiting for it to either get
1714 	 * queued or lose PENDING.  Grabbing PENDING and queueing should
1715 	 * happen with IRQ disabled.
1716 	 */
1717 	lockdep_assert_irqs_disabled();
1718 
1719 
1720 	/*
1721 	 * For a draining wq, only works from the same workqueue are
1722 	 * allowed. The __WQ_DESTROYING helps to spot the issue that
1723 	 * queues a new work item to a wq after destroy_workqueue(wq).
1724 	 */
1725 	if (unlikely(wq->flags & (__WQ_DESTROYING | __WQ_DRAINING) &&
1726 		     WARN_ON_ONCE(!is_chained_work(wq))))
1727 		return;
1728 	rcu_read_lock();
1729 retry:
1730 	/* pwq which will be used unless @work is executing elsewhere */
1731 	if (req_cpu == WORK_CPU_UNBOUND) {
1732 		if (wq->flags & WQ_UNBOUND)
1733 			cpu = wq_select_unbound_cpu(raw_smp_processor_id());
1734 		else
1735 			cpu = raw_smp_processor_id();
1736 	}
1737 
1738 	pwq = rcu_dereference(*per_cpu_ptr(wq->cpu_pwq, cpu));
1739 	pool = pwq->pool;
1740 
1741 	/*
1742 	 * If @work was previously on a different pool, it might still be
1743 	 * running there, in which case the work needs to be queued on that
1744 	 * pool to guarantee non-reentrancy.
1745 	 */
1746 	last_pool = get_work_pool(work);
1747 	if (last_pool && last_pool != pool) {
1748 		struct worker *worker;
1749 
1750 		raw_spin_lock(&last_pool->lock);
1751 
1752 		worker = find_worker_executing_work(last_pool, work);
1753 
1754 		if (worker && worker->current_pwq->wq == wq) {
1755 			pwq = worker->current_pwq;
1756 			pool = pwq->pool;
1757 			WARN_ON_ONCE(pool != last_pool);
1758 		} else {
1759 			/* meh... not running there, queue here */
1760 			raw_spin_unlock(&last_pool->lock);
1761 			raw_spin_lock(&pool->lock);
1762 		}
1763 	} else {
1764 		raw_spin_lock(&pool->lock);
1765 	}
1766 
1767 	/*
1768 	 * pwq is determined and locked. For unbound pools, we could have raced
1769 	 * with pwq release and it could already be dead. If its refcnt is zero,
1770 	 * repeat pwq selection. Note that unbound pwqs never die without
1771 	 * another pwq replacing it in cpu_pwq or while work items are executing
1772 	 * on it, so the retrying is guaranteed to make forward-progress.
1773 	 */
1774 	if (unlikely(!pwq->refcnt)) {
1775 		if (wq->flags & WQ_UNBOUND) {
1776 			raw_spin_unlock(&pool->lock);
1777 			cpu_relax();
1778 			goto retry;
1779 		}
1780 		/* oops */
1781 		WARN_ONCE(true, "workqueue: per-cpu pwq for %s on cpu%d has 0 refcnt",
1782 			  wq->name, cpu);
1783 	}
1784 
1785 	/* pwq determined, queue */
1786 	trace_workqueue_queue_work(req_cpu, pwq, work);
1787 
1788 	if (WARN_ON(!list_empty(&work->entry)))
1789 		goto out;
1790 
1791 	pwq->nr_in_flight[pwq->work_color]++;
1792 	work_flags = work_color_to_flags(pwq->work_color);
1793 
1794 	if (likely(pwq->nr_active < pwq->max_active)) {
1795 		if (list_empty(&pool->worklist))
1796 			pool->watchdog_ts = jiffies;
1797 
1798 		trace_workqueue_activate_work(work);
1799 		pwq->nr_active++;
1800 		insert_work(pwq, work, &pool->worklist, work_flags);
1801 		kick_pool(pool);
1802 	} else {
1803 		work_flags |= WORK_STRUCT_INACTIVE;
1804 		insert_work(pwq, work, &pwq->inactive_works, work_flags);
1805 	}
1806 
1807 out:
1808 	raw_spin_unlock(&pool->lock);
1809 	rcu_read_unlock();
1810 }
1811 
1812 /**
1813  * queue_work_on - queue work on specific cpu
1814  * @cpu: CPU number to execute work on
1815  * @wq: workqueue to use
1816  * @work: work to queue
1817  *
1818  * We queue the work to a specific CPU, the caller must ensure it
1819  * can't go away.  Callers that fail to ensure that the specified
1820  * CPU cannot go away will execute on a randomly chosen CPU.
1821  * But note well that callers specifying a CPU that never has been
1822  * online will get a splat.
1823  *
1824  * Return: %false if @work was already on a queue, %true otherwise.
1825  */
queue_work_on(int cpu,struct workqueue_struct * wq,struct work_struct * work)1826 bool queue_work_on(int cpu, struct workqueue_struct *wq,
1827 		   struct work_struct *work)
1828 {
1829 	bool ret = false;
1830 	unsigned long flags;
1831 
1832 	local_irq_save(flags);
1833 
1834 	if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
1835 		__queue_work(cpu, wq, work);
1836 		ret = true;
1837 	}
1838 
1839 	local_irq_restore(flags);
1840 	return ret;
1841 }
1842 EXPORT_SYMBOL(queue_work_on);
1843 
1844 /**
1845  * select_numa_node_cpu - Select a CPU based on NUMA node
1846  * @node: NUMA node ID that we want to select a CPU from
1847  *
1848  * This function will attempt to find a "random" cpu available on a given
1849  * node. If there are no CPUs available on the given node it will return
1850  * WORK_CPU_UNBOUND indicating that we should just schedule to any
1851  * available CPU if we need to schedule this work.
1852  */
select_numa_node_cpu(int node)1853 static int select_numa_node_cpu(int node)
1854 {
1855 	int cpu;
1856 
1857 	/* Delay binding to CPU if node is not valid or online */
1858 	if (node < 0 || node >= MAX_NUMNODES || !node_online(node))
1859 		return WORK_CPU_UNBOUND;
1860 
1861 	/* Use local node/cpu if we are already there */
1862 	cpu = raw_smp_processor_id();
1863 	if (node == cpu_to_node(cpu))
1864 		return cpu;
1865 
1866 	/* Use "random" otherwise know as "first" online CPU of node */
1867 	cpu = cpumask_any_and(cpumask_of_node(node), cpu_online_mask);
1868 
1869 	/* If CPU is valid return that, otherwise just defer */
1870 	return cpu < nr_cpu_ids ? cpu : WORK_CPU_UNBOUND;
1871 }
1872 
1873 /**
1874  * queue_work_node - queue work on a "random" cpu for a given NUMA node
1875  * @node: NUMA node that we are targeting the work for
1876  * @wq: workqueue to use
1877  * @work: work to queue
1878  *
1879  * We queue the work to a "random" CPU within a given NUMA node. The basic
1880  * idea here is to provide a way to somehow associate work with a given
1881  * NUMA node.
1882  *
1883  * This function will only make a best effort attempt at getting this onto
1884  * the right NUMA node. If no node is requested or the requested node is
1885  * offline then we just fall back to standard queue_work behavior.
1886  *
1887  * Currently the "random" CPU ends up being the first available CPU in the
1888  * intersection of cpu_online_mask and the cpumask of the node, unless we
1889  * are running on the node. In that case we just use the current CPU.
1890  *
1891  * Return: %false if @work was already on a queue, %true otherwise.
1892  */
queue_work_node(int node,struct workqueue_struct * wq,struct work_struct * work)1893 bool queue_work_node(int node, struct workqueue_struct *wq,
1894 		     struct work_struct *work)
1895 {
1896 	unsigned long flags;
1897 	bool ret = false;
1898 
1899 	/*
1900 	 * This current implementation is specific to unbound workqueues.
1901 	 * Specifically we only return the first available CPU for a given
1902 	 * node instead of cycling through individual CPUs within the node.
1903 	 *
1904 	 * If this is used with a per-cpu workqueue then the logic in
1905 	 * workqueue_select_cpu_near would need to be updated to allow for
1906 	 * some round robin type logic.
1907 	 */
1908 	WARN_ON_ONCE(!(wq->flags & WQ_UNBOUND));
1909 
1910 	local_irq_save(flags);
1911 
1912 	if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
1913 		int cpu = select_numa_node_cpu(node);
1914 
1915 		__queue_work(cpu, wq, work);
1916 		ret = true;
1917 	}
1918 
1919 	local_irq_restore(flags);
1920 	return ret;
1921 }
1922 EXPORT_SYMBOL_GPL(queue_work_node);
1923 
delayed_work_timer_fn(struct timer_list * t)1924 void delayed_work_timer_fn(struct timer_list *t)
1925 {
1926 	struct delayed_work *dwork = from_timer(dwork, t, timer);
1927 
1928 	/* should have been called from irqsafe timer with irq already off */
1929 	__queue_work(dwork->cpu, dwork->wq, &dwork->work);
1930 }
1931 EXPORT_SYMBOL(delayed_work_timer_fn);
1932 
__queue_delayed_work(int cpu,struct workqueue_struct * wq,struct delayed_work * dwork,unsigned long delay)1933 static void __queue_delayed_work(int cpu, struct workqueue_struct *wq,
1934 				struct delayed_work *dwork, unsigned long delay)
1935 {
1936 	struct timer_list *timer = &dwork->timer;
1937 	struct work_struct *work = &dwork->work;
1938 
1939 	WARN_ON_ONCE(!wq);
1940 	WARN_ON_ONCE(timer->function != delayed_work_timer_fn);
1941 	WARN_ON_ONCE(timer_pending(timer));
1942 	WARN_ON_ONCE(!list_empty(&work->entry));
1943 
1944 	/*
1945 	 * If @delay is 0, queue @dwork->work immediately.  This is for
1946 	 * both optimization and correctness.  The earliest @timer can
1947 	 * expire is on the closest next tick and delayed_work users depend
1948 	 * on that there's no such delay when @delay is 0.
1949 	 */
1950 	if (!delay) {
1951 		__queue_work(cpu, wq, &dwork->work);
1952 		return;
1953 	}
1954 
1955 	dwork->wq = wq;
1956 	dwork->cpu = cpu;
1957 	timer->expires = jiffies + delay;
1958 
1959 	if (unlikely(cpu != WORK_CPU_UNBOUND))
1960 		add_timer_on(timer, cpu);
1961 	else
1962 		add_timer(timer);
1963 }
1964 
1965 /**
1966  * queue_delayed_work_on - queue work on specific CPU after delay
1967  * @cpu: CPU number to execute work on
1968  * @wq: workqueue to use
1969  * @dwork: work to queue
1970  * @delay: number of jiffies to wait before queueing
1971  *
1972  * Return: %false if @work was already on a queue, %true otherwise.  If
1973  * @delay is zero and @dwork is idle, it will be scheduled for immediate
1974  * execution.
1975  */
queue_delayed_work_on(int cpu,struct workqueue_struct * wq,struct delayed_work * dwork,unsigned long delay)1976 bool queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
1977 			   struct delayed_work *dwork, unsigned long delay)
1978 {
1979 	struct work_struct *work = &dwork->work;
1980 	bool ret = false;
1981 	unsigned long flags;
1982 
1983 	/* read the comment in __queue_work() */
1984 	local_irq_save(flags);
1985 
1986 	if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
1987 		__queue_delayed_work(cpu, wq, dwork, delay);
1988 		ret = true;
1989 	}
1990 
1991 	local_irq_restore(flags);
1992 	return ret;
1993 }
1994 EXPORT_SYMBOL(queue_delayed_work_on);
1995 
1996 /**
1997  * mod_delayed_work_on - modify delay of or queue a delayed work on specific CPU
1998  * @cpu: CPU number to execute work on
1999  * @wq: workqueue to use
2000  * @dwork: work to queue
2001  * @delay: number of jiffies to wait before queueing
2002  *
2003  * If @dwork is idle, equivalent to queue_delayed_work_on(); otherwise,
2004  * modify @dwork's timer so that it expires after @delay.  If @delay is
2005  * zero, @work is guaranteed to be scheduled immediately regardless of its
2006  * current state.
2007  *
2008  * Return: %false if @dwork was idle and queued, %true if @dwork was
2009  * pending and its timer was modified.
2010  *
2011  * This function is safe to call from any context including IRQ handler.
2012  * See try_to_grab_pending() for details.
2013  */
mod_delayed_work_on(int cpu,struct workqueue_struct * wq,struct delayed_work * dwork,unsigned long delay)2014 bool mod_delayed_work_on(int cpu, struct workqueue_struct *wq,
2015 			 struct delayed_work *dwork, unsigned long delay)
2016 {
2017 	unsigned long flags;
2018 	int ret;
2019 
2020 	do {
2021 		ret = try_to_grab_pending(&dwork->work, true, &flags);
2022 	} while (unlikely(ret == -EAGAIN));
2023 
2024 	if (likely(ret >= 0)) {
2025 		__queue_delayed_work(cpu, wq, dwork, delay);
2026 		local_irq_restore(flags);
2027 	}
2028 
2029 	/* -ENOENT from try_to_grab_pending() becomes %true */
2030 	return ret;
2031 }
2032 EXPORT_SYMBOL_GPL(mod_delayed_work_on);
2033 
rcu_work_rcufn(struct rcu_head * rcu)2034 static void rcu_work_rcufn(struct rcu_head *rcu)
2035 {
2036 	struct rcu_work *rwork = container_of(rcu, struct rcu_work, rcu);
2037 
2038 	/* read the comment in __queue_work() */
2039 	local_irq_disable();
2040 	__queue_work(WORK_CPU_UNBOUND, rwork->wq, &rwork->work);
2041 	local_irq_enable();
2042 }
2043 
2044 /**
2045  * queue_rcu_work - queue work after a RCU grace period
2046  * @wq: workqueue to use
2047  * @rwork: work to queue
2048  *
2049  * Return: %false if @rwork was already pending, %true otherwise.  Note
2050  * that a full RCU grace period is guaranteed only after a %true return.
2051  * While @rwork is guaranteed to be executed after a %false return, the
2052  * execution may happen before a full RCU grace period has passed.
2053  */
queue_rcu_work(struct workqueue_struct * wq,struct rcu_work * rwork)2054 bool queue_rcu_work(struct workqueue_struct *wq, struct rcu_work *rwork)
2055 {
2056 	struct work_struct *work = &rwork->work;
2057 
2058 	if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
2059 		rwork->wq = wq;
2060 		call_rcu_hurry(&rwork->rcu, rcu_work_rcufn);
2061 		return true;
2062 	}
2063 
2064 	return false;
2065 }
2066 EXPORT_SYMBOL(queue_rcu_work);
2067 
alloc_worker(int node)2068 static struct worker *alloc_worker(int node)
2069 {
2070 	struct worker *worker;
2071 
2072 	worker = kzalloc_node(sizeof(*worker), GFP_KERNEL, node);
2073 	if (worker) {
2074 		INIT_LIST_HEAD(&worker->entry);
2075 		INIT_LIST_HEAD(&worker->scheduled);
2076 		INIT_LIST_HEAD(&worker->node);
2077 		/* on creation a worker is in !idle && prep state */
2078 		worker->flags = WORKER_PREP;
2079 	}
2080 	return worker;
2081 }
2082 
pool_allowed_cpus(struct worker_pool * pool)2083 static cpumask_t *pool_allowed_cpus(struct worker_pool *pool)
2084 {
2085 	if (pool->cpu < 0 && pool->attrs->affn_strict)
2086 		return pool->attrs->__pod_cpumask;
2087 	else
2088 		return pool->attrs->cpumask;
2089 }
2090 
2091 /**
2092  * worker_attach_to_pool() - attach a worker to a pool
2093  * @worker: worker to be attached
2094  * @pool: the target pool
2095  *
2096  * Attach @worker to @pool.  Once attached, the %WORKER_UNBOUND flag and
2097  * cpu-binding of @worker are kept coordinated with the pool across
2098  * cpu-[un]hotplugs.
2099  */
worker_attach_to_pool(struct worker * worker,struct worker_pool * pool)2100 static void worker_attach_to_pool(struct worker *worker,
2101 				   struct worker_pool *pool)
2102 {
2103 	mutex_lock(&wq_pool_attach_mutex);
2104 
2105 	/*
2106 	 * The wq_pool_attach_mutex ensures %POOL_DISASSOCIATED remains
2107 	 * stable across this function.  See the comments above the flag
2108 	 * definition for details.
2109 	 */
2110 	if (pool->flags & POOL_DISASSOCIATED)
2111 		worker->flags |= WORKER_UNBOUND;
2112 	else
2113 		kthread_set_per_cpu(worker->task, pool->cpu);
2114 
2115 	if (worker->rescue_wq)
2116 		set_cpus_allowed_ptr(worker->task, pool_allowed_cpus(pool));
2117 
2118 	list_add_tail(&worker->node, &pool->workers);
2119 	worker->pool = pool;
2120 
2121 	mutex_unlock(&wq_pool_attach_mutex);
2122 }
2123 
2124 /**
2125  * worker_detach_from_pool() - detach a worker from its pool
2126  * @worker: worker which is attached to its pool
2127  *
2128  * Undo the attaching which had been done in worker_attach_to_pool().  The
2129  * caller worker shouldn't access to the pool after detached except it has
2130  * other reference to the pool.
2131  */
worker_detach_from_pool(struct worker * worker)2132 static void worker_detach_from_pool(struct worker *worker)
2133 {
2134 	struct worker_pool *pool = worker->pool;
2135 	struct completion *detach_completion = NULL;
2136 
2137 	mutex_lock(&wq_pool_attach_mutex);
2138 
2139 	kthread_set_per_cpu(worker->task, -1);
2140 	list_del(&worker->node);
2141 	worker->pool = NULL;
2142 
2143 	if (list_empty(&pool->workers) && list_empty(&pool->dying_workers))
2144 		detach_completion = pool->detach_completion;
2145 	mutex_unlock(&wq_pool_attach_mutex);
2146 
2147 	/* clear leftover flags without pool->lock after it is detached */
2148 	worker->flags &= ~(WORKER_UNBOUND | WORKER_REBOUND);
2149 
2150 	if (detach_completion)
2151 		complete(detach_completion);
2152 }
2153 
2154 /**
2155  * create_worker - create a new workqueue worker
2156  * @pool: pool the new worker will belong to
2157  *
2158  * Create and start a new worker which is attached to @pool.
2159  *
2160  * CONTEXT:
2161  * Might sleep.  Does GFP_KERNEL allocations.
2162  *
2163  * Return:
2164  * Pointer to the newly created worker.
2165  */
create_worker(struct worker_pool * pool)2166 static struct worker *create_worker(struct worker_pool *pool)
2167 {
2168 	struct worker *worker;
2169 	int id;
2170 	char id_buf[23];
2171 
2172 	/* ID is needed to determine kthread name */
2173 	id = ida_alloc(&pool->worker_ida, GFP_KERNEL);
2174 	if (id < 0) {
2175 		pr_err_once("workqueue: Failed to allocate a worker ID: %pe\n",
2176 			    ERR_PTR(id));
2177 		return NULL;
2178 	}
2179 
2180 	worker = alloc_worker(pool->node);
2181 	if (!worker) {
2182 		pr_err_once("workqueue: Failed to allocate a worker\n");
2183 		goto fail;
2184 	}
2185 
2186 	worker->id = id;
2187 
2188 	if (pool->cpu >= 0)
2189 		snprintf(id_buf, sizeof(id_buf), "%d:%d%s", pool->cpu, id,
2190 			 pool->attrs->nice < 0  ? "H" : "");
2191 	else
2192 		snprintf(id_buf, sizeof(id_buf), "u%d:%d", pool->id, id);
2193 
2194 	worker->task = kthread_create_on_node(worker_thread, worker, pool->node,
2195 					      "kworker/%s", id_buf);
2196 	if (IS_ERR(worker->task)) {
2197 		if (PTR_ERR(worker->task) == -EINTR) {
2198 			pr_err("workqueue: Interrupted when creating a worker thread \"kworker/%s\"\n",
2199 			       id_buf);
2200 		} else {
2201 			pr_err_once("workqueue: Failed to create a worker thread: %pe",
2202 				    worker->task);
2203 		}
2204 		goto fail;
2205 	}
2206 
2207 	set_user_nice(worker->task, pool->attrs->nice);
2208 	kthread_bind_mask(worker->task, pool_allowed_cpus(pool));
2209 
2210 	/* successful, attach the worker to the pool */
2211 	worker_attach_to_pool(worker, pool);
2212 
2213 	/* start the newly created worker */
2214 	raw_spin_lock_irq(&pool->lock);
2215 
2216 	worker->pool->nr_workers++;
2217 	worker_enter_idle(worker);
2218 	kick_pool(pool);
2219 
2220 	/*
2221 	 * @worker is waiting on a completion in kthread() and will trigger hung
2222 	 * check if not woken up soon. As kick_pool() might not have waken it
2223 	 * up, wake it up explicitly once more.
2224 	 */
2225 	wake_up_process(worker->task);
2226 
2227 	raw_spin_unlock_irq(&pool->lock);
2228 
2229 	return worker;
2230 
2231 fail:
2232 	ida_free(&pool->worker_ida, id);
2233 	kfree(worker);
2234 	return NULL;
2235 }
2236 
unbind_worker(struct worker * worker)2237 static void unbind_worker(struct worker *worker)
2238 {
2239 	lockdep_assert_held(&wq_pool_attach_mutex);
2240 
2241 	kthread_set_per_cpu(worker->task, -1);
2242 	if (cpumask_intersects(wq_unbound_cpumask, cpu_active_mask))
2243 		WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task, wq_unbound_cpumask) < 0);
2244 	else
2245 		WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task, cpu_possible_mask) < 0);
2246 }
2247 
wake_dying_workers(struct list_head * cull_list)2248 static void wake_dying_workers(struct list_head *cull_list)
2249 {
2250 	struct worker *worker, *tmp;
2251 
2252 	list_for_each_entry_safe(worker, tmp, cull_list, entry) {
2253 		list_del_init(&worker->entry);
2254 		unbind_worker(worker);
2255 		/*
2256 		 * If the worker was somehow already running, then it had to be
2257 		 * in pool->idle_list when set_worker_dying() happened or we
2258 		 * wouldn't have gotten here.
2259 		 *
2260 		 * Thus, the worker must either have observed the WORKER_DIE
2261 		 * flag, or have set its state to TASK_IDLE. Either way, the
2262 		 * below will be observed by the worker and is safe to do
2263 		 * outside of pool->lock.
2264 		 */
2265 		wake_up_process(worker->task);
2266 	}
2267 }
2268 
2269 /**
2270  * set_worker_dying - Tag a worker for destruction
2271  * @worker: worker to be destroyed
2272  * @list: transfer worker away from its pool->idle_list and into list
2273  *
2274  * Tag @worker for destruction and adjust @pool stats accordingly.  The worker
2275  * should be idle.
2276  *
2277  * CONTEXT:
2278  * raw_spin_lock_irq(pool->lock).
2279  */
set_worker_dying(struct worker * worker,struct list_head * list)2280 static void set_worker_dying(struct worker *worker, struct list_head *list)
2281 {
2282 	struct worker_pool *pool = worker->pool;
2283 
2284 	lockdep_assert_held(&pool->lock);
2285 	lockdep_assert_held(&wq_pool_attach_mutex);
2286 
2287 	/* sanity check frenzy */
2288 	if (WARN_ON(worker->current_work) ||
2289 	    WARN_ON(!list_empty(&worker->scheduled)) ||
2290 	    WARN_ON(!(worker->flags & WORKER_IDLE)))
2291 		return;
2292 
2293 	pool->nr_workers--;
2294 	pool->nr_idle--;
2295 
2296 	worker->flags |= WORKER_DIE;
2297 
2298 	list_move(&worker->entry, list);
2299 	list_move(&worker->node, &pool->dying_workers);
2300 }
2301 
2302 /**
2303  * idle_worker_timeout - check if some idle workers can now be deleted.
2304  * @t: The pool's idle_timer that just expired
2305  *
2306  * The timer is armed in worker_enter_idle(). Note that it isn't disarmed in
2307  * worker_leave_idle(), as a worker flicking between idle and active while its
2308  * pool is at the too_many_workers() tipping point would cause too much timer
2309  * housekeeping overhead. Since IDLE_WORKER_TIMEOUT is long enough, we just let
2310  * it expire and re-evaluate things from there.
2311  */
idle_worker_timeout(struct timer_list * t)2312 static void idle_worker_timeout(struct timer_list *t)
2313 {
2314 	struct worker_pool *pool = from_timer(pool, t, idle_timer);
2315 	bool do_cull = false;
2316 
2317 	if (work_pending(&pool->idle_cull_work))
2318 		return;
2319 
2320 	raw_spin_lock_irq(&pool->lock);
2321 
2322 	if (too_many_workers(pool)) {
2323 		struct worker *worker;
2324 		unsigned long expires;
2325 
2326 		/* idle_list is kept in LIFO order, check the last one */
2327 		worker = list_entry(pool->idle_list.prev, struct worker, entry);
2328 		expires = worker->last_active + IDLE_WORKER_TIMEOUT;
2329 		do_cull = !time_before(jiffies, expires);
2330 
2331 		if (!do_cull)
2332 			mod_timer(&pool->idle_timer, expires);
2333 	}
2334 	raw_spin_unlock_irq(&pool->lock);
2335 
2336 	if (do_cull)
2337 		queue_work(system_unbound_wq, &pool->idle_cull_work);
2338 }
2339 
2340 /**
2341  * idle_cull_fn - cull workers that have been idle for too long.
2342  * @work: the pool's work for handling these idle workers
2343  *
2344  * This goes through a pool's idle workers and gets rid of those that have been
2345  * idle for at least IDLE_WORKER_TIMEOUT seconds.
2346  *
2347  * We don't want to disturb isolated CPUs because of a pcpu kworker being
2348  * culled, so this also resets worker affinity. This requires a sleepable
2349  * context, hence the split between timer callback and work item.
2350  */
idle_cull_fn(struct work_struct * work)2351 static void idle_cull_fn(struct work_struct *work)
2352 {
2353 	struct worker_pool *pool = container_of(work, struct worker_pool, idle_cull_work);
2354 	LIST_HEAD(cull_list);
2355 
2356 	/*
2357 	 * Grabbing wq_pool_attach_mutex here ensures an already-running worker
2358 	 * cannot proceed beyong worker_detach_from_pool() in its self-destruct
2359 	 * path. This is required as a previously-preempted worker could run after
2360 	 * set_worker_dying() has happened but before wake_dying_workers() did.
2361 	 */
2362 	mutex_lock(&wq_pool_attach_mutex);
2363 	raw_spin_lock_irq(&pool->lock);
2364 
2365 	while (too_many_workers(pool)) {
2366 		struct worker *worker;
2367 		unsigned long expires;
2368 
2369 		worker = list_entry(pool->idle_list.prev, struct worker, entry);
2370 		expires = worker->last_active + IDLE_WORKER_TIMEOUT;
2371 
2372 		if (time_before(jiffies, expires)) {
2373 			mod_timer(&pool->idle_timer, expires);
2374 			break;
2375 		}
2376 
2377 		set_worker_dying(worker, &cull_list);
2378 	}
2379 
2380 	raw_spin_unlock_irq(&pool->lock);
2381 	wake_dying_workers(&cull_list);
2382 	mutex_unlock(&wq_pool_attach_mutex);
2383 }
2384 
send_mayday(struct work_struct * work)2385 static void send_mayday(struct work_struct *work)
2386 {
2387 	struct pool_workqueue *pwq = get_work_pwq(work);
2388 	struct workqueue_struct *wq = pwq->wq;
2389 
2390 	lockdep_assert_held(&wq_mayday_lock);
2391 
2392 	if (!wq->rescuer)
2393 		return;
2394 
2395 	/* mayday mayday mayday */
2396 	if (list_empty(&pwq->mayday_node)) {
2397 		/*
2398 		 * If @pwq is for an unbound wq, its base ref may be put at
2399 		 * any time due to an attribute change.  Pin @pwq until the
2400 		 * rescuer is done with it.
2401 		 */
2402 		get_pwq(pwq);
2403 		list_add_tail(&pwq->mayday_node, &wq->maydays);
2404 		wake_up_process(wq->rescuer->task);
2405 		pwq->stats[PWQ_STAT_MAYDAY]++;
2406 	}
2407 }
2408 
pool_mayday_timeout(struct timer_list * t)2409 static void pool_mayday_timeout(struct timer_list *t)
2410 {
2411 	struct worker_pool *pool = from_timer(pool, t, mayday_timer);
2412 	struct work_struct *work;
2413 
2414 	raw_spin_lock_irq(&pool->lock);
2415 	raw_spin_lock(&wq_mayday_lock);		/* for wq->maydays */
2416 
2417 	if (need_to_create_worker(pool)) {
2418 		/*
2419 		 * We've been trying to create a new worker but
2420 		 * haven't been successful.  We might be hitting an
2421 		 * allocation deadlock.  Send distress signals to
2422 		 * rescuers.
2423 		 */
2424 		list_for_each_entry(work, &pool->worklist, entry)
2425 			send_mayday(work);
2426 	}
2427 
2428 	raw_spin_unlock(&wq_mayday_lock);
2429 	raw_spin_unlock_irq(&pool->lock);
2430 
2431 	mod_timer(&pool->mayday_timer, jiffies + MAYDAY_INTERVAL);
2432 }
2433 
2434 /**
2435  * maybe_create_worker - create a new worker if necessary
2436  * @pool: pool to create a new worker for
2437  *
2438  * Create a new worker for @pool if necessary.  @pool is guaranteed to
2439  * have at least one idle worker on return from this function.  If
2440  * creating a new worker takes longer than MAYDAY_INTERVAL, mayday is
2441  * sent to all rescuers with works scheduled on @pool to resolve
2442  * possible allocation deadlock.
2443  *
2444  * On return, need_to_create_worker() is guaranteed to be %false and
2445  * may_start_working() %true.
2446  *
2447  * LOCKING:
2448  * raw_spin_lock_irq(pool->lock) which may be released and regrabbed
2449  * multiple times.  Does GFP_KERNEL allocations.  Called only from
2450  * manager.
2451  */
maybe_create_worker(struct worker_pool * pool)2452 static void maybe_create_worker(struct worker_pool *pool)
2453 __releases(&pool->lock)
2454 __acquires(&pool->lock)
2455 {
2456 restart:
2457 	raw_spin_unlock_irq(&pool->lock);
2458 
2459 	/* if we don't make progress in MAYDAY_INITIAL_TIMEOUT, call for help */
2460 	mod_timer(&pool->mayday_timer, jiffies + MAYDAY_INITIAL_TIMEOUT);
2461 
2462 	while (true) {
2463 		if (create_worker(pool) || !need_to_create_worker(pool))
2464 			break;
2465 
2466 		schedule_timeout_interruptible(CREATE_COOLDOWN);
2467 
2468 		if (!need_to_create_worker(pool))
2469 			break;
2470 	}
2471 
2472 	del_timer_sync(&pool->mayday_timer);
2473 	raw_spin_lock_irq(&pool->lock);
2474 	/*
2475 	 * This is necessary even after a new worker was just successfully
2476 	 * created as @pool->lock was dropped and the new worker might have
2477 	 * already become busy.
2478 	 */
2479 	if (need_to_create_worker(pool))
2480 		goto restart;
2481 }
2482 
2483 /**
2484  * manage_workers - manage worker pool
2485  * @worker: self
2486  *
2487  * Assume the manager role and manage the worker pool @worker belongs
2488  * to.  At any given time, there can be only zero or one manager per
2489  * pool.  The exclusion is handled automatically by this function.
2490  *
2491  * The caller can safely start processing works on false return.  On
2492  * true return, it's guaranteed that need_to_create_worker() is false
2493  * and may_start_working() is true.
2494  *
2495  * CONTEXT:
2496  * raw_spin_lock_irq(pool->lock) which may be released and regrabbed
2497  * multiple times.  Does GFP_KERNEL allocations.
2498  *
2499  * Return:
2500  * %false if the pool doesn't need management and the caller can safely
2501  * start processing works, %true if management function was performed and
2502  * the conditions that the caller verified before calling the function may
2503  * no longer be true.
2504  */
manage_workers(struct worker * worker)2505 static bool manage_workers(struct worker *worker)
2506 {
2507 	struct worker_pool *pool = worker->pool;
2508 
2509 	if (pool->flags & POOL_MANAGER_ACTIVE)
2510 		return false;
2511 
2512 	pool->flags |= POOL_MANAGER_ACTIVE;
2513 	pool->manager = worker;
2514 
2515 	maybe_create_worker(pool);
2516 
2517 	pool->manager = NULL;
2518 	pool->flags &= ~POOL_MANAGER_ACTIVE;
2519 	rcuwait_wake_up(&manager_wait);
2520 	return true;
2521 }
2522 
2523 /**
2524  * process_one_work - process single work
2525  * @worker: self
2526  * @work: work to process
2527  *
2528  * Process @work.  This function contains all the logics necessary to
2529  * process a single work including synchronization against and
2530  * interaction with other workers on the same cpu, queueing and
2531  * flushing.  As long as context requirement is met, any worker can
2532  * call this function to process a work.
2533  *
2534  * CONTEXT:
2535  * raw_spin_lock_irq(pool->lock) which is released and regrabbed.
2536  */
process_one_work(struct worker * worker,struct work_struct * work)2537 static void process_one_work(struct worker *worker, struct work_struct *work)
2538 __releases(&pool->lock)
2539 __acquires(&pool->lock)
2540 {
2541 	struct pool_workqueue *pwq = get_work_pwq(work);
2542 	struct worker_pool *pool = worker->pool;
2543 	unsigned long work_data;
2544 #ifdef CONFIG_LOCKDEP
2545 	/*
2546 	 * It is permissible to free the struct work_struct from
2547 	 * inside the function that is called from it, this we need to
2548 	 * take into account for lockdep too.  To avoid bogus "held
2549 	 * lock freed" warnings as well as problems when looking into
2550 	 * work->lockdep_map, make a copy and use that here.
2551 	 */
2552 	struct lockdep_map lockdep_map;
2553 
2554 	lockdep_copy_map(&lockdep_map, &work->lockdep_map);
2555 #endif
2556 	/* ensure we're on the correct CPU */
2557 	WARN_ON_ONCE(!(pool->flags & POOL_DISASSOCIATED) &&
2558 		     raw_smp_processor_id() != pool->cpu);
2559 
2560 	/* claim and dequeue */
2561 	debug_work_deactivate(work);
2562 	hash_add(pool->busy_hash, &worker->hentry, (unsigned long)work);
2563 	worker->current_work = work;
2564 	worker->current_func = work->func;
2565 	worker->current_pwq = pwq;
2566 	worker->current_at = worker->task->se.sum_exec_runtime;
2567 	work_data = *work_data_bits(work);
2568 	worker->current_color = get_work_color(work_data);
2569 
2570 	/*
2571 	 * Record wq name for cmdline and debug reporting, may get
2572 	 * overridden through set_worker_desc().
2573 	 */
2574 	strscpy(worker->desc, pwq->wq->name, WORKER_DESC_LEN);
2575 
2576 	list_del_init(&work->entry);
2577 
2578 	/*
2579 	 * CPU intensive works don't participate in concurrency management.
2580 	 * They're the scheduler's responsibility.  This takes @worker out
2581 	 * of concurrency management and the next code block will chain
2582 	 * execution of the pending work items.
2583 	 */
2584 	if (unlikely(pwq->wq->flags & WQ_CPU_INTENSIVE))
2585 		worker_set_flags(worker, WORKER_CPU_INTENSIVE);
2586 
2587 	/*
2588 	 * Kick @pool if necessary. It's always noop for per-cpu worker pools
2589 	 * since nr_running would always be >= 1 at this point. This is used to
2590 	 * chain execution of the pending work items for WORKER_NOT_RUNNING
2591 	 * workers such as the UNBOUND and CPU_INTENSIVE ones.
2592 	 */
2593 	kick_pool(pool);
2594 
2595 	/*
2596 	 * Record the last pool and clear PENDING which should be the last
2597 	 * update to @work.  Also, do this inside @pool->lock so that
2598 	 * PENDING and queued state changes happen together while IRQ is
2599 	 * disabled.
2600 	 */
2601 	set_work_pool_and_clear_pending(work, pool->id);
2602 
2603 	pwq->stats[PWQ_STAT_STARTED]++;
2604 	raw_spin_unlock_irq(&pool->lock);
2605 
2606 	lock_map_acquire(&pwq->wq->lockdep_map);
2607 	lock_map_acquire(&lockdep_map);
2608 	/*
2609 	 * Strictly speaking we should mark the invariant state without holding
2610 	 * any locks, that is, before these two lock_map_acquire()'s.
2611 	 *
2612 	 * However, that would result in:
2613 	 *
2614 	 *   A(W1)
2615 	 *   WFC(C)
2616 	 *		A(W1)
2617 	 *		C(C)
2618 	 *
2619 	 * Which would create W1->C->W1 dependencies, even though there is no
2620 	 * actual deadlock possible. There are two solutions, using a
2621 	 * read-recursive acquire on the work(queue) 'locks', but this will then
2622 	 * hit the lockdep limitation on recursive locks, or simply discard
2623 	 * these locks.
2624 	 *
2625 	 * AFAICT there is no possible deadlock scenario between the
2626 	 * flush_work() and complete() primitives (except for single-threaded
2627 	 * workqueues), so hiding them isn't a problem.
2628 	 */
2629 	lockdep_invariant_state(true);
2630 	trace_workqueue_execute_start(work);
2631 	worker->current_func(work);
2632 	/*
2633 	 * While we must be careful to not use "work" after this, the trace
2634 	 * point will only record its address.
2635 	 */
2636 	trace_workqueue_execute_end(work, worker->current_func);
2637 	pwq->stats[PWQ_STAT_COMPLETED]++;
2638 	lock_map_release(&lockdep_map);
2639 	lock_map_release(&pwq->wq->lockdep_map);
2640 
2641 	if (unlikely(in_atomic() || lockdep_depth(current) > 0)) {
2642 		pr_err("BUG: workqueue leaked lock or atomic: %s/0x%08x/%d\n"
2643 		       "     last function: %ps\n",
2644 		       current->comm, preempt_count(), task_pid_nr(current),
2645 		       worker->current_func);
2646 		debug_show_held_locks(current);
2647 		dump_stack();
2648 	}
2649 
2650 	/*
2651 	 * The following prevents a kworker from hogging CPU on !PREEMPTION
2652 	 * kernels, where a requeueing work item waiting for something to
2653 	 * happen could deadlock with stop_machine as such work item could
2654 	 * indefinitely requeue itself while all other CPUs are trapped in
2655 	 * stop_machine. At the same time, report a quiescent RCU state so
2656 	 * the same condition doesn't freeze RCU.
2657 	 */
2658 	cond_resched();
2659 
2660 	raw_spin_lock_irq(&pool->lock);
2661 
2662 	/*
2663 	 * In addition to %WQ_CPU_INTENSIVE, @worker may also have been marked
2664 	 * CPU intensive by wq_worker_tick() if @work hogged CPU longer than
2665 	 * wq_cpu_intensive_thresh_us. Clear it.
2666 	 */
2667 	worker_clr_flags(worker, WORKER_CPU_INTENSIVE);
2668 
2669 	/* tag the worker for identification in schedule() */
2670 	worker->last_func = worker->current_func;
2671 
2672 	/* we're done with it, release */
2673 	hash_del(&worker->hentry);
2674 	worker->current_work = NULL;
2675 	worker->current_func = NULL;
2676 	worker->current_pwq = NULL;
2677 	worker->current_color = INT_MAX;
2678 	pwq_dec_nr_in_flight(pwq, work_data);
2679 }
2680 
2681 /**
2682  * process_scheduled_works - process scheduled works
2683  * @worker: self
2684  *
2685  * Process all scheduled works.  Please note that the scheduled list
2686  * may change while processing a work, so this function repeatedly
2687  * fetches a work from the top and executes it.
2688  *
2689  * CONTEXT:
2690  * raw_spin_lock_irq(pool->lock) which may be released and regrabbed
2691  * multiple times.
2692  */
process_scheduled_works(struct worker * worker)2693 static void process_scheduled_works(struct worker *worker)
2694 {
2695 	struct work_struct *work;
2696 	bool first = true;
2697 
2698 	while ((work = list_first_entry_or_null(&worker->scheduled,
2699 						struct work_struct, entry))) {
2700 		if (first) {
2701 			worker->pool->watchdog_ts = jiffies;
2702 			first = false;
2703 		}
2704 		process_one_work(worker, work);
2705 	}
2706 }
2707 
set_pf_worker(bool val)2708 static void set_pf_worker(bool val)
2709 {
2710 	mutex_lock(&wq_pool_attach_mutex);
2711 	if (val)
2712 		current->flags |= PF_WQ_WORKER;
2713 	else
2714 		current->flags &= ~PF_WQ_WORKER;
2715 	mutex_unlock(&wq_pool_attach_mutex);
2716 }
2717 
2718 /**
2719  * worker_thread - the worker thread function
2720  * @__worker: self
2721  *
2722  * The worker thread function.  All workers belong to a worker_pool -
2723  * either a per-cpu one or dynamic unbound one.  These workers process all
2724  * work items regardless of their specific target workqueue.  The only
2725  * exception is work items which belong to workqueues with a rescuer which
2726  * will be explained in rescuer_thread().
2727  *
2728  * Return: 0
2729  */
worker_thread(void * __worker)2730 static int worker_thread(void *__worker)
2731 {
2732 	struct worker *worker = __worker;
2733 	struct worker_pool *pool = worker->pool;
2734 
2735 	/* tell the scheduler that this is a workqueue worker */
2736 	set_pf_worker(true);
2737 woke_up:
2738 	raw_spin_lock_irq(&pool->lock);
2739 
2740 	/* am I supposed to die? */
2741 	if (unlikely(worker->flags & WORKER_DIE)) {
2742 		raw_spin_unlock_irq(&pool->lock);
2743 		set_pf_worker(false);
2744 
2745 		set_task_comm(worker->task, "kworker/dying");
2746 		ida_free(&pool->worker_ida, worker->id);
2747 		worker_detach_from_pool(worker);
2748 		WARN_ON_ONCE(!list_empty(&worker->entry));
2749 		kfree(worker);
2750 		return 0;
2751 	}
2752 
2753 	worker_leave_idle(worker);
2754 recheck:
2755 	/* no more worker necessary? */
2756 	if (!need_more_worker(pool))
2757 		goto sleep;
2758 
2759 	/* do we need to manage? */
2760 	if (unlikely(!may_start_working(pool)) && manage_workers(worker))
2761 		goto recheck;
2762 
2763 	/*
2764 	 * ->scheduled list can only be filled while a worker is
2765 	 * preparing to process a work or actually processing it.
2766 	 * Make sure nobody diddled with it while I was sleeping.
2767 	 */
2768 	WARN_ON_ONCE(!list_empty(&worker->scheduled));
2769 
2770 	/*
2771 	 * Finish PREP stage.  We're guaranteed to have at least one idle
2772 	 * worker or that someone else has already assumed the manager
2773 	 * role.  This is where @worker starts participating in concurrency
2774 	 * management if applicable and concurrency management is restored
2775 	 * after being rebound.  See rebind_workers() for details.
2776 	 */
2777 	worker_clr_flags(worker, WORKER_PREP | WORKER_REBOUND);
2778 
2779 	do {
2780 		struct work_struct *work =
2781 			list_first_entry(&pool->worklist,
2782 					 struct work_struct, entry);
2783 
2784 		if (assign_work(work, worker, NULL))
2785 			process_scheduled_works(worker);
2786 	} while (keep_working(pool));
2787 
2788 	worker_set_flags(worker, WORKER_PREP);
2789 sleep:
2790 	/*
2791 	 * pool->lock is held and there's no work to process and no need to
2792 	 * manage, sleep.  Workers are woken up only while holding
2793 	 * pool->lock or from local cpu, so setting the current state
2794 	 * before releasing pool->lock is enough to prevent losing any
2795 	 * event.
2796 	 */
2797 	worker_enter_idle(worker);
2798 	__set_current_state(TASK_IDLE);
2799 	raw_spin_unlock_irq(&pool->lock);
2800 	schedule();
2801 	goto woke_up;
2802 }
2803 
2804 /**
2805  * rescuer_thread - the rescuer thread function
2806  * @__rescuer: self
2807  *
2808  * Workqueue rescuer thread function.  There's one rescuer for each
2809  * workqueue which has WQ_MEM_RECLAIM set.
2810  *
2811  * Regular work processing on a pool may block trying to create a new
2812  * worker which uses GFP_KERNEL allocation which has slight chance of
2813  * developing into deadlock if some works currently on the same queue
2814  * need to be processed to satisfy the GFP_KERNEL allocation.  This is
2815  * the problem rescuer solves.
2816  *
2817  * When such condition is possible, the pool summons rescuers of all
2818  * workqueues which have works queued on the pool and let them process
2819  * those works so that forward progress can be guaranteed.
2820  *
2821  * This should happen rarely.
2822  *
2823  * Return: 0
2824  */
rescuer_thread(void * __rescuer)2825 static int rescuer_thread(void *__rescuer)
2826 {
2827 	struct worker *rescuer = __rescuer;
2828 	struct workqueue_struct *wq = rescuer->rescue_wq;
2829 	bool should_stop;
2830 
2831 	set_user_nice(current, RESCUER_NICE_LEVEL);
2832 
2833 	/*
2834 	 * Mark rescuer as worker too.  As WORKER_PREP is never cleared, it
2835 	 * doesn't participate in concurrency management.
2836 	 */
2837 	set_pf_worker(true);
2838 repeat:
2839 	set_current_state(TASK_IDLE);
2840 
2841 	/*
2842 	 * By the time the rescuer is requested to stop, the workqueue
2843 	 * shouldn't have any work pending, but @wq->maydays may still have
2844 	 * pwq(s) queued.  This can happen by non-rescuer workers consuming
2845 	 * all the work items before the rescuer got to them.  Go through
2846 	 * @wq->maydays processing before acting on should_stop so that the
2847 	 * list is always empty on exit.
2848 	 */
2849 	should_stop = kthread_should_stop();
2850 
2851 	/* see whether any pwq is asking for help */
2852 	raw_spin_lock_irq(&wq_mayday_lock);
2853 
2854 	while (!list_empty(&wq->maydays)) {
2855 		struct pool_workqueue *pwq = list_first_entry(&wq->maydays,
2856 					struct pool_workqueue, mayday_node);
2857 		struct worker_pool *pool = pwq->pool;
2858 		struct work_struct *work, *n;
2859 
2860 		__set_current_state(TASK_RUNNING);
2861 		list_del_init(&pwq->mayday_node);
2862 
2863 		raw_spin_unlock_irq(&wq_mayday_lock);
2864 
2865 		worker_attach_to_pool(rescuer, pool);
2866 
2867 		raw_spin_lock_irq(&pool->lock);
2868 
2869 		/*
2870 		 * Slurp in all works issued via this workqueue and
2871 		 * process'em.
2872 		 */
2873 		WARN_ON_ONCE(!list_empty(&rescuer->scheduled));
2874 		list_for_each_entry_safe(work, n, &pool->worklist, entry) {
2875 			if (get_work_pwq(work) == pwq &&
2876 			    assign_work(work, rescuer, &n))
2877 				pwq->stats[PWQ_STAT_RESCUED]++;
2878 		}
2879 
2880 		if (!list_empty(&rescuer->scheduled)) {
2881 			process_scheduled_works(rescuer);
2882 
2883 			/*
2884 			 * The above execution of rescued work items could
2885 			 * have created more to rescue through
2886 			 * pwq_activate_first_inactive() or chained
2887 			 * queueing.  Let's put @pwq back on mayday list so
2888 			 * that such back-to-back work items, which may be
2889 			 * being used to relieve memory pressure, don't
2890 			 * incur MAYDAY_INTERVAL delay inbetween.
2891 			 */
2892 			if (pwq->nr_active && need_to_create_worker(pool)) {
2893 				raw_spin_lock(&wq_mayday_lock);
2894 				/*
2895 				 * Queue iff we aren't racing destruction
2896 				 * and somebody else hasn't queued it already.
2897 				 */
2898 				if (wq->rescuer && list_empty(&pwq->mayday_node)) {
2899 					get_pwq(pwq);
2900 					list_add_tail(&pwq->mayday_node, &wq->maydays);
2901 				}
2902 				raw_spin_unlock(&wq_mayday_lock);
2903 			}
2904 		}
2905 
2906 		/*
2907 		 * Put the reference grabbed by send_mayday().  @pool won't
2908 		 * go away while we're still attached to it.
2909 		 */
2910 		put_pwq(pwq);
2911 
2912 		/*
2913 		 * Leave this pool. Notify regular workers; otherwise, we end up
2914 		 * with 0 concurrency and stalling the execution.
2915 		 */
2916 		kick_pool(pool);
2917 
2918 		raw_spin_unlock_irq(&pool->lock);
2919 
2920 		worker_detach_from_pool(rescuer);
2921 
2922 		raw_spin_lock_irq(&wq_mayday_lock);
2923 	}
2924 
2925 	raw_spin_unlock_irq(&wq_mayday_lock);
2926 
2927 	if (should_stop) {
2928 		__set_current_state(TASK_RUNNING);
2929 		set_pf_worker(false);
2930 		return 0;
2931 	}
2932 
2933 	/* rescuers should never participate in concurrency management */
2934 	WARN_ON_ONCE(!(rescuer->flags & WORKER_NOT_RUNNING));
2935 	schedule();
2936 	goto repeat;
2937 }
2938 
2939 /**
2940  * check_flush_dependency - check for flush dependency sanity
2941  * @target_wq: workqueue being flushed
2942  * @target_work: work item being flushed (NULL for workqueue flushes)
2943  *
2944  * %current is trying to flush the whole @target_wq or @target_work on it.
2945  * If @target_wq doesn't have %WQ_MEM_RECLAIM, verify that %current is not
2946  * reclaiming memory or running on a workqueue which doesn't have
2947  * %WQ_MEM_RECLAIM as that can break forward-progress guarantee leading to
2948  * a deadlock.
2949  */
check_flush_dependency(struct workqueue_struct * target_wq,struct work_struct * target_work)2950 static void check_flush_dependency(struct workqueue_struct *target_wq,
2951 				   struct work_struct *target_work)
2952 {
2953 	work_func_t target_func = target_work ? target_work->func : NULL;
2954 	struct worker *worker;
2955 
2956 	if (target_wq->flags & WQ_MEM_RECLAIM)
2957 		return;
2958 
2959 	worker = current_wq_worker();
2960 
2961 	WARN_ONCE(current->flags & PF_MEMALLOC,
2962 		  "workqueue: PF_MEMALLOC task %d(%s) is flushing !WQ_MEM_RECLAIM %s:%ps",
2963 		  current->pid, current->comm, target_wq->name, target_func);
2964 	WARN_ONCE(worker && ((worker->current_pwq->wq->flags &
2965 			      (WQ_MEM_RECLAIM | __WQ_LEGACY)) == WQ_MEM_RECLAIM),
2966 		  "workqueue: WQ_MEM_RECLAIM %s:%ps is flushing !WQ_MEM_RECLAIM %s:%ps",
2967 		  worker->current_pwq->wq->name, worker->current_func,
2968 		  target_wq->name, target_func);
2969 }
2970 
2971 struct wq_barrier {
2972 	struct work_struct	work;
2973 	struct completion	done;
2974 	struct task_struct	*task;	/* purely informational */
2975 };
2976 
wq_barrier_func(struct work_struct * work)2977 static void wq_barrier_func(struct work_struct *work)
2978 {
2979 	struct wq_barrier *barr = container_of(work, struct wq_barrier, work);
2980 	complete(&barr->done);
2981 }
2982 
2983 /**
2984  * insert_wq_barrier - insert a barrier work
2985  * @pwq: pwq to insert barrier into
2986  * @barr: wq_barrier to insert
2987  * @target: target work to attach @barr to
2988  * @worker: worker currently executing @target, NULL if @target is not executing
2989  *
2990  * @barr is linked to @target such that @barr is completed only after
2991  * @target finishes execution.  Please note that the ordering
2992  * guarantee is observed only with respect to @target and on the local
2993  * cpu.
2994  *
2995  * Currently, a queued barrier can't be canceled.  This is because
2996  * try_to_grab_pending() can't determine whether the work to be
2997  * grabbed is at the head of the queue and thus can't clear LINKED
2998  * flag of the previous work while there must be a valid next work
2999  * after a work with LINKED flag set.
3000  *
3001  * Note that when @worker is non-NULL, @target may be modified
3002  * underneath us, so we can't reliably determine pwq from @target.
3003  *
3004  * CONTEXT:
3005  * raw_spin_lock_irq(pool->lock).
3006  */
insert_wq_barrier(struct pool_workqueue * pwq,struct wq_barrier * barr,struct work_struct * target,struct worker * worker)3007 static void insert_wq_barrier(struct pool_workqueue *pwq,
3008 			      struct wq_barrier *barr,
3009 			      struct work_struct *target, struct worker *worker)
3010 {
3011 	unsigned int work_flags = 0;
3012 	unsigned int work_color;
3013 	struct list_head *head;
3014 
3015 	/*
3016 	 * debugobject calls are safe here even with pool->lock locked
3017 	 * as we know for sure that this will not trigger any of the
3018 	 * checks and call back into the fixup functions where we
3019 	 * might deadlock.
3020 	 */
3021 	INIT_WORK_ONSTACK(&barr->work, wq_barrier_func);
3022 	__set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(&barr->work));
3023 
3024 	init_completion_map(&barr->done, &target->lockdep_map);
3025 
3026 	barr->task = current;
3027 
3028 	/* The barrier work item does not participate in pwq->nr_active. */
3029 	work_flags |= WORK_STRUCT_INACTIVE;
3030 
3031 	/*
3032 	 * If @target is currently being executed, schedule the
3033 	 * barrier to the worker; otherwise, put it after @target.
3034 	 */
3035 	if (worker) {
3036 		head = worker->scheduled.next;
3037 		work_color = worker->current_color;
3038 	} else {
3039 		unsigned long *bits = work_data_bits(target);
3040 
3041 		head = target->entry.next;
3042 		/* there can already be other linked works, inherit and set */
3043 		work_flags |= *bits & WORK_STRUCT_LINKED;
3044 		work_color = get_work_color(*bits);
3045 		__set_bit(WORK_STRUCT_LINKED_BIT, bits);
3046 	}
3047 
3048 	pwq->nr_in_flight[work_color]++;
3049 	work_flags |= work_color_to_flags(work_color);
3050 
3051 	insert_work(pwq, &barr->work, head, work_flags);
3052 }
3053 
3054 /**
3055  * flush_workqueue_prep_pwqs - prepare pwqs for workqueue flushing
3056  * @wq: workqueue being flushed
3057  * @flush_color: new flush color, < 0 for no-op
3058  * @work_color: new work color, < 0 for no-op
3059  *
3060  * Prepare pwqs for workqueue flushing.
3061  *
3062  * If @flush_color is non-negative, flush_color on all pwqs should be
3063  * -1.  If no pwq has in-flight commands at the specified color, all
3064  * pwq->flush_color's stay at -1 and %false is returned.  If any pwq
3065  * has in flight commands, its pwq->flush_color is set to
3066  * @flush_color, @wq->nr_pwqs_to_flush is updated accordingly, pwq
3067  * wakeup logic is armed and %true is returned.
3068  *
3069  * The caller should have initialized @wq->first_flusher prior to
3070  * calling this function with non-negative @flush_color.  If
3071  * @flush_color is negative, no flush color update is done and %false
3072  * is returned.
3073  *
3074  * If @work_color is non-negative, all pwqs should have the same
3075  * work_color which is previous to @work_color and all will be
3076  * advanced to @work_color.
3077  *
3078  * CONTEXT:
3079  * mutex_lock(wq->mutex).
3080  *
3081  * Return:
3082  * %true if @flush_color >= 0 and there's something to flush.  %false
3083  * otherwise.
3084  */
flush_workqueue_prep_pwqs(struct workqueue_struct * wq,int flush_color,int work_color)3085 static bool flush_workqueue_prep_pwqs(struct workqueue_struct *wq,
3086 				      int flush_color, int work_color)
3087 {
3088 	bool wait = false;
3089 	struct pool_workqueue *pwq;
3090 
3091 	if (flush_color >= 0) {
3092 		WARN_ON_ONCE(atomic_read(&wq->nr_pwqs_to_flush));
3093 		atomic_set(&wq->nr_pwqs_to_flush, 1);
3094 	}
3095 
3096 	for_each_pwq(pwq, wq) {
3097 		struct worker_pool *pool = pwq->pool;
3098 
3099 		raw_spin_lock_irq(&pool->lock);
3100 
3101 		if (flush_color >= 0) {
3102 			WARN_ON_ONCE(pwq->flush_color != -1);
3103 
3104 			if (pwq->nr_in_flight[flush_color]) {
3105 				pwq->flush_color = flush_color;
3106 				atomic_inc(&wq->nr_pwqs_to_flush);
3107 				wait = true;
3108 			}
3109 		}
3110 
3111 		if (work_color >= 0) {
3112 			WARN_ON_ONCE(work_color != work_next_color(pwq->work_color));
3113 			pwq->work_color = work_color;
3114 		}
3115 
3116 		raw_spin_unlock_irq(&pool->lock);
3117 	}
3118 
3119 	if (flush_color >= 0 && atomic_dec_and_test(&wq->nr_pwqs_to_flush))
3120 		complete(&wq->first_flusher->done);
3121 
3122 	return wait;
3123 }
3124 
3125 /**
3126  * __flush_workqueue - ensure that any scheduled work has run to completion.
3127  * @wq: workqueue to flush
3128  *
3129  * This function sleeps until all work items which were queued on entry
3130  * have finished execution, but it is not livelocked by new incoming ones.
3131  */
__flush_workqueue(struct workqueue_struct * wq)3132 void __flush_workqueue(struct workqueue_struct *wq)
3133 {
3134 	struct wq_flusher this_flusher = {
3135 		.list = LIST_HEAD_INIT(this_flusher.list),
3136 		.flush_color = -1,
3137 		.done = COMPLETION_INITIALIZER_ONSTACK_MAP(this_flusher.done, wq->lockdep_map),
3138 	};
3139 	int next_color;
3140 
3141 	if (WARN_ON(!wq_online))
3142 		return;
3143 
3144 	lock_map_acquire(&wq->lockdep_map);
3145 	lock_map_release(&wq->lockdep_map);
3146 
3147 	mutex_lock(&wq->mutex);
3148 
3149 	/*
3150 	 * Start-to-wait phase
3151 	 */
3152 	next_color = work_next_color(wq->work_color);
3153 
3154 	if (next_color != wq->flush_color) {
3155 		/*
3156 		 * Color space is not full.  The current work_color
3157 		 * becomes our flush_color and work_color is advanced
3158 		 * by one.
3159 		 */
3160 		WARN_ON_ONCE(!list_empty(&wq->flusher_overflow));
3161 		this_flusher.flush_color = wq->work_color;
3162 		wq->work_color = next_color;
3163 
3164 		if (!wq->first_flusher) {
3165 			/* no flush in progress, become the first flusher */
3166 			WARN_ON_ONCE(wq->flush_color != this_flusher.flush_color);
3167 
3168 			wq->first_flusher = &this_flusher;
3169 
3170 			if (!flush_workqueue_prep_pwqs(wq, wq->flush_color,
3171 						       wq->work_color)) {
3172 				/* nothing to flush, done */
3173 				wq->flush_color = next_color;
3174 				wq->first_flusher = NULL;
3175 				goto out_unlock;
3176 			}
3177 		} else {
3178 			/* wait in queue */
3179 			WARN_ON_ONCE(wq->flush_color == this_flusher.flush_color);
3180 			list_add_tail(&this_flusher.list, &wq->flusher_queue);
3181 			flush_workqueue_prep_pwqs(wq, -1, wq->work_color);
3182 		}
3183 	} else {
3184 		/*
3185 		 * Oops, color space is full, wait on overflow queue.
3186 		 * The next flush completion will assign us
3187 		 * flush_color and transfer to flusher_queue.
3188 		 */
3189 		list_add_tail(&this_flusher.list, &wq->flusher_overflow);
3190 	}
3191 
3192 	check_flush_dependency(wq, NULL);
3193 
3194 	mutex_unlock(&wq->mutex);
3195 
3196 	wait_for_completion(&this_flusher.done);
3197 
3198 	/*
3199 	 * Wake-up-and-cascade phase
3200 	 *
3201 	 * First flushers are responsible for cascading flushes and
3202 	 * handling overflow.  Non-first flushers can simply return.
3203 	 */
3204 	if (READ_ONCE(wq->first_flusher) != &this_flusher)
3205 		return;
3206 
3207 	mutex_lock(&wq->mutex);
3208 
3209 	/* we might have raced, check again with mutex held */
3210 	if (wq->first_flusher != &this_flusher)
3211 		goto out_unlock;
3212 
3213 	WRITE_ONCE(wq->first_flusher, NULL);
3214 
3215 	WARN_ON_ONCE(!list_empty(&this_flusher.list));
3216 	WARN_ON_ONCE(wq->flush_color != this_flusher.flush_color);
3217 
3218 	while (true) {
3219 		struct wq_flusher *next, *tmp;
3220 
3221 		/* complete all the flushers sharing the current flush color */
3222 		list_for_each_entry_safe(next, tmp, &wq->flusher_queue, list) {
3223 			if (next->flush_color != wq->flush_color)
3224 				break;
3225 			list_del_init(&next->list);
3226 			complete(&next->done);
3227 		}
3228 
3229 		WARN_ON_ONCE(!list_empty(&wq->flusher_overflow) &&
3230 			     wq->flush_color != work_next_color(wq->work_color));
3231 
3232 		/* this flush_color is finished, advance by one */
3233 		wq->flush_color = work_next_color(wq->flush_color);
3234 
3235 		/* one color has been freed, handle overflow queue */
3236 		if (!list_empty(&wq->flusher_overflow)) {
3237 			/*
3238 			 * Assign the same color to all overflowed
3239 			 * flushers, advance work_color and append to
3240 			 * flusher_queue.  This is the start-to-wait
3241 			 * phase for these overflowed flushers.
3242 			 */
3243 			list_for_each_entry(tmp, &wq->flusher_overflow, list)
3244 				tmp->flush_color = wq->work_color;
3245 
3246 			wq->work_color = work_next_color(wq->work_color);
3247 
3248 			list_splice_tail_init(&wq->flusher_overflow,
3249 					      &wq->flusher_queue);
3250 			flush_workqueue_prep_pwqs(wq, -1, wq->work_color);
3251 		}
3252 
3253 		if (list_empty(&wq->flusher_queue)) {
3254 			WARN_ON_ONCE(wq->flush_color != wq->work_color);
3255 			break;
3256 		}
3257 
3258 		/*
3259 		 * Need to flush more colors.  Make the next flusher
3260 		 * the new first flusher and arm pwqs.
3261 		 */
3262 		WARN_ON_ONCE(wq->flush_color == wq->work_color);
3263 		WARN_ON_ONCE(wq->flush_color != next->flush_color);
3264 
3265 		list_del_init(&next->list);
3266 		wq->first_flusher = next;
3267 
3268 		if (flush_workqueue_prep_pwqs(wq, wq->flush_color, -1))
3269 			break;
3270 
3271 		/*
3272 		 * Meh... this color is already done, clear first
3273 		 * flusher and repeat cascading.
3274 		 */
3275 		wq->first_flusher = NULL;
3276 	}
3277 
3278 out_unlock:
3279 	mutex_unlock(&wq->mutex);
3280 }
3281 EXPORT_SYMBOL(__flush_workqueue);
3282 
3283 /**
3284  * drain_workqueue - drain a workqueue
3285  * @wq: workqueue to drain
3286  *
3287  * Wait until the workqueue becomes empty.  While draining is in progress,
3288  * only chain queueing is allowed.  IOW, only currently pending or running
3289  * work items on @wq can queue further work items on it.  @wq is flushed
3290  * repeatedly until it becomes empty.  The number of flushing is determined
3291  * by the depth of chaining and should be relatively short.  Whine if it
3292  * takes too long.
3293  */
drain_workqueue(struct workqueue_struct * wq)3294 void drain_workqueue(struct workqueue_struct *wq)
3295 {
3296 	unsigned int flush_cnt = 0;
3297 	struct pool_workqueue *pwq;
3298 
3299 	/*
3300 	 * __queue_work() needs to test whether there are drainers, is much
3301 	 * hotter than drain_workqueue() and already looks at @wq->flags.
3302 	 * Use __WQ_DRAINING so that queue doesn't have to check nr_drainers.
3303 	 */
3304 	mutex_lock(&wq->mutex);
3305 	if (!wq->nr_drainers++)
3306 		wq->flags |= __WQ_DRAINING;
3307 	mutex_unlock(&wq->mutex);
3308 reflush:
3309 	__flush_workqueue(wq);
3310 
3311 	mutex_lock(&wq->mutex);
3312 
3313 	for_each_pwq(pwq, wq) {
3314 		bool drained;
3315 
3316 		raw_spin_lock_irq(&pwq->pool->lock);
3317 		drained = !pwq->nr_active && list_empty(&pwq->inactive_works);
3318 		raw_spin_unlock_irq(&pwq->pool->lock);
3319 
3320 		if (drained)
3321 			continue;
3322 
3323 		if (++flush_cnt == 10 ||
3324 		    (flush_cnt % 100 == 0 && flush_cnt <= 1000))
3325 			pr_warn("workqueue %s: %s() isn't complete after %u tries\n",
3326 				wq->name, __func__, flush_cnt);
3327 
3328 		mutex_unlock(&wq->mutex);
3329 		goto reflush;
3330 	}
3331 
3332 	if (!--wq->nr_drainers)
3333 		wq->flags &= ~__WQ_DRAINING;
3334 	mutex_unlock(&wq->mutex);
3335 }
3336 EXPORT_SYMBOL_GPL(drain_workqueue);
3337 
start_flush_work(struct work_struct * work,struct wq_barrier * barr,bool from_cancel)3338 static bool start_flush_work(struct work_struct *work, struct wq_barrier *barr,
3339 			     bool from_cancel)
3340 {
3341 	struct worker *worker = NULL;
3342 	struct worker_pool *pool;
3343 	struct pool_workqueue *pwq;
3344 
3345 	might_sleep();
3346 
3347 	rcu_read_lock();
3348 	pool = get_work_pool(work);
3349 	if (!pool) {
3350 		rcu_read_unlock();
3351 		return false;
3352 	}
3353 
3354 	raw_spin_lock_irq(&pool->lock);
3355 	/* see the comment in try_to_grab_pending() with the same code */
3356 	pwq = get_work_pwq(work);
3357 	if (pwq) {
3358 		if (unlikely(pwq->pool != pool))
3359 			goto already_gone;
3360 	} else {
3361 		worker = find_worker_executing_work(pool, work);
3362 		if (!worker)
3363 			goto already_gone;
3364 		pwq = worker->current_pwq;
3365 	}
3366 
3367 	check_flush_dependency(pwq->wq, work);
3368 
3369 	insert_wq_barrier(pwq, barr, work, worker);
3370 	raw_spin_unlock_irq(&pool->lock);
3371 
3372 	/*
3373 	 * Force a lock recursion deadlock when using flush_work() inside a
3374 	 * single-threaded or rescuer equipped workqueue.
3375 	 *
3376 	 * For single threaded workqueues the deadlock happens when the work
3377 	 * is after the work issuing the flush_work(). For rescuer equipped
3378 	 * workqueues the deadlock happens when the rescuer stalls, blocking
3379 	 * forward progress.
3380 	 */
3381 	if (!from_cancel &&
3382 	    (pwq->wq->saved_max_active == 1 || pwq->wq->rescuer)) {
3383 		lock_map_acquire(&pwq->wq->lockdep_map);
3384 		lock_map_release(&pwq->wq->lockdep_map);
3385 	}
3386 	rcu_read_unlock();
3387 	return true;
3388 already_gone:
3389 	raw_spin_unlock_irq(&pool->lock);
3390 	rcu_read_unlock();
3391 	return false;
3392 }
3393 
__flush_work(struct work_struct * work,bool from_cancel)3394 static bool __flush_work(struct work_struct *work, bool from_cancel)
3395 {
3396 	struct wq_barrier barr;
3397 
3398 	if (WARN_ON(!wq_online))
3399 		return false;
3400 
3401 	if (WARN_ON(!work->func))
3402 		return false;
3403 
3404 	lock_map_acquire(&work->lockdep_map);
3405 	lock_map_release(&work->lockdep_map);
3406 
3407 	if (start_flush_work(work, &barr, from_cancel)) {
3408 		wait_for_completion(&barr.done);
3409 		destroy_work_on_stack(&barr.work);
3410 		return true;
3411 	} else {
3412 		return false;
3413 	}
3414 }
3415 
3416 /**
3417  * flush_work - wait for a work to finish executing the last queueing instance
3418  * @work: the work to flush
3419  *
3420  * Wait until @work has finished execution.  @work is guaranteed to be idle
3421  * on return if it hasn't been requeued since flush started.
3422  *
3423  * Return:
3424  * %true if flush_work() waited for the work to finish execution,
3425  * %false if it was already idle.
3426  */
flush_work(struct work_struct * work)3427 bool flush_work(struct work_struct *work)
3428 {
3429 	return __flush_work(work, false);
3430 }
3431 EXPORT_SYMBOL_GPL(flush_work);
3432 
3433 struct cwt_wait {
3434 	wait_queue_entry_t		wait;
3435 	struct work_struct	*work;
3436 };
3437 
cwt_wakefn(wait_queue_entry_t * wait,unsigned mode,int sync,void * key)3438 static int cwt_wakefn(wait_queue_entry_t *wait, unsigned mode, int sync, void *key)
3439 {
3440 	struct cwt_wait *cwait = container_of(wait, struct cwt_wait, wait);
3441 
3442 	if (cwait->work != key)
3443 		return 0;
3444 	return autoremove_wake_function(wait, mode, sync, key);
3445 }
3446 
__cancel_work_timer(struct work_struct * work,bool is_dwork)3447 static bool __cancel_work_timer(struct work_struct *work, bool is_dwork)
3448 {
3449 	static DECLARE_WAIT_QUEUE_HEAD(cancel_waitq);
3450 	unsigned long flags;
3451 	int ret;
3452 
3453 	do {
3454 		ret = try_to_grab_pending(work, is_dwork, &flags);
3455 		/*
3456 		 * If someone else is already canceling, wait for it to
3457 		 * finish.  flush_work() doesn't work for PREEMPT_NONE
3458 		 * because we may get scheduled between @work's completion
3459 		 * and the other canceling task resuming and clearing
3460 		 * CANCELING - flush_work() will return false immediately
3461 		 * as @work is no longer busy, try_to_grab_pending() will
3462 		 * return -ENOENT as @work is still being canceled and the
3463 		 * other canceling task won't be able to clear CANCELING as
3464 		 * we're hogging the CPU.
3465 		 *
3466 		 * Let's wait for completion using a waitqueue.  As this
3467 		 * may lead to the thundering herd problem, use a custom
3468 		 * wake function which matches @work along with exclusive
3469 		 * wait and wakeup.
3470 		 */
3471 		if (unlikely(ret == -ENOENT)) {
3472 			struct cwt_wait cwait;
3473 
3474 			init_wait(&cwait.wait);
3475 			cwait.wait.func = cwt_wakefn;
3476 			cwait.work = work;
3477 
3478 			prepare_to_wait_exclusive(&cancel_waitq, &cwait.wait,
3479 						  TASK_UNINTERRUPTIBLE);
3480 			if (work_is_canceling(work))
3481 				schedule();
3482 			finish_wait(&cancel_waitq, &cwait.wait);
3483 		}
3484 	} while (unlikely(ret < 0));
3485 
3486 	/* tell other tasks trying to grab @work to back off */
3487 	mark_work_canceling(work);
3488 	local_irq_restore(flags);
3489 
3490 	/*
3491 	 * This allows canceling during early boot.  We know that @work
3492 	 * isn't executing.
3493 	 */
3494 	if (wq_online)
3495 		__flush_work(work, true);
3496 
3497 	clear_work_data(work);
3498 
3499 	/*
3500 	 * Paired with prepare_to_wait() above so that either
3501 	 * waitqueue_active() is visible here or !work_is_canceling() is
3502 	 * visible there.
3503 	 */
3504 	smp_mb();
3505 	if (waitqueue_active(&cancel_waitq))
3506 		__wake_up(&cancel_waitq, TASK_NORMAL, 1, work);
3507 
3508 	return ret;
3509 }
3510 
3511 /**
3512  * cancel_work_sync - cancel a work and wait for it to finish
3513  * @work: the work to cancel
3514  *
3515  * Cancel @work and wait for its execution to finish.  This function
3516  * can be used even if the work re-queues itself or migrates to
3517  * another workqueue.  On return from this function, @work is
3518  * guaranteed to be not pending or executing on any CPU.
3519  *
3520  * cancel_work_sync(&delayed_work->work) must not be used for
3521  * delayed_work's.  Use cancel_delayed_work_sync() instead.
3522  *
3523  * The caller must ensure that the workqueue on which @work was last
3524  * queued can't be destroyed before this function returns.
3525  *
3526  * Return:
3527  * %true if @work was pending, %false otherwise.
3528  */
cancel_work_sync(struct work_struct * work)3529 bool cancel_work_sync(struct work_struct *work)
3530 {
3531 	return __cancel_work_timer(work, false);
3532 }
3533 EXPORT_SYMBOL_GPL(cancel_work_sync);
3534 
3535 /**
3536  * flush_delayed_work - wait for a dwork to finish executing the last queueing
3537  * @dwork: the delayed work to flush
3538  *
3539  * Delayed timer is cancelled and the pending work is queued for
3540  * immediate execution.  Like flush_work(), this function only
3541  * considers the last queueing instance of @dwork.
3542  *
3543  * Return:
3544  * %true if flush_work() waited for the work to finish execution,
3545  * %false if it was already idle.
3546  */
flush_delayed_work(struct delayed_work * dwork)3547 bool flush_delayed_work(struct delayed_work *dwork)
3548 {
3549 	local_irq_disable();
3550 	if (del_timer_sync(&dwork->timer))
3551 		__queue_work(dwork->cpu, dwork->wq, &dwork->work);
3552 	local_irq_enable();
3553 	return flush_work(&dwork->work);
3554 }
3555 EXPORT_SYMBOL(flush_delayed_work);
3556 
3557 /**
3558  * flush_rcu_work - wait for a rwork to finish executing the last queueing
3559  * @rwork: the rcu work to flush
3560  *
3561  * Return:
3562  * %true if flush_rcu_work() waited for the work to finish execution,
3563  * %false if it was already idle.
3564  */
flush_rcu_work(struct rcu_work * rwork)3565 bool flush_rcu_work(struct rcu_work *rwork)
3566 {
3567 	if (test_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(&rwork->work))) {
3568 		rcu_barrier();
3569 		flush_work(&rwork->work);
3570 		return true;
3571 	} else {
3572 		return flush_work(&rwork->work);
3573 	}
3574 }
3575 EXPORT_SYMBOL(flush_rcu_work);
3576 
__cancel_work(struct work_struct * work,bool is_dwork)3577 static bool __cancel_work(struct work_struct *work, bool is_dwork)
3578 {
3579 	unsigned long flags;
3580 	int ret;
3581 
3582 	do {
3583 		ret = try_to_grab_pending(work, is_dwork, &flags);
3584 	} while (unlikely(ret == -EAGAIN));
3585 
3586 	if (unlikely(ret < 0))
3587 		return false;
3588 
3589 	set_work_pool_and_clear_pending(work, get_work_pool_id(work));
3590 	local_irq_restore(flags);
3591 	return ret;
3592 }
3593 
3594 /*
3595  * See cancel_delayed_work()
3596  */
cancel_work(struct work_struct * work)3597 bool cancel_work(struct work_struct *work)
3598 {
3599 	return __cancel_work(work, false);
3600 }
3601 EXPORT_SYMBOL(cancel_work);
3602 
3603 /**
3604  * cancel_delayed_work - cancel a delayed work
3605  * @dwork: delayed_work to cancel
3606  *
3607  * Kill off a pending delayed_work.
3608  *
3609  * Return: %true if @dwork was pending and canceled; %false if it wasn't
3610  * pending.
3611  *
3612  * Note:
3613  * The work callback function may still be running on return, unless
3614  * it returns %true and the work doesn't re-arm itself.  Explicitly flush or
3615  * use cancel_delayed_work_sync() to wait on it.
3616  *
3617  * This function is safe to call from any context including IRQ handler.
3618  */
cancel_delayed_work(struct delayed_work * dwork)3619 bool cancel_delayed_work(struct delayed_work *dwork)
3620 {
3621 	return __cancel_work(&dwork->work, true);
3622 }
3623 EXPORT_SYMBOL(cancel_delayed_work);
3624 
3625 /**
3626  * cancel_delayed_work_sync - cancel a delayed work and wait for it to finish
3627  * @dwork: the delayed work cancel
3628  *
3629  * This is cancel_work_sync() for delayed works.
3630  *
3631  * Return:
3632  * %true if @dwork was pending, %false otherwise.
3633  */
cancel_delayed_work_sync(struct delayed_work * dwork)3634 bool cancel_delayed_work_sync(struct delayed_work *dwork)
3635 {
3636 	return __cancel_work_timer(&dwork->work, true);
3637 }
3638 EXPORT_SYMBOL(cancel_delayed_work_sync);
3639 
3640 /**
3641  * schedule_on_each_cpu - execute a function synchronously on each online CPU
3642  * @func: the function to call
3643  *
3644  * schedule_on_each_cpu() executes @func on each online CPU using the
3645  * system workqueue and blocks until all CPUs have completed.
3646  * schedule_on_each_cpu() is very slow.
3647  *
3648  * Return:
3649  * 0 on success, -errno on failure.
3650  */
schedule_on_each_cpu(work_func_t func)3651 int schedule_on_each_cpu(work_func_t func)
3652 {
3653 	int cpu;
3654 	struct work_struct __percpu *works;
3655 
3656 	works = alloc_percpu(struct work_struct);
3657 	if (!works)
3658 		return -ENOMEM;
3659 
3660 	cpus_read_lock();
3661 
3662 	for_each_online_cpu(cpu) {
3663 		struct work_struct *work = per_cpu_ptr(works, cpu);
3664 
3665 		INIT_WORK(work, func);
3666 		schedule_work_on(cpu, work);
3667 	}
3668 
3669 	for_each_online_cpu(cpu)
3670 		flush_work(per_cpu_ptr(works, cpu));
3671 
3672 	cpus_read_unlock();
3673 	free_percpu(works);
3674 	return 0;
3675 }
3676 
3677 /**
3678  * execute_in_process_context - reliably execute the routine with user context
3679  * @fn:		the function to execute
3680  * @ew:		guaranteed storage for the execute work structure (must
3681  *		be available when the work executes)
3682  *
3683  * Executes the function immediately if process context is available,
3684  * otherwise schedules the function for delayed execution.
3685  *
3686  * Return:	0 - function was executed
3687  *		1 - function was scheduled for execution
3688  */
execute_in_process_context(work_func_t fn,struct execute_work * ew)3689 int execute_in_process_context(work_func_t fn, struct execute_work *ew)
3690 {
3691 	if (!in_interrupt()) {
3692 		fn(&ew->work);
3693 		return 0;
3694 	}
3695 
3696 	INIT_WORK(&ew->work, fn);
3697 	schedule_work(&ew->work);
3698 
3699 	return 1;
3700 }
3701 EXPORT_SYMBOL_GPL(execute_in_process_context);
3702 
3703 /**
3704  * free_workqueue_attrs - free a workqueue_attrs
3705  * @attrs: workqueue_attrs to free
3706  *
3707  * Undo alloc_workqueue_attrs().
3708  */
free_workqueue_attrs(struct workqueue_attrs * attrs)3709 void free_workqueue_attrs(struct workqueue_attrs *attrs)
3710 {
3711 	if (attrs) {
3712 		free_cpumask_var(attrs->cpumask);
3713 		free_cpumask_var(attrs->__pod_cpumask);
3714 		kfree(attrs);
3715 	}
3716 }
3717 
3718 /**
3719  * alloc_workqueue_attrs - allocate a workqueue_attrs
3720  *
3721  * Allocate a new workqueue_attrs, initialize with default settings and
3722  * return it.
3723  *
3724  * Return: The allocated new workqueue_attr on success. %NULL on failure.
3725  */
alloc_workqueue_attrs(void)3726 struct workqueue_attrs *alloc_workqueue_attrs(void)
3727 {
3728 	struct workqueue_attrs *attrs;
3729 
3730 	attrs = kzalloc(sizeof(*attrs), GFP_KERNEL);
3731 	if (!attrs)
3732 		goto fail;
3733 	if (!alloc_cpumask_var(&attrs->cpumask, GFP_KERNEL))
3734 		goto fail;
3735 	if (!alloc_cpumask_var(&attrs->__pod_cpumask, GFP_KERNEL))
3736 		goto fail;
3737 
3738 	cpumask_copy(attrs->cpumask, cpu_possible_mask);
3739 	attrs->affn_scope = WQ_AFFN_DFL;
3740 	return attrs;
3741 fail:
3742 	free_workqueue_attrs(attrs);
3743 	return NULL;
3744 }
3745 
copy_workqueue_attrs(struct workqueue_attrs * to,const struct workqueue_attrs * from)3746 static void copy_workqueue_attrs(struct workqueue_attrs *to,
3747 				 const struct workqueue_attrs *from)
3748 {
3749 	to->nice = from->nice;
3750 	cpumask_copy(to->cpumask, from->cpumask);
3751 	cpumask_copy(to->__pod_cpumask, from->__pod_cpumask);
3752 	to->affn_strict = from->affn_strict;
3753 
3754 	/*
3755 	 * Unlike hash and equality test, copying shouldn't ignore wq-only
3756 	 * fields as copying is used for both pool and wq attrs. Instead,
3757 	 * get_unbound_pool() explicitly clears the fields.
3758 	 */
3759 	to->affn_scope = from->affn_scope;
3760 	to->ordered = from->ordered;
3761 }
3762 
3763 /*
3764  * Some attrs fields are workqueue-only. Clear them for worker_pool's. See the
3765  * comments in 'struct workqueue_attrs' definition.
3766  */
wqattrs_clear_for_pool(struct workqueue_attrs * attrs)3767 static void wqattrs_clear_for_pool(struct workqueue_attrs *attrs)
3768 {
3769 	attrs->affn_scope = WQ_AFFN_NR_TYPES;
3770 	attrs->ordered = false;
3771 }
3772 
3773 /* hash value of the content of @attr */
wqattrs_hash(const struct workqueue_attrs * attrs)3774 static u32 wqattrs_hash(const struct workqueue_attrs *attrs)
3775 {
3776 	u32 hash = 0;
3777 
3778 	hash = jhash_1word(attrs->nice, hash);
3779 	hash = jhash(cpumask_bits(attrs->cpumask),
3780 		     BITS_TO_LONGS(nr_cpumask_bits) * sizeof(long), hash);
3781 	hash = jhash(cpumask_bits(attrs->__pod_cpumask),
3782 		     BITS_TO_LONGS(nr_cpumask_bits) * sizeof(long), hash);
3783 	hash = jhash_1word(attrs->affn_strict, hash);
3784 	return hash;
3785 }
3786 
3787 /* content equality test */
wqattrs_equal(const struct workqueue_attrs * a,const struct workqueue_attrs * b)3788 static bool wqattrs_equal(const struct workqueue_attrs *a,
3789 			  const struct workqueue_attrs *b)
3790 {
3791 	if (a->nice != b->nice)
3792 		return false;
3793 	if (!cpumask_equal(a->cpumask, b->cpumask))
3794 		return false;
3795 	if (!cpumask_equal(a->__pod_cpumask, b->__pod_cpumask))
3796 		return false;
3797 	if (a->affn_strict != b->affn_strict)
3798 		return false;
3799 	return true;
3800 }
3801 
3802 /* Update @attrs with actually available CPUs */
wqattrs_actualize_cpumask(struct workqueue_attrs * attrs,const cpumask_t * unbound_cpumask)3803 static void wqattrs_actualize_cpumask(struct workqueue_attrs *attrs,
3804 				      const cpumask_t *unbound_cpumask)
3805 {
3806 	/*
3807 	 * Calculate the effective CPU mask of @attrs given @unbound_cpumask. If
3808 	 * @attrs->cpumask doesn't overlap with @unbound_cpumask, we fallback to
3809 	 * @unbound_cpumask.
3810 	 */
3811 	cpumask_and(attrs->cpumask, attrs->cpumask, unbound_cpumask);
3812 	if (unlikely(cpumask_empty(attrs->cpumask)))
3813 		cpumask_copy(attrs->cpumask, unbound_cpumask);
3814 }
3815 
3816 /* find wq_pod_type to use for @attrs */
3817 static const struct wq_pod_type *
wqattrs_pod_type(const struct workqueue_attrs * attrs)3818 wqattrs_pod_type(const struct workqueue_attrs *attrs)
3819 {
3820 	enum wq_affn_scope scope;
3821 	struct wq_pod_type *pt;
3822 
3823 	/* to synchronize access to wq_affn_dfl */
3824 	lockdep_assert_held(&wq_pool_mutex);
3825 
3826 	if (attrs->affn_scope == WQ_AFFN_DFL)
3827 		scope = wq_affn_dfl;
3828 	else
3829 		scope = attrs->affn_scope;
3830 
3831 	pt = &wq_pod_types[scope];
3832 
3833 	if (!WARN_ON_ONCE(attrs->affn_scope == WQ_AFFN_NR_TYPES) &&
3834 	    likely(pt->nr_pods))
3835 		return pt;
3836 
3837 	/*
3838 	 * Before workqueue_init_topology(), only SYSTEM is available which is
3839 	 * initialized in workqueue_init_early().
3840 	 */
3841 	pt = &wq_pod_types[WQ_AFFN_SYSTEM];
3842 	BUG_ON(!pt->nr_pods);
3843 	return pt;
3844 }
3845 
3846 /**
3847  * init_worker_pool - initialize a newly zalloc'd worker_pool
3848  * @pool: worker_pool to initialize
3849  *
3850  * Initialize a newly zalloc'd @pool.  It also allocates @pool->attrs.
3851  *
3852  * Return: 0 on success, -errno on failure.  Even on failure, all fields
3853  * inside @pool proper are initialized and put_unbound_pool() can be called
3854  * on @pool safely to release it.
3855  */
init_worker_pool(struct worker_pool * pool)3856 static int init_worker_pool(struct worker_pool *pool)
3857 {
3858 	raw_spin_lock_init(&pool->lock);
3859 	pool->id = -1;
3860 	pool->cpu = -1;
3861 	pool->node = NUMA_NO_NODE;
3862 	pool->flags |= POOL_DISASSOCIATED;
3863 	pool->watchdog_ts = jiffies;
3864 	INIT_LIST_HEAD(&pool->worklist);
3865 	INIT_LIST_HEAD(&pool->idle_list);
3866 	hash_init(pool->busy_hash);
3867 
3868 	timer_setup(&pool->idle_timer, idle_worker_timeout, TIMER_DEFERRABLE);
3869 	INIT_WORK(&pool->idle_cull_work, idle_cull_fn);
3870 
3871 	timer_setup(&pool->mayday_timer, pool_mayday_timeout, 0);
3872 
3873 	INIT_LIST_HEAD(&pool->workers);
3874 	INIT_LIST_HEAD(&pool->dying_workers);
3875 
3876 	ida_init(&pool->worker_ida);
3877 	INIT_HLIST_NODE(&pool->hash_node);
3878 	pool->refcnt = 1;
3879 
3880 	/* shouldn't fail above this point */
3881 	pool->attrs = alloc_workqueue_attrs();
3882 	if (!pool->attrs)
3883 		return -ENOMEM;
3884 
3885 	wqattrs_clear_for_pool(pool->attrs);
3886 
3887 	return 0;
3888 }
3889 
3890 #ifdef CONFIG_LOCKDEP
wq_init_lockdep(struct workqueue_struct * wq)3891 static void wq_init_lockdep(struct workqueue_struct *wq)
3892 {
3893 	char *lock_name;
3894 
3895 	lockdep_register_key(&wq->key);
3896 	lock_name = kasprintf(GFP_KERNEL, "%s%s", "(wq_completion)", wq->name);
3897 	if (!lock_name)
3898 		lock_name = wq->name;
3899 
3900 	wq->lock_name = lock_name;
3901 	lockdep_init_map(&wq->lockdep_map, lock_name, &wq->key, 0);
3902 }
3903 
wq_unregister_lockdep(struct workqueue_struct * wq)3904 static void wq_unregister_lockdep(struct workqueue_struct *wq)
3905 {
3906 	lockdep_unregister_key(&wq->key);
3907 }
3908 
wq_free_lockdep(struct workqueue_struct * wq)3909 static void wq_free_lockdep(struct workqueue_struct *wq)
3910 {
3911 	if (wq->lock_name != wq->name)
3912 		kfree(wq->lock_name);
3913 }
3914 #else
wq_init_lockdep(struct workqueue_struct * wq)3915 static void wq_init_lockdep(struct workqueue_struct *wq)
3916 {
3917 }
3918 
wq_unregister_lockdep(struct workqueue_struct * wq)3919 static void wq_unregister_lockdep(struct workqueue_struct *wq)
3920 {
3921 }
3922 
wq_free_lockdep(struct workqueue_struct * wq)3923 static void wq_free_lockdep(struct workqueue_struct *wq)
3924 {
3925 }
3926 #endif
3927 
rcu_free_wq(struct rcu_head * rcu)3928 static void rcu_free_wq(struct rcu_head *rcu)
3929 {
3930 	struct workqueue_struct *wq =
3931 		container_of(rcu, struct workqueue_struct, rcu);
3932 
3933 	wq_free_lockdep(wq);
3934 	free_percpu(wq->cpu_pwq);
3935 	free_workqueue_attrs(wq->unbound_attrs);
3936 	kfree(wq);
3937 }
3938 
rcu_free_pool(struct rcu_head * rcu)3939 static void rcu_free_pool(struct rcu_head *rcu)
3940 {
3941 	struct worker_pool *pool = container_of(rcu, struct worker_pool, rcu);
3942 
3943 	ida_destroy(&pool->worker_ida);
3944 	free_workqueue_attrs(pool->attrs);
3945 	kfree(pool);
3946 }
3947 
3948 /**
3949  * put_unbound_pool - put a worker_pool
3950  * @pool: worker_pool to put
3951  *
3952  * Put @pool.  If its refcnt reaches zero, it gets destroyed in RCU
3953  * safe manner.  get_unbound_pool() calls this function on its failure path
3954  * and this function should be able to release pools which went through,
3955  * successfully or not, init_worker_pool().
3956  *
3957  * Should be called with wq_pool_mutex held.
3958  */
put_unbound_pool(struct worker_pool * pool)3959 static void put_unbound_pool(struct worker_pool *pool)
3960 {
3961 	DECLARE_COMPLETION_ONSTACK(detach_completion);
3962 	struct worker *worker;
3963 	LIST_HEAD(cull_list);
3964 
3965 	lockdep_assert_held(&wq_pool_mutex);
3966 
3967 	if (--pool->refcnt)
3968 		return;
3969 
3970 	/* sanity checks */
3971 	if (WARN_ON(!(pool->cpu < 0)) ||
3972 	    WARN_ON(!list_empty(&pool->worklist)))
3973 		return;
3974 
3975 	/* release id and unhash */
3976 	if (pool->id >= 0)
3977 		idr_remove(&worker_pool_idr, pool->id);
3978 	hash_del(&pool->hash_node);
3979 
3980 	/*
3981 	 * Become the manager and destroy all workers.  This prevents
3982 	 * @pool's workers from blocking on attach_mutex.  We're the last
3983 	 * manager and @pool gets freed with the flag set.
3984 	 *
3985 	 * Having a concurrent manager is quite unlikely to happen as we can
3986 	 * only get here with
3987 	 *   pwq->refcnt == pool->refcnt == 0
3988 	 * which implies no work queued to the pool, which implies no worker can
3989 	 * become the manager. However a worker could have taken the role of
3990 	 * manager before the refcnts dropped to 0, since maybe_create_worker()
3991 	 * drops pool->lock
3992 	 */
3993 	while (true) {
3994 		rcuwait_wait_event(&manager_wait,
3995 				   !(pool->flags & POOL_MANAGER_ACTIVE),
3996 				   TASK_UNINTERRUPTIBLE);
3997 
3998 		mutex_lock(&wq_pool_attach_mutex);
3999 		raw_spin_lock_irq(&pool->lock);
4000 		if (!(pool->flags & POOL_MANAGER_ACTIVE)) {
4001 			pool->flags |= POOL_MANAGER_ACTIVE;
4002 			break;
4003 		}
4004 		raw_spin_unlock_irq(&pool->lock);
4005 		mutex_unlock(&wq_pool_attach_mutex);
4006 	}
4007 
4008 	while ((worker = first_idle_worker(pool)))
4009 		set_worker_dying(worker, &cull_list);
4010 	WARN_ON(pool->nr_workers || pool->nr_idle);
4011 	raw_spin_unlock_irq(&pool->lock);
4012 
4013 	wake_dying_workers(&cull_list);
4014 
4015 	if (!list_empty(&pool->workers) || !list_empty(&pool->dying_workers))
4016 		pool->detach_completion = &detach_completion;
4017 	mutex_unlock(&wq_pool_attach_mutex);
4018 
4019 	if (pool->detach_completion)
4020 		wait_for_completion(pool->detach_completion);
4021 
4022 	/* shut down the timers */
4023 	del_timer_sync(&pool->idle_timer);
4024 	cancel_work_sync(&pool->idle_cull_work);
4025 	del_timer_sync(&pool->mayday_timer);
4026 
4027 	/* RCU protected to allow dereferences from get_work_pool() */
4028 	call_rcu(&pool->rcu, rcu_free_pool);
4029 }
4030 
4031 /**
4032  * get_unbound_pool - get a worker_pool with the specified attributes
4033  * @attrs: the attributes of the worker_pool to get
4034  *
4035  * Obtain a worker_pool which has the same attributes as @attrs, bump the
4036  * reference count and return it.  If there already is a matching
4037  * worker_pool, it will be used; otherwise, this function attempts to
4038  * create a new one.
4039  *
4040  * Should be called with wq_pool_mutex held.
4041  *
4042  * Return: On success, a worker_pool with the same attributes as @attrs.
4043  * On failure, %NULL.
4044  */
get_unbound_pool(const struct workqueue_attrs * attrs)4045 static struct worker_pool *get_unbound_pool(const struct workqueue_attrs *attrs)
4046 {
4047 	struct wq_pod_type *pt = &wq_pod_types[WQ_AFFN_NUMA];
4048 	u32 hash = wqattrs_hash(attrs);
4049 	struct worker_pool *pool;
4050 	int pod, node = NUMA_NO_NODE;
4051 
4052 	lockdep_assert_held(&wq_pool_mutex);
4053 
4054 	/* do we already have a matching pool? */
4055 	hash_for_each_possible(unbound_pool_hash, pool, hash_node, hash) {
4056 		if (wqattrs_equal(pool->attrs, attrs)) {
4057 			pool->refcnt++;
4058 			return pool;
4059 		}
4060 	}
4061 
4062 	/* If __pod_cpumask is contained inside a NUMA pod, that's our node */
4063 	for (pod = 0; pod < pt->nr_pods; pod++) {
4064 		if (cpumask_subset(attrs->__pod_cpumask, pt->pod_cpus[pod])) {
4065 			node = pt->pod_node[pod];
4066 			break;
4067 		}
4068 	}
4069 
4070 	/* nope, create a new one */
4071 	pool = kzalloc_node(sizeof(*pool), GFP_KERNEL, node);
4072 	if (!pool || init_worker_pool(pool) < 0)
4073 		goto fail;
4074 
4075 	pool->node = node;
4076 	copy_workqueue_attrs(pool->attrs, attrs);
4077 	wqattrs_clear_for_pool(pool->attrs);
4078 
4079 	if (worker_pool_assign_id(pool) < 0)
4080 		goto fail;
4081 
4082 	/* create and start the initial worker */
4083 	if (wq_online && !create_worker(pool))
4084 		goto fail;
4085 
4086 	/* install */
4087 	hash_add(unbound_pool_hash, &pool->hash_node, hash);
4088 
4089 	return pool;
4090 fail:
4091 	if (pool)
4092 		put_unbound_pool(pool);
4093 	return NULL;
4094 }
4095 
rcu_free_pwq(struct rcu_head * rcu)4096 static void rcu_free_pwq(struct rcu_head *rcu)
4097 {
4098 	kmem_cache_free(pwq_cache,
4099 			container_of(rcu, struct pool_workqueue, rcu));
4100 }
4101 
4102 /*
4103  * Scheduled on pwq_release_worker by put_pwq() when an unbound pwq hits zero
4104  * refcnt and needs to be destroyed.
4105  */
pwq_release_workfn(struct kthread_work * work)4106 static void pwq_release_workfn(struct kthread_work *work)
4107 {
4108 	struct pool_workqueue *pwq = container_of(work, struct pool_workqueue,
4109 						  release_work);
4110 	struct workqueue_struct *wq = pwq->wq;
4111 	struct worker_pool *pool = pwq->pool;
4112 	bool is_last = false;
4113 
4114 	/*
4115 	 * When @pwq is not linked, it doesn't hold any reference to the
4116 	 * @wq, and @wq is invalid to access.
4117 	 */
4118 	if (!list_empty(&pwq->pwqs_node)) {
4119 		mutex_lock(&wq->mutex);
4120 		list_del_rcu(&pwq->pwqs_node);
4121 		is_last = list_empty(&wq->pwqs);
4122 		mutex_unlock(&wq->mutex);
4123 	}
4124 
4125 	if (wq->flags & WQ_UNBOUND) {
4126 		mutex_lock(&wq_pool_mutex);
4127 		put_unbound_pool(pool);
4128 		mutex_unlock(&wq_pool_mutex);
4129 	}
4130 
4131 	call_rcu(&pwq->rcu, rcu_free_pwq);
4132 
4133 	/*
4134 	 * If we're the last pwq going away, @wq is already dead and no one
4135 	 * is gonna access it anymore.  Schedule RCU free.
4136 	 */
4137 	if (is_last) {
4138 		wq_unregister_lockdep(wq);
4139 		call_rcu(&wq->rcu, rcu_free_wq);
4140 	}
4141 }
4142 
4143 /**
4144  * pwq_adjust_max_active - update a pwq's max_active to the current setting
4145  * @pwq: target pool_workqueue
4146  *
4147  * If @pwq isn't freezing, set @pwq->max_active to the associated
4148  * workqueue's saved_max_active and activate inactive work items
4149  * accordingly.  If @pwq is freezing, clear @pwq->max_active to zero.
4150  */
pwq_adjust_max_active(struct pool_workqueue * pwq)4151 static void pwq_adjust_max_active(struct pool_workqueue *pwq)
4152 {
4153 	struct workqueue_struct *wq = pwq->wq;
4154 	bool freezable = wq->flags & WQ_FREEZABLE;
4155 	unsigned long flags;
4156 
4157 	/* for @wq->saved_max_active */
4158 	lockdep_assert_held(&wq->mutex);
4159 
4160 	/* fast exit for non-freezable wqs */
4161 	if (!freezable && pwq->max_active == wq->saved_max_active)
4162 		return;
4163 
4164 	/* this function can be called during early boot w/ irq disabled */
4165 	raw_spin_lock_irqsave(&pwq->pool->lock, flags);
4166 
4167 	/*
4168 	 * During [un]freezing, the caller is responsible for ensuring that
4169 	 * this function is called at least once after @workqueue_freezing
4170 	 * is updated and visible.
4171 	 */
4172 	if (!freezable || !workqueue_freezing) {
4173 		pwq->max_active = wq->saved_max_active;
4174 
4175 		while (!list_empty(&pwq->inactive_works) &&
4176 		       pwq->nr_active < pwq->max_active)
4177 			pwq_activate_first_inactive(pwq);
4178 
4179 		kick_pool(pwq->pool);
4180 	} else {
4181 		pwq->max_active = 0;
4182 	}
4183 
4184 	raw_spin_unlock_irqrestore(&pwq->pool->lock, flags);
4185 }
4186 
4187 /* initialize newly allocated @pwq which is associated with @wq and @pool */
init_pwq(struct pool_workqueue * pwq,struct workqueue_struct * wq,struct worker_pool * pool)4188 static void init_pwq(struct pool_workqueue *pwq, struct workqueue_struct *wq,
4189 		     struct worker_pool *pool)
4190 {
4191 	BUG_ON((unsigned long)pwq & WORK_STRUCT_FLAG_MASK);
4192 
4193 	memset(pwq, 0, sizeof(*pwq));
4194 
4195 	pwq->pool = pool;
4196 	pwq->wq = wq;
4197 	pwq->flush_color = -1;
4198 	pwq->refcnt = 1;
4199 	INIT_LIST_HEAD(&pwq->inactive_works);
4200 	INIT_LIST_HEAD(&pwq->pwqs_node);
4201 	INIT_LIST_HEAD(&pwq->mayday_node);
4202 	kthread_init_work(&pwq->release_work, pwq_release_workfn);
4203 }
4204 
4205 /* sync @pwq with the current state of its associated wq and link it */
link_pwq(struct pool_workqueue * pwq)4206 static void link_pwq(struct pool_workqueue *pwq)
4207 {
4208 	struct workqueue_struct *wq = pwq->wq;
4209 
4210 	lockdep_assert_held(&wq->mutex);
4211 
4212 	/* may be called multiple times, ignore if already linked */
4213 	if (!list_empty(&pwq->pwqs_node))
4214 		return;
4215 
4216 	/* set the matching work_color */
4217 	pwq->work_color = wq->work_color;
4218 
4219 	/* sync max_active to the current setting */
4220 	pwq_adjust_max_active(pwq);
4221 
4222 	/* link in @pwq */
4223 	list_add_rcu(&pwq->pwqs_node, &wq->pwqs);
4224 }
4225 
4226 /* obtain a pool matching @attr and create a pwq associating the pool and @wq */
alloc_unbound_pwq(struct workqueue_struct * wq,const struct workqueue_attrs * attrs)4227 static struct pool_workqueue *alloc_unbound_pwq(struct workqueue_struct *wq,
4228 					const struct workqueue_attrs *attrs)
4229 {
4230 	struct worker_pool *pool;
4231 	struct pool_workqueue *pwq;
4232 
4233 	lockdep_assert_held(&wq_pool_mutex);
4234 
4235 	pool = get_unbound_pool(attrs);
4236 	if (!pool)
4237 		return NULL;
4238 
4239 	pwq = kmem_cache_alloc_node(pwq_cache, GFP_KERNEL, pool->node);
4240 	if (!pwq) {
4241 		put_unbound_pool(pool);
4242 		return NULL;
4243 	}
4244 
4245 	init_pwq(pwq, wq, pool);
4246 	return pwq;
4247 }
4248 
4249 /**
4250  * wq_calc_pod_cpumask - calculate a wq_attrs' cpumask for a pod
4251  * @attrs: the wq_attrs of the default pwq of the target workqueue
4252  * @cpu: the target CPU
4253  * @cpu_going_down: if >= 0, the CPU to consider as offline
4254  *
4255  * Calculate the cpumask a workqueue with @attrs should use on @pod. If
4256  * @cpu_going_down is >= 0, that cpu is considered offline during calculation.
4257  * The result is stored in @attrs->__pod_cpumask.
4258  *
4259  * If pod affinity is not enabled, @attrs->cpumask is always used. If enabled
4260  * and @pod has online CPUs requested by @attrs, the returned cpumask is the
4261  * intersection of the possible CPUs of @pod and @attrs->cpumask.
4262  *
4263  * The caller is responsible for ensuring that the cpumask of @pod stays stable.
4264  */
wq_calc_pod_cpumask(struct workqueue_attrs * attrs,int cpu,int cpu_going_down)4265 static void wq_calc_pod_cpumask(struct workqueue_attrs *attrs, int cpu,
4266 				int cpu_going_down)
4267 {
4268 	const struct wq_pod_type *pt = wqattrs_pod_type(attrs);
4269 	int pod = pt->cpu_pod[cpu];
4270 
4271 	/* does @pod have any online CPUs @attrs wants? */
4272 	cpumask_and(attrs->__pod_cpumask, pt->pod_cpus[pod], attrs->cpumask);
4273 	cpumask_and(attrs->__pod_cpumask, attrs->__pod_cpumask, cpu_online_mask);
4274 	if (cpu_going_down >= 0)
4275 		cpumask_clear_cpu(cpu_going_down, attrs->__pod_cpumask);
4276 
4277 	if (cpumask_empty(attrs->__pod_cpumask)) {
4278 		cpumask_copy(attrs->__pod_cpumask, attrs->cpumask);
4279 		return;
4280 	}
4281 
4282 	/* yeap, return possible CPUs in @pod that @attrs wants */
4283 	cpumask_and(attrs->__pod_cpumask, attrs->cpumask, pt->pod_cpus[pod]);
4284 
4285 	if (cpumask_empty(attrs->__pod_cpumask))
4286 		pr_warn_once("WARNING: workqueue cpumask: online intersect > "
4287 				"possible intersect\n");
4288 }
4289 
4290 /* install @pwq into @wq's cpu_pwq and return the old pwq */
install_unbound_pwq(struct workqueue_struct * wq,int cpu,struct pool_workqueue * pwq)4291 static struct pool_workqueue *install_unbound_pwq(struct workqueue_struct *wq,
4292 					int cpu, struct pool_workqueue *pwq)
4293 {
4294 	struct pool_workqueue *old_pwq;
4295 
4296 	lockdep_assert_held(&wq_pool_mutex);
4297 	lockdep_assert_held(&wq->mutex);
4298 
4299 	/* link_pwq() can handle duplicate calls */
4300 	link_pwq(pwq);
4301 
4302 	old_pwq = rcu_access_pointer(*per_cpu_ptr(wq->cpu_pwq, cpu));
4303 	rcu_assign_pointer(*per_cpu_ptr(wq->cpu_pwq, cpu), pwq);
4304 	return old_pwq;
4305 }
4306 
4307 /* context to store the prepared attrs & pwqs before applying */
4308 struct apply_wqattrs_ctx {
4309 	struct workqueue_struct	*wq;		/* target workqueue */
4310 	struct workqueue_attrs	*attrs;		/* attrs to apply */
4311 	struct list_head	list;		/* queued for batching commit */
4312 	struct pool_workqueue	*dfl_pwq;
4313 	struct pool_workqueue	*pwq_tbl[];
4314 };
4315 
4316 /* free the resources after success or abort */
apply_wqattrs_cleanup(struct apply_wqattrs_ctx * ctx)4317 static void apply_wqattrs_cleanup(struct apply_wqattrs_ctx *ctx)
4318 {
4319 	if (ctx) {
4320 		int cpu;
4321 
4322 		for_each_possible_cpu(cpu)
4323 			put_pwq_unlocked(ctx->pwq_tbl[cpu]);
4324 		put_pwq_unlocked(ctx->dfl_pwq);
4325 
4326 		free_workqueue_attrs(ctx->attrs);
4327 
4328 		kfree(ctx);
4329 	}
4330 }
4331 
4332 /* allocate the attrs and pwqs for later installation */
4333 static struct apply_wqattrs_ctx *
apply_wqattrs_prepare(struct workqueue_struct * wq,const struct workqueue_attrs * attrs,const cpumask_var_t unbound_cpumask)4334 apply_wqattrs_prepare(struct workqueue_struct *wq,
4335 		      const struct workqueue_attrs *attrs,
4336 		      const cpumask_var_t unbound_cpumask)
4337 {
4338 	struct apply_wqattrs_ctx *ctx;
4339 	struct workqueue_attrs *new_attrs;
4340 	int cpu;
4341 
4342 	lockdep_assert_held(&wq_pool_mutex);
4343 
4344 	if (WARN_ON(attrs->affn_scope < 0 ||
4345 		    attrs->affn_scope >= WQ_AFFN_NR_TYPES))
4346 		return ERR_PTR(-EINVAL);
4347 
4348 	ctx = kzalloc(struct_size(ctx, pwq_tbl, nr_cpu_ids), GFP_KERNEL);
4349 
4350 	new_attrs = alloc_workqueue_attrs();
4351 	if (!ctx || !new_attrs)
4352 		goto out_free;
4353 
4354 	/*
4355 	 * If something goes wrong during CPU up/down, we'll fall back to
4356 	 * the default pwq covering whole @attrs->cpumask.  Always create
4357 	 * it even if we don't use it immediately.
4358 	 */
4359 	copy_workqueue_attrs(new_attrs, attrs);
4360 	wqattrs_actualize_cpumask(new_attrs, unbound_cpumask);
4361 	cpumask_copy(new_attrs->__pod_cpumask, new_attrs->cpumask);
4362 	ctx->dfl_pwq = alloc_unbound_pwq(wq, new_attrs);
4363 	if (!ctx->dfl_pwq)
4364 		goto out_free;
4365 
4366 	for_each_possible_cpu(cpu) {
4367 		if (new_attrs->ordered) {
4368 			ctx->dfl_pwq->refcnt++;
4369 			ctx->pwq_tbl[cpu] = ctx->dfl_pwq;
4370 		} else {
4371 			wq_calc_pod_cpumask(new_attrs, cpu, -1);
4372 			ctx->pwq_tbl[cpu] = alloc_unbound_pwq(wq, new_attrs);
4373 			if (!ctx->pwq_tbl[cpu])
4374 				goto out_free;
4375 		}
4376 	}
4377 
4378 	/* save the user configured attrs and sanitize it. */
4379 	copy_workqueue_attrs(new_attrs, attrs);
4380 	cpumask_and(new_attrs->cpumask, new_attrs->cpumask, cpu_possible_mask);
4381 	cpumask_copy(new_attrs->__pod_cpumask, new_attrs->cpumask);
4382 	ctx->attrs = new_attrs;
4383 
4384 	ctx->wq = wq;
4385 	return ctx;
4386 
4387 out_free:
4388 	free_workqueue_attrs(new_attrs);
4389 	apply_wqattrs_cleanup(ctx);
4390 	return ERR_PTR(-ENOMEM);
4391 }
4392 
4393 /* set attrs and install prepared pwqs, @ctx points to old pwqs on return */
apply_wqattrs_commit(struct apply_wqattrs_ctx * ctx)4394 static void apply_wqattrs_commit(struct apply_wqattrs_ctx *ctx)
4395 {
4396 	int cpu;
4397 
4398 	/* all pwqs have been created successfully, let's install'em */
4399 	mutex_lock(&ctx->wq->mutex);
4400 
4401 	copy_workqueue_attrs(ctx->wq->unbound_attrs, ctx->attrs);
4402 
4403 	/* save the previous pwq and install the new one */
4404 	for_each_possible_cpu(cpu)
4405 		ctx->pwq_tbl[cpu] = install_unbound_pwq(ctx->wq, cpu,
4406 							ctx->pwq_tbl[cpu]);
4407 
4408 	/* @dfl_pwq might not have been used, ensure it's linked */
4409 	link_pwq(ctx->dfl_pwq);
4410 	swap(ctx->wq->dfl_pwq, ctx->dfl_pwq);
4411 
4412 	mutex_unlock(&ctx->wq->mutex);
4413 }
4414 
apply_wqattrs_lock(void)4415 static void apply_wqattrs_lock(void)
4416 {
4417 	/* CPUs should stay stable across pwq creations and installations */
4418 	cpus_read_lock();
4419 	mutex_lock(&wq_pool_mutex);
4420 }
4421 
apply_wqattrs_unlock(void)4422 static void apply_wqattrs_unlock(void)
4423 {
4424 	mutex_unlock(&wq_pool_mutex);
4425 	cpus_read_unlock();
4426 }
4427 
apply_workqueue_attrs_locked(struct workqueue_struct * wq,const struct workqueue_attrs * attrs)4428 static int apply_workqueue_attrs_locked(struct workqueue_struct *wq,
4429 					const struct workqueue_attrs *attrs)
4430 {
4431 	struct apply_wqattrs_ctx *ctx;
4432 
4433 	/* only unbound workqueues can change attributes */
4434 	if (WARN_ON(!(wq->flags & WQ_UNBOUND)))
4435 		return -EINVAL;
4436 
4437 	/* creating multiple pwqs breaks ordering guarantee */
4438 	if (!list_empty(&wq->pwqs)) {
4439 		if (WARN_ON(wq->flags & __WQ_ORDERED_EXPLICIT))
4440 			return -EINVAL;
4441 
4442 		wq->flags &= ~__WQ_ORDERED;
4443 	}
4444 
4445 	ctx = apply_wqattrs_prepare(wq, attrs, wq_unbound_cpumask);
4446 	if (IS_ERR(ctx))
4447 		return PTR_ERR(ctx);
4448 
4449 	/* the ctx has been prepared successfully, let's commit it */
4450 	apply_wqattrs_commit(ctx);
4451 	apply_wqattrs_cleanup(ctx);
4452 
4453 	return 0;
4454 }
4455 
4456 /**
4457  * apply_workqueue_attrs - apply new workqueue_attrs to an unbound workqueue
4458  * @wq: the target workqueue
4459  * @attrs: the workqueue_attrs to apply, allocated with alloc_workqueue_attrs()
4460  *
4461  * Apply @attrs to an unbound workqueue @wq. Unless disabled, this function maps
4462  * a separate pwq to each CPU pod with possibles CPUs in @attrs->cpumask so that
4463  * work items are affine to the pod it was issued on. Older pwqs are released as
4464  * in-flight work items finish. Note that a work item which repeatedly requeues
4465  * itself back-to-back will stay on its current pwq.
4466  *
4467  * Performs GFP_KERNEL allocations.
4468  *
4469  * Assumes caller has CPU hotplug read exclusion, i.e. cpus_read_lock().
4470  *
4471  * Return: 0 on success and -errno on failure.
4472  */
apply_workqueue_attrs(struct workqueue_struct * wq,const struct workqueue_attrs * attrs)4473 int apply_workqueue_attrs(struct workqueue_struct *wq,
4474 			  const struct workqueue_attrs *attrs)
4475 {
4476 	int ret;
4477 
4478 	lockdep_assert_cpus_held();
4479 
4480 	mutex_lock(&wq_pool_mutex);
4481 	ret = apply_workqueue_attrs_locked(wq, attrs);
4482 	mutex_unlock(&wq_pool_mutex);
4483 
4484 	return ret;
4485 }
4486 
4487 /**
4488  * wq_update_pod - update pod affinity of a wq for CPU hot[un]plug
4489  * @wq: the target workqueue
4490  * @cpu: the CPU to update pool association for
4491  * @hotplug_cpu: the CPU coming up or going down
4492  * @online: whether @cpu is coming up or going down
4493  *
4494  * This function is to be called from %CPU_DOWN_PREPARE, %CPU_ONLINE and
4495  * %CPU_DOWN_FAILED.  @cpu is being hot[un]plugged, update pod affinity of
4496  * @wq accordingly.
4497  *
4498  *
4499  * If pod affinity can't be adjusted due to memory allocation failure, it falls
4500  * back to @wq->dfl_pwq which may not be optimal but is always correct.
4501  *
4502  * Note that when the last allowed CPU of a pod goes offline for a workqueue
4503  * with a cpumask spanning multiple pods, the workers which were already
4504  * executing the work items for the workqueue will lose their CPU affinity and
4505  * may execute on any CPU. This is similar to how per-cpu workqueues behave on
4506  * CPU_DOWN. If a workqueue user wants strict affinity, it's the user's
4507  * responsibility to flush the work item from CPU_DOWN_PREPARE.
4508  */
wq_update_pod(struct workqueue_struct * wq,int cpu,int hotplug_cpu,bool online)4509 static void wq_update_pod(struct workqueue_struct *wq, int cpu,
4510 			  int hotplug_cpu, bool online)
4511 {
4512 	int off_cpu = online ? -1 : hotplug_cpu;
4513 	struct pool_workqueue *old_pwq = NULL, *pwq;
4514 	struct workqueue_attrs *target_attrs;
4515 
4516 	lockdep_assert_held(&wq_pool_mutex);
4517 
4518 	if (!(wq->flags & WQ_UNBOUND) || wq->unbound_attrs->ordered)
4519 		return;
4520 
4521 	/*
4522 	 * We don't wanna alloc/free wq_attrs for each wq for each CPU.
4523 	 * Let's use a preallocated one.  The following buf is protected by
4524 	 * CPU hotplug exclusion.
4525 	 */
4526 	target_attrs = wq_update_pod_attrs_buf;
4527 
4528 	copy_workqueue_attrs(target_attrs, wq->unbound_attrs);
4529 	wqattrs_actualize_cpumask(target_attrs, wq_unbound_cpumask);
4530 
4531 	/* nothing to do if the target cpumask matches the current pwq */
4532 	wq_calc_pod_cpumask(target_attrs, cpu, off_cpu);
4533 	pwq = rcu_dereference_protected(*per_cpu_ptr(wq->cpu_pwq, cpu),
4534 					lockdep_is_held(&wq_pool_mutex));
4535 	if (wqattrs_equal(target_attrs, pwq->pool->attrs))
4536 		return;
4537 
4538 	/* create a new pwq */
4539 	pwq = alloc_unbound_pwq(wq, target_attrs);
4540 	if (!pwq) {
4541 		pr_warn("workqueue: allocation failed while updating CPU pod affinity of \"%s\"\n",
4542 			wq->name);
4543 		goto use_dfl_pwq;
4544 	}
4545 
4546 	/* Install the new pwq. */
4547 	mutex_lock(&wq->mutex);
4548 	old_pwq = install_unbound_pwq(wq, cpu, pwq);
4549 	goto out_unlock;
4550 
4551 use_dfl_pwq:
4552 	mutex_lock(&wq->mutex);
4553 	raw_spin_lock_irq(&wq->dfl_pwq->pool->lock);
4554 	get_pwq(wq->dfl_pwq);
4555 	raw_spin_unlock_irq(&wq->dfl_pwq->pool->lock);
4556 	old_pwq = install_unbound_pwq(wq, cpu, wq->dfl_pwq);
4557 out_unlock:
4558 	mutex_unlock(&wq->mutex);
4559 	put_pwq_unlocked(old_pwq);
4560 }
4561 
alloc_and_link_pwqs(struct workqueue_struct * wq)4562 static int alloc_and_link_pwqs(struct workqueue_struct *wq)
4563 {
4564 	bool highpri = wq->flags & WQ_HIGHPRI;
4565 	int cpu, ret;
4566 
4567 	wq->cpu_pwq = alloc_percpu(struct pool_workqueue *);
4568 	if (!wq->cpu_pwq)
4569 		goto enomem;
4570 
4571 	if (!(wq->flags & WQ_UNBOUND)) {
4572 		for_each_possible_cpu(cpu) {
4573 			struct pool_workqueue **pwq_p =
4574 				per_cpu_ptr(wq->cpu_pwq, cpu);
4575 			struct worker_pool *pool =
4576 				&(per_cpu_ptr(cpu_worker_pools, cpu)[highpri]);
4577 
4578 			*pwq_p = kmem_cache_alloc_node(pwq_cache, GFP_KERNEL,
4579 						       pool->node);
4580 			if (!*pwq_p)
4581 				goto enomem;
4582 
4583 			init_pwq(*pwq_p, wq, pool);
4584 
4585 			mutex_lock(&wq->mutex);
4586 			link_pwq(*pwq_p);
4587 			mutex_unlock(&wq->mutex);
4588 		}
4589 		return 0;
4590 	}
4591 
4592 	cpus_read_lock();
4593 	if (wq->flags & __WQ_ORDERED) {
4594 		ret = apply_workqueue_attrs(wq, ordered_wq_attrs[highpri]);
4595 		/* there should only be single pwq for ordering guarantee */
4596 		WARN(!ret && (wq->pwqs.next != &wq->dfl_pwq->pwqs_node ||
4597 			      wq->pwqs.prev != &wq->dfl_pwq->pwqs_node),
4598 		     "ordering guarantee broken for workqueue %s\n", wq->name);
4599 	} else {
4600 		ret = apply_workqueue_attrs(wq, unbound_std_wq_attrs[highpri]);
4601 	}
4602 	cpus_read_unlock();
4603 
4604 	/* for unbound pwq, flush the pwq_release_worker ensures that the
4605 	 * pwq_release_workfn() completes before calling kfree(wq).
4606 	 */
4607 	if (ret)
4608 		kthread_flush_worker(pwq_release_worker);
4609 
4610 	return ret;
4611 
4612 enomem:
4613 	if (wq->cpu_pwq) {
4614 		for_each_possible_cpu(cpu) {
4615 			struct pool_workqueue *pwq = *per_cpu_ptr(wq->cpu_pwq, cpu);
4616 
4617 			if (pwq)
4618 				kmem_cache_free(pwq_cache, pwq);
4619 		}
4620 		free_percpu(wq->cpu_pwq);
4621 		wq->cpu_pwq = NULL;
4622 	}
4623 	return -ENOMEM;
4624 }
4625 
wq_clamp_max_active(int max_active,unsigned int flags,const char * name)4626 static int wq_clamp_max_active(int max_active, unsigned int flags,
4627 			       const char *name)
4628 {
4629 	if (max_active < 1 || max_active > WQ_MAX_ACTIVE)
4630 		pr_warn("workqueue: max_active %d requested for %s is out of range, clamping between %d and %d\n",
4631 			max_active, name, 1, WQ_MAX_ACTIVE);
4632 
4633 	return clamp_val(max_active, 1, WQ_MAX_ACTIVE);
4634 }
4635 
4636 /*
4637  * Workqueues which may be used during memory reclaim should have a rescuer
4638  * to guarantee forward progress.
4639  */
init_rescuer(struct workqueue_struct * wq)4640 static int init_rescuer(struct workqueue_struct *wq)
4641 {
4642 	struct worker *rescuer;
4643 	int ret;
4644 
4645 	if (!(wq->flags & WQ_MEM_RECLAIM))
4646 		return 0;
4647 
4648 	rescuer = alloc_worker(NUMA_NO_NODE);
4649 	if (!rescuer) {
4650 		pr_err("workqueue: Failed to allocate a rescuer for wq \"%s\"\n",
4651 		       wq->name);
4652 		return -ENOMEM;
4653 	}
4654 
4655 	rescuer->rescue_wq = wq;
4656 	rescuer->task = kthread_create(rescuer_thread, rescuer, "kworker/R-%s", wq->name);
4657 	if (IS_ERR(rescuer->task)) {
4658 		ret = PTR_ERR(rescuer->task);
4659 		pr_err("workqueue: Failed to create a rescuer kthread for wq \"%s\": %pe",
4660 		       wq->name, ERR_PTR(ret));
4661 		kfree(rescuer);
4662 		return ret;
4663 	}
4664 
4665 	wq->rescuer = rescuer;
4666 	kthread_bind_mask(rescuer->task, cpu_possible_mask);
4667 	wake_up_process(rescuer->task);
4668 
4669 	return 0;
4670 }
4671 
4672 __printf(1, 4)
alloc_workqueue(const char * fmt,unsigned int flags,int max_active,...)4673 struct workqueue_struct *alloc_workqueue(const char *fmt,
4674 					 unsigned int flags,
4675 					 int max_active, ...)
4676 {
4677 	va_list args;
4678 	struct workqueue_struct *wq;
4679 	struct pool_workqueue *pwq;
4680 
4681 	/*
4682 	 * Unbound && max_active == 1 used to imply ordered, which is no longer
4683 	 * the case on many machines due to per-pod pools. While
4684 	 * alloc_ordered_workqueue() is the right way to create an ordered
4685 	 * workqueue, keep the previous behavior to avoid subtle breakages.
4686 	 */
4687 	if ((flags & WQ_UNBOUND) && max_active == 1)
4688 		flags |= __WQ_ORDERED;
4689 
4690 	/* see the comment above the definition of WQ_POWER_EFFICIENT */
4691 	if ((flags & WQ_POWER_EFFICIENT) && wq_power_efficient)
4692 		flags |= WQ_UNBOUND;
4693 
4694 	/* allocate wq and format name */
4695 	wq = kzalloc(sizeof(*wq), GFP_KERNEL);
4696 	if (!wq)
4697 		return NULL;
4698 
4699 	if (flags & WQ_UNBOUND) {
4700 		wq->unbound_attrs = alloc_workqueue_attrs();
4701 		if (!wq->unbound_attrs)
4702 			goto err_free_wq;
4703 	}
4704 
4705 	va_start(args, max_active);
4706 	vsnprintf(wq->name, sizeof(wq->name), fmt, args);
4707 	va_end(args);
4708 
4709 	max_active = max_active ?: WQ_DFL_ACTIVE;
4710 	max_active = wq_clamp_max_active(max_active, flags, wq->name);
4711 
4712 	/* init wq */
4713 	wq->flags = flags;
4714 	wq->saved_max_active = max_active;
4715 	mutex_init(&wq->mutex);
4716 	atomic_set(&wq->nr_pwqs_to_flush, 0);
4717 	INIT_LIST_HEAD(&wq->pwqs);
4718 	INIT_LIST_HEAD(&wq->flusher_queue);
4719 	INIT_LIST_HEAD(&wq->flusher_overflow);
4720 	INIT_LIST_HEAD(&wq->maydays);
4721 
4722 	wq_init_lockdep(wq);
4723 	INIT_LIST_HEAD(&wq->list);
4724 
4725 	if (alloc_and_link_pwqs(wq) < 0)
4726 		goto err_unreg_lockdep;
4727 
4728 	if (wq_online && init_rescuer(wq) < 0)
4729 		goto err_destroy;
4730 
4731 	if ((wq->flags & WQ_SYSFS) && workqueue_sysfs_register(wq))
4732 		goto err_destroy;
4733 
4734 	/*
4735 	 * wq_pool_mutex protects global freeze state and workqueues list.
4736 	 * Grab it, adjust max_active and add the new @wq to workqueues
4737 	 * list.
4738 	 */
4739 	mutex_lock(&wq_pool_mutex);
4740 
4741 	mutex_lock(&wq->mutex);
4742 	for_each_pwq(pwq, wq)
4743 		pwq_adjust_max_active(pwq);
4744 	mutex_unlock(&wq->mutex);
4745 
4746 	list_add_tail_rcu(&wq->list, &workqueues);
4747 
4748 	mutex_unlock(&wq_pool_mutex);
4749 
4750 	return wq;
4751 
4752 err_unreg_lockdep:
4753 	wq_unregister_lockdep(wq);
4754 	wq_free_lockdep(wq);
4755 err_free_wq:
4756 	free_workqueue_attrs(wq->unbound_attrs);
4757 	kfree(wq);
4758 	return NULL;
4759 err_destroy:
4760 	destroy_workqueue(wq);
4761 	return NULL;
4762 }
4763 EXPORT_SYMBOL_GPL(alloc_workqueue);
4764 
pwq_busy(struct pool_workqueue * pwq)4765 static bool pwq_busy(struct pool_workqueue *pwq)
4766 {
4767 	int i;
4768 
4769 	for (i = 0; i < WORK_NR_COLORS; i++)
4770 		if (pwq->nr_in_flight[i])
4771 			return true;
4772 
4773 	if ((pwq != pwq->wq->dfl_pwq) && (pwq->refcnt > 1))
4774 		return true;
4775 	if (pwq->nr_active || !list_empty(&pwq->inactive_works))
4776 		return true;
4777 
4778 	return false;
4779 }
4780 
4781 /**
4782  * destroy_workqueue - safely terminate a workqueue
4783  * @wq: target workqueue
4784  *
4785  * Safely destroy a workqueue. All work currently pending will be done first.
4786  */
destroy_workqueue(struct workqueue_struct * wq)4787 void destroy_workqueue(struct workqueue_struct *wq)
4788 {
4789 	struct pool_workqueue *pwq;
4790 	int cpu;
4791 
4792 	/*
4793 	 * Remove it from sysfs first so that sanity check failure doesn't
4794 	 * lead to sysfs name conflicts.
4795 	 */
4796 	workqueue_sysfs_unregister(wq);
4797 
4798 	/* mark the workqueue destruction is in progress */
4799 	mutex_lock(&wq->mutex);
4800 	wq->flags |= __WQ_DESTROYING;
4801 	mutex_unlock(&wq->mutex);
4802 
4803 	/* drain it before proceeding with destruction */
4804 	drain_workqueue(wq);
4805 
4806 	/* kill rescuer, if sanity checks fail, leave it w/o rescuer */
4807 	if (wq->rescuer) {
4808 		struct worker *rescuer = wq->rescuer;
4809 
4810 		/* this prevents new queueing */
4811 		raw_spin_lock_irq(&wq_mayday_lock);
4812 		wq->rescuer = NULL;
4813 		raw_spin_unlock_irq(&wq_mayday_lock);
4814 
4815 		/* rescuer will empty maydays list before exiting */
4816 		kthread_stop(rescuer->task);
4817 		kfree(rescuer);
4818 	}
4819 
4820 	/*
4821 	 * Sanity checks - grab all the locks so that we wait for all
4822 	 * in-flight operations which may do put_pwq().
4823 	 */
4824 	mutex_lock(&wq_pool_mutex);
4825 	mutex_lock(&wq->mutex);
4826 	for_each_pwq(pwq, wq) {
4827 		raw_spin_lock_irq(&pwq->pool->lock);
4828 		if (WARN_ON(pwq_busy(pwq))) {
4829 			pr_warn("%s: %s has the following busy pwq\n",
4830 				__func__, wq->name);
4831 			show_pwq(pwq);
4832 			raw_spin_unlock_irq(&pwq->pool->lock);
4833 			mutex_unlock(&wq->mutex);
4834 			mutex_unlock(&wq_pool_mutex);
4835 			show_one_workqueue(wq);
4836 			return;
4837 		}
4838 		raw_spin_unlock_irq(&pwq->pool->lock);
4839 	}
4840 	mutex_unlock(&wq->mutex);
4841 
4842 	/*
4843 	 * wq list is used to freeze wq, remove from list after
4844 	 * flushing is complete in case freeze races us.
4845 	 */
4846 	list_del_rcu(&wq->list);
4847 	mutex_unlock(&wq_pool_mutex);
4848 
4849 	/*
4850 	 * We're the sole accessor of @wq. Directly access cpu_pwq and dfl_pwq
4851 	 * to put the base refs. @wq will be auto-destroyed from the last
4852 	 * pwq_put. RCU read lock prevents @wq from going away from under us.
4853 	 */
4854 	rcu_read_lock();
4855 
4856 	for_each_possible_cpu(cpu) {
4857 		pwq = rcu_access_pointer(*per_cpu_ptr(wq->cpu_pwq, cpu));
4858 		RCU_INIT_POINTER(*per_cpu_ptr(wq->cpu_pwq, cpu), NULL);
4859 		put_pwq_unlocked(pwq);
4860 	}
4861 
4862 	put_pwq_unlocked(wq->dfl_pwq);
4863 	wq->dfl_pwq = NULL;
4864 
4865 	rcu_read_unlock();
4866 }
4867 EXPORT_SYMBOL_GPL(destroy_workqueue);
4868 
4869 /**
4870  * workqueue_set_max_active - adjust max_active of a workqueue
4871  * @wq: target workqueue
4872  * @max_active: new max_active value.
4873  *
4874  * Set max_active of @wq to @max_active.
4875  *
4876  * CONTEXT:
4877  * Don't call from IRQ context.
4878  */
workqueue_set_max_active(struct workqueue_struct * wq,int max_active)4879 void workqueue_set_max_active(struct workqueue_struct *wq, int max_active)
4880 {
4881 	struct pool_workqueue *pwq;
4882 
4883 	/* disallow meddling with max_active for ordered workqueues */
4884 	if (WARN_ON(wq->flags & __WQ_ORDERED_EXPLICIT))
4885 		return;
4886 
4887 	max_active = wq_clamp_max_active(max_active, wq->flags, wq->name);
4888 
4889 	mutex_lock(&wq->mutex);
4890 
4891 	wq->flags &= ~__WQ_ORDERED;
4892 	wq->saved_max_active = max_active;
4893 
4894 	for_each_pwq(pwq, wq)
4895 		pwq_adjust_max_active(pwq);
4896 
4897 	mutex_unlock(&wq->mutex);
4898 }
4899 EXPORT_SYMBOL_GPL(workqueue_set_max_active);
4900 
4901 /**
4902  * current_work - retrieve %current task's work struct
4903  *
4904  * Determine if %current task is a workqueue worker and what it's working on.
4905  * Useful to find out the context that the %current task is running in.
4906  *
4907  * Return: work struct if %current task is a workqueue worker, %NULL otherwise.
4908  */
current_work(void)4909 struct work_struct *current_work(void)
4910 {
4911 	struct worker *worker = current_wq_worker();
4912 
4913 	return worker ? worker->current_work : NULL;
4914 }
4915 EXPORT_SYMBOL(current_work);
4916 
4917 /**
4918  * current_is_workqueue_rescuer - is %current workqueue rescuer?
4919  *
4920  * Determine whether %current is a workqueue rescuer.  Can be used from
4921  * work functions to determine whether it's being run off the rescuer task.
4922  *
4923  * Return: %true if %current is a workqueue rescuer. %false otherwise.
4924  */
current_is_workqueue_rescuer(void)4925 bool current_is_workqueue_rescuer(void)
4926 {
4927 	struct worker *worker = current_wq_worker();
4928 
4929 	return worker && worker->rescue_wq;
4930 }
4931 
4932 /**
4933  * workqueue_congested - test whether a workqueue is congested
4934  * @cpu: CPU in question
4935  * @wq: target workqueue
4936  *
4937  * Test whether @wq's cpu workqueue for @cpu is congested.  There is
4938  * no synchronization around this function and the test result is
4939  * unreliable and only useful as advisory hints or for debugging.
4940  *
4941  * If @cpu is WORK_CPU_UNBOUND, the test is performed on the local CPU.
4942  *
4943  * With the exception of ordered workqueues, all workqueues have per-cpu
4944  * pool_workqueues, each with its own congested state. A workqueue being
4945  * congested on one CPU doesn't mean that the workqueue is contested on any
4946  * other CPUs.
4947  *
4948  * Return:
4949  * %true if congested, %false otherwise.
4950  */
workqueue_congested(int cpu,struct workqueue_struct * wq)4951 bool workqueue_congested(int cpu, struct workqueue_struct *wq)
4952 {
4953 	struct pool_workqueue *pwq;
4954 	bool ret;
4955 
4956 	rcu_read_lock();
4957 	preempt_disable();
4958 
4959 	if (cpu == WORK_CPU_UNBOUND)
4960 		cpu = smp_processor_id();
4961 
4962 	pwq = *per_cpu_ptr(wq->cpu_pwq, cpu);
4963 	ret = !list_empty(&pwq->inactive_works);
4964 
4965 	preempt_enable();
4966 	rcu_read_unlock();
4967 
4968 	return ret;
4969 }
4970 EXPORT_SYMBOL_GPL(workqueue_congested);
4971 
4972 /**
4973  * work_busy - test whether a work is currently pending or running
4974  * @work: the work to be tested
4975  *
4976  * Test whether @work is currently pending or running.  There is no
4977  * synchronization around this function and the test result is
4978  * unreliable and only useful as advisory hints or for debugging.
4979  *
4980  * Return:
4981  * OR'd bitmask of WORK_BUSY_* bits.
4982  */
work_busy(struct work_struct * work)4983 unsigned int work_busy(struct work_struct *work)
4984 {
4985 	struct worker_pool *pool;
4986 	unsigned long flags;
4987 	unsigned int ret = 0;
4988 
4989 	if (work_pending(work))
4990 		ret |= WORK_BUSY_PENDING;
4991 
4992 	rcu_read_lock();
4993 	pool = get_work_pool(work);
4994 	if (pool) {
4995 		raw_spin_lock_irqsave(&pool->lock, flags);
4996 		if (find_worker_executing_work(pool, work))
4997 			ret |= WORK_BUSY_RUNNING;
4998 		raw_spin_unlock_irqrestore(&pool->lock, flags);
4999 	}
5000 	rcu_read_unlock();
5001 
5002 	return ret;
5003 }
5004 EXPORT_SYMBOL_GPL(work_busy);
5005 
5006 /**
5007  * set_worker_desc - set description for the current work item
5008  * @fmt: printf-style format string
5009  * @...: arguments for the format string
5010  *
5011  * This function can be called by a running work function to describe what
5012  * the work item is about.  If the worker task gets dumped, this
5013  * information will be printed out together to help debugging.  The
5014  * description can be at most WORKER_DESC_LEN including the trailing '\0'.
5015  */
set_worker_desc(const char * fmt,...)5016 void set_worker_desc(const char *fmt, ...)
5017 {
5018 	struct worker *worker = current_wq_worker();
5019 	va_list args;
5020 
5021 	if (worker) {
5022 		va_start(args, fmt);
5023 		vsnprintf(worker->desc, sizeof(worker->desc), fmt, args);
5024 		va_end(args);
5025 	}
5026 }
5027 EXPORT_SYMBOL_GPL(set_worker_desc);
5028 
5029 /**
5030  * print_worker_info - print out worker information and description
5031  * @log_lvl: the log level to use when printing
5032  * @task: target task
5033  *
5034  * If @task is a worker and currently executing a work item, print out the
5035  * name of the workqueue being serviced and worker description set with
5036  * set_worker_desc() by the currently executing work item.
5037  *
5038  * This function can be safely called on any task as long as the
5039  * task_struct itself is accessible.  While safe, this function isn't
5040  * synchronized and may print out mixups or garbages of limited length.
5041  */
print_worker_info(const char * log_lvl,struct task_struct * task)5042 void print_worker_info(const char *log_lvl, struct task_struct *task)
5043 {
5044 	work_func_t *fn = NULL;
5045 	char name[WQ_NAME_LEN] = { };
5046 	char desc[WORKER_DESC_LEN] = { };
5047 	struct pool_workqueue *pwq = NULL;
5048 	struct workqueue_struct *wq = NULL;
5049 	struct worker *worker;
5050 
5051 	if (!(task->flags & PF_WQ_WORKER))
5052 		return;
5053 
5054 	/*
5055 	 * This function is called without any synchronization and @task
5056 	 * could be in any state.  Be careful with dereferences.
5057 	 */
5058 	worker = kthread_probe_data(task);
5059 
5060 	/*
5061 	 * Carefully copy the associated workqueue's workfn, name and desc.
5062 	 * Keep the original last '\0' in case the original is garbage.
5063 	 */
5064 	copy_from_kernel_nofault(&fn, &worker->current_func, sizeof(fn));
5065 	copy_from_kernel_nofault(&pwq, &worker->current_pwq, sizeof(pwq));
5066 	copy_from_kernel_nofault(&wq, &pwq->wq, sizeof(wq));
5067 	copy_from_kernel_nofault(name, wq->name, sizeof(name) - 1);
5068 	copy_from_kernel_nofault(desc, worker->desc, sizeof(desc) - 1);
5069 
5070 	if (fn || name[0] || desc[0]) {
5071 		printk("%sWorkqueue: %s %ps", log_lvl, name, fn);
5072 		if (strcmp(name, desc))
5073 			pr_cont(" (%s)", desc);
5074 		pr_cont("\n");
5075 	}
5076 }
5077 
pr_cont_pool_info(struct worker_pool * pool)5078 static void pr_cont_pool_info(struct worker_pool *pool)
5079 {
5080 	pr_cont(" cpus=%*pbl", nr_cpumask_bits, pool->attrs->cpumask);
5081 	if (pool->node != NUMA_NO_NODE)
5082 		pr_cont(" node=%d", pool->node);
5083 	pr_cont(" flags=0x%x nice=%d", pool->flags, pool->attrs->nice);
5084 }
5085 
5086 struct pr_cont_work_struct {
5087 	bool comma;
5088 	work_func_t func;
5089 	long ctr;
5090 };
5091 
pr_cont_work_flush(bool comma,work_func_t func,struct pr_cont_work_struct * pcwsp)5092 static void pr_cont_work_flush(bool comma, work_func_t func, struct pr_cont_work_struct *pcwsp)
5093 {
5094 	if (!pcwsp->ctr)
5095 		goto out_record;
5096 	if (func == pcwsp->func) {
5097 		pcwsp->ctr++;
5098 		return;
5099 	}
5100 	if (pcwsp->ctr == 1)
5101 		pr_cont("%s %ps", pcwsp->comma ? "," : "", pcwsp->func);
5102 	else
5103 		pr_cont("%s %ld*%ps", pcwsp->comma ? "," : "", pcwsp->ctr, pcwsp->func);
5104 	pcwsp->ctr = 0;
5105 out_record:
5106 	if ((long)func == -1L)
5107 		return;
5108 	pcwsp->comma = comma;
5109 	pcwsp->func = func;
5110 	pcwsp->ctr = 1;
5111 }
5112 
pr_cont_work(bool comma,struct work_struct * work,struct pr_cont_work_struct * pcwsp)5113 static void pr_cont_work(bool comma, struct work_struct *work, struct pr_cont_work_struct *pcwsp)
5114 {
5115 	if (work->func == wq_barrier_func) {
5116 		struct wq_barrier *barr;
5117 
5118 		barr = container_of(work, struct wq_barrier, work);
5119 
5120 		pr_cont_work_flush(comma, (work_func_t)-1, pcwsp);
5121 		pr_cont("%s BAR(%d)", comma ? "," : "",
5122 			task_pid_nr(barr->task));
5123 	} else {
5124 		if (!comma)
5125 			pr_cont_work_flush(comma, (work_func_t)-1, pcwsp);
5126 		pr_cont_work_flush(comma, work->func, pcwsp);
5127 	}
5128 }
5129 
show_pwq(struct pool_workqueue * pwq)5130 static void show_pwq(struct pool_workqueue *pwq)
5131 {
5132 	struct pr_cont_work_struct pcws = { .ctr = 0, };
5133 	struct worker_pool *pool = pwq->pool;
5134 	struct work_struct *work;
5135 	struct worker *worker;
5136 	bool has_in_flight = false, has_pending = false;
5137 	int bkt;
5138 
5139 	pr_info("  pwq %d:", pool->id);
5140 	pr_cont_pool_info(pool);
5141 
5142 	pr_cont(" active=%d/%d refcnt=%d%s\n",
5143 		pwq->nr_active, pwq->max_active, pwq->refcnt,
5144 		!list_empty(&pwq->mayday_node) ? " MAYDAY" : "");
5145 
5146 	hash_for_each(pool->busy_hash, bkt, worker, hentry) {
5147 		if (worker->current_pwq == pwq) {
5148 			has_in_flight = true;
5149 			break;
5150 		}
5151 	}
5152 	if (has_in_flight) {
5153 		bool comma = false;
5154 
5155 		pr_info("    in-flight:");
5156 		hash_for_each(pool->busy_hash, bkt, worker, hentry) {
5157 			if (worker->current_pwq != pwq)
5158 				continue;
5159 
5160 			pr_cont("%s %d%s:%ps", comma ? "," : "",
5161 				task_pid_nr(worker->task),
5162 				worker->rescue_wq ? "(RESCUER)" : "",
5163 				worker->current_func);
5164 			list_for_each_entry(work, &worker->scheduled, entry)
5165 				pr_cont_work(false, work, &pcws);
5166 			pr_cont_work_flush(comma, (work_func_t)-1L, &pcws);
5167 			comma = true;
5168 		}
5169 		pr_cont("\n");
5170 	}
5171 
5172 	list_for_each_entry(work, &pool->worklist, entry) {
5173 		if (get_work_pwq(work) == pwq) {
5174 			has_pending = true;
5175 			break;
5176 		}
5177 	}
5178 	if (has_pending) {
5179 		bool comma = false;
5180 
5181 		pr_info("    pending:");
5182 		list_for_each_entry(work, &pool->worklist, entry) {
5183 			if (get_work_pwq(work) != pwq)
5184 				continue;
5185 
5186 			pr_cont_work(comma, work, &pcws);
5187 			comma = !(*work_data_bits(work) & WORK_STRUCT_LINKED);
5188 		}
5189 		pr_cont_work_flush(comma, (work_func_t)-1L, &pcws);
5190 		pr_cont("\n");
5191 	}
5192 
5193 	if (!list_empty(&pwq->inactive_works)) {
5194 		bool comma = false;
5195 
5196 		pr_info("    inactive:");
5197 		list_for_each_entry(work, &pwq->inactive_works, entry) {
5198 			pr_cont_work(comma, work, &pcws);
5199 			comma = !(*work_data_bits(work) & WORK_STRUCT_LINKED);
5200 		}
5201 		pr_cont_work_flush(comma, (work_func_t)-1L, &pcws);
5202 		pr_cont("\n");
5203 	}
5204 }
5205 
5206 /**
5207  * show_one_workqueue - dump state of specified workqueue
5208  * @wq: workqueue whose state will be printed
5209  */
show_one_workqueue(struct workqueue_struct * wq)5210 void show_one_workqueue(struct workqueue_struct *wq)
5211 {
5212 	struct pool_workqueue *pwq;
5213 	bool idle = true;
5214 	unsigned long flags;
5215 
5216 	for_each_pwq(pwq, wq) {
5217 		if (pwq->nr_active || !list_empty(&pwq->inactive_works)) {
5218 			idle = false;
5219 			break;
5220 		}
5221 	}
5222 	if (idle) /* Nothing to print for idle workqueue */
5223 		return;
5224 
5225 	pr_info("workqueue %s: flags=0x%x\n", wq->name, wq->flags);
5226 
5227 	for_each_pwq(pwq, wq) {
5228 		raw_spin_lock_irqsave(&pwq->pool->lock, flags);
5229 		if (pwq->nr_active || !list_empty(&pwq->inactive_works)) {
5230 			/*
5231 			 * Defer printing to avoid deadlocks in console
5232 			 * drivers that queue work while holding locks
5233 			 * also taken in their write paths.
5234 			 */
5235 			printk_deferred_enter();
5236 			show_pwq(pwq);
5237 			printk_deferred_exit();
5238 		}
5239 		raw_spin_unlock_irqrestore(&pwq->pool->lock, flags);
5240 		/*
5241 		 * We could be printing a lot from atomic context, e.g.
5242 		 * sysrq-t -> show_all_workqueues(). Avoid triggering
5243 		 * hard lockup.
5244 		 */
5245 		touch_nmi_watchdog();
5246 	}
5247 
5248 }
5249 
5250 /**
5251  * show_one_worker_pool - dump state of specified worker pool
5252  * @pool: worker pool whose state will be printed
5253  */
show_one_worker_pool(struct worker_pool * pool)5254 static void show_one_worker_pool(struct worker_pool *pool)
5255 {
5256 	struct worker *worker;
5257 	bool first = true;
5258 	unsigned long flags;
5259 	unsigned long hung = 0;
5260 
5261 	raw_spin_lock_irqsave(&pool->lock, flags);
5262 	if (pool->nr_workers == pool->nr_idle)
5263 		goto next_pool;
5264 
5265 	/* How long the first pending work is waiting for a worker. */
5266 	if (!list_empty(&pool->worklist))
5267 		hung = jiffies_to_msecs(jiffies - pool->watchdog_ts) / 1000;
5268 
5269 	/*
5270 	 * Defer printing to avoid deadlocks in console drivers that
5271 	 * queue work while holding locks also taken in their write
5272 	 * paths.
5273 	 */
5274 	printk_deferred_enter();
5275 	pr_info("pool %d:", pool->id);
5276 	pr_cont_pool_info(pool);
5277 	pr_cont(" hung=%lus workers=%d", hung, pool->nr_workers);
5278 	if (pool->manager)
5279 		pr_cont(" manager: %d",
5280 			task_pid_nr(pool->manager->task));
5281 	list_for_each_entry(worker, &pool->idle_list, entry) {
5282 		pr_cont(" %s%d", first ? "idle: " : "",
5283 			task_pid_nr(worker->task));
5284 		first = false;
5285 	}
5286 	pr_cont("\n");
5287 	printk_deferred_exit();
5288 next_pool:
5289 	raw_spin_unlock_irqrestore(&pool->lock, flags);
5290 	/*
5291 	 * We could be printing a lot from atomic context, e.g.
5292 	 * sysrq-t -> show_all_workqueues(). Avoid triggering
5293 	 * hard lockup.
5294 	 */
5295 	touch_nmi_watchdog();
5296 
5297 }
5298 
5299 /**
5300  * show_all_workqueues - dump workqueue state
5301  *
5302  * Called from a sysrq handler and prints out all busy workqueues and pools.
5303  */
show_all_workqueues(void)5304 void show_all_workqueues(void)
5305 {
5306 	struct workqueue_struct *wq;
5307 	struct worker_pool *pool;
5308 	int pi;
5309 
5310 	rcu_read_lock();
5311 
5312 	pr_info("Showing busy workqueues and worker pools:\n");
5313 
5314 	list_for_each_entry_rcu(wq, &workqueues, list)
5315 		show_one_workqueue(wq);
5316 
5317 	for_each_pool(pool, pi)
5318 		show_one_worker_pool(pool);
5319 
5320 	rcu_read_unlock();
5321 }
5322 
5323 /**
5324  * show_freezable_workqueues - dump freezable workqueue state
5325  *
5326  * Called from try_to_freeze_tasks() and prints out all freezable workqueues
5327  * still busy.
5328  */
show_freezable_workqueues(void)5329 void show_freezable_workqueues(void)
5330 {
5331 	struct workqueue_struct *wq;
5332 
5333 	rcu_read_lock();
5334 
5335 	pr_info("Showing freezable workqueues that are still busy:\n");
5336 
5337 	list_for_each_entry_rcu(wq, &workqueues, list) {
5338 		if (!(wq->flags & WQ_FREEZABLE))
5339 			continue;
5340 		show_one_workqueue(wq);
5341 	}
5342 
5343 	rcu_read_unlock();
5344 }
5345 
5346 /* used to show worker information through /proc/PID/{comm,stat,status} */
wq_worker_comm(char * buf,size_t size,struct task_struct * task)5347 void wq_worker_comm(char *buf, size_t size, struct task_struct *task)
5348 {
5349 	int off;
5350 
5351 	/* always show the actual comm */
5352 	off = strscpy(buf, task->comm, size);
5353 	if (off < 0)
5354 		return;
5355 
5356 	/* stabilize PF_WQ_WORKER and worker pool association */
5357 	mutex_lock(&wq_pool_attach_mutex);
5358 
5359 	if (task->flags & PF_WQ_WORKER) {
5360 		struct worker *worker = kthread_data(task);
5361 		struct worker_pool *pool = worker->pool;
5362 
5363 		if (pool) {
5364 			raw_spin_lock_irq(&pool->lock);
5365 			/*
5366 			 * ->desc tracks information (wq name or
5367 			 * set_worker_desc()) for the latest execution.  If
5368 			 * current, prepend '+', otherwise '-'.
5369 			 */
5370 			if (worker->desc[0] != '\0') {
5371 				if (worker->current_work)
5372 					scnprintf(buf + off, size - off, "+%s",
5373 						  worker->desc);
5374 				else
5375 					scnprintf(buf + off, size - off, "-%s",
5376 						  worker->desc);
5377 			}
5378 			raw_spin_unlock_irq(&pool->lock);
5379 		}
5380 	}
5381 
5382 	mutex_unlock(&wq_pool_attach_mutex);
5383 }
5384 
5385 #ifdef CONFIG_SMP
5386 
5387 /*
5388  * CPU hotplug.
5389  *
5390  * There are two challenges in supporting CPU hotplug.  Firstly, there
5391  * are a lot of assumptions on strong associations among work, pwq and
5392  * pool which make migrating pending and scheduled works very
5393  * difficult to implement without impacting hot paths.  Secondly,
5394  * worker pools serve mix of short, long and very long running works making
5395  * blocked draining impractical.
5396  *
5397  * This is solved by allowing the pools to be disassociated from the CPU
5398  * running as an unbound one and allowing it to be reattached later if the
5399  * cpu comes back online.
5400  */
5401 
unbind_workers(int cpu)5402 static void unbind_workers(int cpu)
5403 {
5404 	struct worker_pool *pool;
5405 	struct worker *worker;
5406 
5407 	for_each_cpu_worker_pool(pool, cpu) {
5408 		mutex_lock(&wq_pool_attach_mutex);
5409 		raw_spin_lock_irq(&pool->lock);
5410 
5411 		/*
5412 		 * We've blocked all attach/detach operations. Make all workers
5413 		 * unbound and set DISASSOCIATED.  Before this, all workers
5414 		 * must be on the cpu.  After this, they may become diasporas.
5415 		 * And the preemption disabled section in their sched callbacks
5416 		 * are guaranteed to see WORKER_UNBOUND since the code here
5417 		 * is on the same cpu.
5418 		 */
5419 		for_each_pool_worker(worker, pool)
5420 			worker->flags |= WORKER_UNBOUND;
5421 
5422 		pool->flags |= POOL_DISASSOCIATED;
5423 
5424 		/*
5425 		 * The handling of nr_running in sched callbacks are disabled
5426 		 * now.  Zap nr_running.  After this, nr_running stays zero and
5427 		 * need_more_worker() and keep_working() are always true as
5428 		 * long as the worklist is not empty.  This pool now behaves as
5429 		 * an unbound (in terms of concurrency management) pool which
5430 		 * are served by workers tied to the pool.
5431 		 */
5432 		pool->nr_running = 0;
5433 
5434 		/*
5435 		 * With concurrency management just turned off, a busy
5436 		 * worker blocking could lead to lengthy stalls.  Kick off
5437 		 * unbound chain execution of currently pending work items.
5438 		 */
5439 		kick_pool(pool);
5440 
5441 		raw_spin_unlock_irq(&pool->lock);
5442 
5443 		for_each_pool_worker(worker, pool)
5444 			unbind_worker(worker);
5445 
5446 		mutex_unlock(&wq_pool_attach_mutex);
5447 	}
5448 }
5449 
5450 /**
5451  * rebind_workers - rebind all workers of a pool to the associated CPU
5452  * @pool: pool of interest
5453  *
5454  * @pool->cpu is coming online.  Rebind all workers to the CPU.
5455  */
rebind_workers(struct worker_pool * pool)5456 static void rebind_workers(struct worker_pool *pool)
5457 {
5458 	struct worker *worker;
5459 
5460 	lockdep_assert_held(&wq_pool_attach_mutex);
5461 
5462 	/*
5463 	 * Restore CPU affinity of all workers.  As all idle workers should
5464 	 * be on the run-queue of the associated CPU before any local
5465 	 * wake-ups for concurrency management happen, restore CPU affinity
5466 	 * of all workers first and then clear UNBOUND.  As we're called
5467 	 * from CPU_ONLINE, the following shouldn't fail.
5468 	 */
5469 	for_each_pool_worker(worker, pool) {
5470 		kthread_set_per_cpu(worker->task, pool->cpu);
5471 		WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task,
5472 						  pool_allowed_cpus(pool)) < 0);
5473 	}
5474 
5475 	raw_spin_lock_irq(&pool->lock);
5476 
5477 	pool->flags &= ~POOL_DISASSOCIATED;
5478 
5479 	for_each_pool_worker(worker, pool) {
5480 		unsigned int worker_flags = worker->flags;
5481 
5482 		/*
5483 		 * We want to clear UNBOUND but can't directly call
5484 		 * worker_clr_flags() or adjust nr_running.  Atomically
5485 		 * replace UNBOUND with another NOT_RUNNING flag REBOUND.
5486 		 * @worker will clear REBOUND using worker_clr_flags() when
5487 		 * it initiates the next execution cycle thus restoring
5488 		 * concurrency management.  Note that when or whether
5489 		 * @worker clears REBOUND doesn't affect correctness.
5490 		 *
5491 		 * WRITE_ONCE() is necessary because @worker->flags may be
5492 		 * tested without holding any lock in
5493 		 * wq_worker_running().  Without it, NOT_RUNNING test may
5494 		 * fail incorrectly leading to premature concurrency
5495 		 * management operations.
5496 		 */
5497 		WARN_ON_ONCE(!(worker_flags & WORKER_UNBOUND));
5498 		worker_flags |= WORKER_REBOUND;
5499 		worker_flags &= ~WORKER_UNBOUND;
5500 		WRITE_ONCE(worker->flags, worker_flags);
5501 	}
5502 
5503 	raw_spin_unlock_irq(&pool->lock);
5504 }
5505 
5506 /**
5507  * restore_unbound_workers_cpumask - restore cpumask of unbound workers
5508  * @pool: unbound pool of interest
5509  * @cpu: the CPU which is coming up
5510  *
5511  * An unbound pool may end up with a cpumask which doesn't have any online
5512  * CPUs.  When a worker of such pool get scheduled, the scheduler resets
5513  * its cpus_allowed.  If @cpu is in @pool's cpumask which didn't have any
5514  * online CPU before, cpus_allowed of all its workers should be restored.
5515  */
restore_unbound_workers_cpumask(struct worker_pool * pool,int cpu)5516 static void restore_unbound_workers_cpumask(struct worker_pool *pool, int cpu)
5517 {
5518 	static cpumask_t cpumask;
5519 	struct worker *worker;
5520 
5521 	lockdep_assert_held(&wq_pool_attach_mutex);
5522 
5523 	/* is @cpu allowed for @pool? */
5524 	if (!cpumask_test_cpu(cpu, pool->attrs->cpumask))
5525 		return;
5526 
5527 	cpumask_and(&cpumask, pool->attrs->cpumask, cpu_online_mask);
5528 
5529 	/* as we're called from CPU_ONLINE, the following shouldn't fail */
5530 	for_each_pool_worker(worker, pool)
5531 		WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task, &cpumask) < 0);
5532 }
5533 
workqueue_prepare_cpu(unsigned int cpu)5534 int workqueue_prepare_cpu(unsigned int cpu)
5535 {
5536 	struct worker_pool *pool;
5537 
5538 	for_each_cpu_worker_pool(pool, cpu) {
5539 		if (pool->nr_workers)
5540 			continue;
5541 		if (!create_worker(pool))
5542 			return -ENOMEM;
5543 	}
5544 	return 0;
5545 }
5546 
workqueue_online_cpu(unsigned int cpu)5547 int workqueue_online_cpu(unsigned int cpu)
5548 {
5549 	struct worker_pool *pool;
5550 	struct workqueue_struct *wq;
5551 	int pi;
5552 
5553 	mutex_lock(&wq_pool_mutex);
5554 
5555 	for_each_pool(pool, pi) {
5556 		mutex_lock(&wq_pool_attach_mutex);
5557 
5558 		if (pool->cpu == cpu)
5559 			rebind_workers(pool);
5560 		else if (pool->cpu < 0)
5561 			restore_unbound_workers_cpumask(pool, cpu);
5562 
5563 		mutex_unlock(&wq_pool_attach_mutex);
5564 	}
5565 
5566 	/* update pod affinity of unbound workqueues */
5567 	list_for_each_entry(wq, &workqueues, list) {
5568 		struct workqueue_attrs *attrs = wq->unbound_attrs;
5569 
5570 		if (attrs) {
5571 			const struct wq_pod_type *pt = wqattrs_pod_type(attrs);
5572 			int tcpu;
5573 
5574 			for_each_cpu(tcpu, pt->pod_cpus[pt->cpu_pod[cpu]])
5575 				wq_update_pod(wq, tcpu, cpu, true);
5576 		}
5577 	}
5578 
5579 	mutex_unlock(&wq_pool_mutex);
5580 	return 0;
5581 }
5582 
workqueue_offline_cpu(unsigned int cpu)5583 int workqueue_offline_cpu(unsigned int cpu)
5584 {
5585 	struct workqueue_struct *wq;
5586 
5587 	/* unbinding per-cpu workers should happen on the local CPU */
5588 	if (WARN_ON(cpu != smp_processor_id()))
5589 		return -1;
5590 
5591 	unbind_workers(cpu);
5592 
5593 	/* update pod affinity of unbound workqueues */
5594 	mutex_lock(&wq_pool_mutex);
5595 	list_for_each_entry(wq, &workqueues, list) {
5596 		struct workqueue_attrs *attrs = wq->unbound_attrs;
5597 
5598 		if (attrs) {
5599 			const struct wq_pod_type *pt = wqattrs_pod_type(attrs);
5600 			int tcpu;
5601 
5602 			for_each_cpu(tcpu, pt->pod_cpus[pt->cpu_pod[cpu]])
5603 				wq_update_pod(wq, tcpu, cpu, false);
5604 		}
5605 	}
5606 	mutex_unlock(&wq_pool_mutex);
5607 
5608 	return 0;
5609 }
5610 
5611 struct work_for_cpu {
5612 	struct work_struct work;
5613 	long (*fn)(void *);
5614 	void *arg;
5615 	long ret;
5616 };
5617 
work_for_cpu_fn(struct work_struct * work)5618 static void work_for_cpu_fn(struct work_struct *work)
5619 {
5620 	struct work_for_cpu *wfc = container_of(work, struct work_for_cpu, work);
5621 
5622 	wfc->ret = wfc->fn(wfc->arg);
5623 }
5624 
5625 /**
5626  * work_on_cpu_key - run a function in thread context on a particular cpu
5627  * @cpu: the cpu to run on
5628  * @fn: the function to run
5629  * @arg: the function arg
5630  * @key: The lock class key for lock debugging purposes
5631  *
5632  * It is up to the caller to ensure that the cpu doesn't go offline.
5633  * The caller must not hold any locks which would prevent @fn from completing.
5634  *
5635  * Return: The value @fn returns.
5636  */
work_on_cpu_key(int cpu,long (* fn)(void *),void * arg,struct lock_class_key * key)5637 long work_on_cpu_key(int cpu, long (*fn)(void *),
5638 		     void *arg, struct lock_class_key *key)
5639 {
5640 	struct work_for_cpu wfc = { .fn = fn, .arg = arg };
5641 
5642 	INIT_WORK_ONSTACK_KEY(&wfc.work, work_for_cpu_fn, key);
5643 	schedule_work_on(cpu, &wfc.work);
5644 	flush_work(&wfc.work);
5645 	destroy_work_on_stack(&wfc.work);
5646 	return wfc.ret;
5647 }
5648 EXPORT_SYMBOL_GPL(work_on_cpu_key);
5649 
5650 /**
5651  * work_on_cpu_safe_key - run a function in thread context on a particular cpu
5652  * @cpu: the cpu to run on
5653  * @fn:  the function to run
5654  * @arg: the function argument
5655  * @key: The lock class key for lock debugging purposes
5656  *
5657  * Disables CPU hotplug and calls work_on_cpu(). The caller must not hold
5658  * any locks which would prevent @fn from completing.
5659  *
5660  * Return: The value @fn returns.
5661  */
work_on_cpu_safe_key(int cpu,long (* fn)(void *),void * arg,struct lock_class_key * key)5662 long work_on_cpu_safe_key(int cpu, long (*fn)(void *),
5663 			  void *arg, struct lock_class_key *key)
5664 {
5665 	long ret = -ENODEV;
5666 
5667 	cpus_read_lock();
5668 	if (cpu_online(cpu))
5669 		ret = work_on_cpu_key(cpu, fn, arg, key);
5670 	cpus_read_unlock();
5671 	return ret;
5672 }
5673 EXPORT_SYMBOL_GPL(work_on_cpu_safe_key);
5674 #endif /* CONFIG_SMP */
5675 
5676 #ifdef CONFIG_FREEZER
5677 
5678 /**
5679  * freeze_workqueues_begin - begin freezing workqueues
5680  *
5681  * Start freezing workqueues.  After this function returns, all freezable
5682  * workqueues will queue new works to their inactive_works list instead of
5683  * pool->worklist.
5684  *
5685  * CONTEXT:
5686  * Grabs and releases wq_pool_mutex, wq->mutex and pool->lock's.
5687  */
freeze_workqueues_begin(void)5688 void freeze_workqueues_begin(void)
5689 {
5690 	struct workqueue_struct *wq;
5691 	struct pool_workqueue *pwq;
5692 
5693 	mutex_lock(&wq_pool_mutex);
5694 
5695 	WARN_ON_ONCE(workqueue_freezing);
5696 	workqueue_freezing = true;
5697 
5698 	list_for_each_entry(wq, &workqueues, list) {
5699 		mutex_lock(&wq->mutex);
5700 		for_each_pwq(pwq, wq)
5701 			pwq_adjust_max_active(pwq);
5702 		mutex_unlock(&wq->mutex);
5703 	}
5704 
5705 	mutex_unlock(&wq_pool_mutex);
5706 }
5707 
5708 /**
5709  * freeze_workqueues_busy - are freezable workqueues still busy?
5710  *
5711  * Check whether freezing is complete.  This function must be called
5712  * between freeze_workqueues_begin() and thaw_workqueues().
5713  *
5714  * CONTEXT:
5715  * Grabs and releases wq_pool_mutex.
5716  *
5717  * Return:
5718  * %true if some freezable workqueues are still busy.  %false if freezing
5719  * is complete.
5720  */
freeze_workqueues_busy(void)5721 bool freeze_workqueues_busy(void)
5722 {
5723 	bool busy = false;
5724 	struct workqueue_struct *wq;
5725 	struct pool_workqueue *pwq;
5726 
5727 	mutex_lock(&wq_pool_mutex);
5728 
5729 	WARN_ON_ONCE(!workqueue_freezing);
5730 
5731 	list_for_each_entry(wq, &workqueues, list) {
5732 		if (!(wq->flags & WQ_FREEZABLE))
5733 			continue;
5734 		/*
5735 		 * nr_active is monotonically decreasing.  It's safe
5736 		 * to peek without lock.
5737 		 */
5738 		rcu_read_lock();
5739 		for_each_pwq(pwq, wq) {
5740 			WARN_ON_ONCE(pwq->nr_active < 0);
5741 			if (pwq->nr_active) {
5742 				busy = true;
5743 				rcu_read_unlock();
5744 				goto out_unlock;
5745 			}
5746 		}
5747 		rcu_read_unlock();
5748 	}
5749 out_unlock:
5750 	mutex_unlock(&wq_pool_mutex);
5751 	return busy;
5752 }
5753 
5754 /**
5755  * thaw_workqueues - thaw workqueues
5756  *
5757  * Thaw workqueues.  Normal queueing is restored and all collected
5758  * frozen works are transferred to their respective pool worklists.
5759  *
5760  * CONTEXT:
5761  * Grabs and releases wq_pool_mutex, wq->mutex and pool->lock's.
5762  */
thaw_workqueues(void)5763 void thaw_workqueues(void)
5764 {
5765 	struct workqueue_struct *wq;
5766 	struct pool_workqueue *pwq;
5767 
5768 	mutex_lock(&wq_pool_mutex);
5769 
5770 	if (!workqueue_freezing)
5771 		goto out_unlock;
5772 
5773 	workqueue_freezing = false;
5774 
5775 	/* restore max_active and repopulate worklist */
5776 	list_for_each_entry(wq, &workqueues, list) {
5777 		mutex_lock(&wq->mutex);
5778 		for_each_pwq(pwq, wq)
5779 			pwq_adjust_max_active(pwq);
5780 		mutex_unlock(&wq->mutex);
5781 	}
5782 
5783 out_unlock:
5784 	mutex_unlock(&wq_pool_mutex);
5785 }
5786 #endif /* CONFIG_FREEZER */
5787 
workqueue_apply_unbound_cpumask(const cpumask_var_t unbound_cpumask)5788 static int workqueue_apply_unbound_cpumask(const cpumask_var_t unbound_cpumask)
5789 {
5790 	LIST_HEAD(ctxs);
5791 	int ret = 0;
5792 	struct workqueue_struct *wq;
5793 	struct apply_wqattrs_ctx *ctx, *n;
5794 
5795 	lockdep_assert_held(&wq_pool_mutex);
5796 
5797 	list_for_each_entry(wq, &workqueues, list) {
5798 		if (!(wq->flags & WQ_UNBOUND))
5799 			continue;
5800 		/* creating multiple pwqs breaks ordering guarantee */
5801 		if (wq->flags & __WQ_ORDERED)
5802 			continue;
5803 
5804 		ctx = apply_wqattrs_prepare(wq, wq->unbound_attrs, unbound_cpumask);
5805 		if (IS_ERR(ctx)) {
5806 			ret = PTR_ERR(ctx);
5807 			break;
5808 		}
5809 
5810 		list_add_tail(&ctx->list, &ctxs);
5811 	}
5812 
5813 	list_for_each_entry_safe(ctx, n, &ctxs, list) {
5814 		if (!ret)
5815 			apply_wqattrs_commit(ctx);
5816 		apply_wqattrs_cleanup(ctx);
5817 	}
5818 
5819 	if (!ret) {
5820 		mutex_lock(&wq_pool_attach_mutex);
5821 		cpumask_copy(wq_unbound_cpumask, unbound_cpumask);
5822 		mutex_unlock(&wq_pool_attach_mutex);
5823 	}
5824 	return ret;
5825 }
5826 
5827 /**
5828  *  workqueue_set_unbound_cpumask - Set the low-level unbound cpumask
5829  *  @cpumask: the cpumask to set
5830  *
5831  *  The low-level workqueues cpumask is a global cpumask that limits
5832  *  the affinity of all unbound workqueues.  This function check the @cpumask
5833  *  and apply it to all unbound workqueues and updates all pwqs of them.
5834  *
5835  *  Return:	0	- Success
5836  *  		-EINVAL	- Invalid @cpumask
5837  *  		-ENOMEM	- Failed to allocate memory for attrs or pwqs.
5838  */
workqueue_set_unbound_cpumask(cpumask_var_t cpumask)5839 int workqueue_set_unbound_cpumask(cpumask_var_t cpumask)
5840 {
5841 	int ret = -EINVAL;
5842 
5843 	/*
5844 	 * Not excluding isolated cpus on purpose.
5845 	 * If the user wishes to include them, we allow that.
5846 	 */
5847 	cpumask_and(cpumask, cpumask, cpu_possible_mask);
5848 	if (!cpumask_empty(cpumask)) {
5849 		apply_wqattrs_lock();
5850 		if (cpumask_equal(cpumask, wq_unbound_cpumask)) {
5851 			ret = 0;
5852 			goto out_unlock;
5853 		}
5854 
5855 		ret = workqueue_apply_unbound_cpumask(cpumask);
5856 
5857 out_unlock:
5858 		apply_wqattrs_unlock();
5859 	}
5860 
5861 	return ret;
5862 }
5863 
parse_affn_scope(const char * val)5864 static int parse_affn_scope(const char *val)
5865 {
5866 	int i;
5867 
5868 	for (i = 0; i < ARRAY_SIZE(wq_affn_names); i++) {
5869 		if (!strncasecmp(val, wq_affn_names[i], strlen(wq_affn_names[i])))
5870 			return i;
5871 	}
5872 	return -EINVAL;
5873 }
5874 
wq_affn_dfl_set(const char * val,const struct kernel_param * kp)5875 static int wq_affn_dfl_set(const char *val, const struct kernel_param *kp)
5876 {
5877 	struct workqueue_struct *wq;
5878 	int affn, cpu;
5879 
5880 	affn = parse_affn_scope(val);
5881 	if (affn < 0)
5882 		return affn;
5883 	if (affn == WQ_AFFN_DFL)
5884 		return -EINVAL;
5885 
5886 	cpus_read_lock();
5887 	mutex_lock(&wq_pool_mutex);
5888 
5889 	wq_affn_dfl = affn;
5890 
5891 	list_for_each_entry(wq, &workqueues, list) {
5892 		for_each_online_cpu(cpu) {
5893 			wq_update_pod(wq, cpu, cpu, true);
5894 		}
5895 	}
5896 
5897 	mutex_unlock(&wq_pool_mutex);
5898 	cpus_read_unlock();
5899 
5900 	return 0;
5901 }
5902 
wq_affn_dfl_get(char * buffer,const struct kernel_param * kp)5903 static int wq_affn_dfl_get(char *buffer, const struct kernel_param *kp)
5904 {
5905 	return scnprintf(buffer, PAGE_SIZE, "%s\n", wq_affn_names[wq_affn_dfl]);
5906 }
5907 
5908 static const struct kernel_param_ops wq_affn_dfl_ops = {
5909 	.set	= wq_affn_dfl_set,
5910 	.get	= wq_affn_dfl_get,
5911 };
5912 
5913 module_param_cb(default_affinity_scope, &wq_affn_dfl_ops, NULL, 0644);
5914 
5915 #ifdef CONFIG_SYSFS
5916 /*
5917  * Workqueues with WQ_SYSFS flag set is visible to userland via
5918  * /sys/bus/workqueue/devices/WQ_NAME.  All visible workqueues have the
5919  * following attributes.
5920  *
5921  *  per_cpu		RO bool	: whether the workqueue is per-cpu or unbound
5922  *  max_active		RW int	: maximum number of in-flight work items
5923  *
5924  * Unbound workqueues have the following extra attributes.
5925  *
5926  *  nice		RW int	: nice value of the workers
5927  *  cpumask		RW mask	: bitmask of allowed CPUs for the workers
5928  *  affinity_scope	RW str  : worker CPU affinity scope (cache, numa, none)
5929  *  affinity_strict	RW bool : worker CPU affinity is strict
5930  */
5931 struct wq_device {
5932 	struct workqueue_struct		*wq;
5933 	struct device			dev;
5934 };
5935 
dev_to_wq(struct device * dev)5936 static struct workqueue_struct *dev_to_wq(struct device *dev)
5937 {
5938 	struct wq_device *wq_dev = container_of(dev, struct wq_device, dev);
5939 
5940 	return wq_dev->wq;
5941 }
5942 
per_cpu_show(struct device * dev,struct device_attribute * attr,char * buf)5943 static ssize_t per_cpu_show(struct device *dev, struct device_attribute *attr,
5944 			    char *buf)
5945 {
5946 	struct workqueue_struct *wq = dev_to_wq(dev);
5947 
5948 	return scnprintf(buf, PAGE_SIZE, "%d\n", (bool)!(wq->flags & WQ_UNBOUND));
5949 }
5950 static DEVICE_ATTR_RO(per_cpu);
5951 
max_active_show(struct device * dev,struct device_attribute * attr,char * buf)5952 static ssize_t max_active_show(struct device *dev,
5953 			       struct device_attribute *attr, char *buf)
5954 {
5955 	struct workqueue_struct *wq = dev_to_wq(dev);
5956 
5957 	return scnprintf(buf, PAGE_SIZE, "%d\n", wq->saved_max_active);
5958 }
5959 
max_active_store(struct device * dev,struct device_attribute * attr,const char * buf,size_t count)5960 static ssize_t max_active_store(struct device *dev,
5961 				struct device_attribute *attr, const char *buf,
5962 				size_t count)
5963 {
5964 	struct workqueue_struct *wq = dev_to_wq(dev);
5965 	int val;
5966 
5967 	if (sscanf(buf, "%d", &val) != 1 || val <= 0)
5968 		return -EINVAL;
5969 
5970 	workqueue_set_max_active(wq, val);
5971 	return count;
5972 }
5973 static DEVICE_ATTR_RW(max_active);
5974 
5975 static struct attribute *wq_sysfs_attrs[] = {
5976 	&dev_attr_per_cpu.attr,
5977 	&dev_attr_max_active.attr,
5978 	NULL,
5979 };
5980 ATTRIBUTE_GROUPS(wq_sysfs);
5981 
wq_nice_show(struct device * dev,struct device_attribute * attr,char * buf)5982 static ssize_t wq_nice_show(struct device *dev, struct device_attribute *attr,
5983 			    char *buf)
5984 {
5985 	struct workqueue_struct *wq = dev_to_wq(dev);
5986 	int written;
5987 
5988 	mutex_lock(&wq->mutex);
5989 	written = scnprintf(buf, PAGE_SIZE, "%d\n", wq->unbound_attrs->nice);
5990 	mutex_unlock(&wq->mutex);
5991 
5992 	return written;
5993 }
5994 
5995 /* prepare workqueue_attrs for sysfs store operations */
wq_sysfs_prep_attrs(struct workqueue_struct * wq)5996 static struct workqueue_attrs *wq_sysfs_prep_attrs(struct workqueue_struct *wq)
5997 {
5998 	struct workqueue_attrs *attrs;
5999 
6000 	lockdep_assert_held(&wq_pool_mutex);
6001 
6002 	attrs = alloc_workqueue_attrs();
6003 	if (!attrs)
6004 		return NULL;
6005 
6006 	copy_workqueue_attrs(attrs, wq->unbound_attrs);
6007 	return attrs;
6008 }
6009 
wq_nice_store(struct device * dev,struct device_attribute * attr,const char * buf,size_t count)6010 static ssize_t wq_nice_store(struct device *dev, struct device_attribute *attr,
6011 			     const char *buf, size_t count)
6012 {
6013 	struct workqueue_struct *wq = dev_to_wq(dev);
6014 	struct workqueue_attrs *attrs;
6015 	int ret = -ENOMEM;
6016 
6017 	apply_wqattrs_lock();
6018 
6019 	attrs = wq_sysfs_prep_attrs(wq);
6020 	if (!attrs)
6021 		goto out_unlock;
6022 
6023 	if (sscanf(buf, "%d", &attrs->nice) == 1 &&
6024 	    attrs->nice >= MIN_NICE && attrs->nice <= MAX_NICE)
6025 		ret = apply_workqueue_attrs_locked(wq, attrs);
6026 	else
6027 		ret = -EINVAL;
6028 
6029 out_unlock:
6030 	apply_wqattrs_unlock();
6031 	free_workqueue_attrs(attrs);
6032 	return ret ?: count;
6033 }
6034 
wq_cpumask_show(struct device * dev,struct device_attribute * attr,char * buf)6035 static ssize_t wq_cpumask_show(struct device *dev,
6036 			       struct device_attribute *attr, char *buf)
6037 {
6038 	struct workqueue_struct *wq = dev_to_wq(dev);
6039 	int written;
6040 
6041 	mutex_lock(&wq->mutex);
6042 	written = scnprintf(buf, PAGE_SIZE, "%*pb\n",
6043 			    cpumask_pr_args(wq->unbound_attrs->cpumask));
6044 	mutex_unlock(&wq->mutex);
6045 	return written;
6046 }
6047 
wq_cpumask_store(struct device * dev,struct device_attribute * attr,const char * buf,size_t count)6048 static ssize_t wq_cpumask_store(struct device *dev,
6049 				struct device_attribute *attr,
6050 				const char *buf, size_t count)
6051 {
6052 	struct workqueue_struct *wq = dev_to_wq(dev);
6053 	struct workqueue_attrs *attrs;
6054 	int ret = -ENOMEM;
6055 
6056 	apply_wqattrs_lock();
6057 
6058 	attrs = wq_sysfs_prep_attrs(wq);
6059 	if (!attrs)
6060 		goto out_unlock;
6061 
6062 	ret = cpumask_parse(buf, attrs->cpumask);
6063 	if (!ret)
6064 		ret = apply_workqueue_attrs_locked(wq, attrs);
6065 
6066 out_unlock:
6067 	apply_wqattrs_unlock();
6068 	free_workqueue_attrs(attrs);
6069 	return ret ?: count;
6070 }
6071 
wq_affn_scope_show(struct device * dev,struct device_attribute * attr,char * buf)6072 static ssize_t wq_affn_scope_show(struct device *dev,
6073 				  struct device_attribute *attr, char *buf)
6074 {
6075 	struct workqueue_struct *wq = dev_to_wq(dev);
6076 	int written;
6077 
6078 	mutex_lock(&wq->mutex);
6079 	if (wq->unbound_attrs->affn_scope == WQ_AFFN_DFL)
6080 		written = scnprintf(buf, PAGE_SIZE, "%s (%s)\n",
6081 				    wq_affn_names[WQ_AFFN_DFL],
6082 				    wq_affn_names[wq_affn_dfl]);
6083 	else
6084 		written = scnprintf(buf, PAGE_SIZE, "%s\n",
6085 				    wq_affn_names[wq->unbound_attrs->affn_scope]);
6086 	mutex_unlock(&wq->mutex);
6087 
6088 	return written;
6089 }
6090 
wq_affn_scope_store(struct device * dev,struct device_attribute * attr,const char * buf,size_t count)6091 static ssize_t wq_affn_scope_store(struct device *dev,
6092 				   struct device_attribute *attr,
6093 				   const char *buf, size_t count)
6094 {
6095 	struct workqueue_struct *wq = dev_to_wq(dev);
6096 	struct workqueue_attrs *attrs;
6097 	int affn, ret = -ENOMEM;
6098 
6099 	affn = parse_affn_scope(buf);
6100 	if (affn < 0)
6101 		return affn;
6102 
6103 	apply_wqattrs_lock();
6104 	attrs = wq_sysfs_prep_attrs(wq);
6105 	if (attrs) {
6106 		attrs->affn_scope = affn;
6107 		ret = apply_workqueue_attrs_locked(wq, attrs);
6108 	}
6109 	apply_wqattrs_unlock();
6110 	free_workqueue_attrs(attrs);
6111 	return ret ?: count;
6112 }
6113 
wq_affinity_strict_show(struct device * dev,struct device_attribute * attr,char * buf)6114 static ssize_t wq_affinity_strict_show(struct device *dev,
6115 				       struct device_attribute *attr, char *buf)
6116 {
6117 	struct workqueue_struct *wq = dev_to_wq(dev);
6118 
6119 	return scnprintf(buf, PAGE_SIZE, "%d\n",
6120 			 wq->unbound_attrs->affn_strict);
6121 }
6122 
wq_affinity_strict_store(struct device * dev,struct device_attribute * attr,const char * buf,size_t count)6123 static ssize_t wq_affinity_strict_store(struct device *dev,
6124 					struct device_attribute *attr,
6125 					const char *buf, size_t count)
6126 {
6127 	struct workqueue_struct *wq = dev_to_wq(dev);
6128 	struct workqueue_attrs *attrs;
6129 	int v, ret = -ENOMEM;
6130 
6131 	if (sscanf(buf, "%d", &v) != 1)
6132 		return -EINVAL;
6133 
6134 	apply_wqattrs_lock();
6135 	attrs = wq_sysfs_prep_attrs(wq);
6136 	if (attrs) {
6137 		attrs->affn_strict = (bool)v;
6138 		ret = apply_workqueue_attrs_locked(wq, attrs);
6139 	}
6140 	apply_wqattrs_unlock();
6141 	free_workqueue_attrs(attrs);
6142 	return ret ?: count;
6143 }
6144 
6145 static struct device_attribute wq_sysfs_unbound_attrs[] = {
6146 	__ATTR(nice, 0644, wq_nice_show, wq_nice_store),
6147 	__ATTR(cpumask, 0644, wq_cpumask_show, wq_cpumask_store),
6148 	__ATTR(affinity_scope, 0644, wq_affn_scope_show, wq_affn_scope_store),
6149 	__ATTR(affinity_strict, 0644, wq_affinity_strict_show, wq_affinity_strict_store),
6150 	__ATTR_NULL,
6151 };
6152 
6153 static struct bus_type wq_subsys = {
6154 	.name				= "workqueue",
6155 	.dev_groups			= wq_sysfs_groups,
6156 };
6157 
wq_unbound_cpumask_show(struct device * dev,struct device_attribute * attr,char * buf)6158 static ssize_t wq_unbound_cpumask_show(struct device *dev,
6159 		struct device_attribute *attr, char *buf)
6160 {
6161 	int written;
6162 
6163 	mutex_lock(&wq_pool_mutex);
6164 	written = scnprintf(buf, PAGE_SIZE, "%*pb\n",
6165 			    cpumask_pr_args(wq_unbound_cpumask));
6166 	mutex_unlock(&wq_pool_mutex);
6167 
6168 	return written;
6169 }
6170 
wq_unbound_cpumask_store(struct device * dev,struct device_attribute * attr,const char * buf,size_t count)6171 static ssize_t wq_unbound_cpumask_store(struct device *dev,
6172 		struct device_attribute *attr, const char *buf, size_t count)
6173 {
6174 	cpumask_var_t cpumask;
6175 	int ret;
6176 
6177 	if (!zalloc_cpumask_var(&cpumask, GFP_KERNEL))
6178 		return -ENOMEM;
6179 
6180 	ret = cpumask_parse(buf, cpumask);
6181 	if (!ret)
6182 		ret = workqueue_set_unbound_cpumask(cpumask);
6183 
6184 	free_cpumask_var(cpumask);
6185 	return ret ? ret : count;
6186 }
6187 
6188 static struct device_attribute wq_sysfs_cpumask_attr =
6189 	__ATTR(cpumask, 0644, wq_unbound_cpumask_show,
6190 	       wq_unbound_cpumask_store);
6191 
wq_sysfs_init(void)6192 static int __init wq_sysfs_init(void)
6193 {
6194 	struct device *dev_root;
6195 	int err;
6196 
6197 	err = subsys_virtual_register(&wq_subsys, NULL);
6198 	if (err)
6199 		return err;
6200 
6201 	dev_root = bus_get_dev_root(&wq_subsys);
6202 	if (dev_root) {
6203 		err = device_create_file(dev_root, &wq_sysfs_cpumask_attr);
6204 		put_device(dev_root);
6205 	}
6206 	return err;
6207 }
6208 core_initcall(wq_sysfs_init);
6209 
wq_device_release(struct device * dev)6210 static void wq_device_release(struct device *dev)
6211 {
6212 	struct wq_device *wq_dev = container_of(dev, struct wq_device, dev);
6213 
6214 	kfree(wq_dev);
6215 }
6216 
6217 /**
6218  * workqueue_sysfs_register - make a workqueue visible in sysfs
6219  * @wq: the workqueue to register
6220  *
6221  * Expose @wq in sysfs under /sys/bus/workqueue/devices.
6222  * alloc_workqueue*() automatically calls this function if WQ_SYSFS is set
6223  * which is the preferred method.
6224  *
6225  * Workqueue user should use this function directly iff it wants to apply
6226  * workqueue_attrs before making the workqueue visible in sysfs; otherwise,
6227  * apply_workqueue_attrs() may race against userland updating the
6228  * attributes.
6229  *
6230  * Return: 0 on success, -errno on failure.
6231  */
workqueue_sysfs_register(struct workqueue_struct * wq)6232 int workqueue_sysfs_register(struct workqueue_struct *wq)
6233 {
6234 	struct wq_device *wq_dev;
6235 	int ret;
6236 
6237 	/*
6238 	 * Adjusting max_active or creating new pwqs by applying
6239 	 * attributes breaks ordering guarantee.  Disallow exposing ordered
6240 	 * workqueues.
6241 	 */
6242 	if (WARN_ON(wq->flags & __WQ_ORDERED_EXPLICIT))
6243 		return -EINVAL;
6244 
6245 	wq->wq_dev = wq_dev = kzalloc(sizeof(*wq_dev), GFP_KERNEL);
6246 	if (!wq_dev)
6247 		return -ENOMEM;
6248 
6249 	wq_dev->wq = wq;
6250 	wq_dev->dev.bus = &wq_subsys;
6251 	wq_dev->dev.release = wq_device_release;
6252 	dev_set_name(&wq_dev->dev, "%s", wq->name);
6253 
6254 	/*
6255 	 * unbound_attrs are created separately.  Suppress uevent until
6256 	 * everything is ready.
6257 	 */
6258 	dev_set_uevent_suppress(&wq_dev->dev, true);
6259 
6260 	ret = device_register(&wq_dev->dev);
6261 	if (ret) {
6262 		put_device(&wq_dev->dev);
6263 		wq->wq_dev = NULL;
6264 		return ret;
6265 	}
6266 
6267 	if (wq->flags & WQ_UNBOUND) {
6268 		struct device_attribute *attr;
6269 
6270 		for (attr = wq_sysfs_unbound_attrs; attr->attr.name; attr++) {
6271 			ret = device_create_file(&wq_dev->dev, attr);
6272 			if (ret) {
6273 				device_unregister(&wq_dev->dev);
6274 				wq->wq_dev = NULL;
6275 				return ret;
6276 			}
6277 		}
6278 	}
6279 
6280 	dev_set_uevent_suppress(&wq_dev->dev, false);
6281 	kobject_uevent(&wq_dev->dev.kobj, KOBJ_ADD);
6282 	return 0;
6283 }
6284 
6285 /**
6286  * workqueue_sysfs_unregister - undo workqueue_sysfs_register()
6287  * @wq: the workqueue to unregister
6288  *
6289  * If @wq is registered to sysfs by workqueue_sysfs_register(), unregister.
6290  */
workqueue_sysfs_unregister(struct workqueue_struct * wq)6291 static void workqueue_sysfs_unregister(struct workqueue_struct *wq)
6292 {
6293 	struct wq_device *wq_dev = wq->wq_dev;
6294 
6295 	if (!wq->wq_dev)
6296 		return;
6297 
6298 	wq->wq_dev = NULL;
6299 	device_unregister(&wq_dev->dev);
6300 }
6301 #else	/* CONFIG_SYSFS */
workqueue_sysfs_unregister(struct workqueue_struct * wq)6302 static void workqueue_sysfs_unregister(struct workqueue_struct *wq)	{ }
6303 #endif	/* CONFIG_SYSFS */
6304 
6305 /*
6306  * Workqueue watchdog.
6307  *
6308  * Stall may be caused by various bugs - missing WQ_MEM_RECLAIM, illegal
6309  * flush dependency, a concurrency managed work item which stays RUNNING
6310  * indefinitely.  Workqueue stalls can be very difficult to debug as the
6311  * usual warning mechanisms don't trigger and internal workqueue state is
6312  * largely opaque.
6313  *
6314  * Workqueue watchdog monitors all worker pools periodically and dumps
6315  * state if some pools failed to make forward progress for a while where
6316  * forward progress is defined as the first item on ->worklist changing.
6317  *
6318  * This mechanism is controlled through the kernel parameter
6319  * "workqueue.watchdog_thresh" which can be updated at runtime through the
6320  * corresponding sysfs parameter file.
6321  */
6322 #ifdef CONFIG_WQ_WATCHDOG
6323 
6324 static unsigned long wq_watchdog_thresh = 30;
6325 static struct timer_list wq_watchdog_timer;
6326 
6327 static unsigned long wq_watchdog_touched = INITIAL_JIFFIES;
6328 static DEFINE_PER_CPU(unsigned long, wq_watchdog_touched_cpu) = INITIAL_JIFFIES;
6329 
6330 /*
6331  * Show workers that might prevent the processing of pending work items.
6332  * The only candidates are CPU-bound workers in the running state.
6333  * Pending work items should be handled by another idle worker
6334  * in all other situations.
6335  */
show_cpu_pool_hog(struct worker_pool * pool)6336 static void show_cpu_pool_hog(struct worker_pool *pool)
6337 {
6338 	struct worker *worker;
6339 	unsigned long flags;
6340 	int bkt;
6341 
6342 	raw_spin_lock_irqsave(&pool->lock, flags);
6343 
6344 	hash_for_each(pool->busy_hash, bkt, worker, hentry) {
6345 		if (task_is_running(worker->task)) {
6346 			/*
6347 			 * Defer printing to avoid deadlocks in console
6348 			 * drivers that queue work while holding locks
6349 			 * also taken in their write paths.
6350 			 */
6351 			printk_deferred_enter();
6352 
6353 			pr_info("pool %d:\n", pool->id);
6354 			sched_show_task(worker->task);
6355 
6356 			printk_deferred_exit();
6357 		}
6358 	}
6359 
6360 	raw_spin_unlock_irqrestore(&pool->lock, flags);
6361 }
6362 
show_cpu_pools_hogs(void)6363 static void show_cpu_pools_hogs(void)
6364 {
6365 	struct worker_pool *pool;
6366 	int pi;
6367 
6368 	pr_info("Showing backtraces of running workers in stalled CPU-bound worker pools:\n");
6369 
6370 	rcu_read_lock();
6371 
6372 	for_each_pool(pool, pi) {
6373 		if (pool->cpu_stall)
6374 			show_cpu_pool_hog(pool);
6375 
6376 	}
6377 
6378 	rcu_read_unlock();
6379 }
6380 
wq_watchdog_reset_touched(void)6381 static void wq_watchdog_reset_touched(void)
6382 {
6383 	int cpu;
6384 
6385 	wq_watchdog_touched = jiffies;
6386 	for_each_possible_cpu(cpu)
6387 		per_cpu(wq_watchdog_touched_cpu, cpu) = jiffies;
6388 }
6389 
wq_watchdog_timer_fn(struct timer_list * unused)6390 static void wq_watchdog_timer_fn(struct timer_list *unused)
6391 {
6392 	unsigned long thresh = READ_ONCE(wq_watchdog_thresh) * HZ;
6393 	bool lockup_detected = false;
6394 	bool cpu_pool_stall = false;
6395 	unsigned long now = jiffies;
6396 	struct worker_pool *pool;
6397 	int pi;
6398 
6399 	if (!thresh)
6400 		return;
6401 
6402 	rcu_read_lock();
6403 
6404 	for_each_pool(pool, pi) {
6405 		unsigned long pool_ts, touched, ts;
6406 
6407 		pool->cpu_stall = false;
6408 		if (list_empty(&pool->worklist))
6409 			continue;
6410 
6411 		/*
6412 		 * If a virtual machine is stopped by the host it can look to
6413 		 * the watchdog like a stall.
6414 		 */
6415 		kvm_check_and_clear_guest_paused();
6416 
6417 		/* get the latest of pool and touched timestamps */
6418 		if (pool->cpu >= 0)
6419 			touched = READ_ONCE(per_cpu(wq_watchdog_touched_cpu, pool->cpu));
6420 		else
6421 			touched = READ_ONCE(wq_watchdog_touched);
6422 		pool_ts = READ_ONCE(pool->watchdog_ts);
6423 
6424 		if (time_after(pool_ts, touched))
6425 			ts = pool_ts;
6426 		else
6427 			ts = touched;
6428 
6429 		/* did we stall? */
6430 		if (time_after(now, ts + thresh)) {
6431 			lockup_detected = true;
6432 			if (pool->cpu >= 0) {
6433 				pool->cpu_stall = true;
6434 				cpu_pool_stall = true;
6435 			}
6436 			pr_emerg("BUG: workqueue lockup - pool");
6437 			pr_cont_pool_info(pool);
6438 			pr_cont(" stuck for %us!\n",
6439 				jiffies_to_msecs(now - pool_ts) / 1000);
6440 		}
6441 
6442 
6443 	}
6444 
6445 	rcu_read_unlock();
6446 
6447 	if (lockup_detected)
6448 		show_all_workqueues();
6449 
6450 	if (cpu_pool_stall)
6451 		show_cpu_pools_hogs();
6452 
6453 	wq_watchdog_reset_touched();
6454 	mod_timer(&wq_watchdog_timer, jiffies + thresh);
6455 }
6456 
wq_watchdog_touch(int cpu)6457 notrace void wq_watchdog_touch(int cpu)
6458 {
6459 	unsigned long thresh = READ_ONCE(wq_watchdog_thresh) * HZ;
6460 	unsigned long touch_ts = READ_ONCE(wq_watchdog_touched);
6461 	unsigned long now = jiffies;
6462 
6463 	if (cpu >= 0)
6464 		per_cpu(wq_watchdog_touched_cpu, cpu) = now;
6465 	else
6466 		WARN_ONCE(1, "%s should be called with valid CPU", __func__);
6467 
6468 	/* Don't unnecessarily store to global cacheline */
6469 	if (time_after(now, touch_ts + thresh / 4))
6470 		WRITE_ONCE(wq_watchdog_touched, jiffies);
6471 }
6472 
wq_watchdog_set_thresh(unsigned long thresh)6473 static void wq_watchdog_set_thresh(unsigned long thresh)
6474 {
6475 	wq_watchdog_thresh = 0;
6476 	del_timer_sync(&wq_watchdog_timer);
6477 
6478 	if (thresh) {
6479 		wq_watchdog_thresh = thresh;
6480 		wq_watchdog_reset_touched();
6481 		mod_timer(&wq_watchdog_timer, jiffies + thresh * HZ);
6482 	}
6483 }
6484 
wq_watchdog_param_set_thresh(const char * val,const struct kernel_param * kp)6485 static int wq_watchdog_param_set_thresh(const char *val,
6486 					const struct kernel_param *kp)
6487 {
6488 	unsigned long thresh;
6489 	int ret;
6490 
6491 	ret = kstrtoul(val, 0, &thresh);
6492 	if (ret)
6493 		return ret;
6494 
6495 	if (system_wq)
6496 		wq_watchdog_set_thresh(thresh);
6497 	else
6498 		wq_watchdog_thresh = thresh;
6499 
6500 	return 0;
6501 }
6502 
6503 static const struct kernel_param_ops wq_watchdog_thresh_ops = {
6504 	.set	= wq_watchdog_param_set_thresh,
6505 	.get	= param_get_ulong,
6506 };
6507 
6508 module_param_cb(watchdog_thresh, &wq_watchdog_thresh_ops, &wq_watchdog_thresh,
6509 		0644);
6510 
wq_watchdog_init(void)6511 static void wq_watchdog_init(void)
6512 {
6513 	timer_setup(&wq_watchdog_timer, wq_watchdog_timer_fn, TIMER_DEFERRABLE);
6514 	wq_watchdog_set_thresh(wq_watchdog_thresh);
6515 }
6516 
6517 #else	/* CONFIG_WQ_WATCHDOG */
6518 
wq_watchdog_init(void)6519 static inline void wq_watchdog_init(void) { }
6520 
6521 #endif	/* CONFIG_WQ_WATCHDOG */
6522 
restrict_unbound_cpumask(const char * name,const struct cpumask * mask)6523 static void __init restrict_unbound_cpumask(const char *name, const struct cpumask *mask)
6524 {
6525 	if (!cpumask_intersects(wq_unbound_cpumask, mask)) {
6526 		pr_warn("workqueue: Restricting unbound_cpumask (%*pb) with %s (%*pb) leaves no CPU, ignoring\n",
6527 			cpumask_pr_args(wq_unbound_cpumask), name, cpumask_pr_args(mask));
6528 		return;
6529 	}
6530 
6531 	cpumask_and(wq_unbound_cpumask, wq_unbound_cpumask, mask);
6532 }
6533 
6534 /**
6535  * workqueue_init_early - early init for workqueue subsystem
6536  *
6537  * This is the first step of three-staged workqueue subsystem initialization and
6538  * invoked as soon as the bare basics - memory allocation, cpumasks and idr are
6539  * up. It sets up all the data structures and system workqueues and allows early
6540  * boot code to create workqueues and queue/cancel work items. Actual work item
6541  * execution starts only after kthreads can be created and scheduled right
6542  * before early initcalls.
6543  */
workqueue_init_early(void)6544 void __init workqueue_init_early(void)
6545 {
6546 	struct wq_pod_type *pt = &wq_pod_types[WQ_AFFN_SYSTEM];
6547 	int std_nice[NR_STD_WORKER_POOLS] = { 0, HIGHPRI_NICE_LEVEL };
6548 	int i, cpu;
6549 
6550 	BUILD_BUG_ON(__alignof__(struct pool_workqueue) < __alignof__(long long));
6551 
6552 	BUG_ON(!alloc_cpumask_var(&wq_unbound_cpumask, GFP_KERNEL));
6553 	cpumask_copy(wq_unbound_cpumask, cpu_possible_mask);
6554 	restrict_unbound_cpumask("HK_TYPE_WQ", housekeeping_cpumask(HK_TYPE_WQ));
6555 	restrict_unbound_cpumask("HK_TYPE_DOMAIN", housekeeping_cpumask(HK_TYPE_DOMAIN));
6556 	if (!cpumask_empty(&wq_cmdline_cpumask))
6557 		restrict_unbound_cpumask("workqueue.unbound_cpus", &wq_cmdline_cpumask);
6558 
6559 	pwq_cache = KMEM_CACHE(pool_workqueue, SLAB_PANIC);
6560 
6561 	wq_update_pod_attrs_buf = alloc_workqueue_attrs();
6562 	BUG_ON(!wq_update_pod_attrs_buf);
6563 
6564 	/* initialize WQ_AFFN_SYSTEM pods */
6565 	pt->pod_cpus = kcalloc(1, sizeof(pt->pod_cpus[0]), GFP_KERNEL);
6566 	pt->pod_node = kcalloc(1, sizeof(pt->pod_node[0]), GFP_KERNEL);
6567 	pt->cpu_pod = kcalloc(nr_cpu_ids, sizeof(pt->cpu_pod[0]), GFP_KERNEL);
6568 	BUG_ON(!pt->pod_cpus || !pt->pod_node || !pt->cpu_pod);
6569 
6570 	BUG_ON(!zalloc_cpumask_var_node(&pt->pod_cpus[0], GFP_KERNEL, NUMA_NO_NODE));
6571 
6572 	pt->nr_pods = 1;
6573 	cpumask_copy(pt->pod_cpus[0], cpu_possible_mask);
6574 	pt->pod_node[0] = NUMA_NO_NODE;
6575 	pt->cpu_pod[0] = 0;
6576 
6577 	/* initialize CPU pools */
6578 	for_each_possible_cpu(cpu) {
6579 		struct worker_pool *pool;
6580 
6581 		i = 0;
6582 		for_each_cpu_worker_pool(pool, cpu) {
6583 			BUG_ON(init_worker_pool(pool));
6584 			pool->cpu = cpu;
6585 			cpumask_copy(pool->attrs->cpumask, cpumask_of(cpu));
6586 			cpumask_copy(pool->attrs->__pod_cpumask, cpumask_of(cpu));
6587 			pool->attrs->nice = std_nice[i++];
6588 			pool->attrs->affn_strict = true;
6589 			pool->node = cpu_to_node(cpu);
6590 
6591 			/* alloc pool ID */
6592 			mutex_lock(&wq_pool_mutex);
6593 			BUG_ON(worker_pool_assign_id(pool));
6594 			mutex_unlock(&wq_pool_mutex);
6595 		}
6596 	}
6597 
6598 	/* create default unbound and ordered wq attrs */
6599 	for (i = 0; i < NR_STD_WORKER_POOLS; i++) {
6600 		struct workqueue_attrs *attrs;
6601 
6602 		BUG_ON(!(attrs = alloc_workqueue_attrs()));
6603 		attrs->nice = std_nice[i];
6604 		unbound_std_wq_attrs[i] = attrs;
6605 
6606 		/*
6607 		 * An ordered wq should have only one pwq as ordering is
6608 		 * guaranteed by max_active which is enforced by pwqs.
6609 		 */
6610 		BUG_ON(!(attrs = alloc_workqueue_attrs()));
6611 		attrs->nice = std_nice[i];
6612 		attrs->ordered = true;
6613 		ordered_wq_attrs[i] = attrs;
6614 	}
6615 
6616 	system_wq = alloc_workqueue("events", 0, 0);
6617 	system_highpri_wq = alloc_workqueue("events_highpri", WQ_HIGHPRI, 0);
6618 	system_long_wq = alloc_workqueue("events_long", 0, 0);
6619 	system_unbound_wq = alloc_workqueue("events_unbound", WQ_UNBOUND,
6620 					    WQ_MAX_ACTIVE);
6621 	system_freezable_wq = alloc_workqueue("events_freezable",
6622 					      WQ_FREEZABLE, 0);
6623 	system_power_efficient_wq = alloc_workqueue("events_power_efficient",
6624 					      WQ_POWER_EFFICIENT, 0);
6625 	system_freezable_power_efficient_wq = alloc_workqueue("events_freezable_power_efficient",
6626 					      WQ_FREEZABLE | WQ_POWER_EFFICIENT,
6627 					      0);
6628 	BUG_ON(!system_wq || !system_highpri_wq || !system_long_wq ||
6629 	       !system_unbound_wq || !system_freezable_wq ||
6630 	       !system_power_efficient_wq ||
6631 	       !system_freezable_power_efficient_wq);
6632 }
6633 
wq_cpu_intensive_thresh_init(void)6634 static void __init wq_cpu_intensive_thresh_init(void)
6635 {
6636 	unsigned long thresh;
6637 	unsigned long bogo;
6638 
6639 	pwq_release_worker = kthread_create_worker(0, "pool_workqueue_release");
6640 	BUG_ON(IS_ERR(pwq_release_worker));
6641 
6642 	/* if the user set it to a specific value, keep it */
6643 	if (wq_cpu_intensive_thresh_us != ULONG_MAX)
6644 		return;
6645 
6646 	/*
6647 	 * The default of 10ms is derived from the fact that most modern (as of
6648 	 * 2023) processors can do a lot in 10ms and that it's just below what
6649 	 * most consider human-perceivable. However, the kernel also runs on a
6650 	 * lot slower CPUs including microcontrollers where the threshold is way
6651 	 * too low.
6652 	 *
6653 	 * Let's scale up the threshold upto 1 second if BogoMips is below 4000.
6654 	 * This is by no means accurate but it doesn't have to be. The mechanism
6655 	 * is still useful even when the threshold is fully scaled up. Also, as
6656 	 * the reports would usually be applicable to everyone, some machines
6657 	 * operating on longer thresholds won't significantly diminish their
6658 	 * usefulness.
6659 	 */
6660 	thresh = 10 * USEC_PER_MSEC;
6661 
6662 	/* see init/calibrate.c for lpj -> BogoMIPS calculation */
6663 	bogo = max_t(unsigned long, loops_per_jiffy / 500000 * HZ, 1);
6664 	if (bogo < 4000)
6665 		thresh = min_t(unsigned long, thresh * 4000 / bogo, USEC_PER_SEC);
6666 
6667 	pr_debug("wq_cpu_intensive_thresh: lpj=%lu BogoMIPS=%lu thresh_us=%lu\n",
6668 		 loops_per_jiffy, bogo, thresh);
6669 
6670 	wq_cpu_intensive_thresh_us = thresh;
6671 }
6672 
6673 /**
6674  * workqueue_init - bring workqueue subsystem fully online
6675  *
6676  * This is the second step of three-staged workqueue subsystem initialization
6677  * and invoked as soon as kthreads can be created and scheduled. Workqueues have
6678  * been created and work items queued on them, but there are no kworkers
6679  * executing the work items yet. Populate the worker pools with the initial
6680  * workers and enable future kworker creations.
6681  */
workqueue_init(void)6682 void __init workqueue_init(void)
6683 {
6684 	struct workqueue_struct *wq;
6685 	struct worker_pool *pool;
6686 	int cpu, bkt;
6687 
6688 	wq_cpu_intensive_thresh_init();
6689 
6690 	mutex_lock(&wq_pool_mutex);
6691 
6692 	/*
6693 	 * Per-cpu pools created earlier could be missing node hint. Fix them
6694 	 * up. Also, create a rescuer for workqueues that requested it.
6695 	 */
6696 	for_each_possible_cpu(cpu) {
6697 		for_each_cpu_worker_pool(pool, cpu) {
6698 			pool->node = cpu_to_node(cpu);
6699 		}
6700 	}
6701 
6702 	list_for_each_entry(wq, &workqueues, list) {
6703 		WARN(init_rescuer(wq),
6704 		     "workqueue: failed to create early rescuer for %s",
6705 		     wq->name);
6706 	}
6707 
6708 	mutex_unlock(&wq_pool_mutex);
6709 
6710 	/* create the initial workers */
6711 	for_each_online_cpu(cpu) {
6712 		for_each_cpu_worker_pool(pool, cpu) {
6713 			pool->flags &= ~POOL_DISASSOCIATED;
6714 			BUG_ON(!create_worker(pool));
6715 		}
6716 	}
6717 
6718 	hash_for_each(unbound_pool_hash, bkt, pool, hash_node)
6719 		BUG_ON(!create_worker(pool));
6720 
6721 	wq_online = true;
6722 	wq_watchdog_init();
6723 }
6724 
6725 /*
6726  * Initialize @pt by first initializing @pt->cpu_pod[] with pod IDs according to
6727  * @cpu_shares_pod(). Each subset of CPUs that share a pod is assigned a unique
6728  * and consecutive pod ID. The rest of @pt is initialized accordingly.
6729  */
init_pod_type(struct wq_pod_type * pt,bool (* cpus_share_pod)(int,int))6730 static void __init init_pod_type(struct wq_pod_type *pt,
6731 				 bool (*cpus_share_pod)(int, int))
6732 {
6733 	int cur, pre, cpu, pod;
6734 
6735 	pt->nr_pods = 0;
6736 
6737 	/* init @pt->cpu_pod[] according to @cpus_share_pod() */
6738 	pt->cpu_pod = kcalloc(nr_cpu_ids, sizeof(pt->cpu_pod[0]), GFP_KERNEL);
6739 	BUG_ON(!pt->cpu_pod);
6740 
6741 	for_each_possible_cpu(cur) {
6742 		for_each_possible_cpu(pre) {
6743 			if (pre >= cur) {
6744 				pt->cpu_pod[cur] = pt->nr_pods++;
6745 				break;
6746 			}
6747 			if (cpus_share_pod(cur, pre)) {
6748 				pt->cpu_pod[cur] = pt->cpu_pod[pre];
6749 				break;
6750 			}
6751 		}
6752 	}
6753 
6754 	/* init the rest to match @pt->cpu_pod[] */
6755 	pt->pod_cpus = kcalloc(pt->nr_pods, sizeof(pt->pod_cpus[0]), GFP_KERNEL);
6756 	pt->pod_node = kcalloc(pt->nr_pods, sizeof(pt->pod_node[0]), GFP_KERNEL);
6757 	BUG_ON(!pt->pod_cpus || !pt->pod_node);
6758 
6759 	for (pod = 0; pod < pt->nr_pods; pod++)
6760 		BUG_ON(!zalloc_cpumask_var(&pt->pod_cpus[pod], GFP_KERNEL));
6761 
6762 	for_each_possible_cpu(cpu) {
6763 		cpumask_set_cpu(cpu, pt->pod_cpus[pt->cpu_pod[cpu]]);
6764 		pt->pod_node[pt->cpu_pod[cpu]] = cpu_to_node(cpu);
6765 	}
6766 }
6767 
cpus_dont_share(int cpu0,int cpu1)6768 static bool __init cpus_dont_share(int cpu0, int cpu1)
6769 {
6770 	return false;
6771 }
6772 
cpus_share_smt(int cpu0,int cpu1)6773 static bool __init cpus_share_smt(int cpu0, int cpu1)
6774 {
6775 #ifdef CONFIG_SCHED_SMT
6776 	return cpumask_test_cpu(cpu0, cpu_smt_mask(cpu1));
6777 #else
6778 	return false;
6779 #endif
6780 }
6781 
cpus_share_numa(int cpu0,int cpu1)6782 static bool __init cpus_share_numa(int cpu0, int cpu1)
6783 {
6784 	return cpu_to_node(cpu0) == cpu_to_node(cpu1);
6785 }
6786 
6787 /**
6788  * workqueue_init_topology - initialize CPU pods for unbound workqueues
6789  *
6790  * This is the third step of there-staged workqueue subsystem initialization and
6791  * invoked after SMP and topology information are fully initialized. It
6792  * initializes the unbound CPU pods accordingly.
6793  */
workqueue_init_topology(void)6794 void __init workqueue_init_topology(void)
6795 {
6796 	struct workqueue_struct *wq;
6797 	int cpu;
6798 
6799 	init_pod_type(&wq_pod_types[WQ_AFFN_CPU], cpus_dont_share);
6800 	init_pod_type(&wq_pod_types[WQ_AFFN_SMT], cpus_share_smt);
6801 	init_pod_type(&wq_pod_types[WQ_AFFN_CACHE], cpus_share_cache);
6802 	init_pod_type(&wq_pod_types[WQ_AFFN_NUMA], cpus_share_numa);
6803 
6804 	mutex_lock(&wq_pool_mutex);
6805 
6806 	/*
6807 	 * Workqueues allocated earlier would have all CPUs sharing the default
6808 	 * worker pool. Explicitly call wq_update_pod() on all workqueue and CPU
6809 	 * combinations to apply per-pod sharing.
6810 	 */
6811 	list_for_each_entry(wq, &workqueues, list) {
6812 		for_each_online_cpu(cpu) {
6813 			wq_update_pod(wq, cpu, cpu, true);
6814 		}
6815 	}
6816 
6817 	mutex_unlock(&wq_pool_mutex);
6818 }
6819 
__warn_flushing_systemwide_wq(void)6820 void __warn_flushing_systemwide_wq(void)
6821 {
6822 	pr_warn("WARNING: Flushing system-wide workqueues will be prohibited in near future.\n");
6823 	dump_stack();
6824 }
6825 EXPORT_SYMBOL(__warn_flushing_systemwide_wq);
6826 
workqueue_unbound_cpus_setup(char * str)6827 static int __init workqueue_unbound_cpus_setup(char *str)
6828 {
6829 	if (cpulist_parse(str, &wq_cmdline_cpumask) < 0) {
6830 		cpumask_clear(&wq_cmdline_cpumask);
6831 		pr_warn("workqueue.unbound_cpus: incorrect CPU range, using default\n");
6832 	}
6833 
6834 	return 1;
6835 }
6836 __setup("workqueue.unbound_cpus=", workqueue_unbound_cpus_setup);
6837