xref: /openbmc/linux/kernel/rcu/rcu.h (revision 42bc47b3)
1  /*
2   * Read-Copy Update definitions shared among RCU implementations.
3   *
4   * This program is free software; you can redistribute it and/or modify
5   * it under the terms of the GNU General Public License as published by
6   * the Free Software Foundation; either version 2 of the License, or
7   * (at your option) any later version.
8   *
9   * This program is distributed in the hope that it will be useful,
10   * but WITHOUT ANY WARRANTY; without even the implied warranty of
11   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
12   * GNU General Public License for more details.
13   *
14   * You should have received a copy of the GNU General Public License
15   * along with this program; if not, you can access it online at
16   * http://www.gnu.org/licenses/gpl-2.0.html.
17   *
18   * Copyright IBM Corporation, 2011
19   *
20   * Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
21   */
22  
23  #ifndef __LINUX_RCU_H
24  #define __LINUX_RCU_H
25  
26  #include <trace/events/rcu.h>
27  #ifdef CONFIG_RCU_TRACE
28  #define RCU_TRACE(stmt) stmt
29  #else /* #ifdef CONFIG_RCU_TRACE */
30  #define RCU_TRACE(stmt)
31  #endif /* #else #ifdef CONFIG_RCU_TRACE */
32  
33  /* Offset to allow for unmatched rcu_irq_{enter,exit}(). */
34  #define DYNTICK_IRQ_NONIDLE	((LONG_MAX / 2) + 1)
35  
36  
37  /*
38   * Grace-period counter management.
39   */
40  
41  #define RCU_SEQ_CTR_SHIFT	2
42  #define RCU_SEQ_STATE_MASK	((1 << RCU_SEQ_CTR_SHIFT) - 1)
43  
44  /*
45   * Return the counter portion of a sequence number previously returned
46   * by rcu_seq_snap() or rcu_seq_current().
47   */
48  static inline unsigned long rcu_seq_ctr(unsigned long s)
49  {
50  	return s >> RCU_SEQ_CTR_SHIFT;
51  }
52  
53  /*
54   * Return the state portion of a sequence number previously returned
55   * by rcu_seq_snap() or rcu_seq_current().
56   */
57  static inline int rcu_seq_state(unsigned long s)
58  {
59  	return s & RCU_SEQ_STATE_MASK;
60  }
61  
62  /*
63   * Set the state portion of the pointed-to sequence number.
64   * The caller is responsible for preventing conflicting updates.
65   */
66  static inline void rcu_seq_set_state(unsigned long *sp, int newstate)
67  {
68  	WARN_ON_ONCE(newstate & ~RCU_SEQ_STATE_MASK);
69  	WRITE_ONCE(*sp, (*sp & ~RCU_SEQ_STATE_MASK) + newstate);
70  }
71  
72  /* Adjust sequence number for start of update-side operation. */
73  static inline void rcu_seq_start(unsigned long *sp)
74  {
75  	WRITE_ONCE(*sp, *sp + 1);
76  	smp_mb(); /* Ensure update-side operation after counter increment. */
77  	WARN_ON_ONCE(rcu_seq_state(*sp) != 1);
78  }
79  
80  /* Compute the end-of-grace-period value for the specified sequence number. */
81  static inline unsigned long rcu_seq_endval(unsigned long *sp)
82  {
83  	return (*sp | RCU_SEQ_STATE_MASK) + 1;
84  }
85  
86  /* Adjust sequence number for end of update-side operation. */
87  static inline void rcu_seq_end(unsigned long *sp)
88  {
89  	smp_mb(); /* Ensure update-side operation before counter increment. */
90  	WARN_ON_ONCE(!rcu_seq_state(*sp));
91  	WRITE_ONCE(*sp, rcu_seq_endval(sp));
92  }
93  
94  /* Take a snapshot of the update side's sequence number. */
95  static inline unsigned long rcu_seq_snap(unsigned long *sp)
96  {
97  	unsigned long s;
98  
99  	s = (READ_ONCE(*sp) + 2 * RCU_SEQ_STATE_MASK + 1) & ~RCU_SEQ_STATE_MASK;
100  	smp_mb(); /* Above access must not bleed into critical section. */
101  	return s;
102  }
103  
104  /* Return the current value the update side's sequence number, no ordering. */
105  static inline unsigned long rcu_seq_current(unsigned long *sp)
106  {
107  	return READ_ONCE(*sp);
108  }
109  
110  /*
111   * Given a snapshot from rcu_seq_snap(), determine whether or not a
112   * full update-side operation has occurred.
113   */
114  static inline bool rcu_seq_done(unsigned long *sp, unsigned long s)
115  {
116  	return ULONG_CMP_GE(READ_ONCE(*sp), s);
117  }
118  
119  /*
120   * debug_rcu_head_queue()/debug_rcu_head_unqueue() are used internally
121   * by call_rcu() and rcu callback execution, and are therefore not part of the
122   * RCU API. Leaving in rcupdate.h because they are used by all RCU flavors.
123   */
124  
125  #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
126  # define STATE_RCU_HEAD_READY	0
127  # define STATE_RCU_HEAD_QUEUED	1
128  
129  extern struct debug_obj_descr rcuhead_debug_descr;
130  
131  static inline int debug_rcu_head_queue(struct rcu_head *head)
132  {
133  	int r1;
134  
135  	r1 = debug_object_activate(head, &rcuhead_debug_descr);
136  	debug_object_active_state(head, &rcuhead_debug_descr,
137  				  STATE_RCU_HEAD_READY,
138  				  STATE_RCU_HEAD_QUEUED);
139  	return r1;
140  }
141  
142  static inline void debug_rcu_head_unqueue(struct rcu_head *head)
143  {
144  	debug_object_active_state(head, &rcuhead_debug_descr,
145  				  STATE_RCU_HEAD_QUEUED,
146  				  STATE_RCU_HEAD_READY);
147  	debug_object_deactivate(head, &rcuhead_debug_descr);
148  }
149  #else	/* !CONFIG_DEBUG_OBJECTS_RCU_HEAD */
150  static inline int debug_rcu_head_queue(struct rcu_head *head)
151  {
152  	return 0;
153  }
154  
155  static inline void debug_rcu_head_unqueue(struct rcu_head *head)
156  {
157  }
158  #endif	/* #else !CONFIG_DEBUG_OBJECTS_RCU_HEAD */
159  
160  void kfree(const void *);
161  
162  /*
163   * Reclaim the specified callback, either by invoking it (non-lazy case)
164   * or freeing it directly (lazy case).  Return true if lazy, false otherwise.
165   */
166  static inline bool __rcu_reclaim(const char *rn, struct rcu_head *head)
167  {
168  	unsigned long offset = (unsigned long)head->func;
169  
170  	rcu_lock_acquire(&rcu_callback_map);
171  	if (__is_kfree_rcu_offset(offset)) {
172  		RCU_TRACE(trace_rcu_invoke_kfree_callback(rn, head, offset);)
173  		kfree((void *)head - offset);
174  		rcu_lock_release(&rcu_callback_map);
175  		return true;
176  	} else {
177  		RCU_TRACE(trace_rcu_invoke_callback(rn, head);)
178  		head->func(head);
179  		rcu_lock_release(&rcu_callback_map);
180  		return false;
181  	}
182  }
183  
184  #ifdef CONFIG_RCU_STALL_COMMON
185  
186  extern int rcu_cpu_stall_suppress;
187  int rcu_jiffies_till_stall_check(void);
188  
189  #define rcu_ftrace_dump_stall_suppress() \
190  do { \
191  	if (!rcu_cpu_stall_suppress) \
192  		rcu_cpu_stall_suppress = 3; \
193  } while (0)
194  
195  #define rcu_ftrace_dump_stall_unsuppress() \
196  do { \
197  	if (rcu_cpu_stall_suppress == 3) \
198  		rcu_cpu_stall_suppress = 0; \
199  } while (0)
200  
201  #else /* #endif #ifdef CONFIG_RCU_STALL_COMMON */
202  #define rcu_ftrace_dump_stall_suppress()
203  #define rcu_ftrace_dump_stall_unsuppress()
204  #endif /* #ifdef CONFIG_RCU_STALL_COMMON */
205  
206  /*
207   * Strings used in tracepoints need to be exported via the
208   * tracing system such that tools like perf and trace-cmd can
209   * translate the string address pointers to actual text.
210   */
211  #define TPS(x)  tracepoint_string(x)
212  
213  /*
214   * Dump the ftrace buffer, but only one time per callsite per boot.
215   */
216  #define rcu_ftrace_dump(oops_dump_mode) \
217  do { \
218  	static atomic_t ___rfd_beenhere = ATOMIC_INIT(0); \
219  	\
220  	if (!atomic_read(&___rfd_beenhere) && \
221  	    !atomic_xchg(&___rfd_beenhere, 1)) { \
222  		tracing_off(); \
223  		rcu_ftrace_dump_stall_suppress(); \
224  		ftrace_dump(oops_dump_mode); \
225  		rcu_ftrace_dump_stall_unsuppress(); \
226  	} \
227  } while (0)
228  
229  void rcu_early_boot_tests(void);
230  void rcu_test_sync_prims(void);
231  
232  /*
233   * This function really isn't for public consumption, but RCU is special in
234   * that context switches can allow the state machine to make progress.
235   */
236  extern void resched_cpu(int cpu);
237  
238  #if defined(SRCU) || !defined(TINY_RCU)
239  
240  #include <linux/rcu_node_tree.h>
241  
242  extern int rcu_num_lvls;
243  extern int num_rcu_lvl[];
244  extern int rcu_num_nodes;
245  static bool rcu_fanout_exact;
246  static int rcu_fanout_leaf;
247  
248  /*
249   * Compute the per-level fanout, either using the exact fanout specified
250   * or balancing the tree, depending on the rcu_fanout_exact boot parameter.
251   */
252  static inline void rcu_init_levelspread(int *levelspread, const int *levelcnt)
253  {
254  	int i;
255  
256  	if (rcu_fanout_exact) {
257  		levelspread[rcu_num_lvls - 1] = rcu_fanout_leaf;
258  		for (i = rcu_num_lvls - 2; i >= 0; i--)
259  			levelspread[i] = RCU_FANOUT;
260  	} else {
261  		int ccur;
262  		int cprv;
263  
264  		cprv = nr_cpu_ids;
265  		for (i = rcu_num_lvls - 1; i >= 0; i--) {
266  			ccur = levelcnt[i];
267  			levelspread[i] = (cprv + ccur - 1) / ccur;
268  			cprv = ccur;
269  		}
270  	}
271  }
272  
273  /* Returns first leaf rcu_node of the specified RCU flavor. */
274  #define rcu_first_leaf_node(rsp) ((rsp)->level[rcu_num_lvls - 1])
275  
276  /* Is this rcu_node a leaf? */
277  #define rcu_is_leaf_node(rnp) ((rnp)->level == rcu_num_lvls - 1)
278  
279  /*
280   * Do a full breadth-first scan of the rcu_node structures for the
281   * specified rcu_state structure.
282   */
283  #define rcu_for_each_node_breadth_first(rsp, rnp) \
284  	for ((rnp) = &(rsp)->node[0]; \
285  	     (rnp) < &(rsp)->node[rcu_num_nodes]; (rnp)++)
286  
287  /*
288   * Do a breadth-first scan of the non-leaf rcu_node structures for the
289   * specified rcu_state structure.  Note that if there is a singleton
290   * rcu_node tree with but one rcu_node structure, this loop is a no-op.
291   */
292  #define rcu_for_each_nonleaf_node_breadth_first(rsp, rnp) \
293  	for ((rnp) = &(rsp)->node[0]; !rcu_is_leaf_node(rsp, rnp); (rnp)++)
294  
295  /*
296   * Scan the leaves of the rcu_node hierarchy for the specified rcu_state
297   * structure.  Note that if there is a singleton rcu_node tree with but
298   * one rcu_node structure, this loop -will- visit the rcu_node structure.
299   * It is still a leaf node, even if it is also the root node.
300   */
301  #define rcu_for_each_leaf_node(rsp, rnp) \
302  	for ((rnp) = rcu_first_leaf_node(rsp); \
303  	     (rnp) < &(rsp)->node[rcu_num_nodes]; (rnp)++)
304  
305  /*
306   * Iterate over all possible CPUs in a leaf RCU node.
307   */
308  #define for_each_leaf_node_possible_cpu(rnp, cpu) \
309  	for ((cpu) = cpumask_next((rnp)->grplo - 1, cpu_possible_mask); \
310  	     (cpu) <= rnp->grphi; \
311  	     (cpu) = cpumask_next((cpu), cpu_possible_mask))
312  
313  /*
314   * Iterate over all CPUs in a leaf RCU node's specified mask.
315   */
316  #define rcu_find_next_bit(rnp, cpu, mask) \
317  	((rnp)->grplo + find_next_bit(&(mask), BITS_PER_LONG, (cpu)))
318  #define for_each_leaf_node_cpu_mask(rnp, cpu, mask) \
319  	for ((cpu) = rcu_find_next_bit((rnp), 0, (mask)); \
320  	     (cpu) <= rnp->grphi; \
321  	     (cpu) = rcu_find_next_bit((rnp), (cpu) + 1 - (rnp->grplo), (mask)))
322  
323  /*
324   * Wrappers for the rcu_node::lock acquire and release.
325   *
326   * Because the rcu_nodes form a tree, the tree traversal locking will observe
327   * different lock values, this in turn means that an UNLOCK of one level
328   * followed by a LOCK of another level does not imply a full memory barrier;
329   * and most importantly transitivity is lost.
330   *
331   * In order to restore full ordering between tree levels, augment the regular
332   * lock acquire functions with smp_mb__after_unlock_lock().
333   *
334   * As ->lock of struct rcu_node is a __private field, therefore one should use
335   * these wrappers rather than directly call raw_spin_{lock,unlock}* on ->lock.
336   */
337  #define raw_spin_lock_rcu_node(p)					\
338  do {									\
339  	raw_spin_lock(&ACCESS_PRIVATE(p, lock));			\
340  	smp_mb__after_unlock_lock();					\
341  } while (0)
342  
343  #define raw_spin_unlock_rcu_node(p) raw_spin_unlock(&ACCESS_PRIVATE(p, lock))
344  
345  #define raw_spin_lock_irq_rcu_node(p)					\
346  do {									\
347  	raw_spin_lock_irq(&ACCESS_PRIVATE(p, lock));			\
348  	smp_mb__after_unlock_lock();					\
349  } while (0)
350  
351  #define raw_spin_unlock_irq_rcu_node(p)					\
352  	raw_spin_unlock_irq(&ACCESS_PRIVATE(p, lock))
353  
354  #define raw_spin_lock_irqsave_rcu_node(p, flags)			\
355  do {									\
356  	raw_spin_lock_irqsave(&ACCESS_PRIVATE(p, lock), flags);	\
357  	smp_mb__after_unlock_lock();					\
358  } while (0)
359  
360  #define raw_spin_unlock_irqrestore_rcu_node(p, flags)			\
361  	raw_spin_unlock_irqrestore(&ACCESS_PRIVATE(p, lock), flags)
362  
363  #define raw_spin_trylock_rcu_node(p)					\
364  ({									\
365  	bool ___locked = raw_spin_trylock(&ACCESS_PRIVATE(p, lock));	\
366  									\
367  	if (___locked)							\
368  		smp_mb__after_unlock_lock();				\
369  	___locked;							\
370  })
371  
372  #define raw_lockdep_assert_held_rcu_node(p)				\
373  	lockdep_assert_held(&ACCESS_PRIVATE(p, lock))
374  
375  #endif /* #if defined(SRCU) || !defined(TINY_RCU) */
376  
377  #ifdef CONFIG_TINY_RCU
378  /* Tiny RCU doesn't expedite, as its purpose in life is instead to be tiny. */
379  static inline bool rcu_gp_is_normal(void) { return true; }
380  static inline bool rcu_gp_is_expedited(void) { return false; }
381  static inline void rcu_expedite_gp(void) { }
382  static inline void rcu_unexpedite_gp(void) { }
383  static inline void rcu_request_urgent_qs_task(struct task_struct *t) { }
384  #else /* #ifdef CONFIG_TINY_RCU */
385  bool rcu_gp_is_normal(void);     /* Internal RCU use. */
386  bool rcu_gp_is_expedited(void);  /* Internal RCU use. */
387  void rcu_expedite_gp(void);
388  void rcu_unexpedite_gp(void);
389  void rcupdate_announce_bootup_oddness(void);
390  void rcu_request_urgent_qs_task(struct task_struct *t);
391  #endif /* #else #ifdef CONFIG_TINY_RCU */
392  
393  #define RCU_SCHEDULER_INACTIVE	0
394  #define RCU_SCHEDULER_INIT	1
395  #define RCU_SCHEDULER_RUNNING	2
396  
397  enum rcutorture_type {
398  	RCU_FLAVOR,
399  	RCU_BH_FLAVOR,
400  	RCU_SCHED_FLAVOR,
401  	RCU_TASKS_FLAVOR,
402  	SRCU_FLAVOR,
403  	INVALID_RCU_FLAVOR
404  };
405  
406  #if defined(CONFIG_TREE_RCU) || defined(CONFIG_PREEMPT_RCU)
407  void rcutorture_get_gp_data(enum rcutorture_type test_type, int *flags,
408  			    unsigned long *gpnum, unsigned long *completed);
409  void rcutorture_record_test_transition(void);
410  void rcutorture_record_progress(unsigned long vernum);
411  void do_trace_rcu_torture_read(const char *rcutorturename,
412  			       struct rcu_head *rhp,
413  			       unsigned long secs,
414  			       unsigned long c_old,
415  			       unsigned long c);
416  #else
417  static inline void rcutorture_get_gp_data(enum rcutorture_type test_type,
418  					  int *flags,
419  					  unsigned long *gpnum,
420  					  unsigned long *completed)
421  {
422  	*flags = 0;
423  	*gpnum = 0;
424  	*completed = 0;
425  }
426  static inline void rcutorture_record_test_transition(void) { }
427  static inline void rcutorture_record_progress(unsigned long vernum) { }
428  #ifdef CONFIG_RCU_TRACE
429  void do_trace_rcu_torture_read(const char *rcutorturename,
430  			       struct rcu_head *rhp,
431  			       unsigned long secs,
432  			       unsigned long c_old,
433  			       unsigned long c);
434  #else
435  #define do_trace_rcu_torture_read(rcutorturename, rhp, secs, c_old, c) \
436  	do { } while (0)
437  #endif
438  #endif
439  
440  #ifdef CONFIG_TINY_SRCU
441  
442  static inline void srcutorture_get_gp_data(enum rcutorture_type test_type,
443  					   struct srcu_struct *sp, int *flags,
444  					   unsigned long *gpnum,
445  					   unsigned long *completed)
446  {
447  	if (test_type != SRCU_FLAVOR)
448  		return;
449  	*flags = 0;
450  	*completed = sp->srcu_idx;
451  	*gpnum = *completed;
452  }
453  
454  #elif defined(CONFIG_TREE_SRCU)
455  
456  void srcutorture_get_gp_data(enum rcutorture_type test_type,
457  			     struct srcu_struct *sp, int *flags,
458  			     unsigned long *gpnum, unsigned long *completed);
459  
460  #endif
461  
462  #ifdef CONFIG_TINY_RCU
463  static inline unsigned long rcu_batches_started(void) { return 0; }
464  static inline unsigned long rcu_batches_started_bh(void) { return 0; }
465  static inline unsigned long rcu_batches_started_sched(void) { return 0; }
466  static inline unsigned long rcu_batches_completed(void) { return 0; }
467  static inline unsigned long rcu_batches_completed_bh(void) { return 0; }
468  static inline unsigned long rcu_batches_completed_sched(void) { return 0; }
469  static inline unsigned long rcu_exp_batches_completed(void) { return 0; }
470  static inline unsigned long rcu_exp_batches_completed_sched(void) { return 0; }
471  static inline unsigned long
472  srcu_batches_completed(struct srcu_struct *sp) { return 0; }
473  static inline void rcu_force_quiescent_state(void) { }
474  static inline void rcu_bh_force_quiescent_state(void) { }
475  static inline void rcu_sched_force_quiescent_state(void) { }
476  static inline void show_rcu_gp_kthreads(void) { }
477  #else /* #ifdef CONFIG_TINY_RCU */
478  extern unsigned long rcutorture_testseq;
479  extern unsigned long rcutorture_vernum;
480  unsigned long rcu_batches_started(void);
481  unsigned long rcu_batches_started_bh(void);
482  unsigned long rcu_batches_started_sched(void);
483  unsigned long rcu_batches_completed(void);
484  unsigned long rcu_batches_completed_bh(void);
485  unsigned long rcu_batches_completed_sched(void);
486  unsigned long rcu_exp_batches_completed(void);
487  unsigned long rcu_exp_batches_completed_sched(void);
488  unsigned long srcu_batches_completed(struct srcu_struct *sp);
489  void show_rcu_gp_kthreads(void);
490  void rcu_force_quiescent_state(void);
491  void rcu_bh_force_quiescent_state(void);
492  void rcu_sched_force_quiescent_state(void);
493  extern struct workqueue_struct *rcu_gp_wq;
494  extern struct workqueue_struct *rcu_par_gp_wq;
495  #endif /* #else #ifdef CONFIG_TINY_RCU */
496  
497  #ifdef CONFIG_RCU_NOCB_CPU
498  bool rcu_is_nocb_cpu(int cpu);
499  #else
500  static inline bool rcu_is_nocb_cpu(int cpu) { return false; }
501  #endif
502  
503  #endif /* __LINUX_RCU_H */
504