xref: /openbmc/linux/kernel/rcu/rcu.h (revision 27e45f2e)
1 /* SPDX-License-Identifier: GPL-2.0+ */
2 /*
3  * Read-Copy Update definitions shared among RCU implementations.
4  *
5  * Copyright IBM Corporation, 2011
6  *
7  * Author: Paul E. McKenney <paulmck@linux.ibm.com>
8  */
9 
10 #ifndef __LINUX_RCU_H
11 #define __LINUX_RCU_H
12 
13 #include <trace/events/rcu.h>
14 
15 /*
16  * Grace-period counter management.
17  */
18 
19 #define RCU_SEQ_CTR_SHIFT	2
20 #define RCU_SEQ_STATE_MASK	((1 << RCU_SEQ_CTR_SHIFT) - 1)
21 
22 /* Low-order bit definition for polled grace-period APIs. */
23 #define RCU_GET_STATE_COMPLETED	0x1
24 
25 extern int sysctl_sched_rt_runtime;
26 
27 /*
28  * Return the counter portion of a sequence number previously returned
29  * by rcu_seq_snap() or rcu_seq_current().
30  */
31 static inline unsigned long rcu_seq_ctr(unsigned long s)
32 {
33 	return s >> RCU_SEQ_CTR_SHIFT;
34 }
35 
36 /*
37  * Return the state portion of a sequence number previously returned
38  * by rcu_seq_snap() or rcu_seq_current().
39  */
40 static inline int rcu_seq_state(unsigned long s)
41 {
42 	return s & RCU_SEQ_STATE_MASK;
43 }
44 
45 /*
46  * Set the state portion of the pointed-to sequence number.
47  * The caller is responsible for preventing conflicting updates.
48  */
49 static inline void rcu_seq_set_state(unsigned long *sp, int newstate)
50 {
51 	WARN_ON_ONCE(newstate & ~RCU_SEQ_STATE_MASK);
52 	WRITE_ONCE(*sp, (*sp & ~RCU_SEQ_STATE_MASK) + newstate);
53 }
54 
55 /* Adjust sequence number for start of update-side operation. */
56 static inline void rcu_seq_start(unsigned long *sp)
57 {
58 	WRITE_ONCE(*sp, *sp + 1);
59 	smp_mb(); /* Ensure update-side operation after counter increment. */
60 	WARN_ON_ONCE(rcu_seq_state(*sp) != 1);
61 }
62 
63 /* Compute the end-of-grace-period value for the specified sequence number. */
64 static inline unsigned long rcu_seq_endval(unsigned long *sp)
65 {
66 	return (*sp | RCU_SEQ_STATE_MASK) + 1;
67 }
68 
69 /* Adjust sequence number for end of update-side operation. */
70 static inline void rcu_seq_end(unsigned long *sp)
71 {
72 	smp_mb(); /* Ensure update-side operation before counter increment. */
73 	WARN_ON_ONCE(!rcu_seq_state(*sp));
74 	WRITE_ONCE(*sp, rcu_seq_endval(sp));
75 }
76 
77 /*
78  * rcu_seq_snap - Take a snapshot of the update side's sequence number.
79  *
80  * This function returns the earliest value of the grace-period sequence number
81  * that will indicate that a full grace period has elapsed since the current
82  * time.  Once the grace-period sequence number has reached this value, it will
83  * be safe to invoke all callbacks that have been registered prior to the
84  * current time. This value is the current grace-period number plus two to the
85  * power of the number of low-order bits reserved for state, then rounded up to
86  * the next value in which the state bits are all zero.
87  */
88 static inline unsigned long rcu_seq_snap(unsigned long *sp)
89 {
90 	unsigned long s;
91 
92 	s = (READ_ONCE(*sp) + 2 * RCU_SEQ_STATE_MASK + 1) & ~RCU_SEQ_STATE_MASK;
93 	smp_mb(); /* Above access must not bleed into critical section. */
94 	return s;
95 }
96 
97 /* Return the current value the update side's sequence number, no ordering. */
98 static inline unsigned long rcu_seq_current(unsigned long *sp)
99 {
100 	return READ_ONCE(*sp);
101 }
102 
103 /*
104  * Given a snapshot from rcu_seq_snap(), determine whether or not the
105  * corresponding update-side operation has started.
106  */
107 static inline bool rcu_seq_started(unsigned long *sp, unsigned long s)
108 {
109 	return ULONG_CMP_LT((s - 1) & ~RCU_SEQ_STATE_MASK, READ_ONCE(*sp));
110 }
111 
112 /*
113  * Given a snapshot from rcu_seq_snap(), determine whether or not a
114  * full update-side operation has occurred.
115  */
116 static inline bool rcu_seq_done(unsigned long *sp, unsigned long s)
117 {
118 	return ULONG_CMP_GE(READ_ONCE(*sp), s);
119 }
120 
121 /*
122  * Given a snapshot from rcu_seq_snap(), determine whether or not a
123  * full update-side operation has occurred, but do not allow the
124  * (ULONG_MAX / 2) safety-factor/guard-band.
125  */
126 static inline bool rcu_seq_done_exact(unsigned long *sp, unsigned long s)
127 {
128 	unsigned long cur_s = READ_ONCE(*sp);
129 
130 	return ULONG_CMP_GE(cur_s, s) || ULONG_CMP_LT(cur_s, s - (2 * RCU_SEQ_STATE_MASK + 1));
131 }
132 
133 /*
134  * Has a grace period completed since the time the old gp_seq was collected?
135  */
136 static inline bool rcu_seq_completed_gp(unsigned long old, unsigned long new)
137 {
138 	return ULONG_CMP_LT(old, new & ~RCU_SEQ_STATE_MASK);
139 }
140 
141 /*
142  * Has a grace period started since the time the old gp_seq was collected?
143  */
144 static inline bool rcu_seq_new_gp(unsigned long old, unsigned long new)
145 {
146 	return ULONG_CMP_LT((old + RCU_SEQ_STATE_MASK) & ~RCU_SEQ_STATE_MASK,
147 			    new);
148 }
149 
150 /*
151  * Roughly how many full grace periods have elapsed between the collection
152  * of the two specified grace periods?
153  */
154 static inline unsigned long rcu_seq_diff(unsigned long new, unsigned long old)
155 {
156 	unsigned long rnd_diff;
157 
158 	if (old == new)
159 		return 0;
160 	/*
161 	 * Compute the number of grace periods (still shifted up), plus
162 	 * one if either of new and old is not an exact grace period.
163 	 */
164 	rnd_diff = (new & ~RCU_SEQ_STATE_MASK) -
165 		   ((old + RCU_SEQ_STATE_MASK) & ~RCU_SEQ_STATE_MASK) +
166 		   ((new & RCU_SEQ_STATE_MASK) || (old & RCU_SEQ_STATE_MASK));
167 	if (ULONG_CMP_GE(RCU_SEQ_STATE_MASK, rnd_diff))
168 		return 1; /* Definitely no grace period has elapsed. */
169 	return ((rnd_diff - RCU_SEQ_STATE_MASK - 1) >> RCU_SEQ_CTR_SHIFT) + 2;
170 }
171 
172 /*
173  * debug_rcu_head_queue()/debug_rcu_head_unqueue() are used internally
174  * by call_rcu() and rcu callback execution, and are therefore not part
175  * of the RCU API. These are in rcupdate.h because they are used by all
176  * RCU implementations.
177  */
178 
179 #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
180 # define STATE_RCU_HEAD_READY	0
181 # define STATE_RCU_HEAD_QUEUED	1
182 
183 extern const struct debug_obj_descr rcuhead_debug_descr;
184 
185 static inline int debug_rcu_head_queue(struct rcu_head *head)
186 {
187 	int r1;
188 
189 	r1 = debug_object_activate(head, &rcuhead_debug_descr);
190 	debug_object_active_state(head, &rcuhead_debug_descr,
191 				  STATE_RCU_HEAD_READY,
192 				  STATE_RCU_HEAD_QUEUED);
193 	return r1;
194 }
195 
196 static inline void debug_rcu_head_unqueue(struct rcu_head *head)
197 {
198 	debug_object_active_state(head, &rcuhead_debug_descr,
199 				  STATE_RCU_HEAD_QUEUED,
200 				  STATE_RCU_HEAD_READY);
201 	debug_object_deactivate(head, &rcuhead_debug_descr);
202 }
203 #else	/* !CONFIG_DEBUG_OBJECTS_RCU_HEAD */
204 static inline int debug_rcu_head_queue(struct rcu_head *head)
205 {
206 	return 0;
207 }
208 
209 static inline void debug_rcu_head_unqueue(struct rcu_head *head)
210 {
211 }
212 #endif	/* #else !CONFIG_DEBUG_OBJECTS_RCU_HEAD */
213 
214 extern int rcu_cpu_stall_suppress_at_boot;
215 
216 static inline bool rcu_stall_is_suppressed_at_boot(void)
217 {
218 	return rcu_cpu_stall_suppress_at_boot && !rcu_inkernel_boot_has_ended();
219 }
220 
221 #ifdef CONFIG_RCU_STALL_COMMON
222 
223 extern int rcu_cpu_stall_ftrace_dump;
224 extern int rcu_cpu_stall_suppress;
225 extern int rcu_cpu_stall_timeout;
226 extern int rcu_exp_cpu_stall_timeout;
227 int rcu_jiffies_till_stall_check(void);
228 int rcu_exp_jiffies_till_stall_check(void);
229 
230 static inline bool rcu_stall_is_suppressed(void)
231 {
232 	return rcu_stall_is_suppressed_at_boot() || rcu_cpu_stall_suppress;
233 }
234 
235 #define rcu_ftrace_dump_stall_suppress() \
236 do { \
237 	if (!rcu_cpu_stall_suppress) \
238 		rcu_cpu_stall_suppress = 3; \
239 } while (0)
240 
241 #define rcu_ftrace_dump_stall_unsuppress() \
242 do { \
243 	if (rcu_cpu_stall_suppress == 3) \
244 		rcu_cpu_stall_suppress = 0; \
245 } while (0)
246 
247 #else /* #endif #ifdef CONFIG_RCU_STALL_COMMON */
248 
249 static inline bool rcu_stall_is_suppressed(void)
250 {
251 	return rcu_stall_is_suppressed_at_boot();
252 }
253 #define rcu_ftrace_dump_stall_suppress()
254 #define rcu_ftrace_dump_stall_unsuppress()
255 #endif /* #ifdef CONFIG_RCU_STALL_COMMON */
256 
257 /*
258  * Strings used in tracepoints need to be exported via the
259  * tracing system such that tools like perf and trace-cmd can
260  * translate the string address pointers to actual text.
261  */
262 #define TPS(x)  tracepoint_string(x)
263 
264 /*
265  * Dump the ftrace buffer, but only one time per callsite per boot.
266  */
267 #define rcu_ftrace_dump(oops_dump_mode) \
268 do { \
269 	static atomic_t ___rfd_beenhere = ATOMIC_INIT(0); \
270 	\
271 	if (!atomic_read(&___rfd_beenhere) && \
272 	    !atomic_xchg(&___rfd_beenhere, 1)) { \
273 		tracing_off(); \
274 		rcu_ftrace_dump_stall_suppress(); \
275 		ftrace_dump(oops_dump_mode); \
276 		rcu_ftrace_dump_stall_unsuppress(); \
277 	} \
278 } while (0)
279 
280 void rcu_early_boot_tests(void);
281 void rcu_test_sync_prims(void);
282 
283 /*
284  * This function really isn't for public consumption, but RCU is special in
285  * that context switches can allow the state machine to make progress.
286  */
287 extern void resched_cpu(int cpu);
288 
289 #if !defined(CONFIG_TINY_RCU)
290 
291 #include <linux/rcu_node_tree.h>
292 
293 extern int rcu_num_lvls;
294 extern int num_rcu_lvl[];
295 extern int rcu_num_nodes;
296 static bool rcu_fanout_exact;
297 static int rcu_fanout_leaf;
298 
299 /*
300  * Compute the per-level fanout, either using the exact fanout specified
301  * or balancing the tree, depending on the rcu_fanout_exact boot parameter.
302  */
303 static inline void rcu_init_levelspread(int *levelspread, const int *levelcnt)
304 {
305 	int i;
306 
307 	for (i = 0; i < RCU_NUM_LVLS; i++)
308 		levelspread[i] = INT_MIN;
309 	if (rcu_fanout_exact) {
310 		levelspread[rcu_num_lvls - 1] = rcu_fanout_leaf;
311 		for (i = rcu_num_lvls - 2; i >= 0; i--)
312 			levelspread[i] = RCU_FANOUT;
313 	} else {
314 		int ccur;
315 		int cprv;
316 
317 		cprv = nr_cpu_ids;
318 		for (i = rcu_num_lvls - 1; i >= 0; i--) {
319 			ccur = levelcnt[i];
320 			levelspread[i] = (cprv + ccur - 1) / ccur;
321 			cprv = ccur;
322 		}
323 	}
324 }
325 
326 extern void rcu_init_geometry(void);
327 
328 /* Returns a pointer to the first leaf rcu_node structure. */
329 #define rcu_first_leaf_node() (rcu_state.level[rcu_num_lvls - 1])
330 
331 /* Is this rcu_node a leaf? */
332 #define rcu_is_leaf_node(rnp) ((rnp)->level == rcu_num_lvls - 1)
333 
334 /* Is this rcu_node the last leaf? */
335 #define rcu_is_last_leaf_node(rnp) ((rnp) == &rcu_state.node[rcu_num_nodes - 1])
336 
337 /*
338  * Do a full breadth-first scan of the {s,}rcu_node structures for the
339  * specified state structure (for SRCU) or the only rcu_state structure
340  * (for RCU).
341  */
342 #define srcu_for_each_node_breadth_first(sp, rnp) \
343 	for ((rnp) = &(sp)->node[0]; \
344 	     (rnp) < &(sp)->node[rcu_num_nodes]; (rnp)++)
345 #define rcu_for_each_node_breadth_first(rnp) \
346 	srcu_for_each_node_breadth_first(&rcu_state, rnp)
347 
348 /*
349  * Scan the leaves of the rcu_node hierarchy for the rcu_state structure.
350  * Note that if there is a singleton rcu_node tree with but one rcu_node
351  * structure, this loop -will- visit the rcu_node structure.  It is still
352  * a leaf node, even if it is also the root node.
353  */
354 #define rcu_for_each_leaf_node(rnp) \
355 	for ((rnp) = rcu_first_leaf_node(); \
356 	     (rnp) < &rcu_state.node[rcu_num_nodes]; (rnp)++)
357 
358 /*
359  * Iterate over all possible CPUs in a leaf RCU node.
360  */
361 #define for_each_leaf_node_possible_cpu(rnp, cpu) \
362 	for (WARN_ON_ONCE(!rcu_is_leaf_node(rnp)), \
363 	     (cpu) = cpumask_next((rnp)->grplo - 1, cpu_possible_mask); \
364 	     (cpu) <= rnp->grphi; \
365 	     (cpu) = cpumask_next((cpu), cpu_possible_mask))
366 
367 /*
368  * Iterate over all CPUs in a leaf RCU node's specified mask.
369  */
370 #define rcu_find_next_bit(rnp, cpu, mask) \
371 	((rnp)->grplo + find_next_bit(&(mask), BITS_PER_LONG, (cpu)))
372 #define for_each_leaf_node_cpu_mask(rnp, cpu, mask) \
373 	for (WARN_ON_ONCE(!rcu_is_leaf_node(rnp)), \
374 	     (cpu) = rcu_find_next_bit((rnp), 0, (mask)); \
375 	     (cpu) <= rnp->grphi; \
376 	     (cpu) = rcu_find_next_bit((rnp), (cpu) + 1 - (rnp->grplo), (mask)))
377 
378 #endif /* !defined(CONFIG_TINY_RCU) */
379 
380 #if !defined(CONFIG_TINY_RCU) || defined(CONFIG_TASKS_RCU_GENERIC)
381 
382 /*
383  * Wrappers for the rcu_node::lock acquire and release.
384  *
385  * Because the rcu_nodes form a tree, the tree traversal locking will observe
386  * different lock values, this in turn means that an UNLOCK of one level
387  * followed by a LOCK of another level does not imply a full memory barrier;
388  * and most importantly transitivity is lost.
389  *
390  * In order to restore full ordering between tree levels, augment the regular
391  * lock acquire functions with smp_mb__after_unlock_lock().
392  *
393  * As ->lock of struct rcu_node is a __private field, therefore one should use
394  * these wrappers rather than directly call raw_spin_{lock,unlock}* on ->lock.
395  */
396 #define raw_spin_lock_rcu_node(p)					\
397 do {									\
398 	raw_spin_lock(&ACCESS_PRIVATE(p, lock));			\
399 	smp_mb__after_unlock_lock();					\
400 } while (0)
401 
402 #define raw_spin_unlock_rcu_node(p)					\
403 do {									\
404 	lockdep_assert_irqs_disabled();					\
405 	raw_spin_unlock(&ACCESS_PRIVATE(p, lock));			\
406 } while (0)
407 
408 #define raw_spin_lock_irq_rcu_node(p)					\
409 do {									\
410 	raw_spin_lock_irq(&ACCESS_PRIVATE(p, lock));			\
411 	smp_mb__after_unlock_lock();					\
412 } while (0)
413 
414 #define raw_spin_unlock_irq_rcu_node(p)					\
415 do {									\
416 	lockdep_assert_irqs_disabled();					\
417 	raw_spin_unlock_irq(&ACCESS_PRIVATE(p, lock));			\
418 } while (0)
419 
420 #define raw_spin_lock_irqsave_rcu_node(p, flags)			\
421 do {									\
422 	raw_spin_lock_irqsave(&ACCESS_PRIVATE(p, lock), flags);	\
423 	smp_mb__after_unlock_lock();					\
424 } while (0)
425 
426 #define raw_spin_unlock_irqrestore_rcu_node(p, flags)			\
427 do {									\
428 	lockdep_assert_irqs_disabled();					\
429 	raw_spin_unlock_irqrestore(&ACCESS_PRIVATE(p, lock), flags);	\
430 } while (0)
431 
432 #define raw_spin_trylock_rcu_node(p)					\
433 ({									\
434 	bool ___locked = raw_spin_trylock(&ACCESS_PRIVATE(p, lock));	\
435 									\
436 	if (___locked)							\
437 		smp_mb__after_unlock_lock();				\
438 	___locked;							\
439 })
440 
441 #define raw_lockdep_assert_held_rcu_node(p)				\
442 	lockdep_assert_held(&ACCESS_PRIVATE(p, lock))
443 
444 #endif // #if !defined(CONFIG_TINY_RCU) || defined(CONFIG_TASKS_RCU_GENERIC)
445 
446 #ifdef CONFIG_TINY_RCU
447 /* Tiny RCU doesn't expedite, as its purpose in life is instead to be tiny. */
448 static inline bool rcu_gp_is_normal(void) { return true; }
449 static inline bool rcu_gp_is_expedited(void) { return false; }
450 static inline void rcu_expedite_gp(void) { }
451 static inline void rcu_unexpedite_gp(void) { }
452 static inline void rcu_request_urgent_qs_task(struct task_struct *t) { }
453 #else /* #ifdef CONFIG_TINY_RCU */
454 bool rcu_gp_is_normal(void);     /* Internal RCU use. */
455 bool rcu_gp_is_expedited(void);  /* Internal RCU use. */
456 void rcu_expedite_gp(void);
457 void rcu_unexpedite_gp(void);
458 void rcupdate_announce_bootup_oddness(void);
459 #ifdef CONFIG_TASKS_RCU_GENERIC
460 void show_rcu_tasks_gp_kthreads(void);
461 #else /* #ifdef CONFIG_TASKS_RCU_GENERIC */
462 static inline void show_rcu_tasks_gp_kthreads(void) {}
463 #endif /* #else #ifdef CONFIG_TASKS_RCU_GENERIC */
464 void rcu_request_urgent_qs_task(struct task_struct *t);
465 #endif /* #else #ifdef CONFIG_TINY_RCU */
466 
467 #define RCU_SCHEDULER_INACTIVE	0
468 #define RCU_SCHEDULER_INIT	1
469 #define RCU_SCHEDULER_RUNNING	2
470 
471 enum rcutorture_type {
472 	RCU_FLAVOR,
473 	RCU_TASKS_FLAVOR,
474 	RCU_TASKS_RUDE_FLAVOR,
475 	RCU_TASKS_TRACING_FLAVOR,
476 	RCU_TRIVIAL_FLAVOR,
477 	SRCU_FLAVOR,
478 	INVALID_RCU_FLAVOR
479 };
480 
481 #if defined(CONFIG_RCU_LAZY)
482 unsigned long rcu_lazy_get_jiffies_till_flush(void);
483 void rcu_lazy_set_jiffies_till_flush(unsigned long j);
484 #else
485 static inline unsigned long rcu_lazy_get_jiffies_till_flush(void) { return 0; }
486 static inline void rcu_lazy_set_jiffies_till_flush(unsigned long j) { }
487 #endif
488 
489 #if defined(CONFIG_TREE_RCU)
490 void rcutorture_get_gp_data(enum rcutorture_type test_type, int *flags,
491 			    unsigned long *gp_seq);
492 void do_trace_rcu_torture_read(const char *rcutorturename,
493 			       struct rcu_head *rhp,
494 			       unsigned long secs,
495 			       unsigned long c_old,
496 			       unsigned long c);
497 void rcu_gp_set_torture_wait(int duration);
498 #else
499 static inline void rcutorture_get_gp_data(enum rcutorture_type test_type,
500 					  int *flags, unsigned long *gp_seq)
501 {
502 	*flags = 0;
503 	*gp_seq = 0;
504 }
505 #ifdef CONFIG_RCU_TRACE
506 void do_trace_rcu_torture_read(const char *rcutorturename,
507 			       struct rcu_head *rhp,
508 			       unsigned long secs,
509 			       unsigned long c_old,
510 			       unsigned long c);
511 #else
512 #define do_trace_rcu_torture_read(rcutorturename, rhp, secs, c_old, c) \
513 	do { } while (0)
514 #endif
515 static inline void rcu_gp_set_torture_wait(int duration) { }
516 #endif
517 
518 #if IS_ENABLED(CONFIG_RCU_TORTURE_TEST) || IS_MODULE(CONFIG_RCU_TORTURE_TEST)
519 long rcutorture_sched_setaffinity(pid_t pid, const struct cpumask *in_mask);
520 #endif
521 
522 #ifdef CONFIG_TINY_SRCU
523 
524 static inline void srcutorture_get_gp_data(enum rcutorture_type test_type,
525 					   struct srcu_struct *sp, int *flags,
526 					   unsigned long *gp_seq)
527 {
528 	if (test_type != SRCU_FLAVOR)
529 		return;
530 	*flags = 0;
531 	*gp_seq = sp->srcu_idx;
532 }
533 
534 #elif defined(CONFIG_TREE_SRCU)
535 
536 void srcutorture_get_gp_data(enum rcutorture_type test_type,
537 			     struct srcu_struct *sp, int *flags,
538 			     unsigned long *gp_seq);
539 
540 #endif
541 
542 #ifdef CONFIG_TINY_RCU
543 static inline bool rcu_dynticks_zero_in_eqs(int cpu, int *vp) { return false; }
544 static inline unsigned long rcu_get_gp_seq(void) { return 0; }
545 static inline unsigned long rcu_exp_batches_completed(void) { return 0; }
546 static inline unsigned long
547 srcu_batches_completed(struct srcu_struct *sp) { return 0; }
548 static inline void rcu_force_quiescent_state(void) { }
549 static inline bool rcu_check_boost_fail(unsigned long gp_state, int *cpup) { return true; }
550 static inline void show_rcu_gp_kthreads(void) { }
551 static inline int rcu_get_gp_kthreads_prio(void) { return 0; }
552 static inline void rcu_fwd_progress_check(unsigned long j) { }
553 static inline void rcu_gp_slow_register(atomic_t *rgssp) { }
554 static inline void rcu_gp_slow_unregister(atomic_t *rgssp) { }
555 #else /* #ifdef CONFIG_TINY_RCU */
556 bool rcu_dynticks_zero_in_eqs(int cpu, int *vp);
557 unsigned long rcu_get_gp_seq(void);
558 unsigned long rcu_exp_batches_completed(void);
559 unsigned long srcu_batches_completed(struct srcu_struct *sp);
560 bool rcu_check_boost_fail(unsigned long gp_state, int *cpup);
561 void show_rcu_gp_kthreads(void);
562 int rcu_get_gp_kthreads_prio(void);
563 void rcu_fwd_progress_check(unsigned long j);
564 void rcu_force_quiescent_state(void);
565 extern struct workqueue_struct *rcu_gp_wq;
566 #ifdef CONFIG_RCU_EXP_KTHREAD
567 extern struct kthread_worker *rcu_exp_gp_kworker;
568 extern struct kthread_worker *rcu_exp_par_gp_kworker;
569 #else /* !CONFIG_RCU_EXP_KTHREAD */
570 extern struct workqueue_struct *rcu_par_gp_wq;
571 #endif /* CONFIG_RCU_EXP_KTHREAD */
572 void rcu_gp_slow_register(atomic_t *rgssp);
573 void rcu_gp_slow_unregister(atomic_t *rgssp);
574 #endif /* #else #ifdef CONFIG_TINY_RCU */
575 
576 #ifdef CONFIG_RCU_NOCB_CPU
577 void rcu_bind_current_to_nocb(void);
578 #else
579 static inline void rcu_bind_current_to_nocb(void) { }
580 #endif
581 
582 #if !defined(CONFIG_TINY_RCU) && defined(CONFIG_TASKS_RCU)
583 void show_rcu_tasks_classic_gp_kthread(void);
584 #else
585 static inline void show_rcu_tasks_classic_gp_kthread(void) {}
586 #endif
587 #if !defined(CONFIG_TINY_RCU) && defined(CONFIG_TASKS_RUDE_RCU)
588 void show_rcu_tasks_rude_gp_kthread(void);
589 #else
590 static inline void show_rcu_tasks_rude_gp_kthread(void) {}
591 #endif
592 #if !defined(CONFIG_TINY_RCU) && defined(CONFIG_TASKS_TRACE_RCU)
593 void show_rcu_tasks_trace_gp_kthread(void);
594 #else
595 static inline void show_rcu_tasks_trace_gp_kthread(void) {}
596 #endif
597 
598 #endif /* __LINUX_RCU_H */
599