Line data Source code
1 : /*
2 : * Read-Copy Update mechanism for mutual exclusion
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, 2001
19 : *
20 : * Author: Dipankar Sarma <dipankar@in.ibm.com>
21 : *
22 : * Based on the original work by Paul McKenney <paulmck@us.ibm.com>
23 : * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen.
24 : * Papers:
25 : * http://www.rdrop.com/users/paulmck/paper/rclockpdcsproof.pdf
26 : * http://lse.sourceforge.net/locking/rclock_OLS.2001.05.01c.sc.pdf (OLS2001)
27 : *
28 : * For detailed explanation of Read-Copy Update mechanism see -
29 : * http://lse.sourceforge.net/locking/rcupdate.html
30 : *
31 : */
32 :
33 : #ifndef __LINUX_RCUPDATE_H
34 : #define __LINUX_RCUPDATE_H
35 :
36 : #include <linux/types.h>
37 : #include <linux/cache.h>
38 : #include <linux/spinlock.h>
39 : #include <linux/threads.h>
40 : #include <linux/cpumask.h>
41 : #include <linux/seqlock.h>
42 : #include <linux/lockdep.h>
43 : #include <linux/completion.h>
44 : #include <linux/debugobjects.h>
45 : #include <linux/bug.h>
46 : #include <linux/compiler.h>
47 : #include <asm/barrier.h>
48 :
49 : extern int rcu_expedited; /* for sysctl */
50 : #ifdef CONFIG_RCU_TORTURE_TEST
51 : extern int rcutorture_runnable; /* for sysctl */
52 : #endif /* #ifdef CONFIG_RCU_TORTURE_TEST */
53 :
54 : enum rcutorture_type {
55 : RCU_FLAVOR,
56 : RCU_BH_FLAVOR,
57 : RCU_SCHED_FLAVOR,
58 : SRCU_FLAVOR,
59 : INVALID_RCU_FLAVOR
60 : };
61 :
62 : #if defined(CONFIG_TREE_RCU) || defined(CONFIG_TREE_PREEMPT_RCU)
63 : void rcutorture_get_gp_data(enum rcutorture_type test_type, int *flags,
64 : unsigned long *gpnum, unsigned long *completed);
65 : void rcutorture_record_test_transition(void);
66 : void rcutorture_record_progress(unsigned long vernum);
67 : void do_trace_rcu_torture_read(const char *rcutorturename,
68 : struct rcu_head *rhp,
69 : unsigned long secs,
70 : unsigned long c_old,
71 : unsigned long c);
72 : #else
73 : static inline void rcutorture_get_gp_data(enum rcutorture_type test_type,
74 : int *flags,
75 : unsigned long *gpnum,
76 : unsigned long *completed)
77 : {
78 : *flags = 0;
79 : *gpnum = 0;
80 : *completed = 0;
81 : }
82 : static inline void rcutorture_record_test_transition(void)
83 : {
84 : }
85 : static inline void rcutorture_record_progress(unsigned long vernum)
86 : {
87 : }
88 : #ifdef CONFIG_RCU_TRACE
89 : void do_trace_rcu_torture_read(const char *rcutorturename,
90 : struct rcu_head *rhp,
91 : unsigned long secs,
92 : unsigned long c_old,
93 : unsigned long c);
94 : #else
95 : #define do_trace_rcu_torture_read(rcutorturename, rhp, secs, c_old, c) \
96 : do { } while (0)
97 : #endif
98 : #endif
99 :
100 : #define UINT_CMP_GE(a, b) (UINT_MAX / 2 >= (a) - (b))
101 : #define UINT_CMP_LT(a, b) (UINT_MAX / 2 < (a) - (b))
102 : #define ULONG_CMP_GE(a, b) (ULONG_MAX / 2 >= (a) - (b))
103 : #define ULONG_CMP_LT(a, b) (ULONG_MAX / 2 < (a) - (b))
104 : #define ulong2long(a) (*(long *)(&(a)))
105 :
106 : /* Exported common interfaces */
107 :
108 : #ifdef CONFIG_PREEMPT_RCU
109 :
110 : /**
111 : * call_rcu() - Queue an RCU callback for invocation after a grace period.
112 : * @head: structure to be used for queueing the RCU updates.
113 : * @func: actual callback function to be invoked after the grace period
114 : *
115 : * The callback function will be invoked some time after a full grace
116 : * period elapses, in other words after all pre-existing RCU read-side
117 : * critical sections have completed. However, the callback function
118 : * might well execute concurrently with RCU read-side critical sections
119 : * that started after call_rcu() was invoked. RCU read-side critical
120 : * sections are delimited by rcu_read_lock() and rcu_read_unlock(),
121 : * and may be nested.
122 : *
123 : * Note that all CPUs must agree that the grace period extended beyond
124 : * all pre-existing RCU read-side critical section. On systems with more
125 : * than one CPU, this means that when "func()" is invoked, each CPU is
126 : * guaranteed to have executed a full memory barrier since the end of its
127 : * last RCU read-side critical section whose beginning preceded the call
128 : * to call_rcu(). It also means that each CPU executing an RCU read-side
129 : * critical section that continues beyond the start of "func()" must have
130 : * executed a memory barrier after the call_rcu() but before the beginning
131 : * of that RCU read-side critical section. Note that these guarantees
132 : * include CPUs that are offline, idle, or executing in user mode, as
133 : * well as CPUs that are executing in the kernel.
134 : *
135 : * Furthermore, if CPU A invoked call_rcu() and CPU B invoked the
136 : * resulting RCU callback function "func()", then both CPU A and CPU B are
137 : * guaranteed to execute a full memory barrier during the time interval
138 : * between the call to call_rcu() and the invocation of "func()" -- even
139 : * if CPU A and CPU B are the same CPU (but again only if the system has
140 : * more than one CPU).
141 : */
142 : void call_rcu(struct rcu_head *head,
143 : void (*func)(struct rcu_head *head));
144 :
145 : #else /* #ifdef CONFIG_PREEMPT_RCU */
146 :
147 : /* In classic RCU, call_rcu() is just call_rcu_sched(). */
148 : #define call_rcu call_rcu_sched
149 :
150 : #endif /* #else #ifdef CONFIG_PREEMPT_RCU */
151 :
152 : /**
153 : * call_rcu_bh() - Queue an RCU for invocation after a quicker grace period.
154 : * @head: structure to be used for queueing the RCU updates.
155 : * @func: actual callback function to be invoked after the grace period
156 : *
157 : * The callback function will be invoked some time after a full grace
158 : * period elapses, in other words after all currently executing RCU
159 : * read-side critical sections have completed. call_rcu_bh() assumes
160 : * that the read-side critical sections end on completion of a softirq
161 : * handler. This means that read-side critical sections in process
162 : * context must not be interrupted by softirqs. This interface is to be
163 : * used when most of the read-side critical sections are in softirq context.
164 : * RCU read-side critical sections are delimited by :
165 : * - rcu_read_lock() and rcu_read_unlock(), if in interrupt context.
166 : * OR
167 : * - rcu_read_lock_bh() and rcu_read_unlock_bh(), if in process context.
168 : * These may be nested.
169 : *
170 : * See the description of call_rcu() for more detailed information on
171 : * memory ordering guarantees.
172 : */
173 : void call_rcu_bh(struct rcu_head *head,
174 : void (*func)(struct rcu_head *head));
175 :
176 : /**
177 : * call_rcu_sched() - Queue an RCU for invocation after sched grace period.
178 : * @head: structure to be used for queueing the RCU updates.
179 : * @func: actual callback function to be invoked after the grace period
180 : *
181 : * The callback function will be invoked some time after a full grace
182 : * period elapses, in other words after all currently executing RCU
183 : * read-side critical sections have completed. call_rcu_sched() assumes
184 : * that the read-side critical sections end on enabling of preemption
185 : * or on voluntary preemption.
186 : * RCU read-side critical sections are delimited by :
187 : * - rcu_read_lock_sched() and rcu_read_unlock_sched(),
188 : * OR
189 : * anything that disables preemption.
190 : * These may be nested.
191 : *
192 : * See the description of call_rcu() for more detailed information on
193 : * memory ordering guarantees.
194 : */
195 : void call_rcu_sched(struct rcu_head *head,
196 : void (*func)(struct rcu_head *rcu));
197 :
198 : void synchronize_sched(void);
199 :
200 : #ifdef CONFIG_PREEMPT_RCU
201 :
202 : void __rcu_read_lock(void);
203 : void __rcu_read_unlock(void);
204 : void rcu_read_unlock_special(struct task_struct *t);
205 : void synchronize_rcu(void);
206 :
207 : /*
208 : * Defined as a macro as it is a very low level header included from
209 : * areas that don't even know about current. This gives the rcu_read_lock()
210 : * nesting depth, but makes sense only if CONFIG_PREEMPT_RCU -- in other
211 : * types of kernel builds, the rcu_read_lock() nesting depth is unknowable.
212 : */
213 : #define rcu_preempt_depth() (current->rcu_read_lock_nesting)
214 :
215 : #else /* #ifdef CONFIG_PREEMPT_RCU */
216 :
217 : static inline void __rcu_read_lock(void)
218 : {
219 5611392 : preempt_disable();
220 : }
221 :
222 : static inline void __rcu_read_unlock(void)
223 : {
224 5614468 : preempt_enable();
225 : }
226 :
227 0 : static inline void synchronize_rcu(void)
228 : {
229 221 : synchronize_sched();
230 0 : }
231 :
232 : static inline int rcu_preempt_depth(void)
233 : {
234 : return 0;
235 : }
236 :
237 : #endif /* #else #ifdef CONFIG_PREEMPT_RCU */
238 :
239 : /* Internal to kernel */
240 : void rcu_init(void);
241 : void rcu_sched_qs(int cpu);
242 : void rcu_bh_qs(int cpu);
243 : void rcu_check_callbacks(int cpu, int user);
244 : struct notifier_block;
245 : void rcu_idle_enter(void);
246 : void rcu_idle_exit(void);
247 : void rcu_irq_enter(void);
248 : void rcu_irq_exit(void);
249 :
250 : #ifdef CONFIG_RCU_STALL_COMMON
251 : void rcu_sysrq_start(void);
252 : void rcu_sysrq_end(void);
253 : #else /* #ifdef CONFIG_RCU_STALL_COMMON */
254 : static inline void rcu_sysrq_start(void)
255 : {
256 : }
257 : static inline void rcu_sysrq_end(void)
258 : {
259 : }
260 : #endif /* #else #ifdef CONFIG_RCU_STALL_COMMON */
261 :
262 : #ifdef CONFIG_RCU_USER_QS
263 : void rcu_user_enter(void);
264 : void rcu_user_exit(void);
265 : #else
266 : static inline void rcu_user_enter(void) { }
267 : static inline void rcu_user_exit(void) { }
268 : static inline void rcu_user_hooks_switch(struct task_struct *prev,
269 : struct task_struct *next) { }
270 : #endif /* CONFIG_RCU_USER_QS */
271 :
272 : /**
273 : * RCU_NONIDLE - Indicate idle-loop code that needs RCU readers
274 : * @a: Code that RCU needs to pay attention to.
275 : *
276 : * RCU, RCU-bh, and RCU-sched read-side critical sections are forbidden
277 : * in the inner idle loop, that is, between the rcu_idle_enter() and
278 : * the rcu_idle_exit() -- RCU will happily ignore any such read-side
279 : * critical sections. However, things like powertop need tracepoints
280 : * in the inner idle loop.
281 : *
282 : * This macro provides the way out: RCU_NONIDLE(do_something_with_RCU())
283 : * will tell RCU that it needs to pay attending, invoke its argument
284 : * (in this example, a call to the do_something_with_RCU() function),
285 : * and then tell RCU to go back to ignoring this CPU. It is permissible
286 : * to nest RCU_NONIDLE() wrappers, but the nesting level is currently
287 : * quite limited. If deeper nesting is required, it will be necessary
288 : * to adjust DYNTICK_TASK_NESTING_VALUE accordingly.
289 : */
290 : #define RCU_NONIDLE(a) \
291 : do { \
292 : rcu_irq_enter(); \
293 : do { a; } while (0); \
294 : rcu_irq_exit(); \
295 : } while (0)
296 :
297 : #if defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_RCU_TRACE) || defined(CONFIG_SMP)
298 : bool __rcu_is_watching(void);
299 : #endif /* #if defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_RCU_TRACE) || defined(CONFIG_SMP) */
300 :
301 : /*
302 : * Infrastructure to implement the synchronize_() primitives in
303 : * TREE_RCU and rcu_barrier_() primitives in TINY_RCU.
304 : */
305 :
306 : typedef void call_rcu_func_t(struct rcu_head *head,
307 : void (*func)(struct rcu_head *head));
308 : void wait_rcu_gp(call_rcu_func_t crf);
309 :
310 : #if defined(CONFIG_TREE_RCU) || defined(CONFIG_TREE_PREEMPT_RCU)
311 : #include <linux/rcutree.h>
312 : #elif defined(CONFIG_TINY_RCU)
313 : #include <linux/rcutiny.h>
314 : #else
315 : #error "Unknown RCU implementation specified to kernel configuration"
316 : #endif
317 :
318 : /*
319 : * init_rcu_head_on_stack()/destroy_rcu_head_on_stack() are needed for dynamic
320 : * initialization and destruction of rcu_head on the stack. rcu_head structures
321 : * allocated dynamically in the heap or defined statically don't need any
322 : * initialization.
323 : */
324 : #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
325 : void init_rcu_head(struct rcu_head *head);
326 : void destroy_rcu_head(struct rcu_head *head);
327 : void init_rcu_head_on_stack(struct rcu_head *head);
328 : void destroy_rcu_head_on_stack(struct rcu_head *head);
329 : #else /* !CONFIG_DEBUG_OBJECTS_RCU_HEAD */
330 : static inline void init_rcu_head(struct rcu_head *head)
331 : {
332 : }
333 :
334 : static inline void destroy_rcu_head(struct rcu_head *head)
335 : {
336 : }
337 :
338 : static inline void init_rcu_head_on_stack(struct rcu_head *head)
339 : {
340 : }
341 :
342 : static inline void destroy_rcu_head_on_stack(struct rcu_head *head)
343 : {
344 : }
345 : #endif /* #else !CONFIG_DEBUG_OBJECTS_RCU_HEAD */
346 :
347 : #if defined(CONFIG_HOTPLUG_CPU) && defined(CONFIG_PROVE_RCU)
348 : bool rcu_lockdep_current_cpu_online(void);
349 : #else /* #if defined(CONFIG_HOTPLUG_CPU) && defined(CONFIG_PROVE_RCU) */
350 : static inline bool rcu_lockdep_current_cpu_online(void)
351 : {
352 : return 1;
353 : }
354 : #endif /* #else #if defined(CONFIG_HOTPLUG_CPU) && defined(CONFIG_PROVE_RCU) */
355 :
356 : #ifdef CONFIG_DEBUG_LOCK_ALLOC
357 :
358 : static inline void rcu_lock_acquire(struct lockdep_map *map)
359 : {
360 : lock_acquire(map, 0, 0, 2, 0, NULL, _THIS_IP_);
361 : }
362 :
363 : static inline void rcu_lock_release(struct lockdep_map *map)
364 : {
365 : lock_release(map, 1, _THIS_IP_);
366 : }
367 :
368 : extern struct lockdep_map rcu_lock_map;
369 : extern struct lockdep_map rcu_bh_lock_map;
370 : extern struct lockdep_map rcu_sched_lock_map;
371 : extern struct lockdep_map rcu_callback_map;
372 : int debug_lockdep_rcu_enabled(void);
373 :
374 : /**
375 : * rcu_read_lock_held() - might we be in RCU read-side critical section?
376 : *
377 : * If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an RCU
378 : * read-side critical section. In absence of CONFIG_DEBUG_LOCK_ALLOC,
379 : * this assumes we are in an RCU read-side critical section unless it can
380 : * prove otherwise. This is useful for debug checks in functions that
381 : * require that they be called within an RCU read-side critical section.
382 : *
383 : * Checks debug_lockdep_rcu_enabled() to prevent false positives during boot
384 : * and while lockdep is disabled.
385 : *
386 : * Note that rcu_read_lock() and the matching rcu_read_unlock() must
387 : * occur in the same context, for example, it is illegal to invoke
388 : * rcu_read_unlock() in process context if the matching rcu_read_lock()
389 : * was invoked from within an irq handler.
390 : *
391 : * Note that rcu_read_lock() is disallowed if the CPU is either idle or
392 : * offline from an RCU perspective, so check for those as well.
393 : */
394 : static inline int rcu_read_lock_held(void)
395 : {
396 : if (!debug_lockdep_rcu_enabled())
397 : return 1;
398 : if (!rcu_is_watching())
399 : return 0;
400 : if (!rcu_lockdep_current_cpu_online())
401 : return 0;
402 : return lock_is_held(&rcu_lock_map);
403 : }
404 :
405 : /*
406 : * rcu_read_lock_bh_held() is defined out of line to avoid #include-file
407 : * hell.
408 : */
409 : int rcu_read_lock_bh_held(void);
410 :
411 : /**
412 : * rcu_read_lock_sched_held() - might we be in RCU-sched read-side critical section?
413 : *
414 : * If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an
415 : * RCU-sched read-side critical section. In absence of
416 : * CONFIG_DEBUG_LOCK_ALLOC, this assumes we are in an RCU-sched read-side
417 : * critical section unless it can prove otherwise. Note that disabling
418 : * of preemption (including disabling irqs) counts as an RCU-sched
419 : * read-side critical section. This is useful for debug checks in functions
420 : * that required that they be called within an RCU-sched read-side
421 : * critical section.
422 : *
423 : * Check debug_lockdep_rcu_enabled() to prevent false positives during boot
424 : * and while lockdep is disabled.
425 : *
426 : * Note that if the CPU is in the idle loop from an RCU point of
427 : * view (ie: that we are in the section between rcu_idle_enter() and
428 : * rcu_idle_exit()) then rcu_read_lock_held() returns false even if the CPU
429 : * did an rcu_read_lock(). The reason for this is that RCU ignores CPUs
430 : * that are in such a section, considering these as in extended quiescent
431 : * state, so such a CPU is effectively never in an RCU read-side critical
432 : * section regardless of what RCU primitives it invokes. This state of
433 : * affairs is required --- we need to keep an RCU-free window in idle
434 : * where the CPU may possibly enter into low power mode. This way we can
435 : * notice an extended quiescent state to other CPUs that started a grace
436 : * period. Otherwise we would delay any grace period as long as we run in
437 : * the idle task.
438 : *
439 : * Similarly, we avoid claiming an SRCU read lock held if the current
440 : * CPU is offline.
441 : */
442 : #ifdef CONFIG_PREEMPT_COUNT
443 : static inline int rcu_read_lock_sched_held(void)
444 : {
445 : int lockdep_opinion = 0;
446 :
447 : if (!debug_lockdep_rcu_enabled())
448 : return 1;
449 : if (!rcu_is_watching())
450 : return 0;
451 : if (!rcu_lockdep_current_cpu_online())
452 : return 0;
453 : if (debug_locks)
454 : lockdep_opinion = lock_is_held(&rcu_sched_lock_map);
455 : return lockdep_opinion || preempt_count() != 0 || irqs_disabled();
456 : }
457 : #else /* #ifdef CONFIG_PREEMPT_COUNT */
458 : static inline int rcu_read_lock_sched_held(void)
459 : {
460 : return 1;
461 : }
462 : #endif /* #else #ifdef CONFIG_PREEMPT_COUNT */
463 :
464 : #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
465 :
466 : # define rcu_lock_acquire(a) do { } while (0)
467 : # define rcu_lock_release(a) do { } while (0)
468 :
469 : static inline int rcu_read_lock_held(void)
470 : {
471 : return 1;
472 : }
473 :
474 : static inline int rcu_read_lock_bh_held(void)
475 : {
476 : return 1;
477 : }
478 :
479 : #ifdef CONFIG_PREEMPT_COUNT
480 : static inline int rcu_read_lock_sched_held(void)
481 : {
482 : return preempt_count() != 0 || irqs_disabled();
483 : }
484 : #else /* #ifdef CONFIG_PREEMPT_COUNT */
485 : static inline int rcu_read_lock_sched_held(void)
486 : {
487 : return 1;
488 : }
489 : #endif /* #else #ifdef CONFIG_PREEMPT_COUNT */
490 :
491 : #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
492 :
493 : #ifdef CONFIG_PROVE_RCU
494 :
495 : /**
496 : * rcu_lockdep_assert - emit lockdep splat if specified condition not met
497 : * @c: condition to check
498 : * @s: informative message
499 : */
500 : #define rcu_lockdep_assert(c, s) \
501 : do { \
502 : static bool __section(.data.unlikely) __warned; \
503 : if (debug_lockdep_rcu_enabled() && !__warned && !(c)) { \
504 : __warned = true; \
505 : lockdep_rcu_suspicious(__FILE__, __LINE__, s); \
506 : } \
507 : } while (0)
508 :
509 : #if defined(CONFIG_PROVE_RCU) && !defined(CONFIG_PREEMPT_RCU)
510 : static inline void rcu_preempt_sleep_check(void)
511 : {
512 : rcu_lockdep_assert(!lock_is_held(&rcu_lock_map),
513 : "Illegal context switch in RCU read-side critical section");
514 : }
515 : #else /* #ifdef CONFIG_PROVE_RCU */
516 : static inline void rcu_preempt_sleep_check(void)
517 : {
518 : }
519 : #endif /* #else #ifdef CONFIG_PROVE_RCU */
520 :
521 : #define rcu_sleep_check() \
522 : do { \
523 : rcu_preempt_sleep_check(); \
524 : rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map), \
525 : "Illegal context switch in RCU-bh read-side critical section"); \
526 : rcu_lockdep_assert(!lock_is_held(&rcu_sched_lock_map), \
527 : "Illegal context switch in RCU-sched read-side critical section"); \
528 : } while (0)
529 :
530 : #else /* #ifdef CONFIG_PROVE_RCU */
531 :
532 : #define rcu_lockdep_assert(c, s) do { } while (0)
533 : #define rcu_sleep_check() do { } while (0)
534 :
535 : #endif /* #else #ifdef CONFIG_PROVE_RCU */
536 :
537 : /*
538 : * Helper functions for rcu_dereference_check(), rcu_dereference_protected()
539 : * and rcu_assign_pointer(). Some of these could be folded into their
540 : * callers, but they are left separate in order to ease introduction of
541 : * multiple flavors of pointers to match the multiple flavors of RCU
542 : * (e.g., __rcu_bh, * __rcu_sched, and __srcu), should this make sense in
543 : * the future.
544 : */
545 :
546 : #ifdef __CHECKER__
547 : #define rcu_dereference_sparse(p, space) \
548 : ((void)(((typeof(*p) space *)p) == p))
549 : #else /* #ifdef __CHECKER__ */
550 : #define rcu_dereference_sparse(p, space)
551 : #endif /* #else #ifdef __CHECKER__ */
552 :
553 : #define __rcu_access_pointer(p, space) \
554 : ({ \
555 : typeof(*p) *_________p1 = (typeof(*p) *__force)ACCESS_ONCE(p); \
556 : rcu_dereference_sparse(p, space); \
557 : ((typeof(*p) __force __kernel *)(_________p1)); \
558 : })
559 : #define __rcu_dereference_check(p, c, space) \
560 : ({ \
561 : typeof(*p) *_________p1 = (typeof(*p) *__force)ACCESS_ONCE(p); \
562 : rcu_lockdep_assert(c, "suspicious rcu_dereference_check() usage"); \
563 : rcu_dereference_sparse(p, space); \
564 : smp_read_barrier_depends(); /* Dependency order vs. p above. */ \
565 : ((typeof(*p) __force __kernel *)(_________p1)); \
566 : })
567 : #define __rcu_dereference_protected(p, c, space) \
568 : ({ \
569 : rcu_lockdep_assert(c, "suspicious rcu_dereference_protected() usage"); \
570 : rcu_dereference_sparse(p, space); \
571 : ((typeof(*p) __force __kernel *)(p)); \
572 : })
573 :
574 : #define __rcu_access_index(p, space) \
575 : ({ \
576 : typeof(p) _________p1 = ACCESS_ONCE(p); \
577 : rcu_dereference_sparse(p, space); \
578 : (_________p1); \
579 : })
580 : #define __rcu_dereference_index_check(p, c) \
581 : ({ \
582 : typeof(p) _________p1 = ACCESS_ONCE(p); \
583 : rcu_lockdep_assert(c, \
584 : "suspicious rcu_dereference_index_check() usage"); \
585 : smp_read_barrier_depends(); /* Dependency order vs. p above. */ \
586 : (_________p1); \
587 : })
588 :
589 : /**
590 : * RCU_INITIALIZER() - statically initialize an RCU-protected global variable
591 : * @v: The value to statically initialize with.
592 : */
593 : #define RCU_INITIALIZER(v) (typeof(*(v)) __force __rcu *)(v)
594 :
595 : /**
596 : * rcu_assign_pointer() - assign to RCU-protected pointer
597 : * @p: pointer to assign to
598 : * @v: value to assign (publish)
599 : *
600 : * Assigns the specified value to the specified RCU-protected
601 : * pointer, ensuring that any concurrent RCU readers will see
602 : * any prior initialization.
603 : *
604 : * Inserts memory barriers on architectures that require them
605 : * (which is most of them), and also prevents the compiler from
606 : * reordering the code that initializes the structure after the pointer
607 : * assignment. More importantly, this call documents which pointers
608 : * will be dereferenced by RCU read-side code.
609 : *
610 : * In some special cases, you may use RCU_INIT_POINTER() instead
611 : * of rcu_assign_pointer(). RCU_INIT_POINTER() is a bit faster due
612 : * to the fact that it does not constrain either the CPU or the compiler.
613 : * That said, using RCU_INIT_POINTER() when you should have used
614 : * rcu_assign_pointer() is a very bad thing that results in
615 : * impossible-to-diagnose memory corruption. So please be careful.
616 : * See the RCU_INIT_POINTER() comment header for details.
617 : *
618 : * Note that rcu_assign_pointer() evaluates each of its arguments only
619 : * once, appearances notwithstanding. One of the "extra" evaluations
620 : * is in typeof() and the other visible only to sparse (__CHECKER__),
621 : * neither of which actually execute the argument. As with most cpp
622 : * macros, this execute-arguments-only-once property is important, so
623 : * please be careful when making changes to rcu_assign_pointer() and the
624 : * other macros that it invokes.
625 : */
626 : #define rcu_assign_pointer(p, v) smp_store_release(&p, RCU_INITIALIZER(v))
627 :
628 : /**
629 : * rcu_access_pointer() - fetch RCU pointer with no dereferencing
630 : * @p: The pointer to read
631 : *
632 : * Return the value of the specified RCU-protected pointer, but omit the
633 : * smp_read_barrier_depends() and keep the ACCESS_ONCE(). This is useful
634 : * when the value of this pointer is accessed, but the pointer is not
635 : * dereferenced, for example, when testing an RCU-protected pointer against
636 : * NULL. Although rcu_access_pointer() may also be used in cases where
637 : * update-side locks prevent the value of the pointer from changing, you
638 : * should instead use rcu_dereference_protected() for this use case.
639 : *
640 : * It is also permissible to use rcu_access_pointer() when read-side
641 : * access to the pointer was removed at least one grace period ago, as
642 : * is the case in the context of the RCU callback that is freeing up
643 : * the data, or after a synchronize_rcu() returns. This can be useful
644 : * when tearing down multi-linked structures after a grace period
645 : * has elapsed.
646 : */
647 : #define rcu_access_pointer(p) __rcu_access_pointer((p), __rcu)
648 :
649 : /**
650 : * rcu_dereference_check() - rcu_dereference with debug checking
651 : * @p: The pointer to read, prior to dereferencing
652 : * @c: The conditions under which the dereference will take place
653 : *
654 : * Do an rcu_dereference(), but check that the conditions under which the
655 : * dereference will take place are correct. Typically the conditions
656 : * indicate the various locking conditions that should be held at that
657 : * point. The check should return true if the conditions are satisfied.
658 : * An implicit check for being in an RCU read-side critical section
659 : * (rcu_read_lock()) is included.
660 : *
661 : * For example:
662 : *
663 : * bar = rcu_dereference_check(foo->bar, lockdep_is_held(&foo->lock));
664 : *
665 : * could be used to indicate to lockdep that foo->bar may only be dereferenced
666 : * if either rcu_read_lock() is held, or that the lock required to replace
667 : * the bar struct at foo->bar is held.
668 : *
669 : * Note that the list of conditions may also include indications of when a lock
670 : * need not be held, for example during initialisation or destruction of the
671 : * target struct:
672 : *
673 : * bar = rcu_dereference_check(foo->bar, lockdep_is_held(&foo->lock) ||
674 : * atomic_read(&foo->usage) == 0);
675 : *
676 : * Inserts memory barriers on architectures that require them
677 : * (currently only the Alpha), prevents the compiler from refetching
678 : * (and from merging fetches), and, more importantly, documents exactly
679 : * which pointers are protected by RCU and checks that the pointer is
680 : * annotated as __rcu.
681 : */
682 : #define rcu_dereference_check(p, c) \
683 : __rcu_dereference_check((p), rcu_read_lock_held() || (c), __rcu)
684 :
685 : /**
686 : * rcu_dereference_bh_check() - rcu_dereference_bh with debug checking
687 : * @p: The pointer to read, prior to dereferencing
688 : * @c: The conditions under which the dereference will take place
689 : *
690 : * This is the RCU-bh counterpart to rcu_dereference_check().
691 : */
692 : #define rcu_dereference_bh_check(p, c) \
693 : __rcu_dereference_check((p), rcu_read_lock_bh_held() || (c), __rcu)
694 :
695 : /**
696 : * rcu_dereference_sched_check() - rcu_dereference_sched with debug checking
697 : * @p: The pointer to read, prior to dereferencing
698 : * @c: The conditions under which the dereference will take place
699 : *
700 : * This is the RCU-sched counterpart to rcu_dereference_check().
701 : */
702 : #define rcu_dereference_sched_check(p, c) \
703 : __rcu_dereference_check((p), rcu_read_lock_sched_held() || (c), \
704 : __rcu)
705 :
706 : #define rcu_dereference_raw(p) rcu_dereference_check(p, 1) /*@@@ needed? @@@*/
707 :
708 : /*
709 : * The tracing infrastructure traces RCU (we want that), but unfortunately
710 : * some of the RCU checks causes tracing to lock up the system.
711 : *
712 : * The tracing version of rcu_dereference_raw() must not call
713 : * rcu_read_lock_held().
714 : */
715 : #define rcu_dereference_raw_notrace(p) __rcu_dereference_check((p), 1, __rcu)
716 :
717 : /**
718 : * rcu_access_index() - fetch RCU index with no dereferencing
719 : * @p: The index to read
720 : *
721 : * Return the value of the specified RCU-protected index, but omit the
722 : * smp_read_barrier_depends() and keep the ACCESS_ONCE(). This is useful
723 : * when the value of this index is accessed, but the index is not
724 : * dereferenced, for example, when testing an RCU-protected index against
725 : * -1. Although rcu_access_index() may also be used in cases where
726 : * update-side locks prevent the value of the index from changing, you
727 : * should instead use rcu_dereference_index_protected() for this use case.
728 : */
729 : #define rcu_access_index(p) __rcu_access_index((p), __rcu)
730 :
731 : /**
732 : * rcu_dereference_index_check() - rcu_dereference for indices with debug checking
733 : * @p: The pointer to read, prior to dereferencing
734 : * @c: The conditions under which the dereference will take place
735 : *
736 : * Similar to rcu_dereference_check(), but omits the sparse checking.
737 : * This allows rcu_dereference_index_check() to be used on integers,
738 : * which can then be used as array indices. Attempting to use
739 : * rcu_dereference_check() on an integer will give compiler warnings
740 : * because the sparse address-space mechanism relies on dereferencing
741 : * the RCU-protected pointer. Dereferencing integers is not something
742 : * that even gcc will put up with.
743 : *
744 : * Note that this function does not implicitly check for RCU read-side
745 : * critical sections. If this function gains lots of uses, it might
746 : * make sense to provide versions for each flavor of RCU, but it does
747 : * not make sense as of early 2010.
748 : */
749 : #define rcu_dereference_index_check(p, c) \
750 : __rcu_dereference_index_check((p), (c))
751 :
752 : /**
753 : * rcu_dereference_protected() - fetch RCU pointer when updates prevented
754 : * @p: The pointer to read, prior to dereferencing
755 : * @c: The conditions under which the dereference will take place
756 : *
757 : * Return the value of the specified RCU-protected pointer, but omit
758 : * both the smp_read_barrier_depends() and the ACCESS_ONCE(). This
759 : * is useful in cases where update-side locks prevent the value of the
760 : * pointer from changing. Please note that this primitive does -not-
761 : * prevent the compiler from repeating this reference or combining it
762 : * with other references, so it should not be used without protection
763 : * of appropriate locks.
764 : *
765 : * This function is only for update-side use. Using this function
766 : * when protected only by rcu_read_lock() will result in infrequent
767 : * but very ugly failures.
768 : */
769 : #define rcu_dereference_protected(p, c) \
770 : __rcu_dereference_protected((p), (c), __rcu)
771 :
772 :
773 : /**
774 : * rcu_dereference() - fetch RCU-protected pointer for dereferencing
775 : * @p: The pointer to read, prior to dereferencing
776 : *
777 : * This is a simple wrapper around rcu_dereference_check().
778 : */
779 : #define rcu_dereference(p) rcu_dereference_check(p, 0)
780 :
781 : /**
782 : * rcu_dereference_bh() - fetch an RCU-bh-protected pointer for dereferencing
783 : * @p: The pointer to read, prior to dereferencing
784 : *
785 : * Makes rcu_dereference_check() do the dirty work.
786 : */
787 : #define rcu_dereference_bh(p) rcu_dereference_bh_check(p, 0)
788 :
789 : /**
790 : * rcu_dereference_sched() - fetch RCU-sched-protected pointer for dereferencing
791 : * @p: The pointer to read, prior to dereferencing
792 : *
793 : * Makes rcu_dereference_check() do the dirty work.
794 : */
795 : #define rcu_dereference_sched(p) rcu_dereference_sched_check(p, 0)
796 :
797 : /**
798 : * rcu_read_lock() - mark the beginning of an RCU read-side critical section
799 : *
800 : * When synchronize_rcu() is invoked on one CPU while other CPUs
801 : * are within RCU read-side critical sections, then the
802 : * synchronize_rcu() is guaranteed to block until after all the other
803 : * CPUs exit their critical sections. Similarly, if call_rcu() is invoked
804 : * on one CPU while other CPUs are within RCU read-side critical
805 : * sections, invocation of the corresponding RCU callback is deferred
806 : * until after the all the other CPUs exit their critical sections.
807 : *
808 : * Note, however, that RCU callbacks are permitted to run concurrently
809 : * with new RCU read-side critical sections. One way that this can happen
810 : * is via the following sequence of events: (1) CPU 0 enters an RCU
811 : * read-side critical section, (2) CPU 1 invokes call_rcu() to register
812 : * an RCU callback, (3) CPU 0 exits the RCU read-side critical section,
813 : * (4) CPU 2 enters a RCU read-side critical section, (5) the RCU
814 : * callback is invoked. This is legal, because the RCU read-side critical
815 : * section that was running concurrently with the call_rcu() (and which
816 : * therefore might be referencing something that the corresponding RCU
817 : * callback would free up) has completed before the corresponding
818 : * RCU callback is invoked.
819 : *
820 : * RCU read-side critical sections may be nested. Any deferred actions
821 : * will be deferred until the outermost RCU read-side critical section
822 : * completes.
823 : *
824 : * You can avoid reading and understanding the next paragraph by
825 : * following this rule: don't put anything in an rcu_read_lock() RCU
826 : * read-side critical section that would block in a !PREEMPT kernel.
827 : * But if you want the full story, read on!
828 : *
829 : * In non-preemptible RCU implementations (TREE_RCU and TINY_RCU),
830 : * it is illegal to block while in an RCU read-side critical section.
831 : * In preemptible RCU implementations (TREE_PREEMPT_RCU) in CONFIG_PREEMPT
832 : * kernel builds, RCU read-side critical sections may be preempted,
833 : * but explicit blocking is illegal. Finally, in preemptible RCU
834 : * implementations in real-time (with -rt patchset) kernel builds, RCU
835 : * read-side critical sections may be preempted and they may also block, but
836 : * only when acquiring spinlocks that are subject to priority inheritance.
837 : */
838 : static inline void rcu_read_lock(void)
839 : {
840 : __rcu_read_lock();
841 : __acquire(RCU);
842 : rcu_lock_acquire(&rcu_lock_map);
843 : rcu_lockdep_assert(rcu_is_watching(),
844 : "rcu_read_lock() used illegally while idle");
845 : }
846 :
847 : /*
848 : * So where is rcu_write_lock()? It does not exist, as there is no
849 : * way for writers to lock out RCU readers. This is a feature, not
850 : * a bug -- this property is what provides RCU's performance benefits.
851 : * Of course, writers must coordinate with each other. The normal
852 : * spinlock primitives work well for this, but any other technique may be
853 : * used as well. RCU does not care how the writers keep out of each
854 : * others' way, as long as they do so.
855 : */
856 :
857 : /**
858 : * rcu_read_unlock() - marks the end of an RCU read-side critical section.
859 : *
860 : * In most situations, rcu_read_unlock() is immune from deadlock.
861 : * However, in kernels built with CONFIG_RCU_BOOST, rcu_read_unlock()
862 : * is responsible for deboosting, which it does via rt_mutex_unlock().
863 : * Unfortunately, this function acquires the scheduler's runqueue and
864 : * priority-inheritance spinlocks. This means that deadlock could result
865 : * if the caller of rcu_read_unlock() already holds one of these locks or
866 : * any lock that is ever acquired while holding them.
867 : *
868 : * That said, RCU readers are never priority boosted unless they were
869 : * preempted. Therefore, one way to avoid deadlock is to make sure
870 : * that preemption never happens within any RCU read-side critical
871 : * section whose outermost rcu_read_unlock() is called with one of
872 : * rt_mutex_unlock()'s locks held. Such preemption can be avoided in
873 : * a number of ways, for example, by invoking preempt_disable() before
874 : * critical section's outermost rcu_read_lock().
875 : *
876 : * Given that the set of locks acquired by rt_mutex_unlock() might change
877 : * at any time, a somewhat more future-proofed approach is to make sure
878 : * that that preemption never happens within any RCU read-side critical
879 : * section whose outermost rcu_read_unlock() is called with irqs disabled.
880 : * This approach relies on the fact that rt_mutex_unlock() currently only
881 : * acquires irq-disabled locks.
882 : *
883 : * The second of these two approaches is best in most situations,
884 : * however, the first approach can also be useful, at least to those
885 : * developers willing to keep abreast of the set of locks acquired by
886 : * rt_mutex_unlock().
887 : *
888 : * See rcu_read_lock() for more information.
889 : */
890 : static inline void rcu_read_unlock(void)
891 : {
892 : rcu_lockdep_assert(rcu_is_watching(),
893 : "rcu_read_unlock() used illegally while idle");
894 : rcu_lock_release(&rcu_lock_map);
895 : __release(RCU);
896 : __rcu_read_unlock();
897 : }
898 :
899 : /**
900 : * rcu_read_lock_bh() - mark the beginning of an RCU-bh critical section
901 : *
902 : * This is equivalent of rcu_read_lock(), but to be used when updates
903 : * are being done using call_rcu_bh() or synchronize_rcu_bh(). Since
904 : * both call_rcu_bh() and synchronize_rcu_bh() consider completion of a
905 : * softirq handler to be a quiescent state, a process in RCU read-side
906 : * critical section must be protected by disabling softirqs. Read-side
907 : * critical sections in interrupt context can use just rcu_read_lock(),
908 : * though this should at least be commented to avoid confusing people
909 : * reading the code.
910 : *
911 : * Note that rcu_read_lock_bh() and the matching rcu_read_unlock_bh()
912 : * must occur in the same context, for example, it is illegal to invoke
913 : * rcu_read_unlock_bh() from one task if the matching rcu_read_lock_bh()
914 : * was invoked from some other task.
915 : */
916 : static inline void rcu_read_lock_bh(void)
917 : {
918 : local_bh_disable();
919 : __acquire(RCU_BH);
920 : rcu_lock_acquire(&rcu_bh_lock_map);
921 : rcu_lockdep_assert(rcu_is_watching(),
922 : "rcu_read_lock_bh() used illegally while idle");
923 : }
924 :
925 : /*
926 : * rcu_read_unlock_bh - marks the end of a softirq-only RCU critical section
927 : *
928 : * See rcu_read_lock_bh() for more information.
929 : */
930 : static inline void rcu_read_unlock_bh(void)
931 : {
932 : rcu_lockdep_assert(rcu_is_watching(),
933 : "rcu_read_unlock_bh() used illegally while idle");
934 : rcu_lock_release(&rcu_bh_lock_map);
935 : __release(RCU_BH);
936 : local_bh_enable();
937 : }
938 :
939 : /**
940 : * rcu_read_lock_sched() - mark the beginning of a RCU-sched critical section
941 : *
942 : * This is equivalent of rcu_read_lock(), but to be used when updates
943 : * are being done using call_rcu_sched() or synchronize_rcu_sched().
944 : * Read-side critical sections can also be introduced by anything that
945 : * disables preemption, including local_irq_disable() and friends.
946 : *
947 : * Note that rcu_read_lock_sched() and the matching rcu_read_unlock_sched()
948 : * must occur in the same context, for example, it is illegal to invoke
949 : * rcu_read_unlock_sched() from process context if the matching
950 : * rcu_read_lock_sched() was invoked from an NMI handler.
951 : */
952 : static inline void rcu_read_lock_sched(void)
953 : {
954 : preempt_disable();
955 : __acquire(RCU_SCHED);
956 : rcu_lock_acquire(&rcu_sched_lock_map);
957 : rcu_lockdep_assert(rcu_is_watching(),
958 : "rcu_read_lock_sched() used illegally while idle");
959 : }
960 :
961 : /* Used by lockdep and tracing: cannot be traced, cannot call lockdep. */
962 : static inline notrace void rcu_read_lock_sched_notrace(void)
963 : {
964 0 : preempt_disable_notrace();
965 : __acquire(RCU_SCHED);
966 : }
967 :
968 : /*
969 : * rcu_read_unlock_sched - marks the end of a RCU-classic critical section
970 : *
971 : * See rcu_read_lock_sched for more information.
972 : */
973 : static inline void rcu_read_unlock_sched(void)
974 : {
975 : rcu_lockdep_assert(rcu_is_watching(),
976 : "rcu_read_unlock_sched() used illegally while idle");
977 : rcu_lock_release(&rcu_sched_lock_map);
978 : __release(RCU_SCHED);
979 : preempt_enable();
980 : }
981 :
982 : /* Used by lockdep and tracing: cannot be traced, cannot call lockdep. */
983 : static inline notrace void rcu_read_unlock_sched_notrace(void)
984 : {
985 : __release(RCU_SCHED);
986 0 : preempt_enable_notrace();
987 : }
988 :
989 : /**
990 : * RCU_INIT_POINTER() - initialize an RCU protected pointer
991 : *
992 : * Initialize an RCU-protected pointer in special cases where readers
993 : * do not need ordering constraints on the CPU or the compiler. These
994 : * special cases are:
995 : *
996 : * 1. This use of RCU_INIT_POINTER() is NULLing out the pointer -or-
997 : * 2. The caller has taken whatever steps are required to prevent
998 : * RCU readers from concurrently accessing this pointer -or-
999 : * 3. The referenced data structure has already been exposed to
1000 : * readers either at compile time or via rcu_assign_pointer() -and-
1001 : * a. You have not made -any- reader-visible changes to
1002 : * this structure since then -or-
1003 : * b. It is OK for readers accessing this structure from its
1004 : * new location to see the old state of the structure. (For
1005 : * example, the changes were to statistical counters or to
1006 : * other state where exact synchronization is not required.)
1007 : *
1008 : * Failure to follow these rules governing use of RCU_INIT_POINTER() will
1009 : * result in impossible-to-diagnose memory corruption. As in the structures
1010 : * will look OK in crash dumps, but any concurrent RCU readers might
1011 : * see pre-initialized values of the referenced data structure. So
1012 : * please be very careful how you use RCU_INIT_POINTER()!!!
1013 : *
1014 : * If you are creating an RCU-protected linked structure that is accessed
1015 : * by a single external-to-structure RCU-protected pointer, then you may
1016 : * use RCU_INIT_POINTER() to initialize the internal RCU-protected
1017 : * pointers, but you must use rcu_assign_pointer() to initialize the
1018 : * external-to-structure pointer -after- you have completely initialized
1019 : * the reader-accessible portions of the linked structure.
1020 : *
1021 : * Note that unlike rcu_assign_pointer(), RCU_INIT_POINTER() provides no
1022 : * ordering guarantees for either the CPU or the compiler.
1023 : */
1024 : #define RCU_INIT_POINTER(p, v) \
1025 : do { \
1026 : p = RCU_INITIALIZER(v); \
1027 : } while (0)
1028 :
1029 : /**
1030 : * RCU_POINTER_INITIALIZER() - statically initialize an RCU protected pointer
1031 : *
1032 : * GCC-style initialization for an RCU-protected pointer in a structure field.
1033 : */
1034 : #define RCU_POINTER_INITIALIZER(p, v) \
1035 : .p = RCU_INITIALIZER(v)
1036 :
1037 : /*
1038 : * Does the specified offset indicate that the corresponding rcu_head
1039 : * structure can be handled by kfree_rcu()?
1040 : */
1041 : #define __is_kfree_rcu_offset(offset) ((offset) < 4096)
1042 :
1043 : /*
1044 : * Helper macro for kfree_rcu() to prevent argument-expansion eyestrain.
1045 : */
1046 : #define __kfree_rcu(head, offset) \
1047 : do { \
1048 : BUILD_BUG_ON(!__is_kfree_rcu_offset(offset)); \
1049 : kfree_call_rcu(head, (void (*)(struct rcu_head *))(unsigned long)(offset)); \
1050 : } while (0)
1051 :
1052 : /**
1053 : * kfree_rcu() - kfree an object after a grace period.
1054 : * @ptr: pointer to kfree
1055 : * @rcu_head: the name of the struct rcu_head within the type of @ptr.
1056 : *
1057 : * Many rcu callbacks functions just call kfree() on the base structure.
1058 : * These functions are trivial, but their size adds up, and furthermore
1059 : * when they are used in a kernel module, that module must invoke the
1060 : * high-latency rcu_barrier() function at module-unload time.
1061 : *
1062 : * The kfree_rcu() function handles this issue. Rather than encoding a
1063 : * function address in the embedded rcu_head structure, kfree_rcu() instead
1064 : * encodes the offset of the rcu_head structure within the base structure.
1065 : * Because the functions are not allowed in the low-order 4096 bytes of
1066 : * kernel virtual memory, offsets up to 4095 bytes can be accommodated.
1067 : * If the offset is larger than 4095 bytes, a compile-time error will
1068 : * be generated in __kfree_rcu(). If this error is triggered, you can
1069 : * either fall back to use of call_rcu() or rearrange the structure to
1070 : * position the rcu_head structure into the first 4096 bytes.
1071 : *
1072 : * Note that the allowable offset might decrease in the future, for example,
1073 : * to allow something like kmem_cache_free_rcu().
1074 : *
1075 : * The BUILD_BUG_ON check must not involve any function calls, hence the
1076 : * checks are done in macros here.
1077 : */
1078 : #define kfree_rcu(ptr, rcu_head) \
1079 : __kfree_rcu(&((ptr)->rcu_head), offsetof(typeof(*(ptr)), rcu_head))
1080 :
1081 : #if defined(CONFIG_TINY_RCU) || defined(CONFIG_RCU_NOCB_CPU_ALL)
1082 : static inline int rcu_needs_cpu(int cpu, unsigned long *delta_jiffies)
1083 : {
1084 : *delta_jiffies = ULONG_MAX;
1085 : return 0;
1086 : }
1087 : #endif /* #if defined(CONFIG_TINY_RCU) || defined(CONFIG_RCU_NOCB_CPU_ALL) */
1088 :
1089 : #if defined(CONFIG_RCU_NOCB_CPU_ALL)
1090 : static inline bool rcu_is_nocb_cpu(int cpu) { return true; }
1091 : #elif defined(CONFIG_RCU_NOCB_CPU)
1092 : bool rcu_is_nocb_cpu(int cpu);
1093 : #else
1094 : static inline bool rcu_is_nocb_cpu(int cpu) { return false; }
1095 : #endif
1096 :
1097 :
1098 : /* Only for use by adaptive-ticks code. */
1099 : #ifdef CONFIG_NO_HZ_FULL_SYSIDLE
1100 : bool rcu_sys_is_idle(void);
1101 : void rcu_sysidle_force_exit(void);
1102 : #else /* #ifdef CONFIG_NO_HZ_FULL_SYSIDLE */
1103 :
1104 : static inline bool rcu_sys_is_idle(void)
1105 : {
1106 : return false;
1107 : }
1108 :
1109 : static inline void rcu_sysidle_force_exit(void)
1110 : {
1111 : }
1112 :
1113 : #endif /* #else #ifdef CONFIG_NO_HZ_FULL_SYSIDLE */
1114 :
1115 :
1116 : #endif /* __LINUX_RCUPDATE_H */
|
