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1da177e4 | 1 | /* |
a71fca58 | 2 | * Read-Copy Update mechanism for mutual exclusion |
1da177e4 LT |
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, write to the Free Software | |
16 | * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. | |
17 | * | |
01c1c660 | 18 | * Copyright IBM Corporation, 2001 |
1da177e4 LT |
19 | * |
20 | * Author: Dipankar Sarma <dipankar@in.ibm.com> | |
a71fca58 | 21 | * |
595182bc | 22 | * Based on the original work by Paul McKenney <paulmck@us.ibm.com> |
1da177e4 LT |
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 - | |
a71fca58 | 29 | * http://lse.sourceforge.net/locking/rcupdate.html |
1da177e4 LT |
30 | * |
31 | */ | |
32 | ||
33 | #ifndef __LINUX_RCUPDATE_H | |
34 | #define __LINUX_RCUPDATE_H | |
35 | ||
1da177e4 LT |
36 | #include <linux/cache.h> |
37 | #include <linux/spinlock.h> | |
38 | #include <linux/threads.h> | |
1da177e4 LT |
39 | #include <linux/cpumask.h> |
40 | #include <linux/seqlock.h> | |
851a67b8 | 41 | #include <linux/lockdep.h> |
4446a36f | 42 | #include <linux/completion.h> |
1da177e4 | 43 | |
e5ab6772 DY |
44 | #ifdef CONFIG_RCU_TORTURE_TEST |
45 | extern int rcutorture_runnable; /* for sysctl */ | |
46 | #endif /* #ifdef CONFIG_RCU_TORTURE_TEST */ | |
47 | ||
1da177e4 LT |
48 | /** |
49 | * struct rcu_head - callback structure for use with RCU | |
50 | * @next: next update requests in a list | |
51 | * @func: actual update function to call after the grace period. | |
52 | */ | |
53 | struct rcu_head { | |
54 | struct rcu_head *next; | |
55 | void (*func)(struct rcu_head *head); | |
56 | }; | |
57 | ||
03b042bf | 58 | /* Exported common interfaces */ |
03b042bf | 59 | extern void synchronize_rcu_bh(void); |
16e30811 | 60 | extern void synchronize_sched(void); |
03b042bf PM |
61 | extern void rcu_barrier(void); |
62 | extern void rcu_barrier_bh(void); | |
63 | extern void rcu_barrier_sched(void); | |
64 | extern void synchronize_sched_expedited(void); | |
65 | extern int sched_expedited_torture_stats(char *page); | |
66 | ||
67 | /* Internal to kernel */ | |
68 | extern void rcu_init(void); | |
d9f1bb6a PM |
69 | extern int rcu_scheduler_active; |
70 | extern void rcu_scheduler_starting(void); | |
a6826048 | 71 | |
f41d911f | 72 | #if defined(CONFIG_TREE_RCU) || defined(CONFIG_TREE_PREEMPT_RCU) |
64db4cff | 73 | #include <linux/rcutree.h> |
2c28e245 | 74 | #elif defined(CONFIG_TINY_RCU) |
9b1d82fa | 75 | #include <linux/rcutiny.h> |
64db4cff PM |
76 | #else |
77 | #error "Unknown RCU implementation specified to kernel configuration" | |
6b3ef48a | 78 | #endif |
01c1c660 | 79 | |
3d76c082 | 80 | #define RCU_HEAD_INIT { .next = NULL, .func = NULL } |
8b6490e5 | 81 | #define RCU_HEAD(head) struct rcu_head head = RCU_HEAD_INIT |
1da177e4 LT |
82 | #define INIT_RCU_HEAD(ptr) do { \ |
83 | (ptr)->next = NULL; (ptr)->func = NULL; \ | |
84 | } while (0) | |
85 | ||
bc33f24b | 86 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
632ee200 | 87 | |
bc33f24b | 88 | extern struct lockdep_map rcu_lock_map; |
632ee200 PM |
89 | # define rcu_read_acquire() \ |
90 | lock_acquire(&rcu_lock_map, 0, 0, 2, 1, NULL, _THIS_IP_) | |
bc33f24b | 91 | # define rcu_read_release() lock_release(&rcu_lock_map, 1, _THIS_IP_) |
632ee200 PM |
92 | |
93 | extern struct lockdep_map rcu_bh_lock_map; | |
94 | # define rcu_read_acquire_bh() \ | |
95 | lock_acquire(&rcu_bh_lock_map, 0, 0, 2, 1, NULL, _THIS_IP_) | |
96 | # define rcu_read_release_bh() lock_release(&rcu_bh_lock_map, 1, _THIS_IP_) | |
97 | ||
98 | extern struct lockdep_map rcu_sched_lock_map; | |
99 | # define rcu_read_acquire_sched() \ | |
100 | lock_acquire(&rcu_sched_lock_map, 0, 0, 2, 1, NULL, _THIS_IP_) | |
101 | # define rcu_read_release_sched() \ | |
102 | lock_release(&rcu_sched_lock_map, 1, _THIS_IP_) | |
103 | ||
bc293d62 | 104 | extern int debug_lockdep_rcu_enabled(void); |
54dbf96c | 105 | |
632ee200 PM |
106 | /** |
107 | * rcu_read_lock_held - might we be in RCU read-side critical section? | |
108 | * | |
109 | * If CONFIG_PROVE_LOCKING is selected and enabled, returns nonzero iff in | |
110 | * an RCU read-side critical section. In absence of CONFIG_PROVE_LOCKING, | |
111 | * this assumes we are in an RCU read-side critical section unless it can | |
112 | * prove otherwise. | |
54dbf96c PM |
113 | * |
114 | * Check rcu_scheduler_active to prevent false positives during boot. | |
632ee200 PM |
115 | */ |
116 | static inline int rcu_read_lock_held(void) | |
117 | { | |
54dbf96c PM |
118 | if (!debug_lockdep_rcu_enabled()) |
119 | return 1; | |
120 | return lock_is_held(&rcu_lock_map); | |
632ee200 PM |
121 | } |
122 | ||
e3818b8d PM |
123 | /* |
124 | * rcu_read_lock_bh_held() is defined out of line to avoid #include-file | |
125 | * hell. | |
632ee200 | 126 | */ |
e3818b8d | 127 | extern int rcu_read_lock_bh_held(void); |
632ee200 PM |
128 | |
129 | /** | |
130 | * rcu_read_lock_sched_held - might we be in RCU-sched read-side critical section? | |
131 | * | |
132 | * If CONFIG_PROVE_LOCKING is selected and enabled, returns nonzero iff in an | |
133 | * RCU-sched read-side critical section. In absence of CONFIG_PROVE_LOCKING, | |
134 | * this assumes we are in an RCU-sched read-side critical section unless it | |
135 | * can prove otherwise. Note that disabling of preemption (including | |
136 | * disabling irqs) counts as an RCU-sched read-side critical section. | |
54dbf96c PM |
137 | * |
138 | * Check rcu_scheduler_active to prevent false positives during boot. | |
632ee200 | 139 | */ |
e6033e3b | 140 | #ifdef CONFIG_PREEMPT |
632ee200 PM |
141 | static inline int rcu_read_lock_sched_held(void) |
142 | { | |
143 | int lockdep_opinion = 0; | |
144 | ||
54dbf96c PM |
145 | if (!debug_lockdep_rcu_enabled()) |
146 | return 1; | |
632ee200 PM |
147 | if (debug_locks) |
148 | lockdep_opinion = lock_is_held(&rcu_sched_lock_map); | |
0cff810f | 149 | return lockdep_opinion || preempt_count() != 0 || irqs_disabled(); |
632ee200 | 150 | } |
e6033e3b PM |
151 | #else /* #ifdef CONFIG_PREEMPT */ |
152 | static inline int rcu_read_lock_sched_held(void) | |
153 | { | |
154 | return 1; | |
632ee200 | 155 | } |
e6033e3b | 156 | #endif /* #else #ifdef CONFIG_PREEMPT */ |
632ee200 PM |
157 | |
158 | #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ | |
159 | ||
160 | # define rcu_read_acquire() do { } while (0) | |
161 | # define rcu_read_release() do { } while (0) | |
162 | # define rcu_read_acquire_bh() do { } while (0) | |
163 | # define rcu_read_release_bh() do { } while (0) | |
164 | # define rcu_read_acquire_sched() do { } while (0) | |
165 | # define rcu_read_release_sched() do { } while (0) | |
166 | ||
167 | static inline int rcu_read_lock_held(void) | |
168 | { | |
169 | return 1; | |
170 | } | |
171 | ||
172 | static inline int rcu_read_lock_bh_held(void) | |
173 | { | |
174 | return 1; | |
175 | } | |
176 | ||
e6033e3b | 177 | #ifdef CONFIG_PREEMPT |
632ee200 PM |
178 | static inline int rcu_read_lock_sched_held(void) |
179 | { | |
0cff810f | 180 | return !rcu_scheduler_active || preempt_count() != 0 || irqs_disabled(); |
632ee200 | 181 | } |
e6033e3b PM |
182 | #else /* #ifdef CONFIG_PREEMPT */ |
183 | static inline int rcu_read_lock_sched_held(void) | |
184 | { | |
185 | return 1; | |
632ee200 | 186 | } |
e6033e3b | 187 | #endif /* #else #ifdef CONFIG_PREEMPT */ |
632ee200 PM |
188 | |
189 | #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */ | |
190 | ||
191 | #ifdef CONFIG_PROVE_RCU | |
192 | ||
193 | /** | |
194 | * rcu_dereference_check - rcu_dereference with debug checking | |
c08c68dd DH |
195 | * @p: The pointer to read, prior to dereferencing |
196 | * @c: The conditions under which the dereference will take place | |
632ee200 | 197 | * |
c08c68dd DH |
198 | * Do an rcu_dereference(), but check that the conditions under which the |
199 | * dereference will take place are correct. Typically the conditions indicate | |
200 | * the various locking conditions that should be held at that point. The check | |
201 | * should return true if the conditions are satisfied. | |
202 | * | |
203 | * For example: | |
204 | * | |
205 | * bar = rcu_dereference_check(foo->bar, rcu_read_lock_held() || | |
206 | * lockdep_is_held(&foo->lock)); | |
207 | * | |
208 | * could be used to indicate to lockdep that foo->bar may only be dereferenced | |
209 | * if either the RCU read lock is held, or that the lock required to replace | |
210 | * the bar struct at foo->bar is held. | |
211 | * | |
212 | * Note that the list of conditions may also include indications of when a lock | |
213 | * need not be held, for example during initialisation or destruction of the | |
214 | * target struct: | |
215 | * | |
216 | * bar = rcu_dereference_check(foo->bar, rcu_read_lock_held() || | |
217 | * lockdep_is_held(&foo->lock) || | |
218 | * atomic_read(&foo->usage) == 0); | |
632ee200 PM |
219 | */ |
220 | #define rcu_dereference_check(p, c) \ | |
221 | ({ \ | |
54dbf96c | 222 | if (debug_lockdep_rcu_enabled() && !(c)) \ |
0632eb3d | 223 | lockdep_rcu_dereference(__FILE__, __LINE__); \ |
c26d34a5 | 224 | rcu_dereference_raw(p); \ |
632ee200 PM |
225 | }) |
226 | ||
b62730ba PM |
227 | /** |
228 | * rcu_dereference_protected - fetch RCU pointer when updates prevented | |
229 | * | |
230 | * Return the value of the specified RCU-protected pointer, but omit | |
231 | * both the smp_read_barrier_depends() and the ACCESS_ONCE(). This | |
232 | * is useful in cases where update-side locks prevent the value of the | |
233 | * pointer from changing. Please note that this primitive does -not- | |
234 | * prevent the compiler from repeating this reference or combining it | |
235 | * with other references, so it should not be used without protection | |
236 | * of appropriate locks. | |
237 | */ | |
238 | #define rcu_dereference_protected(p, c) \ | |
239 | ({ \ | |
240 | if (debug_lockdep_rcu_enabled() && !(c)) \ | |
241 | lockdep_rcu_dereference(__FILE__, __LINE__); \ | |
242 | (p); \ | |
243 | }) | |
244 | ||
632ee200 PM |
245 | #else /* #ifdef CONFIG_PROVE_RCU */ |
246 | ||
c26d34a5 | 247 | #define rcu_dereference_check(p, c) rcu_dereference_raw(p) |
b62730ba | 248 | #define rcu_dereference_protected(p, c) (p) |
632ee200 PM |
249 | |
250 | #endif /* #else #ifdef CONFIG_PROVE_RCU */ | |
bc33f24b | 251 | |
b62730ba PM |
252 | /** |
253 | * rcu_access_pointer - fetch RCU pointer with no dereferencing | |
254 | * | |
255 | * Return the value of the specified RCU-protected pointer, but omit the | |
256 | * smp_read_barrier_depends() and keep the ACCESS_ONCE(). This is useful | |
257 | * when the value of this pointer is accessed, but the pointer is not | |
258 | * dereferenced, for example, when testing an RCU-protected pointer against | |
259 | * NULL. This may also be used in cases where update-side locks prevent | |
260 | * the value of the pointer from changing, but rcu_dereference_protected() | |
261 | * is a lighter-weight primitive for this use case. | |
262 | */ | |
263 | #define rcu_access_pointer(p) ACCESS_ONCE(p) | |
264 | ||
1da177e4 LT |
265 | /** |
266 | * rcu_read_lock - mark the beginning of an RCU read-side critical section. | |
267 | * | |
9b06e818 | 268 | * When synchronize_rcu() is invoked on one CPU while other CPUs |
1da177e4 | 269 | * are within RCU read-side critical sections, then the |
9b06e818 | 270 | * synchronize_rcu() is guaranteed to block until after all the other |
1da177e4 LT |
271 | * CPUs exit their critical sections. Similarly, if call_rcu() is invoked |
272 | * on one CPU while other CPUs are within RCU read-side critical | |
273 | * sections, invocation of the corresponding RCU callback is deferred | |
274 | * until after the all the other CPUs exit their critical sections. | |
275 | * | |
276 | * Note, however, that RCU callbacks are permitted to run concurrently | |
277 | * with RCU read-side critical sections. One way that this can happen | |
278 | * is via the following sequence of events: (1) CPU 0 enters an RCU | |
279 | * read-side critical section, (2) CPU 1 invokes call_rcu() to register | |
280 | * an RCU callback, (3) CPU 0 exits the RCU read-side critical section, | |
281 | * (4) CPU 2 enters a RCU read-side critical section, (5) the RCU | |
282 | * callback is invoked. This is legal, because the RCU read-side critical | |
283 | * section that was running concurrently with the call_rcu() (and which | |
284 | * therefore might be referencing something that the corresponding RCU | |
285 | * callback would free up) has completed before the corresponding | |
286 | * RCU callback is invoked. | |
287 | * | |
288 | * RCU read-side critical sections may be nested. Any deferred actions | |
289 | * will be deferred until the outermost RCU read-side critical section | |
290 | * completes. | |
291 | * | |
292 | * It is illegal to block while in an RCU read-side critical section. | |
293 | */ | |
bc33f24b PM |
294 | static inline void rcu_read_lock(void) |
295 | { | |
296 | __rcu_read_lock(); | |
297 | __acquire(RCU); | |
298 | rcu_read_acquire(); | |
299 | } | |
1da177e4 | 300 | |
1da177e4 LT |
301 | /* |
302 | * So where is rcu_write_lock()? It does not exist, as there is no | |
303 | * way for writers to lock out RCU readers. This is a feature, not | |
304 | * a bug -- this property is what provides RCU's performance benefits. | |
305 | * Of course, writers must coordinate with each other. The normal | |
306 | * spinlock primitives work well for this, but any other technique may be | |
307 | * used as well. RCU does not care how the writers keep out of each | |
308 | * others' way, as long as they do so. | |
309 | */ | |
3d76c082 PM |
310 | |
311 | /** | |
312 | * rcu_read_unlock - marks the end of an RCU read-side critical section. | |
313 | * | |
314 | * See rcu_read_lock() for more information. | |
315 | */ | |
bc33f24b PM |
316 | static inline void rcu_read_unlock(void) |
317 | { | |
318 | rcu_read_release(); | |
319 | __release(RCU); | |
320 | __rcu_read_unlock(); | |
321 | } | |
1da177e4 LT |
322 | |
323 | /** | |
324 | * rcu_read_lock_bh - mark the beginning of a softirq-only RCU critical section | |
325 | * | |
326 | * This is equivalent of rcu_read_lock(), but to be used when updates | |
327 | * are being done using call_rcu_bh(). Since call_rcu_bh() callbacks | |
328 | * consider completion of a softirq handler to be a quiescent state, | |
329 | * a process in RCU read-side critical section must be protected by | |
330 | * disabling softirqs. Read-side critical sections in interrupt context | |
331 | * can use just rcu_read_lock(). | |
332 | * | |
333 | */ | |
bc33f24b PM |
334 | static inline void rcu_read_lock_bh(void) |
335 | { | |
336 | __rcu_read_lock_bh(); | |
337 | __acquire(RCU_BH); | |
632ee200 | 338 | rcu_read_acquire_bh(); |
bc33f24b | 339 | } |
1da177e4 LT |
340 | |
341 | /* | |
342 | * rcu_read_unlock_bh - marks the end of a softirq-only RCU critical section | |
343 | * | |
344 | * See rcu_read_lock_bh() for more information. | |
345 | */ | |
bc33f24b PM |
346 | static inline void rcu_read_unlock_bh(void) |
347 | { | |
632ee200 | 348 | rcu_read_release_bh(); |
bc33f24b PM |
349 | __release(RCU_BH); |
350 | __rcu_read_unlock_bh(); | |
351 | } | |
1da177e4 | 352 | |
1c50b728 MD |
353 | /** |
354 | * rcu_read_lock_sched - mark the beginning of a RCU-classic critical section | |
355 | * | |
356 | * Should be used with either | |
357 | * - synchronize_sched() | |
358 | * or | |
359 | * - call_rcu_sched() and rcu_barrier_sched() | |
360 | * on the write-side to insure proper synchronization. | |
361 | */ | |
d6714c22 PM |
362 | static inline void rcu_read_lock_sched(void) |
363 | { | |
364 | preempt_disable(); | |
bc33f24b | 365 | __acquire(RCU_SCHED); |
632ee200 | 366 | rcu_read_acquire_sched(); |
d6714c22 | 367 | } |
1eba8f84 PM |
368 | |
369 | /* Used by lockdep and tracing: cannot be traced, cannot call lockdep. */ | |
7c614d64 | 370 | static inline notrace void rcu_read_lock_sched_notrace(void) |
d6714c22 PM |
371 | { |
372 | preempt_disable_notrace(); | |
bc33f24b | 373 | __acquire(RCU_SCHED); |
d6714c22 | 374 | } |
1c50b728 MD |
375 | |
376 | /* | |
377 | * rcu_read_unlock_sched - marks the end of a RCU-classic critical section | |
378 | * | |
379 | * See rcu_read_lock_sched for more information. | |
380 | */ | |
d6714c22 PM |
381 | static inline void rcu_read_unlock_sched(void) |
382 | { | |
632ee200 | 383 | rcu_read_release_sched(); |
bc33f24b | 384 | __release(RCU_SCHED); |
d6714c22 PM |
385 | preempt_enable(); |
386 | } | |
1eba8f84 PM |
387 | |
388 | /* Used by lockdep and tracing: cannot be traced, cannot call lockdep. */ | |
7c614d64 | 389 | static inline notrace void rcu_read_unlock_sched_notrace(void) |
d6714c22 | 390 | { |
bc33f24b | 391 | __release(RCU_SCHED); |
d6714c22 PM |
392 | preempt_enable_notrace(); |
393 | } | |
1c50b728 MD |
394 | |
395 | ||
1da177e4 | 396 | /** |
c26d34a5 PM |
397 | * rcu_dereference_raw - fetch an RCU-protected pointer |
398 | * | |
399 | * The caller must be within some flavor of RCU read-side critical | |
400 | * section, or must be otherwise preventing the pointer from changing, | |
401 | * for example, by holding an appropriate lock. This pointer may later | |
402 | * be safely dereferenced. It is the caller's responsibility to have | |
403 | * done the right thing, as this primitive does no checking of any kind. | |
1da177e4 LT |
404 | * |
405 | * Inserts memory barriers on architectures that require them | |
406 | * (currently only the Alpha), and, more importantly, documents | |
407 | * exactly which pointers are protected by RCU. | |
408 | */ | |
c26d34a5 | 409 | #define rcu_dereference_raw(p) ({ \ |
97b43032 | 410 | typeof(p) _________p1 = ACCESS_ONCE(p); \ |
1da177e4 LT |
411 | smp_read_barrier_depends(); \ |
412 | (_________p1); \ | |
413 | }) | |
414 | ||
c26d34a5 PM |
415 | /** |
416 | * rcu_dereference - fetch an RCU-protected pointer, checking for RCU | |
417 | * | |
418 | * Makes rcu_dereference_check() do the dirty work. | |
419 | */ | |
420 | #define rcu_dereference(p) \ | |
421 | rcu_dereference_check(p, rcu_read_lock_held()) | |
422 | ||
423 | /** | |
424 | * rcu_dereference_bh - fetch an RCU-protected pointer, checking for RCU-bh | |
425 | * | |
426 | * Makes rcu_dereference_check() do the dirty work. | |
427 | */ | |
428 | #define rcu_dereference_bh(p) \ | |
429 | rcu_dereference_check(p, rcu_read_lock_bh_held()) | |
430 | ||
431 | /** | |
432 | * rcu_dereference_sched - fetch RCU-protected pointer, checking for RCU-sched | |
433 | * | |
434 | * Makes rcu_dereference_check() do the dirty work. | |
435 | */ | |
436 | #define rcu_dereference_sched(p) \ | |
437 | rcu_dereference_check(p, rcu_read_lock_sched_held()) | |
438 | ||
1da177e4 LT |
439 | /** |
440 | * rcu_assign_pointer - assign (publicize) a pointer to a newly | |
441 | * initialized structure that will be dereferenced by RCU read-side | |
442 | * critical sections. Returns the value assigned. | |
443 | * | |
444 | * Inserts memory barriers on architectures that require them | |
445 | * (pretty much all of them other than x86), and also prevents | |
446 | * the compiler from reordering the code that initializes the | |
447 | * structure after the pointer assignment. More importantly, this | |
448 | * call documents which pointers will be dereferenced by RCU read-side | |
449 | * code. | |
450 | */ | |
451 | ||
d99c4f6b PM |
452 | #define rcu_assign_pointer(p, v) \ |
453 | ({ \ | |
454 | if (!__builtin_constant_p(v) || \ | |
455 | ((v) != NULL)) \ | |
456 | smp_wmb(); \ | |
457 | (p) = (v); \ | |
458 | }) | |
1da177e4 | 459 | |
4446a36f PM |
460 | /* Infrastructure to implement the synchronize_() primitives. */ |
461 | ||
462 | struct rcu_synchronize { | |
463 | struct rcu_head head; | |
464 | struct completion completion; | |
465 | }; | |
466 | ||
467 | extern void wakeme_after_rcu(struct rcu_head *head); | |
468 | ||
01c1c660 PM |
469 | /** |
470 | * call_rcu - Queue an RCU callback for invocation after a grace period. | |
471 | * @head: structure to be used for queueing the RCU updates. | |
472 | * @func: actual update function to be invoked after the grace period | |
473 | * | |
474 | * The update function will be invoked some time after a full grace | |
475 | * period elapses, in other words after all currently executing RCU | |
476 | * read-side critical sections have completed. RCU read-side critical | |
477 | * sections are delimited by rcu_read_lock() and rcu_read_unlock(), | |
478 | * and may be nested. | |
479 | */ | |
480 | extern void call_rcu(struct rcu_head *head, | |
481 | void (*func)(struct rcu_head *head)); | |
482 | ||
483 | /** | |
484 | * call_rcu_bh - Queue an RCU for invocation after a quicker grace period. | |
485 | * @head: structure to be used for queueing the RCU updates. | |
486 | * @func: actual update function to be invoked after the grace period | |
487 | * | |
488 | * The update function will be invoked some time after a full grace | |
489 | * period elapses, in other words after all currently executing RCU | |
490 | * read-side critical sections have completed. call_rcu_bh() assumes | |
491 | * that the read-side critical sections end on completion of a softirq | |
492 | * handler. This means that read-side critical sections in process | |
493 | * context must not be interrupted by softirqs. This interface is to be | |
494 | * used when most of the read-side critical sections are in softirq context. | |
495 | * RCU read-side critical sections are delimited by : | |
496 | * - rcu_read_lock() and rcu_read_unlock(), if in interrupt context. | |
497 | * OR | |
498 | * - rcu_read_lock_bh() and rcu_read_unlock_bh(), if in process context. | |
499 | * These may be nested. | |
500 | */ | |
501 | extern void call_rcu_bh(struct rcu_head *head, | |
502 | void (*func)(struct rcu_head *head)); | |
503 | ||
1da177e4 | 504 | #endif /* __LINUX_RCUPDATE_H */ |