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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 | |
87de1cfd PM |
15 | * along with this program; if not, you can access it online at |
16 | * http://www.gnu.org/licenses/gpl-2.0.html. | |
1da177e4 | 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 | ||
99098751 | 36 | #include <linux/types.h> |
ca5ecddf | 37 | #include <linux/compiler.h> |
5f192ab0 | 38 | #include <linux/atomic.h> |
4929c913 | 39 | #include <linux/irqflags.h> |
5f192ab0 PM |
40 | #include <linux/preempt.h> |
41 | #include <linux/bottom_half.h> | |
42 | #include <linux/lockdep.h> | |
43 | #include <asm/processor.h> | |
44 | #include <linux/cpumask.h> | |
c1ad348b | 45 | |
a3dc3fb1 PM |
46 | #define ULONG_CMP_GE(a, b) (ULONG_MAX / 2 >= (a) - (b)) |
47 | #define ULONG_CMP_LT(a, b) (ULONG_MAX / 2 < (a) - (b)) | |
c0f4dfd4 | 48 | #define ulong2long(a) (*(long *)(&(a))) |
a3dc3fb1 | 49 | |
03b042bf | 50 | /* Exported common interfaces */ |
709fdce7 | 51 | void call_rcu(struct rcu_head *head, rcu_callback_t func); |
53c6d4ed | 52 | void rcu_barrier_tasks(void); |
709fdce7 | 53 | void synchronize_rcu(void); |
8315f422 | 54 | |
a3dc3fb1 PM |
55 | #ifdef CONFIG_PREEMPT_RCU |
56 | ||
584dc4ce TB |
57 | void __rcu_read_lock(void); |
58 | void __rcu_read_unlock(void); | |
7b0b759b | 59 | |
a3dc3fb1 PM |
60 | /* |
61 | * Defined as a macro as it is a very low level header included from | |
62 | * areas that don't even know about current. This gives the rcu_read_lock() | |
63 | * nesting depth, but makes sense only if CONFIG_PREEMPT_RCU -- in other | |
64 | * types of kernel builds, the rcu_read_lock() nesting depth is unknowable. | |
65 | */ | |
66 | #define rcu_preempt_depth() (current->rcu_read_lock_nesting) | |
67 | ||
7b0b759b PM |
68 | #else /* #ifdef CONFIG_PREEMPT_RCU */ |
69 | ||
70 | static inline void __rcu_read_lock(void) | |
71 | { | |
bb73c52b BF |
72 | if (IS_ENABLED(CONFIG_PREEMPT_COUNT)) |
73 | preempt_disable(); | |
7b0b759b PM |
74 | } |
75 | ||
76 | static inline void __rcu_read_unlock(void) | |
77 | { | |
bb73c52b BF |
78 | if (IS_ENABLED(CONFIG_PREEMPT_COUNT)) |
79 | preempt_enable(); | |
7b0b759b PM |
80 | } |
81 | ||
7b0b759b PM |
82 | static inline int rcu_preempt_depth(void) |
83 | { | |
84 | return 0; | |
85 | } | |
86 | ||
87 | #endif /* #else #ifdef CONFIG_PREEMPT_RCU */ | |
88 | ||
89 | /* Internal to kernel */ | |
584dc4ce | 90 | void rcu_init(void); |
825c5bd2 | 91 | extern int rcu_scheduler_active __read_mostly; |
c3377c2d | 92 | void rcu_check_callbacks(int user); |
27d50c7e | 93 | void rcu_report_dead(unsigned int cpu); |
a58163d8 | 94 | void rcutree_migrate_callbacks(int cpu); |
2b1d5024 | 95 | |
61f38db3 RR |
96 | #ifdef CONFIG_RCU_STALL_COMMON |
97 | void rcu_sysrq_start(void); | |
98 | void rcu_sysrq_end(void); | |
99 | #else /* #ifdef CONFIG_RCU_STALL_COMMON */ | |
d0df7a34 PM |
100 | static inline void rcu_sysrq_start(void) { } |
101 | static inline void rcu_sysrq_end(void) { } | |
61f38db3 RR |
102 | #endif /* #else #ifdef CONFIG_RCU_STALL_COMMON */ |
103 | ||
d1ec4c34 | 104 | #ifdef CONFIG_NO_HZ_FULL |
584dc4ce TB |
105 | void rcu_user_enter(void); |
106 | void rcu_user_exit(void); | |
2b1d5024 FW |
107 | #else |
108 | static inline void rcu_user_enter(void) { } | |
109 | static inline void rcu_user_exit(void) { } | |
d1ec4c34 | 110 | #endif /* CONFIG_NO_HZ_FULL */ |
2b1d5024 | 111 | |
f4579fc5 PM |
112 | #ifdef CONFIG_RCU_NOCB_CPU |
113 | void rcu_init_nohz(void); | |
114 | #else /* #ifdef CONFIG_RCU_NOCB_CPU */ | |
d0df7a34 | 115 | static inline void rcu_init_nohz(void) { } |
f4579fc5 PM |
116 | #endif /* #else #ifdef CONFIG_RCU_NOCB_CPU */ |
117 | ||
8a2ecf47 PM |
118 | /** |
119 | * RCU_NONIDLE - Indicate idle-loop code that needs RCU readers | |
120 | * @a: Code that RCU needs to pay attention to. | |
121 | * | |
2bd8b1a2 PM |
122 | * RCU read-side critical sections are forbidden in the inner idle loop, |
123 | * that is, between the rcu_idle_enter() and the rcu_idle_exit() -- RCU | |
124 | * will happily ignore any such read-side critical sections. However, | |
125 | * things like powertop need tracepoints in the inner idle loop. | |
8a2ecf47 PM |
126 | * |
127 | * This macro provides the way out: RCU_NONIDLE(do_something_with_RCU()) | |
810ce8b5 PM |
128 | * will tell RCU that it needs to pay attention, invoke its argument |
129 | * (in this example, calling the do_something_with_RCU() function), | |
8a2ecf47 | 130 | * and then tell RCU to go back to ignoring this CPU. It is permissible |
810ce8b5 PM |
131 | * to nest RCU_NONIDLE() wrappers, but not indefinitely (but the limit is |
132 | * on the order of a million or so, even on 32-bit systems). It is | |
133 | * not legal to block within RCU_NONIDLE(), nor is it permissible to | |
134 | * transfer control either into or out of RCU_NONIDLE()'s statement. | |
8a2ecf47 PM |
135 | */ |
136 | #define RCU_NONIDLE(a) \ | |
137 | do { \ | |
7c9906ca | 138 | rcu_irq_enter_irqson(); \ |
8a2ecf47 | 139 | do { a; } while (0); \ |
7c9906ca | 140 | rcu_irq_exit_irqson(); \ |
8a2ecf47 PM |
141 | } while (0) |
142 | ||
8315f422 | 143 | /* |
6f56f714 PM |
144 | * Note a quasi-voluntary context switch for RCU-tasks's benefit. |
145 | * This is a macro rather than an inline function to avoid #include hell. | |
8315f422 PM |
146 | */ |
147 | #ifdef CONFIG_TASKS_RCU | |
6f56f714 | 148 | #define rcu_tasks_qs(t) \ |
8315f422 | 149 | do { \ |
7d0ae808 PM |
150 | if (READ_ONCE((t)->rcu_tasks_holdout)) \ |
151 | WRITE_ONCE((t)->rcu_tasks_holdout, false); \ | |
8315f422 | 152 | } while (0) |
4d232dfe | 153 | #define rcu_note_voluntary_context_switch(t) rcu_tasks_qs(t) |
7e42776d PM |
154 | void call_rcu_tasks(struct rcu_head *head, rcu_callback_t func); |
155 | void synchronize_rcu_tasks(void); | |
ccdd29ff PM |
156 | void exit_tasks_rcu_start(void); |
157 | void exit_tasks_rcu_finish(void); | |
8315f422 | 158 | #else /* #ifdef CONFIG_TASKS_RCU */ |
6f56f714 | 159 | #define rcu_tasks_qs(t) do { } while (0) |
4d232dfe | 160 | #define rcu_note_voluntary_context_switch(t) do { } while (0) |
2bd8b1a2 | 161 | #define call_rcu_tasks call_rcu |
a8bb74ac | 162 | #define synchronize_rcu_tasks synchronize_rcu |
ccdd29ff PM |
163 | static inline void exit_tasks_rcu_start(void) { } |
164 | static inline void exit_tasks_rcu_finish(void) { } | |
8315f422 PM |
165 | #endif /* #else #ifdef CONFIG_TASKS_RCU */ |
166 | ||
bde6c3aa | 167 | /** |
cee43939 | 168 | * cond_resched_tasks_rcu_qs - Report potential quiescent states to RCU |
bde6c3aa PM |
169 | * |
170 | * This macro resembles cond_resched(), except that it is defined to | |
171 | * report potential quiescent states to RCU-tasks even if the cond_resched() | |
172 | * machinery were to be shut off, as some advocate for PREEMPT kernels. | |
173 | */ | |
cee43939 | 174 | #define cond_resched_tasks_rcu_qs() \ |
bde6c3aa | 175 | do { \ |
6f56f714 | 176 | rcu_tasks_qs(current); \ |
07f27570 | 177 | cond_resched(); \ |
bde6c3aa PM |
178 | } while (0) |
179 | ||
2c42818e PM |
180 | /* |
181 | * Infrastructure to implement the synchronize_() primitives in | |
182 | * TREE_RCU and rcu_barrier_() primitives in TINY_RCU. | |
183 | */ | |
184 | ||
28f6569a | 185 | #if defined(CONFIG_TREE_RCU) || defined(CONFIG_PREEMPT_RCU) |
64db4cff | 186 | #include <linux/rcutree.h> |
127781d1 | 187 | #elif defined(CONFIG_TINY_RCU) |
9b1d82fa | 188 | #include <linux/rcutiny.h> |
64db4cff PM |
189 | #else |
190 | #error "Unknown RCU implementation specified to kernel configuration" | |
6b3ef48a | 191 | #endif |
01c1c660 | 192 | |
551d55a9 | 193 | /* |
b5482a06 PM |
194 | * The init_rcu_head_on_stack() and destroy_rcu_head_on_stack() calls |
195 | * are needed for dynamic initialization and destruction of rcu_head | |
196 | * on the stack, and init_rcu_head()/destroy_rcu_head() are needed for | |
197 | * dynamic initialization and destruction of statically allocated rcu_head | |
198 | * structures. However, rcu_head structures allocated dynamically in the | |
199 | * heap don't need any initialization. | |
551d55a9 MD |
200 | */ |
201 | #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD | |
546a9d85 PM |
202 | void init_rcu_head(struct rcu_head *head); |
203 | void destroy_rcu_head(struct rcu_head *head); | |
584dc4ce TB |
204 | void init_rcu_head_on_stack(struct rcu_head *head); |
205 | void destroy_rcu_head_on_stack(struct rcu_head *head); | |
551d55a9 | 206 | #else /* !CONFIG_DEBUG_OBJECTS_RCU_HEAD */ |
d0df7a34 PM |
207 | static inline void init_rcu_head(struct rcu_head *head) { } |
208 | static inline void destroy_rcu_head(struct rcu_head *head) { } | |
209 | static inline void init_rcu_head_on_stack(struct rcu_head *head) { } | |
210 | static inline void destroy_rcu_head_on_stack(struct rcu_head *head) { } | |
551d55a9 | 211 | #endif /* #else !CONFIG_DEBUG_OBJECTS_RCU_HEAD */ |
4376030a | 212 | |
c0d6d01b PM |
213 | #if defined(CONFIG_HOTPLUG_CPU) && defined(CONFIG_PROVE_RCU) |
214 | bool rcu_lockdep_current_cpu_online(void); | |
215 | #else /* #if defined(CONFIG_HOTPLUG_CPU) && defined(CONFIG_PROVE_RCU) */ | |
17a8c187 | 216 | static inline bool rcu_lockdep_current_cpu_online(void) { return true; } |
c0d6d01b PM |
217 | #endif /* #else #if defined(CONFIG_HOTPLUG_CPU) && defined(CONFIG_PROVE_RCU) */ |
218 | ||
bc33f24b | 219 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
632ee200 | 220 | |
00f49e57 FW |
221 | static inline void rcu_lock_acquire(struct lockdep_map *map) |
222 | { | |
fb9edbe9 | 223 | lock_acquire(map, 0, 0, 2, 0, NULL, _THIS_IP_); |
00f49e57 FW |
224 | } |
225 | ||
226 | static inline void rcu_lock_release(struct lockdep_map *map) | |
227 | { | |
00f49e57 FW |
228 | lock_release(map, 1, _THIS_IP_); |
229 | } | |
230 | ||
bc33f24b | 231 | extern struct lockdep_map rcu_lock_map; |
632ee200 | 232 | extern struct lockdep_map rcu_bh_lock_map; |
632ee200 | 233 | extern struct lockdep_map rcu_sched_lock_map; |
24ef659a | 234 | extern struct lockdep_map rcu_callback_map; |
a235c091 | 235 | int debug_lockdep_rcu_enabled(void); |
85b39d30 | 236 | int rcu_read_lock_held(void); |
584dc4ce | 237 | int rcu_read_lock_bh_held(void); |
d5671f6b | 238 | int rcu_read_lock_sched_held(void); |
632ee200 PM |
239 | |
240 | #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ | |
241 | ||
d8ab29f8 PM |
242 | # define rcu_lock_acquire(a) do { } while (0) |
243 | # define rcu_lock_release(a) do { } while (0) | |
632ee200 PM |
244 | |
245 | static inline int rcu_read_lock_held(void) | |
246 | { | |
247 | return 1; | |
248 | } | |
249 | ||
250 | static inline int rcu_read_lock_bh_held(void) | |
251 | { | |
252 | return 1; | |
253 | } | |
254 | ||
255 | static inline int rcu_read_lock_sched_held(void) | |
256 | { | |
293e2421 | 257 | return !preemptible(); |
632ee200 | 258 | } |
632ee200 PM |
259 | #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */ |
260 | ||
261 | #ifdef CONFIG_PROVE_RCU | |
262 | ||
f78f5b90 PM |
263 | /** |
264 | * RCU_LOCKDEP_WARN - emit lockdep splat if specified condition is met | |
265 | * @c: condition to check | |
266 | * @s: informative message | |
267 | */ | |
268 | #define RCU_LOCKDEP_WARN(c, s) \ | |
269 | do { \ | |
270 | static bool __section(.data.unlikely) __warned; \ | |
271 | if (debug_lockdep_rcu_enabled() && !__warned && (c)) { \ | |
272 | __warned = true; \ | |
273 | lockdep_rcu_suspicious(__FILE__, __LINE__, s); \ | |
274 | } \ | |
275 | } while (0) | |
276 | ||
50406b98 PM |
277 | #if defined(CONFIG_PROVE_RCU) && !defined(CONFIG_PREEMPT_RCU) |
278 | static inline void rcu_preempt_sleep_check(void) | |
279 | { | |
f78f5b90 PM |
280 | RCU_LOCKDEP_WARN(lock_is_held(&rcu_lock_map), |
281 | "Illegal context switch in RCU read-side critical section"); | |
50406b98 PM |
282 | } |
283 | #else /* #ifdef CONFIG_PROVE_RCU */ | |
d0df7a34 | 284 | static inline void rcu_preempt_sleep_check(void) { } |
50406b98 PM |
285 | #endif /* #else #ifdef CONFIG_PROVE_RCU */ |
286 | ||
b3fbab05 PM |
287 | #define rcu_sleep_check() \ |
288 | do { \ | |
50406b98 | 289 | rcu_preempt_sleep_check(); \ |
f78f5b90 PM |
290 | RCU_LOCKDEP_WARN(lock_is_held(&rcu_bh_lock_map), \ |
291 | "Illegal context switch in RCU-bh read-side critical section"); \ | |
292 | RCU_LOCKDEP_WARN(lock_is_held(&rcu_sched_lock_map), \ | |
293 | "Illegal context switch in RCU-sched read-side critical section"); \ | |
b3fbab05 PM |
294 | } while (0) |
295 | ||
ca5ecddf PM |
296 | #else /* #ifdef CONFIG_PROVE_RCU */ |
297 | ||
f78f5b90 | 298 | #define RCU_LOCKDEP_WARN(c, s) do { } while (0) |
b3fbab05 | 299 | #define rcu_sleep_check() do { } while (0) |
ca5ecddf PM |
300 | |
301 | #endif /* #else #ifdef CONFIG_PROVE_RCU */ | |
302 | ||
303 | /* | |
304 | * Helper functions for rcu_dereference_check(), rcu_dereference_protected() | |
305 | * and rcu_assign_pointer(). Some of these could be folded into their | |
306 | * callers, but they are left separate in order to ease introduction of | |
2bd8b1a2 PM |
307 | * multiple pointers markings to match different RCU implementations |
308 | * (e.g., __srcu), should this make sense in the future. | |
ca5ecddf | 309 | */ |
53ecfba2 PM |
310 | |
311 | #ifdef __CHECKER__ | |
312 | #define rcu_dereference_sparse(p, space) \ | |
313 | ((void)(((typeof(*p) space *)p) == p)) | |
314 | #else /* #ifdef __CHECKER__ */ | |
315 | #define rcu_dereference_sparse(p, space) | |
316 | #endif /* #else #ifdef __CHECKER__ */ | |
317 | ||
ca5ecddf | 318 | #define __rcu_access_pointer(p, space) \ |
0adab9b9 | 319 | ({ \ |
7d0ae808 | 320 | typeof(*p) *_________p1 = (typeof(*p) *__force)READ_ONCE(p); \ |
0adab9b9 JP |
321 | rcu_dereference_sparse(p, space); \ |
322 | ((typeof(*p) __force __kernel *)(_________p1)); \ | |
323 | }) | |
ca5ecddf | 324 | #define __rcu_dereference_check(p, c, space) \ |
0adab9b9 | 325 | ({ \ |
ac59853c | 326 | /* Dependency order vs. p above. */ \ |
506458ef | 327 | typeof(*p) *________p1 = (typeof(*p) *__force)READ_ONCE(p); \ |
f78f5b90 | 328 | RCU_LOCKDEP_WARN(!(c), "suspicious rcu_dereference_check() usage"); \ |
0adab9b9 | 329 | rcu_dereference_sparse(p, space); \ |
ac59853c | 330 | ((typeof(*p) __force __kernel *)(________p1)); \ |
0adab9b9 | 331 | }) |
ca5ecddf | 332 | #define __rcu_dereference_protected(p, c, space) \ |
0adab9b9 | 333 | ({ \ |
f78f5b90 | 334 | RCU_LOCKDEP_WARN(!(c), "suspicious rcu_dereference_protected() usage"); \ |
0adab9b9 JP |
335 | rcu_dereference_sparse(p, space); \ |
336 | ((typeof(*p) __force __kernel *)(p)); \ | |
337 | }) | |
995f1405 PM |
338 | #define rcu_dereference_raw(p) \ |
339 | ({ \ | |
340 | /* Dependency order vs. p above. */ \ | |
506458ef | 341 | typeof(p) ________p1 = READ_ONCE(p); \ |
995f1405 PM |
342 | ((typeof(*p) __force __kernel *)(________p1)); \ |
343 | }) | |
ca5ecddf | 344 | |
462225ae PM |
345 | /** |
346 | * RCU_INITIALIZER() - statically initialize an RCU-protected global variable | |
347 | * @v: The value to statically initialize with. | |
348 | */ | |
349 | #define RCU_INITIALIZER(v) (typeof(*(v)) __force __rcu *)(v) | |
350 | ||
351 | /** | |
352 | * rcu_assign_pointer() - assign to RCU-protected pointer | |
353 | * @p: pointer to assign to | |
354 | * @v: value to assign (publish) | |
355 | * | |
356 | * Assigns the specified value to the specified RCU-protected | |
357 | * pointer, ensuring that any concurrent RCU readers will see | |
358 | * any prior initialization. | |
359 | * | |
360 | * Inserts memory barriers on architectures that require them | |
361 | * (which is most of them), and also prevents the compiler from | |
362 | * reordering the code that initializes the structure after the pointer | |
363 | * assignment. More importantly, this call documents which pointers | |
364 | * will be dereferenced by RCU read-side code. | |
365 | * | |
366 | * In some special cases, you may use RCU_INIT_POINTER() instead | |
367 | * of rcu_assign_pointer(). RCU_INIT_POINTER() is a bit faster due | |
368 | * to the fact that it does not constrain either the CPU or the compiler. | |
369 | * That said, using RCU_INIT_POINTER() when you should have used | |
370 | * rcu_assign_pointer() is a very bad thing that results in | |
371 | * impossible-to-diagnose memory corruption. So please be careful. | |
372 | * See the RCU_INIT_POINTER() comment header for details. | |
373 | * | |
374 | * Note that rcu_assign_pointer() evaluates each of its arguments only | |
375 | * once, appearances notwithstanding. One of the "extra" evaluations | |
376 | * is in typeof() and the other visible only to sparse (__CHECKER__), | |
377 | * neither of which actually execute the argument. As with most cpp | |
378 | * macros, this execute-arguments-only-once property is important, so | |
379 | * please be careful when making changes to rcu_assign_pointer() and the | |
380 | * other macros that it invokes. | |
381 | */ | |
3a37f727 PM |
382 | #define rcu_assign_pointer(p, v) \ |
383 | ({ \ | |
384 | uintptr_t _r_a_p__v = (uintptr_t)(v); \ | |
385 | \ | |
386 | if (__builtin_constant_p(v) && (_r_a_p__v) == (uintptr_t)NULL) \ | |
387 | WRITE_ONCE((p), (typeof(p))(_r_a_p__v)); \ | |
388 | else \ | |
389 | smp_store_release(&p, RCU_INITIALIZER((typeof(p))_r_a_p__v)); \ | |
390 | _r_a_p__v; \ | |
391 | }) | |
ca5ecddf | 392 | |
26e3e3cb BVA |
393 | /** |
394 | * rcu_swap_protected() - swap an RCU and a regular pointer | |
395 | * @rcu_ptr: RCU pointer | |
396 | * @ptr: regular pointer | |
397 | * @c: the conditions under which the dereference will take place | |
398 | * | |
399 | * Perform swap(@rcu_ptr, @ptr) where @rcu_ptr is an RCU-annotated pointer and | |
400 | * @c is the argument that is passed to the rcu_dereference_protected() call | |
401 | * used to read that pointer. | |
402 | */ | |
403 | #define rcu_swap_protected(rcu_ptr, ptr, c) do { \ | |
404 | typeof(ptr) __tmp = rcu_dereference_protected((rcu_ptr), (c)); \ | |
405 | rcu_assign_pointer((rcu_ptr), (ptr)); \ | |
406 | (ptr) = __tmp; \ | |
407 | } while (0) | |
408 | ||
ca5ecddf PM |
409 | /** |
410 | * rcu_access_pointer() - fetch RCU pointer with no dereferencing | |
411 | * @p: The pointer to read | |
412 | * | |
413 | * Return the value of the specified RCU-protected pointer, but omit the | |
137f61f6 PM |
414 | * lockdep checks for being in an RCU read-side critical section. This is |
415 | * useful when the value of this pointer is accessed, but the pointer is | |
416 | * not dereferenced, for example, when testing an RCU-protected pointer | |
417 | * against NULL. Although rcu_access_pointer() may also be used in cases | |
418 | * where update-side locks prevent the value of the pointer from changing, | |
419 | * you should instead use rcu_dereference_protected() for this use case. | |
5e1ee6e1 PM |
420 | * |
421 | * It is also permissible to use rcu_access_pointer() when read-side | |
422 | * access to the pointer was removed at least one grace period ago, as | |
423 | * is the case in the context of the RCU callback that is freeing up | |
424 | * the data, or after a synchronize_rcu() returns. This can be useful | |
425 | * when tearing down multi-linked structures after a grace period | |
426 | * has elapsed. | |
ca5ecddf PM |
427 | */ |
428 | #define rcu_access_pointer(p) __rcu_access_pointer((p), __rcu) | |
429 | ||
632ee200 | 430 | /** |
ca5ecddf | 431 | * rcu_dereference_check() - rcu_dereference with debug checking |
c08c68dd DH |
432 | * @p: The pointer to read, prior to dereferencing |
433 | * @c: The conditions under which the dereference will take place | |
632ee200 | 434 | * |
c08c68dd | 435 | * Do an rcu_dereference(), but check that the conditions under which the |
ca5ecddf PM |
436 | * dereference will take place are correct. Typically the conditions |
437 | * indicate the various locking conditions that should be held at that | |
438 | * point. The check should return true if the conditions are satisfied. | |
439 | * An implicit check for being in an RCU read-side critical section | |
440 | * (rcu_read_lock()) is included. | |
c08c68dd DH |
441 | * |
442 | * For example: | |
443 | * | |
ca5ecddf | 444 | * bar = rcu_dereference_check(foo->bar, lockdep_is_held(&foo->lock)); |
c08c68dd DH |
445 | * |
446 | * could be used to indicate to lockdep that foo->bar may only be dereferenced | |
ca5ecddf | 447 | * if either rcu_read_lock() is held, or that the lock required to replace |
c08c68dd DH |
448 | * the bar struct at foo->bar is held. |
449 | * | |
450 | * Note that the list of conditions may also include indications of when a lock | |
451 | * need not be held, for example during initialisation or destruction of the | |
452 | * target struct: | |
453 | * | |
ca5ecddf | 454 | * bar = rcu_dereference_check(foo->bar, lockdep_is_held(&foo->lock) || |
c08c68dd | 455 | * atomic_read(&foo->usage) == 0); |
ca5ecddf PM |
456 | * |
457 | * Inserts memory barriers on architectures that require them | |
458 | * (currently only the Alpha), prevents the compiler from refetching | |
459 | * (and from merging fetches), and, more importantly, documents exactly | |
460 | * which pointers are protected by RCU and checks that the pointer is | |
461 | * annotated as __rcu. | |
632ee200 PM |
462 | */ |
463 | #define rcu_dereference_check(p, c) \ | |
b826565a | 464 | __rcu_dereference_check((p), (c) || rcu_read_lock_held(), __rcu) |
ca5ecddf PM |
465 | |
466 | /** | |
467 | * rcu_dereference_bh_check() - rcu_dereference_bh with debug checking | |
468 | * @p: The pointer to read, prior to dereferencing | |
469 | * @c: The conditions under which the dereference will take place | |
470 | * | |
471 | * This is the RCU-bh counterpart to rcu_dereference_check(). | |
472 | */ | |
473 | #define rcu_dereference_bh_check(p, c) \ | |
b826565a | 474 | __rcu_dereference_check((p), (c) || rcu_read_lock_bh_held(), __rcu) |
632ee200 | 475 | |
b62730ba | 476 | /** |
ca5ecddf PM |
477 | * rcu_dereference_sched_check() - rcu_dereference_sched with debug checking |
478 | * @p: The pointer to read, prior to dereferencing | |
479 | * @c: The conditions under which the dereference will take place | |
480 | * | |
481 | * This is the RCU-sched counterpart to rcu_dereference_check(). | |
482 | */ | |
483 | #define rcu_dereference_sched_check(p, c) \ | |
b826565a | 484 | __rcu_dereference_check((p), (c) || rcu_read_lock_sched_held(), \ |
ca5ecddf PM |
485 | __rcu) |
486 | ||
12bcbe66 SR |
487 | /* |
488 | * The tracing infrastructure traces RCU (we want that), but unfortunately | |
489 | * some of the RCU checks causes tracing to lock up the system. | |
490 | * | |
f039f0af | 491 | * The no-tracing version of rcu_dereference_raw() must not call |
12bcbe66 SR |
492 | * rcu_read_lock_held(). |
493 | */ | |
494 | #define rcu_dereference_raw_notrace(p) __rcu_dereference_check((p), 1, __rcu) | |
495 | ||
ca5ecddf PM |
496 | /** |
497 | * rcu_dereference_protected() - fetch RCU pointer when updates prevented | |
498 | * @p: The pointer to read, prior to dereferencing | |
499 | * @c: The conditions under which the dereference will take place | |
b62730ba PM |
500 | * |
501 | * Return the value of the specified RCU-protected pointer, but omit | |
137f61f6 PM |
502 | * the READ_ONCE(). This is useful in cases where update-side locks |
503 | * prevent the value of the pointer from changing. Please note that this | |
504 | * primitive does *not* prevent the compiler from repeating this reference | |
505 | * or combining it with other references, so it should not be used without | |
506 | * protection of appropriate locks. | |
ca5ecddf PM |
507 | * |
508 | * This function is only for update-side use. Using this function | |
509 | * when protected only by rcu_read_lock() will result in infrequent | |
510 | * but very ugly failures. | |
b62730ba PM |
511 | */ |
512 | #define rcu_dereference_protected(p, c) \ | |
ca5ecddf | 513 | __rcu_dereference_protected((p), (c), __rcu) |
b62730ba | 514 | |
bc33f24b | 515 | |
b62730ba | 516 | /** |
ca5ecddf PM |
517 | * rcu_dereference() - fetch RCU-protected pointer for dereferencing |
518 | * @p: The pointer to read, prior to dereferencing | |
b62730ba | 519 | * |
ca5ecddf | 520 | * This is a simple wrapper around rcu_dereference_check(). |
b62730ba | 521 | */ |
ca5ecddf | 522 | #define rcu_dereference(p) rcu_dereference_check(p, 0) |
b62730ba | 523 | |
1da177e4 | 524 | /** |
ca5ecddf PM |
525 | * rcu_dereference_bh() - fetch an RCU-bh-protected pointer for dereferencing |
526 | * @p: The pointer to read, prior to dereferencing | |
527 | * | |
528 | * Makes rcu_dereference_check() do the dirty work. | |
529 | */ | |
530 | #define rcu_dereference_bh(p) rcu_dereference_bh_check(p, 0) | |
531 | ||
532 | /** | |
533 | * rcu_dereference_sched() - fetch RCU-sched-protected pointer for dereferencing | |
534 | * @p: The pointer to read, prior to dereferencing | |
535 | * | |
536 | * Makes rcu_dereference_check() do the dirty work. | |
537 | */ | |
538 | #define rcu_dereference_sched(p) rcu_dereference_sched_check(p, 0) | |
539 | ||
c3ac7cf1 PM |
540 | /** |
541 | * rcu_pointer_handoff() - Hand off a pointer from RCU to other mechanism | |
542 | * @p: The pointer to hand off | |
543 | * | |
544 | * This is simply an identity function, but it documents where a pointer | |
545 | * is handed off from RCU to some other synchronization mechanism, for | |
546 | * example, reference counting or locking. In C11, it would map to | |
1445e917 MCC |
547 | * kill_dependency(). It could be used as follows:: |
548 | * | |
c3ac7cf1 PM |
549 | * rcu_read_lock(); |
550 | * p = rcu_dereference(gp); | |
551 | * long_lived = is_long_lived(p); | |
552 | * if (long_lived) { | |
553 | * if (!atomic_inc_not_zero(p->refcnt)) | |
554 | * long_lived = false; | |
555 | * else | |
556 | * p = rcu_pointer_handoff(p); | |
557 | * } | |
558 | * rcu_read_unlock(); | |
559 | */ | |
560 | #define rcu_pointer_handoff(p) (p) | |
561 | ||
ca5ecddf PM |
562 | /** |
563 | * rcu_read_lock() - mark the beginning of an RCU read-side critical section | |
1da177e4 | 564 | * |
9b06e818 | 565 | * When synchronize_rcu() is invoked on one CPU while other CPUs |
1da177e4 | 566 | * are within RCU read-side critical sections, then the |
9b06e818 | 567 | * synchronize_rcu() is guaranteed to block until after all the other |
1da177e4 LT |
568 | * CPUs exit their critical sections. Similarly, if call_rcu() is invoked |
569 | * on one CPU while other CPUs are within RCU read-side critical | |
570 | * sections, invocation of the corresponding RCU callback is deferred | |
571 | * until after the all the other CPUs exit their critical sections. | |
572 | * | |
573 | * Note, however, that RCU callbacks are permitted to run concurrently | |
77d8485a | 574 | * with new RCU read-side critical sections. One way that this can happen |
1da177e4 LT |
575 | * is via the following sequence of events: (1) CPU 0 enters an RCU |
576 | * read-side critical section, (2) CPU 1 invokes call_rcu() to register | |
577 | * an RCU callback, (3) CPU 0 exits the RCU read-side critical section, | |
578 | * (4) CPU 2 enters a RCU read-side critical section, (5) the RCU | |
579 | * callback is invoked. This is legal, because the RCU read-side critical | |
580 | * section that was running concurrently with the call_rcu() (and which | |
581 | * therefore might be referencing something that the corresponding RCU | |
582 | * callback would free up) has completed before the corresponding | |
583 | * RCU callback is invoked. | |
584 | * | |
585 | * RCU read-side critical sections may be nested. Any deferred actions | |
586 | * will be deferred until the outermost RCU read-side critical section | |
587 | * completes. | |
588 | * | |
9079fd7c PM |
589 | * You can avoid reading and understanding the next paragraph by |
590 | * following this rule: don't put anything in an rcu_read_lock() RCU | |
591 | * read-side critical section that would block in a !PREEMPT kernel. | |
592 | * But if you want the full story, read on! | |
593 | * | |
ab74fdfd PM |
594 | * In non-preemptible RCU implementations (TREE_RCU and TINY_RCU), |
595 | * it is illegal to block while in an RCU read-side critical section. | |
28f6569a | 596 | * In preemptible RCU implementations (PREEMPT_RCU) in CONFIG_PREEMPT |
ab74fdfd PM |
597 | * kernel builds, RCU read-side critical sections may be preempted, |
598 | * but explicit blocking is illegal. Finally, in preemptible RCU | |
599 | * implementations in real-time (with -rt patchset) kernel builds, RCU | |
600 | * read-side critical sections may be preempted and they may also block, but | |
601 | * only when acquiring spinlocks that are subject to priority inheritance. | |
1da177e4 | 602 | */ |
bc33f24b PM |
603 | static inline void rcu_read_lock(void) |
604 | { | |
605 | __rcu_read_lock(); | |
606 | __acquire(RCU); | |
d8ab29f8 | 607 | rcu_lock_acquire(&rcu_lock_map); |
f78f5b90 PM |
608 | RCU_LOCKDEP_WARN(!rcu_is_watching(), |
609 | "rcu_read_lock() used illegally while idle"); | |
bc33f24b | 610 | } |
1da177e4 | 611 | |
1da177e4 LT |
612 | /* |
613 | * So where is rcu_write_lock()? It does not exist, as there is no | |
614 | * way for writers to lock out RCU readers. This is a feature, not | |
615 | * a bug -- this property is what provides RCU's performance benefits. | |
616 | * Of course, writers must coordinate with each other. The normal | |
617 | * spinlock primitives work well for this, but any other technique may be | |
618 | * used as well. RCU does not care how the writers keep out of each | |
619 | * others' way, as long as they do so. | |
620 | */ | |
3d76c082 PM |
621 | |
622 | /** | |
ca5ecddf | 623 | * rcu_read_unlock() - marks the end of an RCU read-side critical section. |
3d76c082 | 624 | * |
f27bc487 PM |
625 | * In most situations, rcu_read_unlock() is immune from deadlock. |
626 | * However, in kernels built with CONFIG_RCU_BOOST, rcu_read_unlock() | |
627 | * is responsible for deboosting, which it does via rt_mutex_unlock(). | |
628 | * Unfortunately, this function acquires the scheduler's runqueue and | |
629 | * priority-inheritance spinlocks. This means that deadlock could result | |
630 | * if the caller of rcu_read_unlock() already holds one of these locks or | |
ec84b27f | 631 | * any lock that is ever acquired while holding them. |
f27bc487 PM |
632 | * |
633 | * That said, RCU readers are never priority boosted unless they were | |
634 | * preempted. Therefore, one way to avoid deadlock is to make sure | |
635 | * that preemption never happens within any RCU read-side critical | |
636 | * section whose outermost rcu_read_unlock() is called with one of | |
637 | * rt_mutex_unlock()'s locks held. Such preemption can be avoided in | |
638 | * a number of ways, for example, by invoking preempt_disable() before | |
639 | * critical section's outermost rcu_read_lock(). | |
640 | * | |
641 | * Given that the set of locks acquired by rt_mutex_unlock() might change | |
642 | * at any time, a somewhat more future-proofed approach is to make sure | |
643 | * that that preemption never happens within any RCU read-side critical | |
644 | * section whose outermost rcu_read_unlock() is called with irqs disabled. | |
645 | * This approach relies on the fact that rt_mutex_unlock() currently only | |
646 | * acquires irq-disabled locks. | |
647 | * | |
648 | * The second of these two approaches is best in most situations, | |
649 | * however, the first approach can also be useful, at least to those | |
650 | * developers willing to keep abreast of the set of locks acquired by | |
651 | * rt_mutex_unlock(). | |
652 | * | |
3d76c082 PM |
653 | * See rcu_read_lock() for more information. |
654 | */ | |
bc33f24b PM |
655 | static inline void rcu_read_unlock(void) |
656 | { | |
f78f5b90 PM |
657 | RCU_LOCKDEP_WARN(!rcu_is_watching(), |
658 | "rcu_read_unlock() used illegally while idle"); | |
bc33f24b PM |
659 | __release(RCU); |
660 | __rcu_read_unlock(); | |
d24209bb | 661 | rcu_lock_release(&rcu_lock_map); /* Keep acq info for rls diags. */ |
bc33f24b | 662 | } |
1da177e4 LT |
663 | |
664 | /** | |
ca5ecddf | 665 | * rcu_read_lock_bh() - mark the beginning of an RCU-bh critical section |
1da177e4 | 666 | * |
82fcecfa | 667 | * This is equivalent of rcu_read_lock(), but also disables softirqs. |
2bd8b1a2 PM |
668 | * Note that anything else that disables softirqs can also serve as |
669 | * an RCU read-side critical section. | |
3842a083 PM |
670 | * |
671 | * Note that rcu_read_lock_bh() and the matching rcu_read_unlock_bh() | |
672 | * must occur in the same context, for example, it is illegal to invoke | |
673 | * rcu_read_unlock_bh() from one task if the matching rcu_read_lock_bh() | |
674 | * was invoked from some other task. | |
1da177e4 | 675 | */ |
bc33f24b PM |
676 | static inline void rcu_read_lock_bh(void) |
677 | { | |
6206ab9b | 678 | local_bh_disable(); |
bc33f24b | 679 | __acquire(RCU_BH); |
d8ab29f8 | 680 | rcu_lock_acquire(&rcu_bh_lock_map); |
f78f5b90 PM |
681 | RCU_LOCKDEP_WARN(!rcu_is_watching(), |
682 | "rcu_read_lock_bh() used illegally while idle"); | |
bc33f24b | 683 | } |
1da177e4 LT |
684 | |
685 | /* | |
686 | * rcu_read_unlock_bh - marks the end of a softirq-only RCU critical section | |
687 | * | |
688 | * See rcu_read_lock_bh() for more information. | |
689 | */ | |
bc33f24b PM |
690 | static inline void rcu_read_unlock_bh(void) |
691 | { | |
f78f5b90 PM |
692 | RCU_LOCKDEP_WARN(!rcu_is_watching(), |
693 | "rcu_read_unlock_bh() used illegally while idle"); | |
d8ab29f8 | 694 | rcu_lock_release(&rcu_bh_lock_map); |
bc33f24b | 695 | __release(RCU_BH); |
6206ab9b | 696 | local_bh_enable(); |
bc33f24b | 697 | } |
1da177e4 | 698 | |
1c50b728 | 699 | /** |
ca5ecddf | 700 | * rcu_read_lock_sched() - mark the beginning of a RCU-sched critical section |
1c50b728 | 701 | * |
2bd8b1a2 PM |
702 | * This is equivalent of rcu_read_lock(), but disables preemption. |
703 | * Read-side critical sections can also be introduced by anything else | |
704 | * that disables preemption, including local_irq_disable() and friends. | |
3842a083 PM |
705 | * |
706 | * Note that rcu_read_lock_sched() and the matching rcu_read_unlock_sched() | |
707 | * must occur in the same context, for example, it is illegal to invoke | |
708 | * rcu_read_unlock_sched() from process context if the matching | |
709 | * rcu_read_lock_sched() was invoked from an NMI handler. | |
1c50b728 | 710 | */ |
d6714c22 PM |
711 | static inline void rcu_read_lock_sched(void) |
712 | { | |
713 | preempt_disable(); | |
bc33f24b | 714 | __acquire(RCU_SCHED); |
d8ab29f8 | 715 | rcu_lock_acquire(&rcu_sched_lock_map); |
f78f5b90 PM |
716 | RCU_LOCKDEP_WARN(!rcu_is_watching(), |
717 | "rcu_read_lock_sched() used illegally while idle"); | |
d6714c22 | 718 | } |
1eba8f84 PM |
719 | |
720 | /* Used by lockdep and tracing: cannot be traced, cannot call lockdep. */ | |
7c614d64 | 721 | static inline notrace void rcu_read_lock_sched_notrace(void) |
d6714c22 PM |
722 | { |
723 | preempt_disable_notrace(); | |
bc33f24b | 724 | __acquire(RCU_SCHED); |
d6714c22 | 725 | } |
1c50b728 MD |
726 | |
727 | /* | |
728 | * rcu_read_unlock_sched - marks the end of a RCU-classic critical section | |
729 | * | |
730 | * See rcu_read_lock_sched for more information. | |
731 | */ | |
d6714c22 PM |
732 | static inline void rcu_read_unlock_sched(void) |
733 | { | |
f78f5b90 PM |
734 | RCU_LOCKDEP_WARN(!rcu_is_watching(), |
735 | "rcu_read_unlock_sched() used illegally while idle"); | |
d8ab29f8 | 736 | rcu_lock_release(&rcu_sched_lock_map); |
bc33f24b | 737 | __release(RCU_SCHED); |
d6714c22 PM |
738 | preempt_enable(); |
739 | } | |
1eba8f84 PM |
740 | |
741 | /* Used by lockdep and tracing: cannot be traced, cannot call lockdep. */ | |
7c614d64 | 742 | static inline notrace void rcu_read_unlock_sched_notrace(void) |
d6714c22 | 743 | { |
bc33f24b | 744 | __release(RCU_SCHED); |
d6714c22 PM |
745 | preempt_enable_notrace(); |
746 | } | |
1c50b728 | 747 | |
ca5ecddf PM |
748 | /** |
749 | * RCU_INIT_POINTER() - initialize an RCU protected pointer | |
27fdb35f PM |
750 | * @p: The pointer to be initialized. |
751 | * @v: The value to initialized the pointer to. | |
ca5ecddf | 752 | * |
6846c0c5 PM |
753 | * Initialize an RCU-protected pointer in special cases where readers |
754 | * do not need ordering constraints on the CPU or the compiler. These | |
755 | * special cases are: | |
756 | * | |
27fdb35f | 757 | * 1. This use of RCU_INIT_POINTER() is NULLing out the pointer *or* |
6846c0c5 | 758 | * 2. The caller has taken whatever steps are required to prevent |
27fdb35f | 759 | * RCU readers from concurrently accessing this pointer *or* |
6846c0c5 | 760 | * 3. The referenced data structure has already been exposed to |
27fdb35f PM |
761 | * readers either at compile time or via rcu_assign_pointer() *and* |
762 | * | |
763 | * a. You have not made *any* reader-visible changes to | |
764 | * this structure since then *or* | |
6846c0c5 PM |
765 | * b. It is OK for readers accessing this structure from its |
766 | * new location to see the old state of the structure. (For | |
767 | * example, the changes were to statistical counters or to | |
768 | * other state where exact synchronization is not required.) | |
769 | * | |
770 | * Failure to follow these rules governing use of RCU_INIT_POINTER() will | |
771 | * result in impossible-to-diagnose memory corruption. As in the structures | |
772 | * will look OK in crash dumps, but any concurrent RCU readers might | |
773 | * see pre-initialized values of the referenced data structure. So | |
774 | * please be very careful how you use RCU_INIT_POINTER()!!! | |
775 | * | |
776 | * If you are creating an RCU-protected linked structure that is accessed | |
777 | * by a single external-to-structure RCU-protected pointer, then you may | |
778 | * use RCU_INIT_POINTER() to initialize the internal RCU-protected | |
779 | * pointers, but you must use rcu_assign_pointer() to initialize the | |
27fdb35f | 780 | * external-to-structure pointer *after* you have completely initialized |
6846c0c5 | 781 | * the reader-accessible portions of the linked structure. |
71a9b269 PM |
782 | * |
783 | * Note that unlike rcu_assign_pointer(), RCU_INIT_POINTER() provides no | |
784 | * ordering guarantees for either the CPU or the compiler. | |
ca5ecddf PM |
785 | */ |
786 | #define RCU_INIT_POINTER(p, v) \ | |
d1b88eb9 | 787 | do { \ |
1a6c9b26 | 788 | rcu_dereference_sparse(p, __rcu); \ |
155d1d12 | 789 | WRITE_ONCE(p, RCU_INITIALIZER(v)); \ |
d1b88eb9 | 790 | } while (0) |
9ab1544e | 791 | |
172708d0 PM |
792 | /** |
793 | * RCU_POINTER_INITIALIZER() - statically initialize an RCU protected pointer | |
27fdb35f PM |
794 | * @p: The pointer to be initialized. |
795 | * @v: The value to initialized the pointer to. | |
172708d0 PM |
796 | * |
797 | * GCC-style initialization for an RCU-protected pointer in a structure field. | |
798 | */ | |
799 | #define RCU_POINTER_INITIALIZER(p, v) \ | |
462225ae | 800 | .p = RCU_INITIALIZER(v) |
9ab1544e | 801 | |
d8169d4c JE |
802 | /* |
803 | * Does the specified offset indicate that the corresponding rcu_head | |
804 | * structure can be handled by kfree_rcu()? | |
805 | */ | |
806 | #define __is_kfree_rcu_offset(offset) ((offset) < 4096) | |
807 | ||
808 | /* | |
809 | * Helper macro for kfree_rcu() to prevent argument-expansion eyestrain. | |
810 | */ | |
811 | #define __kfree_rcu(head, offset) \ | |
812 | do { \ | |
813 | BUILD_BUG_ON(!__is_kfree_rcu_offset(offset)); \ | |
b6a4ae76 | 814 | kfree_call_rcu(head, (rcu_callback_t)(unsigned long)(offset)); \ |
d8169d4c JE |
815 | } while (0) |
816 | ||
9ab1544e LJ |
817 | /** |
818 | * kfree_rcu() - kfree an object after a grace period. | |
819 | * @ptr: pointer to kfree | |
820 | * @rcu_head: the name of the struct rcu_head within the type of @ptr. | |
821 | * | |
822 | * Many rcu callbacks functions just call kfree() on the base structure. | |
823 | * These functions are trivial, but their size adds up, and furthermore | |
824 | * when they are used in a kernel module, that module must invoke the | |
825 | * high-latency rcu_barrier() function at module-unload time. | |
826 | * | |
827 | * The kfree_rcu() function handles this issue. Rather than encoding a | |
828 | * function address in the embedded rcu_head structure, kfree_rcu() instead | |
829 | * encodes the offset of the rcu_head structure within the base structure. | |
830 | * Because the functions are not allowed in the low-order 4096 bytes of | |
831 | * kernel virtual memory, offsets up to 4095 bytes can be accommodated. | |
832 | * If the offset is larger than 4095 bytes, a compile-time error will | |
833 | * be generated in __kfree_rcu(). If this error is triggered, you can | |
834 | * either fall back to use of call_rcu() or rearrange the structure to | |
835 | * position the rcu_head structure into the first 4096 bytes. | |
836 | * | |
837 | * Note that the allowable offset might decrease in the future, for example, | |
838 | * to allow something like kmem_cache_free_rcu(). | |
d8169d4c JE |
839 | * |
840 | * The BUILD_BUG_ON check must not involve any function calls, hence the | |
841 | * checks are done in macros here. | |
9ab1544e LJ |
842 | */ |
843 | #define kfree_rcu(ptr, rcu_head) \ | |
844 | __kfree_rcu(&((ptr)->rcu_head), offsetof(typeof(*(ptr)), rcu_head)) | |
845 | ||
0edd1b17 | 846 | |
d85b62f1 PM |
847 | /* |
848 | * Place this after a lock-acquisition primitive to guarantee that | |
849 | * an UNLOCK+LOCK pair acts as a full barrier. This guarantee applies | |
850 | * if the UNLOCK and LOCK are executed by the same CPU or if the | |
851 | * UNLOCK and LOCK operate on the same lock variable. | |
852 | */ | |
77e58496 | 853 | #ifdef CONFIG_ARCH_WEAK_RELEASE_ACQUIRE |
d85b62f1 | 854 | #define smp_mb__after_unlock_lock() smp_mb() /* Full ordering for lock. */ |
77e58496 | 855 | #else /* #ifdef CONFIG_ARCH_WEAK_RELEASE_ACQUIRE */ |
d85b62f1 | 856 | #define smp_mb__after_unlock_lock() do { } while (0) |
77e58496 | 857 | #endif /* #else #ifdef CONFIG_ARCH_WEAK_RELEASE_ACQUIRE */ |
d85b62f1 | 858 | |
274529ba | 859 | |
74de6960 PM |
860 | /* Has the specified rcu_head structure been handed to call_rcu()? */ |
861 | ||
862 | /* | |
863 | * rcu_head_init - Initialize rcu_head for rcu_head_after_call_rcu() | |
864 | * @rhp: The rcu_head structure to initialize. | |
865 | * | |
866 | * If you intend to invoke rcu_head_after_call_rcu() to test whether a | |
867 | * given rcu_head structure has already been passed to call_rcu(), then | |
868 | * you must also invoke this rcu_head_init() function on it just after | |
869 | * allocating that structure. Calls to this function must not race with | |
870 | * calls to call_rcu(), rcu_head_after_call_rcu(), or callback invocation. | |
871 | */ | |
872 | static inline void rcu_head_init(struct rcu_head *rhp) | |
873 | { | |
874 | rhp->func = (rcu_callback_t)~0L; | |
875 | } | |
876 | ||
877 | /* | |
878 | * rcu_head_after_call_rcu - Has this rcu_head been passed to call_rcu()? | |
879 | * @rhp: The rcu_head structure to test. | |
880 | * @func: The function passed to call_rcu() along with @rhp. | |
881 | * | |
882 | * Returns @true if the @rhp has been passed to call_rcu() with @func, | |
883 | * and @false otherwise. Emits a warning in any other case, including | |
884 | * the case where @rhp has already been invoked after a grace period. | |
885 | * Calls to this function must not race with callback invocation. One way | |
886 | * to avoid such races is to enclose the call to rcu_head_after_call_rcu() | |
887 | * in an RCU read-side critical section that includes a read-side fetch | |
888 | * of the pointer to the structure containing @rhp. | |
889 | */ | |
890 | static inline bool | |
891 | rcu_head_after_call_rcu(struct rcu_head *rhp, rcu_callback_t f) | |
892 | { | |
893 | if (READ_ONCE(rhp->func) == f) | |
894 | return true; | |
895 | WARN_ON_ONCE(READ_ONCE(rhp->func) != (rcu_callback_t)~0L); | |
896 | return false; | |
897 | } | |
898 | ||
899 | ||
4c7e9c14 PM |
900 | /* Transitional pre-consolidation compatibility definitions. */ |
901 | ||
902 | static inline void synchronize_rcu_bh(void) | |
903 | { | |
904 | synchronize_rcu(); | |
905 | } | |
906 | ||
907 | static inline void synchronize_rcu_bh_expedited(void) | |
908 | { | |
909 | synchronize_rcu_expedited(); | |
910 | } | |
911 | ||
912 | static inline void call_rcu_bh(struct rcu_head *head, rcu_callback_t func) | |
913 | { | |
914 | call_rcu(head, func); | |
915 | } | |
916 | ||
917 | static inline void rcu_barrier_bh(void) | |
918 | { | |
919 | rcu_barrier(); | |
920 | } | |
921 | ||
a8bb74ac PM |
922 | static inline void synchronize_sched(void) |
923 | { | |
924 | synchronize_rcu(); | |
925 | } | |
926 | ||
927 | static inline void synchronize_sched_expedited(void) | |
928 | { | |
929 | synchronize_rcu_expedited(); | |
930 | } | |
931 | ||
932 | static inline void call_rcu_sched(struct rcu_head *head, rcu_callback_t func) | |
933 | { | |
934 | call_rcu(head, func); | |
935 | } | |
936 | ||
937 | static inline void rcu_barrier_sched(void) | |
938 | { | |
939 | rcu_barrier(); | |
940 | } | |
941 | ||
942 | static inline unsigned long get_state_synchronize_sched(void) | |
943 | { | |
944 | return get_state_synchronize_rcu(); | |
945 | } | |
946 | ||
947 | static inline void cond_synchronize_sched(unsigned long oldstate) | |
948 | { | |
949 | cond_synchronize_rcu(oldstate); | |
950 | } | |
951 | ||
1da177e4 | 952 | #endif /* __LINUX_RCUPDATE_H */ |