Commit | Line | Data |
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73604da5 | 1 | /* SPDX-License-Identifier: GPL-2.0+ */ |
1da177e4 | 2 | /* |
a71fca58 | 3 | * Read-Copy Update mechanism for mutual exclusion |
1da177e4 | 4 | * |
01c1c660 | 5 | * Copyright IBM Corporation, 2001 |
1da177e4 LT |
6 | * |
7 | * Author: Dipankar Sarma <dipankar@in.ibm.com> | |
a71fca58 | 8 | * |
73604da5 | 9 | * Based on the original work by Paul McKenney <paulmck@vnet.ibm.com> |
1da177e4 LT |
10 | * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen. |
11 | * Papers: | |
12 | * http://www.rdrop.com/users/paulmck/paper/rclockpdcsproof.pdf | |
13 | * http://lse.sourceforge.net/locking/rclock_OLS.2001.05.01c.sc.pdf (OLS2001) | |
14 | * | |
15 | * For detailed explanation of Read-Copy Update mechanism see - | |
a71fca58 | 16 | * http://lse.sourceforge.net/locking/rcupdate.html |
1da177e4 LT |
17 | * |
18 | */ | |
19 | ||
20 | #ifndef __LINUX_RCUPDATE_H | |
21 | #define __LINUX_RCUPDATE_H | |
22 | ||
99098751 | 23 | #include <linux/types.h> |
ca5ecddf | 24 | #include <linux/compiler.h> |
5f192ab0 | 25 | #include <linux/atomic.h> |
4929c913 | 26 | #include <linux/irqflags.h> |
5f192ab0 PM |
27 | #include <linux/preempt.h> |
28 | #include <linux/bottom_half.h> | |
29 | #include <linux/lockdep.h> | |
30 | #include <asm/processor.h> | |
31 | #include <linux/cpumask.h> | |
c1ad348b | 32 | |
a3dc3fb1 PM |
33 | #define ULONG_CMP_GE(a, b) (ULONG_MAX / 2 >= (a) - (b)) |
34 | #define ULONG_CMP_LT(a, b) (ULONG_MAX / 2 < (a) - (b)) | |
c0f4dfd4 | 35 | #define ulong2long(a) (*(long *)(&(a))) |
a3dc3fb1 | 36 | |
03b042bf | 37 | /* Exported common interfaces */ |
709fdce7 | 38 | void call_rcu(struct rcu_head *head, rcu_callback_t func); |
53c6d4ed | 39 | void rcu_barrier_tasks(void); |
c84aad76 | 40 | void rcu_barrier_tasks_rude(void); |
709fdce7 | 41 | void synchronize_rcu(void); |
8315f422 | 42 | |
a3dc3fb1 PM |
43 | #ifdef CONFIG_PREEMPT_RCU |
44 | ||
584dc4ce TB |
45 | void __rcu_read_lock(void); |
46 | void __rcu_read_unlock(void); | |
7b0b759b | 47 | |
a3dc3fb1 PM |
48 | /* |
49 | * Defined as a macro as it is a very low level header included from | |
50 | * areas that don't even know about current. This gives the rcu_read_lock() | |
51 | * nesting depth, but makes sense only if CONFIG_PREEMPT_RCU -- in other | |
52 | * types of kernel builds, the rcu_read_lock() nesting depth is unknowable. | |
53 | */ | |
54 | #define rcu_preempt_depth() (current->rcu_read_lock_nesting) | |
55 | ||
7b0b759b PM |
56 | #else /* #ifdef CONFIG_PREEMPT_RCU */ |
57 | ||
58 | static inline void __rcu_read_lock(void) | |
59 | { | |
66be4e66 | 60 | preempt_disable(); |
7b0b759b PM |
61 | } |
62 | ||
63 | static inline void __rcu_read_unlock(void) | |
64 | { | |
66be4e66 | 65 | preempt_enable(); |
7b0b759b PM |
66 | } |
67 | ||
7b0b759b PM |
68 | static inline int rcu_preempt_depth(void) |
69 | { | |
70 | return 0; | |
71 | } | |
72 | ||
73 | #endif /* #else #ifdef CONFIG_PREEMPT_RCU */ | |
74 | ||
75 | /* Internal to kernel */ | |
584dc4ce | 76 | void rcu_init(void); |
825c5bd2 | 77 | extern int rcu_scheduler_active __read_mostly; |
c98cac60 | 78 | void rcu_sched_clock_irq(int user); |
27d50c7e | 79 | void rcu_report_dead(unsigned int cpu); |
a58163d8 | 80 | void rcutree_migrate_callbacks(int cpu); |
2b1d5024 | 81 | |
61f38db3 RR |
82 | #ifdef CONFIG_RCU_STALL_COMMON |
83 | void rcu_sysrq_start(void); | |
84 | void rcu_sysrq_end(void); | |
85 | #else /* #ifdef CONFIG_RCU_STALL_COMMON */ | |
d0df7a34 PM |
86 | static inline void rcu_sysrq_start(void) { } |
87 | static inline void rcu_sysrq_end(void) { } | |
61f38db3 RR |
88 | #endif /* #else #ifdef CONFIG_RCU_STALL_COMMON */ |
89 | ||
d1ec4c34 | 90 | #ifdef CONFIG_NO_HZ_FULL |
584dc4ce TB |
91 | void rcu_user_enter(void); |
92 | void rcu_user_exit(void); | |
2b1d5024 FW |
93 | #else |
94 | static inline void rcu_user_enter(void) { } | |
95 | static inline void rcu_user_exit(void) { } | |
d1ec4c34 | 96 | #endif /* CONFIG_NO_HZ_FULL */ |
2b1d5024 | 97 | |
f4579fc5 PM |
98 | #ifdef CONFIG_RCU_NOCB_CPU |
99 | void rcu_init_nohz(void); | |
100 | #else /* #ifdef CONFIG_RCU_NOCB_CPU */ | |
d0df7a34 | 101 | static inline void rcu_init_nohz(void) { } |
f4579fc5 PM |
102 | #endif /* #else #ifdef CONFIG_RCU_NOCB_CPU */ |
103 | ||
8a2ecf47 PM |
104 | /** |
105 | * RCU_NONIDLE - Indicate idle-loop code that needs RCU readers | |
106 | * @a: Code that RCU needs to pay attention to. | |
107 | * | |
2bd8b1a2 PM |
108 | * RCU read-side critical sections are forbidden in the inner idle loop, |
109 | * that is, between the rcu_idle_enter() and the rcu_idle_exit() -- RCU | |
110 | * will happily ignore any such read-side critical sections. However, | |
111 | * things like powertop need tracepoints in the inner idle loop. | |
8a2ecf47 PM |
112 | * |
113 | * This macro provides the way out: RCU_NONIDLE(do_something_with_RCU()) | |
810ce8b5 PM |
114 | * will tell RCU that it needs to pay attention, invoke its argument |
115 | * (in this example, calling the do_something_with_RCU() function), | |
8a2ecf47 | 116 | * and then tell RCU to go back to ignoring this CPU. It is permissible |
810ce8b5 PM |
117 | * to nest RCU_NONIDLE() wrappers, but not indefinitely (but the limit is |
118 | * on the order of a million or so, even on 32-bit systems). It is | |
119 | * not legal to block within RCU_NONIDLE(), nor is it permissible to | |
120 | * transfer control either into or out of RCU_NONIDLE()'s statement. | |
8a2ecf47 PM |
121 | */ |
122 | #define RCU_NONIDLE(a) \ | |
123 | do { \ | |
7c9906ca | 124 | rcu_irq_enter_irqson(); \ |
8a2ecf47 | 125 | do { a; } while (0); \ |
7c9906ca | 126 | rcu_irq_exit_irqson(); \ |
8a2ecf47 PM |
127 | } while (0) |
128 | ||
8315f422 | 129 | /* |
6f56f714 PM |
130 | * Note a quasi-voluntary context switch for RCU-tasks's benefit. |
131 | * This is a macro rather than an inline function to avoid #include hell. | |
8315f422 | 132 | */ |
5873b8a9 | 133 | #ifdef CONFIG_TASKS_RCU_GENERIC |
43766c3e PM |
134 | |
135 | # ifdef CONFIG_TASKS_RCU | |
136 | # define rcu_tasks_classic_qs(t, preempt) \ | |
137 | do { \ | |
138 | if (!(preempt) && READ_ONCE((t)->rcu_tasks_holdout)) \ | |
139 | WRITE_ONCE((t)->rcu_tasks_holdout, false); \ | |
8315f422 | 140 | } while (0) |
7e42776d PM |
141 | void call_rcu_tasks(struct rcu_head *head, rcu_callback_t func); |
142 | void synchronize_rcu_tasks(void); | |
43766c3e PM |
143 | # else |
144 | # define rcu_tasks_classic_qs(t, preempt) do { } while (0) | |
145 | # define call_rcu_tasks call_rcu | |
146 | # define synchronize_rcu_tasks synchronize_rcu | |
147 | # endif | |
148 | ||
149 | # ifdef CONFIG_TASKS_RCU_TRACE | |
150 | # define rcu_tasks_trace_qs(t) \ | |
151 | do { \ | |
152 | if (!likely(READ_ONCE((t)->trc_reader_checked)) && \ | |
153 | !unlikely(READ_ONCE((t)->trc_reader_nesting))) { \ | |
154 | smp_store_release(&(t)->trc_reader_checked, true); \ | |
155 | smp_mb(); /* Readers partitioned by store. */ \ | |
156 | } \ | |
157 | } while (0) | |
158 | # else | |
159 | # define rcu_tasks_trace_qs(t) do { } while (0) | |
160 | # endif | |
161 | ||
162 | #define rcu_tasks_qs(t, preempt) \ | |
163 | do { \ | |
164 | rcu_tasks_classic_qs((t), (preempt)); \ | |
165 | rcu_tasks_trace_qs((t)); \ | |
166 | } while (0) | |
167 | ||
168 | # ifdef CONFIG_TASKS_RUDE_RCU | |
c84aad76 PM |
169 | void call_rcu_tasks_rude(struct rcu_head *head, rcu_callback_t func); |
170 | void synchronize_rcu_tasks_rude(void); | |
43766c3e PM |
171 | # endif |
172 | ||
173 | #define rcu_note_voluntary_context_switch(t) rcu_tasks_qs(t, false) | |
ccdd29ff PM |
174 | void exit_tasks_rcu_start(void); |
175 | void exit_tasks_rcu_finish(void); | |
5873b8a9 | 176 | #else /* #ifdef CONFIG_TASKS_RCU_GENERIC */ |
43766c3e | 177 | #define rcu_tasks_qs(t, preempt) do { } while (0) |
4d232dfe | 178 | #define rcu_note_voluntary_context_switch(t) do { } while (0) |
2bd8b1a2 | 179 | #define call_rcu_tasks call_rcu |
a8bb74ac | 180 | #define synchronize_rcu_tasks synchronize_rcu |
ccdd29ff PM |
181 | static inline void exit_tasks_rcu_start(void) { } |
182 | static inline void exit_tasks_rcu_finish(void) { } | |
5873b8a9 | 183 | #endif /* #else #ifdef CONFIG_TASKS_RCU_GENERIC */ |
8315f422 | 184 | |
bde6c3aa | 185 | /** |
cee43939 | 186 | * cond_resched_tasks_rcu_qs - Report potential quiescent states to RCU |
bde6c3aa PM |
187 | * |
188 | * This macro resembles cond_resched(), except that it is defined to | |
189 | * report potential quiescent states to RCU-tasks even if the cond_resched() | |
90326f05 | 190 | * machinery were to be shut off, as some advocate for PREEMPTION kernels. |
bde6c3aa | 191 | */ |
cee43939 | 192 | #define cond_resched_tasks_rcu_qs() \ |
bde6c3aa | 193 | do { \ |
43766c3e | 194 | rcu_tasks_qs(current, false); \ |
07f27570 | 195 | cond_resched(); \ |
bde6c3aa PM |
196 | } while (0) |
197 | ||
2c42818e PM |
198 | /* |
199 | * Infrastructure to implement the synchronize_() primitives in | |
200 | * TREE_RCU and rcu_barrier_() primitives in TINY_RCU. | |
201 | */ | |
202 | ||
b3e627d3 | 203 | #if defined(CONFIG_TREE_RCU) |
64db4cff | 204 | #include <linux/rcutree.h> |
127781d1 | 205 | #elif defined(CONFIG_TINY_RCU) |
9b1d82fa | 206 | #include <linux/rcutiny.h> |
64db4cff PM |
207 | #else |
208 | #error "Unknown RCU implementation specified to kernel configuration" | |
6b3ef48a | 209 | #endif |
01c1c660 | 210 | |
551d55a9 | 211 | /* |
b5482a06 PM |
212 | * The init_rcu_head_on_stack() and destroy_rcu_head_on_stack() calls |
213 | * are needed for dynamic initialization and destruction of rcu_head | |
214 | * on the stack, and init_rcu_head()/destroy_rcu_head() are needed for | |
215 | * dynamic initialization and destruction of statically allocated rcu_head | |
216 | * structures. However, rcu_head structures allocated dynamically in the | |
217 | * heap don't need any initialization. | |
551d55a9 MD |
218 | */ |
219 | #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD | |
546a9d85 PM |
220 | void init_rcu_head(struct rcu_head *head); |
221 | void destroy_rcu_head(struct rcu_head *head); | |
584dc4ce TB |
222 | void init_rcu_head_on_stack(struct rcu_head *head); |
223 | void destroy_rcu_head_on_stack(struct rcu_head *head); | |
551d55a9 | 224 | #else /* !CONFIG_DEBUG_OBJECTS_RCU_HEAD */ |
d0df7a34 PM |
225 | static inline void init_rcu_head(struct rcu_head *head) { } |
226 | static inline void destroy_rcu_head(struct rcu_head *head) { } | |
227 | static inline void init_rcu_head_on_stack(struct rcu_head *head) { } | |
228 | static inline void destroy_rcu_head_on_stack(struct rcu_head *head) { } | |
551d55a9 | 229 | #endif /* #else !CONFIG_DEBUG_OBJECTS_RCU_HEAD */ |
4376030a | 230 | |
c0d6d01b PM |
231 | #if defined(CONFIG_HOTPLUG_CPU) && defined(CONFIG_PROVE_RCU) |
232 | bool rcu_lockdep_current_cpu_online(void); | |
233 | #else /* #if defined(CONFIG_HOTPLUG_CPU) && defined(CONFIG_PROVE_RCU) */ | |
17a8c187 | 234 | static inline bool rcu_lockdep_current_cpu_online(void) { return true; } |
c0d6d01b PM |
235 | #endif /* #else #if defined(CONFIG_HOTPLUG_CPU) && defined(CONFIG_PROVE_RCU) */ |
236 | ||
bc33f24b | 237 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
632ee200 | 238 | |
00f49e57 FW |
239 | static inline void rcu_lock_acquire(struct lockdep_map *map) |
240 | { | |
fb9edbe9 | 241 | lock_acquire(map, 0, 0, 2, 0, NULL, _THIS_IP_); |
00f49e57 FW |
242 | } |
243 | ||
244 | static inline void rcu_lock_release(struct lockdep_map *map) | |
245 | { | |
5facae4f | 246 | lock_release(map, _THIS_IP_); |
00f49e57 FW |
247 | } |
248 | ||
bc33f24b | 249 | extern struct lockdep_map rcu_lock_map; |
632ee200 | 250 | extern struct lockdep_map rcu_bh_lock_map; |
632ee200 | 251 | extern struct lockdep_map rcu_sched_lock_map; |
24ef659a | 252 | extern struct lockdep_map rcu_callback_map; |
a235c091 | 253 | int debug_lockdep_rcu_enabled(void); |
85b39d30 | 254 | int rcu_read_lock_held(void); |
584dc4ce | 255 | int rcu_read_lock_bh_held(void); |
d5671f6b | 256 | int rcu_read_lock_sched_held(void); |
28875945 | 257 | int rcu_read_lock_any_held(void); |
632ee200 PM |
258 | |
259 | #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ | |
260 | ||
d8ab29f8 PM |
261 | # define rcu_lock_acquire(a) do { } while (0) |
262 | # define rcu_lock_release(a) do { } while (0) | |
632ee200 PM |
263 | |
264 | static inline int rcu_read_lock_held(void) | |
265 | { | |
266 | return 1; | |
267 | } | |
268 | ||
269 | static inline int rcu_read_lock_bh_held(void) | |
270 | { | |
271 | return 1; | |
272 | } | |
273 | ||
274 | static inline int rcu_read_lock_sched_held(void) | |
275 | { | |
293e2421 | 276 | return !preemptible(); |
632ee200 | 277 | } |
28875945 JFG |
278 | |
279 | static inline int rcu_read_lock_any_held(void) | |
280 | { | |
281 | return !preemptible(); | |
282 | } | |
283 | ||
632ee200 PM |
284 | #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */ |
285 | ||
286 | #ifdef CONFIG_PROVE_RCU | |
287 | ||
f78f5b90 PM |
288 | /** |
289 | * RCU_LOCKDEP_WARN - emit lockdep splat if specified condition is met | |
290 | * @c: condition to check | |
291 | * @s: informative message | |
292 | */ | |
293 | #define RCU_LOCKDEP_WARN(c, s) \ | |
294 | do { \ | |
295 | static bool __section(.data.unlikely) __warned; \ | |
296 | if (debug_lockdep_rcu_enabled() && !__warned && (c)) { \ | |
297 | __warned = true; \ | |
298 | lockdep_rcu_suspicious(__FILE__, __LINE__, s); \ | |
299 | } \ | |
300 | } while (0) | |
301 | ||
50406b98 PM |
302 | #if defined(CONFIG_PROVE_RCU) && !defined(CONFIG_PREEMPT_RCU) |
303 | static inline void rcu_preempt_sleep_check(void) | |
304 | { | |
f78f5b90 PM |
305 | RCU_LOCKDEP_WARN(lock_is_held(&rcu_lock_map), |
306 | "Illegal context switch in RCU read-side critical section"); | |
50406b98 PM |
307 | } |
308 | #else /* #ifdef CONFIG_PROVE_RCU */ | |
d0df7a34 | 309 | static inline void rcu_preempt_sleep_check(void) { } |
50406b98 PM |
310 | #endif /* #else #ifdef CONFIG_PROVE_RCU */ |
311 | ||
b3fbab05 PM |
312 | #define rcu_sleep_check() \ |
313 | do { \ | |
50406b98 | 314 | rcu_preempt_sleep_check(); \ |
f78f5b90 PM |
315 | RCU_LOCKDEP_WARN(lock_is_held(&rcu_bh_lock_map), \ |
316 | "Illegal context switch in RCU-bh read-side critical section"); \ | |
317 | RCU_LOCKDEP_WARN(lock_is_held(&rcu_sched_lock_map), \ | |
318 | "Illegal context switch in RCU-sched read-side critical section"); \ | |
b3fbab05 PM |
319 | } while (0) |
320 | ||
ca5ecddf PM |
321 | #else /* #ifdef CONFIG_PROVE_RCU */ |
322 | ||
f78f5b90 | 323 | #define RCU_LOCKDEP_WARN(c, s) do { } while (0) |
b3fbab05 | 324 | #define rcu_sleep_check() do { } while (0) |
ca5ecddf PM |
325 | |
326 | #endif /* #else #ifdef CONFIG_PROVE_RCU */ | |
327 | ||
328 | /* | |
329 | * Helper functions for rcu_dereference_check(), rcu_dereference_protected() | |
330 | * and rcu_assign_pointer(). Some of these could be folded into their | |
331 | * callers, but they are left separate in order to ease introduction of | |
2bd8b1a2 PM |
332 | * multiple pointers markings to match different RCU implementations |
333 | * (e.g., __srcu), should this make sense in the future. | |
ca5ecddf | 334 | */ |
53ecfba2 PM |
335 | |
336 | #ifdef __CHECKER__ | |
423a86a6 | 337 | #define rcu_check_sparse(p, space) \ |
53ecfba2 PM |
338 | ((void)(((typeof(*p) space *)p) == p)) |
339 | #else /* #ifdef __CHECKER__ */ | |
423a86a6 | 340 | #define rcu_check_sparse(p, space) |
53ecfba2 PM |
341 | #endif /* #else #ifdef __CHECKER__ */ |
342 | ||
ca5ecddf | 343 | #define __rcu_access_pointer(p, space) \ |
0adab9b9 | 344 | ({ \ |
7d0ae808 | 345 | typeof(*p) *_________p1 = (typeof(*p) *__force)READ_ONCE(p); \ |
423a86a6 | 346 | rcu_check_sparse(p, space); \ |
0adab9b9 JP |
347 | ((typeof(*p) __force __kernel *)(_________p1)); \ |
348 | }) | |
ca5ecddf | 349 | #define __rcu_dereference_check(p, c, space) \ |
0adab9b9 | 350 | ({ \ |
ac59853c | 351 | /* Dependency order vs. p above. */ \ |
506458ef | 352 | typeof(*p) *________p1 = (typeof(*p) *__force)READ_ONCE(p); \ |
f78f5b90 | 353 | RCU_LOCKDEP_WARN(!(c), "suspicious rcu_dereference_check() usage"); \ |
423a86a6 | 354 | rcu_check_sparse(p, space); \ |
ac59853c | 355 | ((typeof(*p) __force __kernel *)(________p1)); \ |
0adab9b9 | 356 | }) |
ca5ecddf | 357 | #define __rcu_dereference_protected(p, c, space) \ |
0adab9b9 | 358 | ({ \ |
f78f5b90 | 359 | RCU_LOCKDEP_WARN(!(c), "suspicious rcu_dereference_protected() usage"); \ |
423a86a6 | 360 | rcu_check_sparse(p, space); \ |
0adab9b9 JP |
361 | ((typeof(*p) __force __kernel *)(p)); \ |
362 | }) | |
995f1405 PM |
363 | #define rcu_dereference_raw(p) \ |
364 | ({ \ | |
365 | /* Dependency order vs. p above. */ \ | |
506458ef | 366 | typeof(p) ________p1 = READ_ONCE(p); \ |
995f1405 PM |
367 | ((typeof(*p) __force __kernel *)(________p1)); \ |
368 | }) | |
ca5ecddf | 369 | |
462225ae PM |
370 | /** |
371 | * RCU_INITIALIZER() - statically initialize an RCU-protected global variable | |
372 | * @v: The value to statically initialize with. | |
373 | */ | |
374 | #define RCU_INITIALIZER(v) (typeof(*(v)) __force __rcu *)(v) | |
375 | ||
376 | /** | |
377 | * rcu_assign_pointer() - assign to RCU-protected pointer | |
378 | * @p: pointer to assign to | |
379 | * @v: value to assign (publish) | |
380 | * | |
381 | * Assigns the specified value to the specified RCU-protected | |
382 | * pointer, ensuring that any concurrent RCU readers will see | |
383 | * any prior initialization. | |
384 | * | |
385 | * Inserts memory barriers on architectures that require them | |
386 | * (which is most of them), and also prevents the compiler from | |
387 | * reordering the code that initializes the structure after the pointer | |
388 | * assignment. More importantly, this call documents which pointers | |
389 | * will be dereferenced by RCU read-side code. | |
390 | * | |
391 | * In some special cases, you may use RCU_INIT_POINTER() instead | |
392 | * of rcu_assign_pointer(). RCU_INIT_POINTER() is a bit faster due | |
393 | * to the fact that it does not constrain either the CPU or the compiler. | |
394 | * That said, using RCU_INIT_POINTER() when you should have used | |
395 | * rcu_assign_pointer() is a very bad thing that results in | |
396 | * impossible-to-diagnose memory corruption. So please be careful. | |
397 | * See the RCU_INIT_POINTER() comment header for details. | |
398 | * | |
399 | * Note that rcu_assign_pointer() evaluates each of its arguments only | |
400 | * once, appearances notwithstanding. One of the "extra" evaluations | |
401 | * is in typeof() and the other visible only to sparse (__CHECKER__), | |
402 | * neither of which actually execute the argument. As with most cpp | |
403 | * macros, this execute-arguments-only-once property is important, so | |
404 | * please be careful when making changes to rcu_assign_pointer() and the | |
405 | * other macros that it invokes. | |
406 | */ | |
3a37f727 | 407 | #define rcu_assign_pointer(p, v) \ |
9129b017 | 408 | do { \ |
3a37f727 | 409 | uintptr_t _r_a_p__v = (uintptr_t)(v); \ |
b3119cde | 410 | rcu_check_sparse(p, __rcu); \ |
3a37f727 PM |
411 | \ |
412 | if (__builtin_constant_p(v) && (_r_a_p__v) == (uintptr_t)NULL) \ | |
413 | WRITE_ONCE((p), (typeof(p))(_r_a_p__v)); \ | |
414 | else \ | |
415 | smp_store_release(&p, RCU_INITIALIZER((typeof(p))_r_a_p__v)); \ | |
9129b017 | 416 | } while (0) |
ca5ecddf | 417 | |
a63fc6b7 PM |
418 | /** |
419 | * rcu_replace_pointer() - replace an RCU pointer, returning its old value | |
420 | * @rcu_ptr: RCU pointer, whose old value is returned | |
421 | * @ptr: regular pointer | |
422 | * @c: the lockdep conditions under which the dereference will take place | |
423 | * | |
424 | * Perform a replacement, where @rcu_ptr is an RCU-annotated | |
425 | * pointer and @c is the lockdep argument that is passed to the | |
426 | * rcu_dereference_protected() call used to read that pointer. The old | |
427 | * value of @rcu_ptr is returned, and @rcu_ptr is set to @ptr. | |
428 | */ | |
429 | #define rcu_replace_pointer(rcu_ptr, ptr, c) \ | |
430 | ({ \ | |
431 | typeof(ptr) __tmp = rcu_dereference_protected((rcu_ptr), (c)); \ | |
432 | rcu_assign_pointer((rcu_ptr), (ptr)); \ | |
433 | __tmp; \ | |
434 | }) | |
435 | ||
ca5ecddf PM |
436 | /** |
437 | * rcu_access_pointer() - fetch RCU pointer with no dereferencing | |
438 | * @p: The pointer to read | |
439 | * | |
440 | * Return the value of the specified RCU-protected pointer, but omit the | |
137f61f6 PM |
441 | * lockdep checks for being in an RCU read-side critical section. This is |
442 | * useful when the value of this pointer is accessed, but the pointer is | |
443 | * not dereferenced, for example, when testing an RCU-protected pointer | |
444 | * against NULL. Although rcu_access_pointer() may also be used in cases | |
445 | * where update-side locks prevent the value of the pointer from changing, | |
446 | * you should instead use rcu_dereference_protected() for this use case. | |
5e1ee6e1 PM |
447 | * |
448 | * It is also permissible to use rcu_access_pointer() when read-side | |
449 | * access to the pointer was removed at least one grace period ago, as | |
450 | * is the case in the context of the RCU callback that is freeing up | |
451 | * the data, or after a synchronize_rcu() returns. This can be useful | |
452 | * when tearing down multi-linked structures after a grace period | |
453 | * has elapsed. | |
ca5ecddf PM |
454 | */ |
455 | #define rcu_access_pointer(p) __rcu_access_pointer((p), __rcu) | |
456 | ||
632ee200 | 457 | /** |
ca5ecddf | 458 | * rcu_dereference_check() - rcu_dereference with debug checking |
c08c68dd DH |
459 | * @p: The pointer to read, prior to dereferencing |
460 | * @c: The conditions under which the dereference will take place | |
632ee200 | 461 | * |
c08c68dd | 462 | * Do an rcu_dereference(), but check that the conditions under which the |
ca5ecddf PM |
463 | * dereference will take place are correct. Typically the conditions |
464 | * indicate the various locking conditions that should be held at that | |
465 | * point. The check should return true if the conditions are satisfied. | |
466 | * An implicit check for being in an RCU read-side critical section | |
467 | * (rcu_read_lock()) is included. | |
c08c68dd DH |
468 | * |
469 | * For example: | |
470 | * | |
ca5ecddf | 471 | * bar = rcu_dereference_check(foo->bar, lockdep_is_held(&foo->lock)); |
c08c68dd DH |
472 | * |
473 | * could be used to indicate to lockdep that foo->bar may only be dereferenced | |
ca5ecddf | 474 | * if either rcu_read_lock() is held, or that the lock required to replace |
c08c68dd DH |
475 | * the bar struct at foo->bar is held. |
476 | * | |
477 | * Note that the list of conditions may also include indications of when a lock | |
478 | * need not be held, for example during initialisation or destruction of the | |
479 | * target struct: | |
480 | * | |
ca5ecddf | 481 | * bar = rcu_dereference_check(foo->bar, lockdep_is_held(&foo->lock) || |
c08c68dd | 482 | * atomic_read(&foo->usage) == 0); |
ca5ecddf PM |
483 | * |
484 | * Inserts memory barriers on architectures that require them | |
485 | * (currently only the Alpha), prevents the compiler from refetching | |
486 | * (and from merging fetches), and, more importantly, documents exactly | |
487 | * which pointers are protected by RCU and checks that the pointer is | |
488 | * annotated as __rcu. | |
632ee200 PM |
489 | */ |
490 | #define rcu_dereference_check(p, c) \ | |
b826565a | 491 | __rcu_dereference_check((p), (c) || rcu_read_lock_held(), __rcu) |
ca5ecddf PM |
492 | |
493 | /** | |
494 | * rcu_dereference_bh_check() - rcu_dereference_bh with debug checking | |
495 | * @p: The pointer to read, prior to dereferencing | |
496 | * @c: The conditions under which the dereference will take place | |
497 | * | |
498 | * This is the RCU-bh counterpart to rcu_dereference_check(). | |
499 | */ | |
500 | #define rcu_dereference_bh_check(p, c) \ | |
b826565a | 501 | __rcu_dereference_check((p), (c) || rcu_read_lock_bh_held(), __rcu) |
632ee200 | 502 | |
b62730ba | 503 | /** |
ca5ecddf PM |
504 | * rcu_dereference_sched_check() - rcu_dereference_sched with debug checking |
505 | * @p: The pointer to read, prior to dereferencing | |
506 | * @c: The conditions under which the dereference will take place | |
507 | * | |
508 | * This is the RCU-sched counterpart to rcu_dereference_check(). | |
509 | */ | |
510 | #define rcu_dereference_sched_check(p, c) \ | |
b826565a | 511 | __rcu_dereference_check((p), (c) || rcu_read_lock_sched_held(), \ |
ca5ecddf PM |
512 | __rcu) |
513 | ||
12bcbe66 SR |
514 | /* |
515 | * The tracing infrastructure traces RCU (we want that), but unfortunately | |
516 | * some of the RCU checks causes tracing to lock up the system. | |
517 | * | |
f039f0af | 518 | * The no-tracing version of rcu_dereference_raw() must not call |
12bcbe66 SR |
519 | * rcu_read_lock_held(). |
520 | */ | |
0a5b99f5 | 521 | #define rcu_dereference_raw_check(p) __rcu_dereference_check((p), 1, __rcu) |
12bcbe66 | 522 | |
ca5ecddf PM |
523 | /** |
524 | * rcu_dereference_protected() - fetch RCU pointer when updates prevented | |
525 | * @p: The pointer to read, prior to dereferencing | |
526 | * @c: The conditions under which the dereference will take place | |
b62730ba PM |
527 | * |
528 | * Return the value of the specified RCU-protected pointer, but omit | |
137f61f6 PM |
529 | * the READ_ONCE(). This is useful in cases where update-side locks |
530 | * prevent the value of the pointer from changing. Please note that this | |
531 | * primitive does *not* prevent the compiler from repeating this reference | |
532 | * or combining it with other references, so it should not be used without | |
533 | * protection of appropriate locks. | |
ca5ecddf PM |
534 | * |
535 | * This function is only for update-side use. Using this function | |
536 | * when protected only by rcu_read_lock() will result in infrequent | |
537 | * but very ugly failures. | |
b62730ba PM |
538 | */ |
539 | #define rcu_dereference_protected(p, c) \ | |
ca5ecddf | 540 | __rcu_dereference_protected((p), (c), __rcu) |
b62730ba | 541 | |
bc33f24b | 542 | |
b62730ba | 543 | /** |
ca5ecddf PM |
544 | * rcu_dereference() - fetch RCU-protected pointer for dereferencing |
545 | * @p: The pointer to read, prior to dereferencing | |
b62730ba | 546 | * |
ca5ecddf | 547 | * This is a simple wrapper around rcu_dereference_check(). |
b62730ba | 548 | */ |
ca5ecddf | 549 | #define rcu_dereference(p) rcu_dereference_check(p, 0) |
b62730ba | 550 | |
1da177e4 | 551 | /** |
ca5ecddf PM |
552 | * rcu_dereference_bh() - fetch an RCU-bh-protected pointer for dereferencing |
553 | * @p: The pointer to read, prior to dereferencing | |
554 | * | |
555 | * Makes rcu_dereference_check() do the dirty work. | |
556 | */ | |
557 | #define rcu_dereference_bh(p) rcu_dereference_bh_check(p, 0) | |
558 | ||
559 | /** | |
560 | * rcu_dereference_sched() - fetch RCU-sched-protected pointer for dereferencing | |
561 | * @p: The pointer to read, prior to dereferencing | |
562 | * | |
563 | * Makes rcu_dereference_check() do the dirty work. | |
564 | */ | |
565 | #define rcu_dereference_sched(p) rcu_dereference_sched_check(p, 0) | |
566 | ||
c3ac7cf1 PM |
567 | /** |
568 | * rcu_pointer_handoff() - Hand off a pointer from RCU to other mechanism | |
569 | * @p: The pointer to hand off | |
570 | * | |
571 | * This is simply an identity function, but it documents where a pointer | |
572 | * is handed off from RCU to some other synchronization mechanism, for | |
573 | * example, reference counting or locking. In C11, it would map to | |
1445e917 MCC |
574 | * kill_dependency(). It could be used as follows:: |
575 | * | |
c3ac7cf1 PM |
576 | * rcu_read_lock(); |
577 | * p = rcu_dereference(gp); | |
578 | * long_lived = is_long_lived(p); | |
579 | * if (long_lived) { | |
580 | * if (!atomic_inc_not_zero(p->refcnt)) | |
581 | * long_lived = false; | |
582 | * else | |
583 | * p = rcu_pointer_handoff(p); | |
584 | * } | |
585 | * rcu_read_unlock(); | |
586 | */ | |
587 | #define rcu_pointer_handoff(p) (p) | |
588 | ||
ca5ecddf PM |
589 | /** |
590 | * rcu_read_lock() - mark the beginning of an RCU read-side critical section | |
1da177e4 | 591 | * |
9b06e818 | 592 | * When synchronize_rcu() is invoked on one CPU while other CPUs |
1da177e4 | 593 | * are within RCU read-side critical sections, then the |
9b06e818 | 594 | * synchronize_rcu() is guaranteed to block until after all the other |
1da177e4 LT |
595 | * CPUs exit their critical sections. Similarly, if call_rcu() is invoked |
596 | * on one CPU while other CPUs are within RCU read-side critical | |
597 | * sections, invocation of the corresponding RCU callback is deferred | |
598 | * until after the all the other CPUs exit their critical sections. | |
599 | * | |
600 | * Note, however, that RCU callbacks are permitted to run concurrently | |
77d8485a | 601 | * with new RCU read-side critical sections. One way that this can happen |
1da177e4 LT |
602 | * is via the following sequence of events: (1) CPU 0 enters an RCU |
603 | * read-side critical section, (2) CPU 1 invokes call_rcu() to register | |
604 | * an RCU callback, (3) CPU 0 exits the RCU read-side critical section, | |
605 | * (4) CPU 2 enters a RCU read-side critical section, (5) the RCU | |
606 | * callback is invoked. This is legal, because the RCU read-side critical | |
607 | * section that was running concurrently with the call_rcu() (and which | |
608 | * therefore might be referencing something that the corresponding RCU | |
609 | * callback would free up) has completed before the corresponding | |
610 | * RCU callback is invoked. | |
611 | * | |
612 | * RCU read-side critical sections may be nested. Any deferred actions | |
613 | * will be deferred until the outermost RCU read-side critical section | |
614 | * completes. | |
615 | * | |
9079fd7c PM |
616 | * You can avoid reading and understanding the next paragraph by |
617 | * following this rule: don't put anything in an rcu_read_lock() RCU | |
90326f05 | 618 | * read-side critical section that would block in a !PREEMPTION kernel. |
9079fd7c PM |
619 | * But if you want the full story, read on! |
620 | * | |
b3e627d3 | 621 | * In non-preemptible RCU implementations (pure TREE_RCU and TINY_RCU), |
ab74fdfd | 622 | * it is illegal to block while in an RCU read-side critical section. |
01b1d88b | 623 | * In preemptible RCU implementations (PREEMPT_RCU) in CONFIG_PREEMPTION |
ab74fdfd PM |
624 | * kernel builds, RCU read-side critical sections may be preempted, |
625 | * but explicit blocking is illegal. Finally, in preemptible RCU | |
626 | * implementations in real-time (with -rt patchset) kernel builds, RCU | |
627 | * read-side critical sections may be preempted and they may also block, but | |
628 | * only when acquiring spinlocks that are subject to priority inheritance. | |
1da177e4 | 629 | */ |
6da9f775 | 630 | static __always_inline void rcu_read_lock(void) |
bc33f24b PM |
631 | { |
632 | __rcu_read_lock(); | |
633 | __acquire(RCU); | |
d8ab29f8 | 634 | rcu_lock_acquire(&rcu_lock_map); |
f78f5b90 PM |
635 | RCU_LOCKDEP_WARN(!rcu_is_watching(), |
636 | "rcu_read_lock() used illegally while idle"); | |
bc33f24b | 637 | } |
1da177e4 | 638 | |
1da177e4 LT |
639 | /* |
640 | * So where is rcu_write_lock()? It does not exist, as there is no | |
641 | * way for writers to lock out RCU readers. This is a feature, not | |
642 | * a bug -- this property is what provides RCU's performance benefits. | |
643 | * Of course, writers must coordinate with each other. The normal | |
644 | * spinlock primitives work well for this, but any other technique may be | |
645 | * used as well. RCU does not care how the writers keep out of each | |
646 | * others' way, as long as they do so. | |
647 | */ | |
3d76c082 PM |
648 | |
649 | /** | |
ca5ecddf | 650 | * rcu_read_unlock() - marks the end of an RCU read-side critical section. |
3d76c082 | 651 | * |
f27bc487 PM |
652 | * In most situations, rcu_read_unlock() is immune from deadlock. |
653 | * However, in kernels built with CONFIG_RCU_BOOST, rcu_read_unlock() | |
654 | * is responsible for deboosting, which it does via rt_mutex_unlock(). | |
655 | * Unfortunately, this function acquires the scheduler's runqueue and | |
656 | * priority-inheritance spinlocks. This means that deadlock could result | |
657 | * if the caller of rcu_read_unlock() already holds one of these locks or | |
ec84b27f | 658 | * any lock that is ever acquired while holding them. |
f27bc487 PM |
659 | * |
660 | * That said, RCU readers are never priority boosted unless they were | |
661 | * preempted. Therefore, one way to avoid deadlock is to make sure | |
662 | * that preemption never happens within any RCU read-side critical | |
663 | * section whose outermost rcu_read_unlock() is called with one of | |
664 | * rt_mutex_unlock()'s locks held. Such preemption can be avoided in | |
665 | * a number of ways, for example, by invoking preempt_disable() before | |
666 | * critical section's outermost rcu_read_lock(). | |
667 | * | |
668 | * Given that the set of locks acquired by rt_mutex_unlock() might change | |
669 | * at any time, a somewhat more future-proofed approach is to make sure | |
670 | * that that preemption never happens within any RCU read-side critical | |
671 | * section whose outermost rcu_read_unlock() is called with irqs disabled. | |
672 | * This approach relies on the fact that rt_mutex_unlock() currently only | |
673 | * acquires irq-disabled locks. | |
674 | * | |
675 | * The second of these two approaches is best in most situations, | |
676 | * however, the first approach can also be useful, at least to those | |
677 | * developers willing to keep abreast of the set of locks acquired by | |
678 | * rt_mutex_unlock(). | |
679 | * | |
3d76c082 PM |
680 | * See rcu_read_lock() for more information. |
681 | */ | |
bc33f24b PM |
682 | static inline void rcu_read_unlock(void) |
683 | { | |
f78f5b90 PM |
684 | RCU_LOCKDEP_WARN(!rcu_is_watching(), |
685 | "rcu_read_unlock() used illegally while idle"); | |
bc33f24b PM |
686 | __release(RCU); |
687 | __rcu_read_unlock(); | |
d24209bb | 688 | rcu_lock_release(&rcu_lock_map); /* Keep acq info for rls diags. */ |
bc33f24b | 689 | } |
1da177e4 LT |
690 | |
691 | /** | |
ca5ecddf | 692 | * rcu_read_lock_bh() - mark the beginning of an RCU-bh critical section |
1da177e4 | 693 | * |
82fcecfa | 694 | * This is equivalent of rcu_read_lock(), but also disables softirqs. |
2bd8b1a2 PM |
695 | * Note that anything else that disables softirqs can also serve as |
696 | * an RCU read-side critical section. | |
3842a083 PM |
697 | * |
698 | * Note that rcu_read_lock_bh() and the matching rcu_read_unlock_bh() | |
699 | * must occur in the same context, for example, it is illegal to invoke | |
700 | * rcu_read_unlock_bh() from one task if the matching rcu_read_lock_bh() | |
701 | * was invoked from some other task. | |
1da177e4 | 702 | */ |
bc33f24b PM |
703 | static inline void rcu_read_lock_bh(void) |
704 | { | |
6206ab9b | 705 | local_bh_disable(); |
bc33f24b | 706 | __acquire(RCU_BH); |
d8ab29f8 | 707 | rcu_lock_acquire(&rcu_bh_lock_map); |
f78f5b90 PM |
708 | RCU_LOCKDEP_WARN(!rcu_is_watching(), |
709 | "rcu_read_lock_bh() used illegally while idle"); | |
bc33f24b | 710 | } |
1da177e4 LT |
711 | |
712 | /* | |
713 | * rcu_read_unlock_bh - marks the end of a softirq-only RCU critical section | |
714 | * | |
715 | * See rcu_read_lock_bh() for more information. | |
716 | */ | |
bc33f24b PM |
717 | static inline void rcu_read_unlock_bh(void) |
718 | { | |
f78f5b90 PM |
719 | RCU_LOCKDEP_WARN(!rcu_is_watching(), |
720 | "rcu_read_unlock_bh() used illegally while idle"); | |
d8ab29f8 | 721 | rcu_lock_release(&rcu_bh_lock_map); |
bc33f24b | 722 | __release(RCU_BH); |
6206ab9b | 723 | local_bh_enable(); |
bc33f24b | 724 | } |
1da177e4 | 725 | |
1c50b728 | 726 | /** |
ca5ecddf | 727 | * rcu_read_lock_sched() - mark the beginning of a RCU-sched critical section |
1c50b728 | 728 | * |
2bd8b1a2 PM |
729 | * This is equivalent of rcu_read_lock(), but disables preemption. |
730 | * Read-side critical sections can also be introduced by anything else | |
731 | * that disables preemption, including local_irq_disable() and friends. | |
3842a083 PM |
732 | * |
733 | * Note that rcu_read_lock_sched() and the matching rcu_read_unlock_sched() | |
734 | * must occur in the same context, for example, it is illegal to invoke | |
735 | * rcu_read_unlock_sched() from process context if the matching | |
736 | * rcu_read_lock_sched() was invoked from an NMI handler. | |
1c50b728 | 737 | */ |
d6714c22 PM |
738 | static inline void rcu_read_lock_sched(void) |
739 | { | |
740 | preempt_disable(); | |
bc33f24b | 741 | __acquire(RCU_SCHED); |
d8ab29f8 | 742 | rcu_lock_acquire(&rcu_sched_lock_map); |
f78f5b90 PM |
743 | RCU_LOCKDEP_WARN(!rcu_is_watching(), |
744 | "rcu_read_lock_sched() used illegally while idle"); | |
d6714c22 | 745 | } |
1eba8f84 PM |
746 | |
747 | /* Used by lockdep and tracing: cannot be traced, cannot call lockdep. */ | |
7c614d64 | 748 | static inline notrace void rcu_read_lock_sched_notrace(void) |
d6714c22 PM |
749 | { |
750 | preempt_disable_notrace(); | |
bc33f24b | 751 | __acquire(RCU_SCHED); |
d6714c22 | 752 | } |
1c50b728 MD |
753 | |
754 | /* | |
755 | * rcu_read_unlock_sched - marks the end of a RCU-classic critical section | |
756 | * | |
757 | * See rcu_read_lock_sched for more information. | |
758 | */ | |
d6714c22 PM |
759 | static inline void rcu_read_unlock_sched(void) |
760 | { | |
f78f5b90 PM |
761 | RCU_LOCKDEP_WARN(!rcu_is_watching(), |
762 | "rcu_read_unlock_sched() used illegally while idle"); | |
d8ab29f8 | 763 | rcu_lock_release(&rcu_sched_lock_map); |
bc33f24b | 764 | __release(RCU_SCHED); |
d6714c22 PM |
765 | preempt_enable(); |
766 | } | |
1eba8f84 PM |
767 | |
768 | /* Used by lockdep and tracing: cannot be traced, cannot call lockdep. */ | |
7c614d64 | 769 | static inline notrace void rcu_read_unlock_sched_notrace(void) |
d6714c22 | 770 | { |
bc33f24b | 771 | __release(RCU_SCHED); |
d6714c22 PM |
772 | preempt_enable_notrace(); |
773 | } | |
1c50b728 | 774 | |
ca5ecddf PM |
775 | /** |
776 | * RCU_INIT_POINTER() - initialize an RCU protected pointer | |
27fdb35f PM |
777 | * @p: The pointer to be initialized. |
778 | * @v: The value to initialized the pointer to. | |
ca5ecddf | 779 | * |
6846c0c5 PM |
780 | * Initialize an RCU-protected pointer in special cases where readers |
781 | * do not need ordering constraints on the CPU or the compiler. These | |
782 | * special cases are: | |
783 | * | |
27fdb35f | 784 | * 1. This use of RCU_INIT_POINTER() is NULLing out the pointer *or* |
6846c0c5 | 785 | * 2. The caller has taken whatever steps are required to prevent |
27fdb35f | 786 | * RCU readers from concurrently accessing this pointer *or* |
6846c0c5 | 787 | * 3. The referenced data structure has already been exposed to |
27fdb35f PM |
788 | * readers either at compile time or via rcu_assign_pointer() *and* |
789 | * | |
790 | * a. You have not made *any* reader-visible changes to | |
791 | * this structure since then *or* | |
6846c0c5 PM |
792 | * b. It is OK for readers accessing this structure from its |
793 | * new location to see the old state of the structure. (For | |
794 | * example, the changes were to statistical counters or to | |
795 | * other state where exact synchronization is not required.) | |
796 | * | |
797 | * Failure to follow these rules governing use of RCU_INIT_POINTER() will | |
798 | * result in impossible-to-diagnose memory corruption. As in the structures | |
799 | * will look OK in crash dumps, but any concurrent RCU readers might | |
800 | * see pre-initialized values of the referenced data structure. So | |
801 | * please be very careful how you use RCU_INIT_POINTER()!!! | |
802 | * | |
803 | * If you are creating an RCU-protected linked structure that is accessed | |
804 | * by a single external-to-structure RCU-protected pointer, then you may | |
805 | * use RCU_INIT_POINTER() to initialize the internal RCU-protected | |
806 | * pointers, but you must use rcu_assign_pointer() to initialize the | |
27fdb35f | 807 | * external-to-structure pointer *after* you have completely initialized |
6846c0c5 | 808 | * the reader-accessible portions of the linked structure. |
71a9b269 PM |
809 | * |
810 | * Note that unlike rcu_assign_pointer(), RCU_INIT_POINTER() provides no | |
811 | * ordering guarantees for either the CPU or the compiler. | |
ca5ecddf PM |
812 | */ |
813 | #define RCU_INIT_POINTER(p, v) \ | |
d1b88eb9 | 814 | do { \ |
423a86a6 | 815 | rcu_check_sparse(p, __rcu); \ |
155d1d12 | 816 | WRITE_ONCE(p, RCU_INITIALIZER(v)); \ |
d1b88eb9 | 817 | } while (0) |
9ab1544e | 818 | |
172708d0 PM |
819 | /** |
820 | * RCU_POINTER_INITIALIZER() - statically initialize an RCU protected pointer | |
27fdb35f PM |
821 | * @p: The pointer to be initialized. |
822 | * @v: The value to initialized the pointer to. | |
172708d0 PM |
823 | * |
824 | * GCC-style initialization for an RCU-protected pointer in a structure field. | |
825 | */ | |
826 | #define RCU_POINTER_INITIALIZER(p, v) \ | |
462225ae | 827 | .p = RCU_INITIALIZER(v) |
9ab1544e | 828 | |
d8169d4c JE |
829 | /* |
830 | * Does the specified offset indicate that the corresponding rcu_head | |
c408b215 | 831 | * structure can be handled by kvfree_rcu()? |
d8169d4c | 832 | */ |
c408b215 | 833 | #define __is_kvfree_rcu_offset(offset) ((offset) < 4096) |
d8169d4c JE |
834 | |
835 | /* | |
836 | * Helper macro for kfree_rcu() to prevent argument-expansion eyestrain. | |
837 | */ | |
c408b215 | 838 | #define __kvfree_rcu(head, offset) \ |
d8169d4c | 839 | do { \ |
c408b215 URS |
840 | BUILD_BUG_ON(!__is_kvfree_rcu_offset(offset)); \ |
841 | kvfree_call_rcu(head, (rcu_callback_t)(unsigned long)(offset)); \ | |
d8169d4c JE |
842 | } while (0) |
843 | ||
9ab1544e LJ |
844 | /** |
845 | * kfree_rcu() - kfree an object after a grace period. | |
846 | * @ptr: pointer to kfree | |
12edff04 | 847 | * @rhf: the name of the struct rcu_head within the type of @ptr. |
9ab1544e LJ |
848 | * |
849 | * Many rcu callbacks functions just call kfree() on the base structure. | |
850 | * These functions are trivial, but their size adds up, and furthermore | |
851 | * when they are used in a kernel module, that module must invoke the | |
852 | * high-latency rcu_barrier() function at module-unload time. | |
853 | * | |
854 | * The kfree_rcu() function handles this issue. Rather than encoding a | |
855 | * function address in the embedded rcu_head structure, kfree_rcu() instead | |
856 | * encodes the offset of the rcu_head structure within the base structure. | |
857 | * Because the functions are not allowed in the low-order 4096 bytes of | |
858 | * kernel virtual memory, offsets up to 4095 bytes can be accommodated. | |
859 | * If the offset is larger than 4095 bytes, a compile-time error will | |
c408b215 | 860 | * be generated in __kvfree_rcu(). If this error is triggered, you can |
9ab1544e LJ |
861 | * either fall back to use of call_rcu() or rearrange the structure to |
862 | * position the rcu_head structure into the first 4096 bytes. | |
863 | * | |
864 | * Note that the allowable offset might decrease in the future, for example, | |
865 | * to allow something like kmem_cache_free_rcu(). | |
d8169d4c JE |
866 | * |
867 | * The BUILD_BUG_ON check must not involve any function calls, hence the | |
868 | * checks are done in macros here. | |
9ab1544e | 869 | */ |
12edff04 PM |
870 | #define kfree_rcu(ptr, rhf) \ |
871 | do { \ | |
872 | typeof (ptr) ___p = (ptr); \ | |
873 | \ | |
874 | if (___p) \ | |
c408b215 | 875 | __kvfree_rcu(&((___p)->rhf), offsetof(typeof(*(ptr)), rhf)); \ |
12edff04 | 876 | } while (0) |
0edd1b17 | 877 | |
ce4dce12 URS |
878 | /** |
879 | * kvfree_rcu() - kvfree an object after a grace period. | |
ce4dce12 | 880 | * |
1835f475 URS |
881 | * This macro consists of one or two arguments and it is |
882 | * based on whether an object is head-less or not. If it | |
883 | * has a head then a semantic stays the same as it used | |
884 | * to be before: | |
885 | * | |
886 | * kvfree_rcu(ptr, rhf); | |
887 | * | |
888 | * where @ptr is a pointer to kvfree(), @rhf is the name | |
889 | * of the rcu_head structure within the type of @ptr. | |
890 | * | |
891 | * When it comes to head-less variant, only one argument | |
892 | * is passed and that is just a pointer which has to be | |
893 | * freed after a grace period. Therefore the semantic is | |
894 | * | |
895 | * kvfree_rcu(ptr); | |
896 | * | |
897 | * where @ptr is a pointer to kvfree(). | |
898 | * | |
899 | * Please note, head-less way of freeing is permitted to | |
900 | * use from a context that has to follow might_sleep() | |
901 | * annotation. Otherwise, please switch and embed the | |
902 | * rcu_head structure within the type of @ptr. | |
ce4dce12 | 903 | */ |
1835f475 URS |
904 | #define kvfree_rcu(...) KVFREE_GET_MACRO(__VA_ARGS__, \ |
905 | kvfree_rcu_arg_2, kvfree_rcu_arg_1)(__VA_ARGS__) | |
906 | ||
907 | #define KVFREE_GET_MACRO(_1, _2, NAME, ...) NAME | |
908 | #define kvfree_rcu_arg_2(ptr, rhf) kfree_rcu(ptr, rhf) | |
909 | #define kvfree_rcu_arg_1(ptr) \ | |
910 | do { \ | |
911 | typeof(ptr) ___p = (ptr); \ | |
912 | \ | |
913 | if (___p) \ | |
914 | kvfree_call_rcu(NULL, (rcu_callback_t) (___p)); \ | |
915 | } while (0) | |
ce4dce12 | 916 | |
d85b62f1 PM |
917 | /* |
918 | * Place this after a lock-acquisition primitive to guarantee that | |
919 | * an UNLOCK+LOCK pair acts as a full barrier. This guarantee applies | |
920 | * if the UNLOCK and LOCK are executed by the same CPU or if the | |
921 | * UNLOCK and LOCK operate on the same lock variable. | |
922 | */ | |
77e58496 | 923 | #ifdef CONFIG_ARCH_WEAK_RELEASE_ACQUIRE |
d85b62f1 | 924 | #define smp_mb__after_unlock_lock() smp_mb() /* Full ordering for lock. */ |
77e58496 | 925 | #else /* #ifdef CONFIG_ARCH_WEAK_RELEASE_ACQUIRE */ |
d85b62f1 | 926 | #define smp_mb__after_unlock_lock() do { } while (0) |
77e58496 | 927 | #endif /* #else #ifdef CONFIG_ARCH_WEAK_RELEASE_ACQUIRE */ |
d85b62f1 | 928 | |
274529ba | 929 | |
74de6960 PM |
930 | /* Has the specified rcu_head structure been handed to call_rcu()? */ |
931 | ||
2aa55030 | 932 | /** |
74de6960 PM |
933 | * rcu_head_init - Initialize rcu_head for rcu_head_after_call_rcu() |
934 | * @rhp: The rcu_head structure to initialize. | |
935 | * | |
936 | * If you intend to invoke rcu_head_after_call_rcu() to test whether a | |
937 | * given rcu_head structure has already been passed to call_rcu(), then | |
938 | * you must also invoke this rcu_head_init() function on it just after | |
939 | * allocating that structure. Calls to this function must not race with | |
940 | * calls to call_rcu(), rcu_head_after_call_rcu(), or callback invocation. | |
941 | */ | |
942 | static inline void rcu_head_init(struct rcu_head *rhp) | |
943 | { | |
944 | rhp->func = (rcu_callback_t)~0L; | |
945 | } | |
946 | ||
2aa55030 | 947 | /** |
74de6960 PM |
948 | * rcu_head_after_call_rcu - Has this rcu_head been passed to call_rcu()? |
949 | * @rhp: The rcu_head structure to test. | |
2aa55030 | 950 | * @f: The function passed to call_rcu() along with @rhp. |
74de6960 PM |
951 | * |
952 | * Returns @true if the @rhp has been passed to call_rcu() with @func, | |
953 | * and @false otherwise. Emits a warning in any other case, including | |
954 | * the case where @rhp has already been invoked after a grace period. | |
955 | * Calls to this function must not race with callback invocation. One way | |
956 | * to avoid such races is to enclose the call to rcu_head_after_call_rcu() | |
957 | * in an RCU read-side critical section that includes a read-side fetch | |
958 | * of the pointer to the structure containing @rhp. | |
959 | */ | |
960 | static inline bool | |
961 | rcu_head_after_call_rcu(struct rcu_head *rhp, rcu_callback_t f) | |
962 | { | |
b699cce1 NU |
963 | rcu_callback_t func = READ_ONCE(rhp->func); |
964 | ||
965 | if (func == f) | |
74de6960 | 966 | return true; |
b699cce1 | 967 | WARN_ON_ONCE(func != (rcu_callback_t)~0L); |
74de6960 PM |
968 | return false; |
969 | } | |
970 | ||
e1350e8e BD |
971 | /* kernel/ksysfs.c definitions */ |
972 | extern int rcu_expedited; | |
973 | extern int rcu_normal; | |
974 | ||
1da177e4 | 975 | #endif /* __LINUX_RCUPDATE_H */ |