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1da177e4 | 1 | /* |
a71fca58 | 2 | * Read-Copy Update mechanism for mutual exclusion |
1da177e4 LT |
3 | * |
4 | * This program is free software; you can redistribute it and/or modify | |
5 | * it under the terms of the GNU General Public License as published by | |
6 | * the Free Software Foundation; either version 2 of the License, or | |
7 | * (at your option) any later version. | |
8 | * | |
9 | * This program is distributed in the hope that it will be useful, | |
10 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
11 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
12 | * GNU General Public License for more details. | |
13 | * | |
14 | * You should have received a copy of the GNU General Public License | |
15 | * along with this program; if not, write to the Free Software | |
16 | * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. | |
17 | * | |
01c1c660 | 18 | * Copyright IBM Corporation, 2001 |
1da177e4 LT |
19 | * |
20 | * Author: Dipankar Sarma <dipankar@in.ibm.com> | |
a71fca58 | 21 | * |
595182bc | 22 | * Based on the original work by Paul McKenney <paulmck@us.ibm.com> |
1da177e4 LT |
23 | * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen. |
24 | * Papers: | |
25 | * http://www.rdrop.com/users/paulmck/paper/rclockpdcsproof.pdf | |
26 | * http://lse.sourceforge.net/locking/rclock_OLS.2001.05.01c.sc.pdf (OLS2001) | |
27 | * | |
28 | * For detailed explanation of Read-Copy Update mechanism see - | |
a71fca58 | 29 | * http://lse.sourceforge.net/locking/rcupdate.html |
1da177e4 LT |
30 | * |
31 | */ | |
32 | ||
33 | #ifndef __LINUX_RCUPDATE_H | |
34 | #define __LINUX_RCUPDATE_H | |
35 | ||
99098751 | 36 | #include <linux/types.h> |
1da177e4 LT |
37 | #include <linux/cache.h> |
38 | #include <linux/spinlock.h> | |
39 | #include <linux/threads.h> | |
1da177e4 LT |
40 | #include <linux/cpumask.h> |
41 | #include <linux/seqlock.h> | |
851a67b8 | 42 | #include <linux/lockdep.h> |
4446a36f | 43 | #include <linux/completion.h> |
551d55a9 | 44 | #include <linux/debugobjects.h> |
187f1882 | 45 | #include <linux/bug.h> |
ca5ecddf | 46 | #include <linux/compiler.h> |
1da177e4 | 47 | |
e5ab6772 DY |
48 | #ifdef CONFIG_RCU_TORTURE_TEST |
49 | extern int rcutorture_runnable; /* for sysctl */ | |
50 | #endif /* #ifdef CONFIG_RCU_TORTURE_TEST */ | |
51 | ||
4a298656 PM |
52 | #if defined(CONFIG_TREE_RCU) || defined(CONFIG_TREE_PREEMPT_RCU) |
53 | extern void rcutorture_record_test_transition(void); | |
54 | extern void rcutorture_record_progress(unsigned long vernum); | |
91afaf30 PM |
55 | extern void do_trace_rcu_torture_read(char *rcutorturename, |
56 | struct rcu_head *rhp); | |
4a298656 PM |
57 | #else |
58 | static inline void rcutorture_record_test_transition(void) | |
59 | { | |
60 | } | |
61 | static inline void rcutorture_record_progress(unsigned long vernum) | |
62 | { | |
63 | } | |
91afaf30 PM |
64 | #ifdef CONFIG_RCU_TRACE |
65 | extern void do_trace_rcu_torture_read(char *rcutorturename, | |
66 | struct rcu_head *rhp); | |
67 | #else | |
68 | #define do_trace_rcu_torture_read(rcutorturename, rhp) do { } while (0) | |
69 | #endif | |
4a298656 PM |
70 | #endif |
71 | ||
e27fc964 TH |
72 | #define UINT_CMP_GE(a, b) (UINT_MAX / 2 >= (a) - (b)) |
73 | #define UINT_CMP_LT(a, b) (UINT_MAX / 2 < (a) - (b)) | |
a3dc3fb1 PM |
74 | #define ULONG_CMP_GE(a, b) (ULONG_MAX / 2 >= (a) - (b)) |
75 | #define ULONG_CMP_LT(a, b) (ULONG_MAX / 2 < (a) - (b)) | |
76 | ||
03b042bf | 77 | /* Exported common interfaces */ |
2c42818e PM |
78 | |
79 | #ifdef CONFIG_PREEMPT_RCU | |
80 | ||
81 | /** | |
82 | * call_rcu() - Queue an RCU callback for invocation after a grace period. | |
83 | * @head: structure to be used for queueing the RCU updates. | |
84 | * @func: actual callback function to be invoked after the grace period | |
85 | * | |
86 | * The callback function will be invoked some time after a full grace | |
87 | * period elapses, in other words after all pre-existing RCU read-side | |
88 | * critical sections have completed. However, the callback function | |
89 | * might well execute concurrently with RCU read-side critical sections | |
90 | * that started after call_rcu() was invoked. RCU read-side critical | |
91 | * sections are delimited by rcu_read_lock() and rcu_read_unlock(), | |
92 | * and may be nested. | |
f0a0e6f2 PM |
93 | * |
94 | * Note that all CPUs must agree that the grace period extended beyond | |
95 | * all pre-existing RCU read-side critical section. On systems with more | |
96 | * than one CPU, this means that when "func()" is invoked, each CPU is | |
97 | * guaranteed to have executed a full memory barrier since the end of its | |
98 | * last RCU read-side critical section whose beginning preceded the call | |
99 | * to call_rcu(). It also means that each CPU executing an RCU read-side | |
100 | * critical section that continues beyond the start of "func()" must have | |
101 | * executed a memory barrier after the call_rcu() but before the beginning | |
102 | * of that RCU read-side critical section. Note that these guarantees | |
103 | * include CPUs that are offline, idle, or executing in user mode, as | |
104 | * well as CPUs that are executing in the kernel. | |
105 | * | |
106 | * Furthermore, if CPU A invoked call_rcu() and CPU B invoked the | |
107 | * resulting RCU callback function "func()", then both CPU A and CPU B are | |
108 | * guaranteed to execute a full memory barrier during the time interval | |
109 | * between the call to call_rcu() and the invocation of "func()" -- even | |
110 | * if CPU A and CPU B are the same CPU (but again only if the system has | |
111 | * more than one CPU). | |
2c42818e PM |
112 | */ |
113 | extern void call_rcu(struct rcu_head *head, | |
114 | void (*func)(struct rcu_head *head)); | |
115 | ||
116 | #else /* #ifdef CONFIG_PREEMPT_RCU */ | |
117 | ||
118 | /* In classic RCU, call_rcu() is just call_rcu_sched(). */ | |
119 | #define call_rcu call_rcu_sched | |
120 | ||
121 | #endif /* #else #ifdef CONFIG_PREEMPT_RCU */ | |
122 | ||
123 | /** | |
124 | * call_rcu_bh() - Queue an RCU for invocation after a quicker grace period. | |
125 | * @head: structure to be used for queueing the RCU updates. | |
126 | * @func: actual callback function to be invoked after the grace period | |
127 | * | |
128 | * The callback function will be invoked some time after a full grace | |
129 | * period elapses, in other words after all currently executing RCU | |
130 | * read-side critical sections have completed. call_rcu_bh() assumes | |
131 | * that the read-side critical sections end on completion of a softirq | |
132 | * handler. This means that read-side critical sections in process | |
133 | * context must not be interrupted by softirqs. This interface is to be | |
134 | * used when most of the read-side critical sections are in softirq context. | |
135 | * RCU read-side critical sections are delimited by : | |
136 | * - rcu_read_lock() and rcu_read_unlock(), if in interrupt context. | |
137 | * OR | |
138 | * - rcu_read_lock_bh() and rcu_read_unlock_bh(), if in process context. | |
139 | * These may be nested. | |
f0a0e6f2 PM |
140 | * |
141 | * See the description of call_rcu() for more detailed information on | |
142 | * memory ordering guarantees. | |
2c42818e PM |
143 | */ |
144 | extern void call_rcu_bh(struct rcu_head *head, | |
145 | void (*func)(struct rcu_head *head)); | |
146 | ||
147 | /** | |
148 | * call_rcu_sched() - Queue an RCU for invocation after sched grace period. | |
149 | * @head: structure to be used for queueing the RCU updates. | |
150 | * @func: actual callback function to be invoked after the grace period | |
151 | * | |
152 | * The callback function will be invoked some time after a full grace | |
153 | * period elapses, in other words after all currently executing RCU | |
154 | * read-side critical sections have completed. call_rcu_sched() assumes | |
155 | * that the read-side critical sections end on enabling of preemption | |
156 | * or on voluntary preemption. | |
157 | * RCU read-side critical sections are delimited by : | |
158 | * - rcu_read_lock_sched() and rcu_read_unlock_sched(), | |
159 | * OR | |
160 | * anything that disables preemption. | |
161 | * These may be nested. | |
f0a0e6f2 PM |
162 | * |
163 | * See the description of call_rcu() for more detailed information on | |
164 | * memory ordering guarantees. | |
2c42818e | 165 | */ |
7b0b759b PM |
166 | extern void call_rcu_sched(struct rcu_head *head, |
167 | void (*func)(struct rcu_head *rcu)); | |
2c42818e | 168 | |
7b0b759b | 169 | extern void synchronize_sched(void); |
03b042bf | 170 | |
a3dc3fb1 PM |
171 | #ifdef CONFIG_PREEMPT_RCU |
172 | ||
7b0b759b PM |
173 | extern void __rcu_read_lock(void); |
174 | extern void __rcu_read_unlock(void); | |
2a3fa843 | 175 | extern void rcu_read_unlock_special(struct task_struct *t); |
7b0b759b PM |
176 | void synchronize_rcu(void); |
177 | ||
a3dc3fb1 PM |
178 | /* |
179 | * Defined as a macro as it is a very low level header included from | |
180 | * areas that don't even know about current. This gives the rcu_read_lock() | |
181 | * nesting depth, but makes sense only if CONFIG_PREEMPT_RCU -- in other | |
182 | * types of kernel builds, the rcu_read_lock() nesting depth is unknowable. | |
183 | */ | |
184 | #define rcu_preempt_depth() (current->rcu_read_lock_nesting) | |
185 | ||
7b0b759b PM |
186 | #else /* #ifdef CONFIG_PREEMPT_RCU */ |
187 | ||
188 | static inline void __rcu_read_lock(void) | |
189 | { | |
190 | preempt_disable(); | |
191 | } | |
192 | ||
193 | static inline void __rcu_read_unlock(void) | |
194 | { | |
195 | preempt_enable(); | |
196 | } | |
197 | ||
198 | static inline void synchronize_rcu(void) | |
199 | { | |
200 | synchronize_sched(); | |
201 | } | |
202 | ||
203 | static inline int rcu_preempt_depth(void) | |
204 | { | |
205 | return 0; | |
206 | } | |
207 | ||
208 | #endif /* #else #ifdef CONFIG_PREEMPT_RCU */ | |
209 | ||
210 | /* Internal to kernel */ | |
7b0b759b PM |
211 | extern void rcu_sched_qs(int cpu); |
212 | extern void rcu_bh_qs(int cpu); | |
213 | extern void rcu_check_callbacks(int cpu, int user); | |
214 | struct notifier_block; | |
9b2e4f18 PM |
215 | extern void rcu_idle_enter(void); |
216 | extern void rcu_idle_exit(void); | |
217 | extern void rcu_irq_enter(void); | |
218 | extern void rcu_irq_exit(void); | |
2b1d5024 FW |
219 | |
220 | #ifdef CONFIG_RCU_USER_QS | |
adf5091e FW |
221 | extern void rcu_user_enter(void); |
222 | extern void rcu_user_exit(void); | |
19dd1591 FW |
223 | extern void rcu_user_enter_after_irq(void); |
224 | extern void rcu_user_exit_after_irq(void); | |
2b1d5024 FW |
225 | #else |
226 | static inline void rcu_user_enter(void) { } | |
227 | static inline void rcu_user_exit(void) { } | |
228 | static inline void rcu_user_enter_after_irq(void) { } | |
229 | static inline void rcu_user_exit_after_irq(void) { } | |
4d9a5d43 FW |
230 | static inline void rcu_user_hooks_switch(struct task_struct *prev, |
231 | struct task_struct *next) { } | |
2b1d5024 FW |
232 | #endif /* CONFIG_RCU_USER_QS */ |
233 | ||
9dd8fb16 | 234 | extern void exit_rcu(void); |
a3dc3fb1 | 235 | |
8a2ecf47 PM |
236 | /** |
237 | * RCU_NONIDLE - Indicate idle-loop code that needs RCU readers | |
238 | * @a: Code that RCU needs to pay attention to. | |
239 | * | |
240 | * RCU, RCU-bh, and RCU-sched read-side critical sections are forbidden | |
241 | * in the inner idle loop, that is, between the rcu_idle_enter() and | |
242 | * the rcu_idle_exit() -- RCU will happily ignore any such read-side | |
243 | * critical sections. However, things like powertop need tracepoints | |
244 | * in the inner idle loop. | |
245 | * | |
246 | * This macro provides the way out: RCU_NONIDLE(do_something_with_RCU()) | |
247 | * will tell RCU that it needs to pay attending, invoke its argument | |
248 | * (in this example, a call to the do_something_with_RCU() function), | |
249 | * and then tell RCU to go back to ignoring this CPU. It is permissible | |
250 | * to nest RCU_NONIDLE() wrappers, but the nesting level is currently | |
251 | * quite limited. If deeper nesting is required, it will be necessary | |
252 | * to adjust DYNTICK_TASK_NESTING_VALUE accordingly. | |
8a2ecf47 PM |
253 | */ |
254 | #define RCU_NONIDLE(a) \ | |
255 | do { \ | |
b4270ee3 | 256 | rcu_irq_enter(); \ |
8a2ecf47 | 257 | do { a; } while (0); \ |
b4270ee3 | 258 | rcu_irq_exit(); \ |
8a2ecf47 PM |
259 | } while (0) |
260 | ||
2c42818e PM |
261 | /* |
262 | * Infrastructure to implement the synchronize_() primitives in | |
263 | * TREE_RCU and rcu_barrier_() primitives in TINY_RCU. | |
264 | */ | |
265 | ||
266 | typedef void call_rcu_func_t(struct rcu_head *head, | |
267 | void (*func)(struct rcu_head *head)); | |
268 | void wait_rcu_gp(call_rcu_func_t crf); | |
269 | ||
f41d911f | 270 | #if defined(CONFIG_TREE_RCU) || defined(CONFIG_TREE_PREEMPT_RCU) |
64db4cff | 271 | #include <linux/rcutree.h> |
a57eb940 | 272 | #elif defined(CONFIG_TINY_RCU) || defined(CONFIG_TINY_PREEMPT_RCU) |
9b1d82fa | 273 | #include <linux/rcutiny.h> |
64db4cff PM |
274 | #else |
275 | #error "Unknown RCU implementation specified to kernel configuration" | |
6b3ef48a | 276 | #endif |
01c1c660 | 277 | |
551d55a9 MD |
278 | /* |
279 | * init_rcu_head_on_stack()/destroy_rcu_head_on_stack() are needed for dynamic | |
280 | * initialization and destruction of rcu_head on the stack. rcu_head structures | |
281 | * allocated dynamically in the heap or defined statically don't need any | |
282 | * initialization. | |
283 | */ | |
284 | #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD | |
285 | extern void init_rcu_head_on_stack(struct rcu_head *head); | |
286 | extern void destroy_rcu_head_on_stack(struct rcu_head *head); | |
287 | #else /* !CONFIG_DEBUG_OBJECTS_RCU_HEAD */ | |
4376030a MD |
288 | static inline void init_rcu_head_on_stack(struct rcu_head *head) |
289 | { | |
290 | } | |
291 | ||
292 | static inline void destroy_rcu_head_on_stack(struct rcu_head *head) | |
293 | { | |
294 | } | |
551d55a9 | 295 | #endif /* #else !CONFIG_DEBUG_OBJECTS_RCU_HEAD */ |
4376030a | 296 | |
62fde6ed PM |
297 | #if defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_SMP) |
298 | extern int rcu_is_cpu_idle(void); | |
299 | #endif /* #if defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_SMP) */ | |
300 | ||
c0d6d01b PM |
301 | #if defined(CONFIG_HOTPLUG_CPU) && defined(CONFIG_PROVE_RCU) |
302 | bool rcu_lockdep_current_cpu_online(void); | |
303 | #else /* #if defined(CONFIG_HOTPLUG_CPU) && defined(CONFIG_PROVE_RCU) */ | |
304 | static inline bool rcu_lockdep_current_cpu_online(void) | |
305 | { | |
306 | return 1; | |
307 | } | |
308 | #endif /* #else #if defined(CONFIG_HOTPLUG_CPU) && defined(CONFIG_PROVE_RCU) */ | |
309 | ||
bc33f24b | 310 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
632ee200 | 311 | |
00f49e57 FW |
312 | static inline void rcu_lock_acquire(struct lockdep_map *map) |
313 | { | |
00f49e57 FW |
314 | lock_acquire(map, 0, 0, 2, 1, NULL, _THIS_IP_); |
315 | } | |
316 | ||
317 | static inline void rcu_lock_release(struct lockdep_map *map) | |
318 | { | |
00f49e57 FW |
319 | lock_release(map, 1, _THIS_IP_); |
320 | } | |
321 | ||
bc33f24b | 322 | extern struct lockdep_map rcu_lock_map; |
632ee200 | 323 | extern struct lockdep_map rcu_bh_lock_map; |
632ee200 | 324 | extern struct lockdep_map rcu_sched_lock_map; |
bc293d62 | 325 | extern int debug_lockdep_rcu_enabled(void); |
54dbf96c | 326 | |
632ee200 | 327 | /** |
ca5ecddf | 328 | * rcu_read_lock_held() - might we be in RCU read-side critical section? |
632ee200 | 329 | * |
d20200b5 PM |
330 | * If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an RCU |
331 | * read-side critical section. In absence of CONFIG_DEBUG_LOCK_ALLOC, | |
632ee200 | 332 | * this assumes we are in an RCU read-side critical section unless it can |
ca5ecddf PM |
333 | * prove otherwise. This is useful for debug checks in functions that |
334 | * require that they be called within an RCU read-side critical section. | |
54dbf96c | 335 | * |
ca5ecddf | 336 | * Checks debug_lockdep_rcu_enabled() to prevent false positives during boot |
32c141a0 | 337 | * and while lockdep is disabled. |
3842a083 PM |
338 | * |
339 | * Note that rcu_read_lock() and the matching rcu_read_unlock() must | |
340 | * occur in the same context, for example, it is illegal to invoke | |
341 | * rcu_read_unlock() in process context if the matching rcu_read_lock() | |
342 | * was invoked from within an irq handler. | |
c0d6d01b PM |
343 | * |
344 | * Note that rcu_read_lock() is disallowed if the CPU is either idle or | |
345 | * offline from an RCU perspective, so check for those as well. | |
632ee200 PM |
346 | */ |
347 | static inline int rcu_read_lock_held(void) | |
348 | { | |
54dbf96c PM |
349 | if (!debug_lockdep_rcu_enabled()) |
350 | return 1; | |
e6b80a3b FW |
351 | if (rcu_is_cpu_idle()) |
352 | return 0; | |
c0d6d01b PM |
353 | if (!rcu_lockdep_current_cpu_online()) |
354 | return 0; | |
54dbf96c | 355 | return lock_is_held(&rcu_lock_map); |
632ee200 PM |
356 | } |
357 | ||
e3818b8d PM |
358 | /* |
359 | * rcu_read_lock_bh_held() is defined out of line to avoid #include-file | |
360 | * hell. | |
632ee200 | 361 | */ |
e3818b8d | 362 | extern int rcu_read_lock_bh_held(void); |
632ee200 PM |
363 | |
364 | /** | |
ca5ecddf | 365 | * rcu_read_lock_sched_held() - might we be in RCU-sched read-side critical section? |
632ee200 | 366 | * |
d20200b5 PM |
367 | * If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an |
368 | * RCU-sched read-side critical section. In absence of | |
369 | * CONFIG_DEBUG_LOCK_ALLOC, this assumes we are in an RCU-sched read-side | |
370 | * critical section unless it can prove otherwise. Note that disabling | |
371 | * of preemption (including disabling irqs) counts as an RCU-sched | |
ca5ecddf PM |
372 | * read-side critical section. This is useful for debug checks in functions |
373 | * that required that they be called within an RCU-sched read-side | |
374 | * critical section. | |
54dbf96c | 375 | * |
32c141a0 PM |
376 | * Check debug_lockdep_rcu_enabled() to prevent false positives during boot |
377 | * and while lockdep is disabled. | |
e6b80a3b FW |
378 | * |
379 | * Note that if the CPU is in the idle loop from an RCU point of | |
380 | * view (ie: that we are in the section between rcu_idle_enter() and | |
381 | * rcu_idle_exit()) then rcu_read_lock_held() returns false even if the CPU | |
382 | * did an rcu_read_lock(). The reason for this is that RCU ignores CPUs | |
383 | * that are in such a section, considering these as in extended quiescent | |
384 | * state, so such a CPU is effectively never in an RCU read-side critical | |
385 | * section regardless of what RCU primitives it invokes. This state of | |
386 | * affairs is required --- we need to keep an RCU-free window in idle | |
387 | * where the CPU may possibly enter into low power mode. This way we can | |
388 | * notice an extended quiescent state to other CPUs that started a grace | |
389 | * period. Otherwise we would delay any grace period as long as we run in | |
390 | * the idle task. | |
c0d6d01b PM |
391 | * |
392 | * Similarly, we avoid claiming an SRCU read lock held if the current | |
393 | * CPU is offline. | |
632ee200 | 394 | */ |
bdd4e85d | 395 | #ifdef CONFIG_PREEMPT_COUNT |
632ee200 PM |
396 | static inline int rcu_read_lock_sched_held(void) |
397 | { | |
398 | int lockdep_opinion = 0; | |
399 | ||
54dbf96c PM |
400 | if (!debug_lockdep_rcu_enabled()) |
401 | return 1; | |
e6b80a3b FW |
402 | if (rcu_is_cpu_idle()) |
403 | return 0; | |
c0d6d01b PM |
404 | if (!rcu_lockdep_current_cpu_online()) |
405 | return 0; | |
632ee200 PM |
406 | if (debug_locks) |
407 | lockdep_opinion = lock_is_held(&rcu_sched_lock_map); | |
0cff810f | 408 | return lockdep_opinion || preempt_count() != 0 || irqs_disabled(); |
632ee200 | 409 | } |
bdd4e85d | 410 | #else /* #ifdef CONFIG_PREEMPT_COUNT */ |
e6033e3b PM |
411 | static inline int rcu_read_lock_sched_held(void) |
412 | { | |
413 | return 1; | |
632ee200 | 414 | } |
bdd4e85d | 415 | #endif /* #else #ifdef CONFIG_PREEMPT_COUNT */ |
632ee200 PM |
416 | |
417 | #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ | |
418 | ||
d8ab29f8 PM |
419 | # define rcu_lock_acquire(a) do { } while (0) |
420 | # define rcu_lock_release(a) do { } while (0) | |
632ee200 PM |
421 | |
422 | static inline int rcu_read_lock_held(void) | |
423 | { | |
424 | return 1; | |
425 | } | |
426 | ||
427 | static inline int rcu_read_lock_bh_held(void) | |
428 | { | |
429 | return 1; | |
430 | } | |
431 | ||
bdd4e85d | 432 | #ifdef CONFIG_PREEMPT_COUNT |
632ee200 PM |
433 | static inline int rcu_read_lock_sched_held(void) |
434 | { | |
bbad9379 | 435 | return preempt_count() != 0 || irqs_disabled(); |
632ee200 | 436 | } |
bdd4e85d | 437 | #else /* #ifdef CONFIG_PREEMPT_COUNT */ |
e6033e3b PM |
438 | static inline int rcu_read_lock_sched_held(void) |
439 | { | |
440 | return 1; | |
632ee200 | 441 | } |
bdd4e85d | 442 | #endif /* #else #ifdef CONFIG_PREEMPT_COUNT */ |
632ee200 PM |
443 | |
444 | #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */ | |
445 | ||
446 | #ifdef CONFIG_PROVE_RCU | |
447 | ||
ee84b824 PM |
448 | extern int rcu_my_thread_group_empty(void); |
449 | ||
4221a991 TH |
450 | /** |
451 | * rcu_lockdep_assert - emit lockdep splat if specified condition not met | |
452 | * @c: condition to check | |
b3fbab05 | 453 | * @s: informative message |
4221a991 | 454 | */ |
b3fbab05 | 455 | #define rcu_lockdep_assert(c, s) \ |
2b3fc35f | 456 | do { \ |
7ccaba53 | 457 | static bool __section(.data.unlikely) __warned; \ |
2b3fc35f LJ |
458 | if (debug_lockdep_rcu_enabled() && !__warned && !(c)) { \ |
459 | __warned = true; \ | |
b3fbab05 | 460 | lockdep_rcu_suspicious(__FILE__, __LINE__, s); \ |
2b3fc35f LJ |
461 | } \ |
462 | } while (0) | |
463 | ||
50406b98 PM |
464 | #if defined(CONFIG_PROVE_RCU) && !defined(CONFIG_PREEMPT_RCU) |
465 | static inline void rcu_preempt_sleep_check(void) | |
466 | { | |
467 | rcu_lockdep_assert(!lock_is_held(&rcu_lock_map), | |
5cf05ad7 | 468 | "Illegal context switch in RCU read-side critical section"); |
50406b98 PM |
469 | } |
470 | #else /* #ifdef CONFIG_PROVE_RCU */ | |
471 | static inline void rcu_preempt_sleep_check(void) | |
472 | { | |
473 | } | |
474 | #endif /* #else #ifdef CONFIG_PROVE_RCU */ | |
475 | ||
b3fbab05 PM |
476 | #define rcu_sleep_check() \ |
477 | do { \ | |
50406b98 | 478 | rcu_preempt_sleep_check(); \ |
b3fbab05 PM |
479 | rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map), \ |
480 | "Illegal context switch in RCU-bh" \ | |
481 | " read-side critical section"); \ | |
482 | rcu_lockdep_assert(!lock_is_held(&rcu_sched_lock_map), \ | |
483 | "Illegal context switch in RCU-sched"\ | |
484 | " read-side critical section"); \ | |
485 | } while (0) | |
486 | ||
ca5ecddf PM |
487 | #else /* #ifdef CONFIG_PROVE_RCU */ |
488 | ||
b3fbab05 PM |
489 | #define rcu_lockdep_assert(c, s) do { } while (0) |
490 | #define rcu_sleep_check() do { } while (0) | |
ca5ecddf PM |
491 | |
492 | #endif /* #else #ifdef CONFIG_PROVE_RCU */ | |
493 | ||
494 | /* | |
495 | * Helper functions for rcu_dereference_check(), rcu_dereference_protected() | |
496 | * and rcu_assign_pointer(). Some of these could be folded into their | |
497 | * callers, but they are left separate in order to ease introduction of | |
498 | * multiple flavors of pointers to match the multiple flavors of RCU | |
499 | * (e.g., __rcu_bh, * __rcu_sched, and __srcu), should this make sense in | |
500 | * the future. | |
501 | */ | |
53ecfba2 PM |
502 | |
503 | #ifdef __CHECKER__ | |
504 | #define rcu_dereference_sparse(p, space) \ | |
505 | ((void)(((typeof(*p) space *)p) == p)) | |
506 | #else /* #ifdef __CHECKER__ */ | |
507 | #define rcu_dereference_sparse(p, space) | |
508 | #endif /* #else #ifdef __CHECKER__ */ | |
509 | ||
ca5ecddf PM |
510 | #define __rcu_access_pointer(p, space) \ |
511 | ({ \ | |
512 | typeof(*p) *_________p1 = (typeof(*p)*__force )ACCESS_ONCE(p); \ | |
53ecfba2 | 513 | rcu_dereference_sparse(p, space); \ |
ca5ecddf PM |
514 | ((typeof(*p) __force __kernel *)(_________p1)); \ |
515 | }) | |
516 | #define __rcu_dereference_check(p, c, space) \ | |
517 | ({ \ | |
518 | typeof(*p) *_________p1 = (typeof(*p)*__force )ACCESS_ONCE(p); \ | |
b3fbab05 PM |
519 | rcu_lockdep_assert(c, "suspicious rcu_dereference_check()" \ |
520 | " usage"); \ | |
53ecfba2 | 521 | rcu_dereference_sparse(p, space); \ |
ca5ecddf PM |
522 | smp_read_barrier_depends(); \ |
523 | ((typeof(*p) __force __kernel *)(_________p1)); \ | |
524 | }) | |
525 | #define __rcu_dereference_protected(p, c, space) \ | |
526 | ({ \ | |
b3fbab05 PM |
527 | rcu_lockdep_assert(c, "suspicious rcu_dereference_protected()" \ |
528 | " usage"); \ | |
53ecfba2 | 529 | rcu_dereference_sparse(p, space); \ |
ca5ecddf PM |
530 | ((typeof(*p) __force __kernel *)(p)); \ |
531 | }) | |
532 | ||
a4dd9925 PM |
533 | #define __rcu_access_index(p, space) \ |
534 | ({ \ | |
535 | typeof(p) _________p1 = ACCESS_ONCE(p); \ | |
536 | rcu_dereference_sparse(p, space); \ | |
537 | (_________p1); \ | |
538 | }) | |
ca5ecddf PM |
539 | #define __rcu_dereference_index_check(p, c) \ |
540 | ({ \ | |
541 | typeof(p) _________p1 = ACCESS_ONCE(p); \ | |
b3fbab05 PM |
542 | rcu_lockdep_assert(c, \ |
543 | "suspicious rcu_dereference_index_check()" \ | |
544 | " usage"); \ | |
ca5ecddf PM |
545 | smp_read_barrier_depends(); \ |
546 | (_________p1); \ | |
547 | }) | |
548 | #define __rcu_assign_pointer(p, v, space) \ | |
e9023c40 | 549 | do { \ |
d322f45c | 550 | smp_wmb(); \ |
ca5ecddf | 551 | (p) = (typeof(*v) __force space *)(v); \ |
e9023c40 | 552 | } while (0) |
ca5ecddf PM |
553 | |
554 | ||
555 | /** | |
556 | * rcu_access_pointer() - fetch RCU pointer with no dereferencing | |
557 | * @p: The pointer to read | |
558 | * | |
559 | * Return the value of the specified RCU-protected pointer, but omit the | |
560 | * smp_read_barrier_depends() and keep the ACCESS_ONCE(). This is useful | |
561 | * when the value of this pointer is accessed, but the pointer is not | |
562 | * dereferenced, for example, when testing an RCU-protected pointer against | |
563 | * NULL. Although rcu_access_pointer() may also be used in cases where | |
564 | * update-side locks prevent the value of the pointer from changing, you | |
565 | * should instead use rcu_dereference_protected() for this use case. | |
5e1ee6e1 PM |
566 | * |
567 | * It is also permissible to use rcu_access_pointer() when read-side | |
568 | * access to the pointer was removed at least one grace period ago, as | |
569 | * is the case in the context of the RCU callback that is freeing up | |
570 | * the data, or after a synchronize_rcu() returns. This can be useful | |
571 | * when tearing down multi-linked structures after a grace period | |
572 | * has elapsed. | |
ca5ecddf PM |
573 | */ |
574 | #define rcu_access_pointer(p) __rcu_access_pointer((p), __rcu) | |
575 | ||
632ee200 | 576 | /** |
ca5ecddf | 577 | * rcu_dereference_check() - rcu_dereference with debug checking |
c08c68dd DH |
578 | * @p: The pointer to read, prior to dereferencing |
579 | * @c: The conditions under which the dereference will take place | |
632ee200 | 580 | * |
c08c68dd | 581 | * Do an rcu_dereference(), but check that the conditions under which the |
ca5ecddf PM |
582 | * dereference will take place are correct. Typically the conditions |
583 | * indicate the various locking conditions that should be held at that | |
584 | * point. The check should return true if the conditions are satisfied. | |
585 | * An implicit check for being in an RCU read-side critical section | |
586 | * (rcu_read_lock()) is included. | |
c08c68dd DH |
587 | * |
588 | * For example: | |
589 | * | |
ca5ecddf | 590 | * bar = rcu_dereference_check(foo->bar, lockdep_is_held(&foo->lock)); |
c08c68dd DH |
591 | * |
592 | * could be used to indicate to lockdep that foo->bar may only be dereferenced | |
ca5ecddf | 593 | * if either rcu_read_lock() is held, or that the lock required to replace |
c08c68dd DH |
594 | * the bar struct at foo->bar is held. |
595 | * | |
596 | * Note that the list of conditions may also include indications of when a lock | |
597 | * need not be held, for example during initialisation or destruction of the | |
598 | * target struct: | |
599 | * | |
ca5ecddf | 600 | * bar = rcu_dereference_check(foo->bar, lockdep_is_held(&foo->lock) || |
c08c68dd | 601 | * atomic_read(&foo->usage) == 0); |
ca5ecddf PM |
602 | * |
603 | * Inserts memory barriers on architectures that require them | |
604 | * (currently only the Alpha), prevents the compiler from refetching | |
605 | * (and from merging fetches), and, more importantly, documents exactly | |
606 | * which pointers are protected by RCU and checks that the pointer is | |
607 | * annotated as __rcu. | |
632ee200 PM |
608 | */ |
609 | #define rcu_dereference_check(p, c) \ | |
ca5ecddf PM |
610 | __rcu_dereference_check((p), rcu_read_lock_held() || (c), __rcu) |
611 | ||
612 | /** | |
613 | * rcu_dereference_bh_check() - rcu_dereference_bh with debug checking | |
614 | * @p: The pointer to read, prior to dereferencing | |
615 | * @c: The conditions under which the dereference will take place | |
616 | * | |
617 | * This is the RCU-bh counterpart to rcu_dereference_check(). | |
618 | */ | |
619 | #define rcu_dereference_bh_check(p, c) \ | |
620 | __rcu_dereference_check((p), rcu_read_lock_bh_held() || (c), __rcu) | |
632ee200 | 621 | |
b62730ba | 622 | /** |
ca5ecddf PM |
623 | * rcu_dereference_sched_check() - rcu_dereference_sched with debug checking |
624 | * @p: The pointer to read, prior to dereferencing | |
625 | * @c: The conditions under which the dereference will take place | |
626 | * | |
627 | * This is the RCU-sched counterpart to rcu_dereference_check(). | |
628 | */ | |
629 | #define rcu_dereference_sched_check(p, c) \ | |
630 | __rcu_dereference_check((p), rcu_read_lock_sched_held() || (c), \ | |
631 | __rcu) | |
632 | ||
633 | #define rcu_dereference_raw(p) rcu_dereference_check(p, 1) /*@@@ needed? @@@*/ | |
634 | ||
a4dd9925 PM |
635 | /** |
636 | * rcu_access_index() - fetch RCU index with no dereferencing | |
637 | * @p: The index to read | |
638 | * | |
639 | * Return the value of the specified RCU-protected index, but omit the | |
640 | * smp_read_barrier_depends() and keep the ACCESS_ONCE(). This is useful | |
641 | * when the value of this index is accessed, but the index is not | |
642 | * dereferenced, for example, when testing an RCU-protected index against | |
643 | * -1. Although rcu_access_index() may also be used in cases where | |
644 | * update-side locks prevent the value of the index from changing, you | |
645 | * should instead use rcu_dereference_index_protected() for this use case. | |
646 | */ | |
647 | #define rcu_access_index(p) __rcu_access_index((p), __rcu) | |
648 | ||
ca5ecddf PM |
649 | /** |
650 | * rcu_dereference_index_check() - rcu_dereference for indices with debug checking | |
651 | * @p: The pointer to read, prior to dereferencing | |
652 | * @c: The conditions under which the dereference will take place | |
653 | * | |
654 | * Similar to rcu_dereference_check(), but omits the sparse checking. | |
655 | * This allows rcu_dereference_index_check() to be used on integers, | |
656 | * which can then be used as array indices. Attempting to use | |
657 | * rcu_dereference_check() on an integer will give compiler warnings | |
658 | * because the sparse address-space mechanism relies on dereferencing | |
659 | * the RCU-protected pointer. Dereferencing integers is not something | |
660 | * that even gcc will put up with. | |
661 | * | |
662 | * Note that this function does not implicitly check for RCU read-side | |
663 | * critical sections. If this function gains lots of uses, it might | |
664 | * make sense to provide versions for each flavor of RCU, but it does | |
665 | * not make sense as of early 2010. | |
666 | */ | |
667 | #define rcu_dereference_index_check(p, c) \ | |
668 | __rcu_dereference_index_check((p), (c)) | |
669 | ||
670 | /** | |
671 | * rcu_dereference_protected() - fetch RCU pointer when updates prevented | |
672 | * @p: The pointer to read, prior to dereferencing | |
673 | * @c: The conditions under which the dereference will take place | |
b62730ba PM |
674 | * |
675 | * Return the value of the specified RCU-protected pointer, but omit | |
676 | * both the smp_read_barrier_depends() and the ACCESS_ONCE(). This | |
677 | * is useful in cases where update-side locks prevent the value of the | |
678 | * pointer from changing. Please note that this primitive does -not- | |
679 | * prevent the compiler from repeating this reference or combining it | |
680 | * with other references, so it should not be used without protection | |
681 | * of appropriate locks. | |
ca5ecddf PM |
682 | * |
683 | * This function is only for update-side use. Using this function | |
684 | * when protected only by rcu_read_lock() will result in infrequent | |
685 | * but very ugly failures. | |
b62730ba PM |
686 | */ |
687 | #define rcu_dereference_protected(p, c) \ | |
ca5ecddf | 688 | __rcu_dereference_protected((p), (c), __rcu) |
b62730ba | 689 | |
bc33f24b | 690 | |
b62730ba | 691 | /** |
ca5ecddf PM |
692 | * rcu_dereference() - fetch RCU-protected pointer for dereferencing |
693 | * @p: The pointer to read, prior to dereferencing | |
b62730ba | 694 | * |
ca5ecddf | 695 | * This is a simple wrapper around rcu_dereference_check(). |
b62730ba | 696 | */ |
ca5ecddf | 697 | #define rcu_dereference(p) rcu_dereference_check(p, 0) |
b62730ba | 698 | |
1da177e4 | 699 | /** |
ca5ecddf PM |
700 | * rcu_dereference_bh() - fetch an RCU-bh-protected pointer for dereferencing |
701 | * @p: The pointer to read, prior to dereferencing | |
702 | * | |
703 | * Makes rcu_dereference_check() do the dirty work. | |
704 | */ | |
705 | #define rcu_dereference_bh(p) rcu_dereference_bh_check(p, 0) | |
706 | ||
707 | /** | |
708 | * rcu_dereference_sched() - fetch RCU-sched-protected pointer for dereferencing | |
709 | * @p: The pointer to read, prior to dereferencing | |
710 | * | |
711 | * Makes rcu_dereference_check() do the dirty work. | |
712 | */ | |
713 | #define rcu_dereference_sched(p) rcu_dereference_sched_check(p, 0) | |
714 | ||
715 | /** | |
716 | * rcu_read_lock() - mark the beginning of an RCU read-side critical section | |
1da177e4 | 717 | * |
9b06e818 | 718 | * When synchronize_rcu() is invoked on one CPU while other CPUs |
1da177e4 | 719 | * are within RCU read-side critical sections, then the |
9b06e818 | 720 | * synchronize_rcu() is guaranteed to block until after all the other |
1da177e4 LT |
721 | * CPUs exit their critical sections. Similarly, if call_rcu() is invoked |
722 | * on one CPU while other CPUs are within RCU read-side critical | |
723 | * sections, invocation of the corresponding RCU callback is deferred | |
724 | * until after the all the other CPUs exit their critical sections. | |
725 | * | |
726 | * Note, however, that RCU callbacks are permitted to run concurrently | |
77d8485a | 727 | * with new RCU read-side critical sections. One way that this can happen |
1da177e4 LT |
728 | * is via the following sequence of events: (1) CPU 0 enters an RCU |
729 | * read-side critical section, (2) CPU 1 invokes call_rcu() to register | |
730 | * an RCU callback, (3) CPU 0 exits the RCU read-side critical section, | |
731 | * (4) CPU 2 enters a RCU read-side critical section, (5) the RCU | |
732 | * callback is invoked. This is legal, because the RCU read-side critical | |
733 | * section that was running concurrently with the call_rcu() (and which | |
734 | * therefore might be referencing something that the corresponding RCU | |
735 | * callback would free up) has completed before the corresponding | |
736 | * RCU callback is invoked. | |
737 | * | |
738 | * RCU read-side critical sections may be nested. Any deferred actions | |
739 | * will be deferred until the outermost RCU read-side critical section | |
740 | * completes. | |
741 | * | |
9079fd7c PM |
742 | * You can avoid reading and understanding the next paragraph by |
743 | * following this rule: don't put anything in an rcu_read_lock() RCU | |
744 | * read-side critical section that would block in a !PREEMPT kernel. | |
745 | * But if you want the full story, read on! | |
746 | * | |
747 | * In non-preemptible RCU implementations (TREE_RCU and TINY_RCU), it | |
748 | * is illegal to block while in an RCU read-side critical section. In | |
749 | * preemptible RCU implementations (TREE_PREEMPT_RCU and TINY_PREEMPT_RCU) | |
750 | * in CONFIG_PREEMPT kernel builds, RCU read-side critical sections may | |
751 | * be preempted, but explicit blocking is illegal. Finally, in preemptible | |
752 | * RCU implementations in real-time (CONFIG_PREEMPT_RT) kernel builds, | |
753 | * RCU read-side critical sections may be preempted and they may also | |
754 | * block, but only when acquiring spinlocks that are subject to priority | |
755 | * inheritance. | |
1da177e4 | 756 | */ |
bc33f24b PM |
757 | static inline void rcu_read_lock(void) |
758 | { | |
759 | __rcu_read_lock(); | |
760 | __acquire(RCU); | |
d8ab29f8 | 761 | rcu_lock_acquire(&rcu_lock_map); |
bde23c68 HC |
762 | rcu_lockdep_assert(!rcu_is_cpu_idle(), |
763 | "rcu_read_lock() used illegally while idle"); | |
bc33f24b | 764 | } |
1da177e4 | 765 | |
1da177e4 LT |
766 | /* |
767 | * So where is rcu_write_lock()? It does not exist, as there is no | |
768 | * way for writers to lock out RCU readers. This is a feature, not | |
769 | * a bug -- this property is what provides RCU's performance benefits. | |
770 | * Of course, writers must coordinate with each other. The normal | |
771 | * spinlock primitives work well for this, but any other technique may be | |
772 | * used as well. RCU does not care how the writers keep out of each | |
773 | * others' way, as long as they do so. | |
774 | */ | |
3d76c082 PM |
775 | |
776 | /** | |
ca5ecddf | 777 | * rcu_read_unlock() - marks the end of an RCU read-side critical section. |
3d76c082 PM |
778 | * |
779 | * See rcu_read_lock() for more information. | |
780 | */ | |
bc33f24b PM |
781 | static inline void rcu_read_unlock(void) |
782 | { | |
bde23c68 HC |
783 | rcu_lockdep_assert(!rcu_is_cpu_idle(), |
784 | "rcu_read_unlock() used illegally while idle"); | |
d8ab29f8 | 785 | rcu_lock_release(&rcu_lock_map); |
bc33f24b PM |
786 | __release(RCU); |
787 | __rcu_read_unlock(); | |
788 | } | |
1da177e4 LT |
789 | |
790 | /** | |
ca5ecddf | 791 | * rcu_read_lock_bh() - mark the beginning of an RCU-bh critical section |
1da177e4 LT |
792 | * |
793 | * This is equivalent of rcu_read_lock(), but to be used when updates | |
ca5ecddf PM |
794 | * are being done using call_rcu_bh() or synchronize_rcu_bh(). Since |
795 | * both call_rcu_bh() and synchronize_rcu_bh() consider completion of a | |
796 | * softirq handler to be a quiescent state, a process in RCU read-side | |
797 | * critical section must be protected by disabling softirqs. Read-side | |
798 | * critical sections in interrupt context can use just rcu_read_lock(), | |
799 | * though this should at least be commented to avoid confusing people | |
800 | * reading the code. | |
3842a083 PM |
801 | * |
802 | * Note that rcu_read_lock_bh() and the matching rcu_read_unlock_bh() | |
803 | * must occur in the same context, for example, it is illegal to invoke | |
804 | * rcu_read_unlock_bh() from one task if the matching rcu_read_lock_bh() | |
805 | * was invoked from some other task. | |
1da177e4 | 806 | */ |
bc33f24b PM |
807 | static inline void rcu_read_lock_bh(void) |
808 | { | |
6206ab9b | 809 | local_bh_disable(); |
bc33f24b | 810 | __acquire(RCU_BH); |
d8ab29f8 | 811 | rcu_lock_acquire(&rcu_bh_lock_map); |
bde23c68 HC |
812 | rcu_lockdep_assert(!rcu_is_cpu_idle(), |
813 | "rcu_read_lock_bh() used illegally while idle"); | |
bc33f24b | 814 | } |
1da177e4 LT |
815 | |
816 | /* | |
817 | * rcu_read_unlock_bh - marks the end of a softirq-only RCU critical section | |
818 | * | |
819 | * See rcu_read_lock_bh() for more information. | |
820 | */ | |
bc33f24b PM |
821 | static inline void rcu_read_unlock_bh(void) |
822 | { | |
bde23c68 HC |
823 | rcu_lockdep_assert(!rcu_is_cpu_idle(), |
824 | "rcu_read_unlock_bh() used illegally while idle"); | |
d8ab29f8 | 825 | rcu_lock_release(&rcu_bh_lock_map); |
bc33f24b | 826 | __release(RCU_BH); |
6206ab9b | 827 | local_bh_enable(); |
bc33f24b | 828 | } |
1da177e4 | 829 | |
1c50b728 | 830 | /** |
ca5ecddf | 831 | * rcu_read_lock_sched() - mark the beginning of a RCU-sched critical section |
1c50b728 | 832 | * |
ca5ecddf PM |
833 | * This is equivalent of rcu_read_lock(), but to be used when updates |
834 | * are being done using call_rcu_sched() or synchronize_rcu_sched(). | |
835 | * Read-side critical sections can also be introduced by anything that | |
836 | * disables preemption, including local_irq_disable() and friends. | |
3842a083 PM |
837 | * |
838 | * Note that rcu_read_lock_sched() and the matching rcu_read_unlock_sched() | |
839 | * must occur in the same context, for example, it is illegal to invoke | |
840 | * rcu_read_unlock_sched() from process context if the matching | |
841 | * rcu_read_lock_sched() was invoked from an NMI handler. | |
1c50b728 | 842 | */ |
d6714c22 PM |
843 | static inline void rcu_read_lock_sched(void) |
844 | { | |
845 | preempt_disable(); | |
bc33f24b | 846 | __acquire(RCU_SCHED); |
d8ab29f8 | 847 | rcu_lock_acquire(&rcu_sched_lock_map); |
bde23c68 HC |
848 | rcu_lockdep_assert(!rcu_is_cpu_idle(), |
849 | "rcu_read_lock_sched() used illegally while idle"); | |
d6714c22 | 850 | } |
1eba8f84 PM |
851 | |
852 | /* Used by lockdep and tracing: cannot be traced, cannot call lockdep. */ | |
7c614d64 | 853 | static inline notrace void rcu_read_lock_sched_notrace(void) |
d6714c22 PM |
854 | { |
855 | preempt_disable_notrace(); | |
bc33f24b | 856 | __acquire(RCU_SCHED); |
d6714c22 | 857 | } |
1c50b728 MD |
858 | |
859 | /* | |
860 | * rcu_read_unlock_sched - marks the end of a RCU-classic critical section | |
861 | * | |
862 | * See rcu_read_lock_sched for more information. | |
863 | */ | |
d6714c22 PM |
864 | static inline void rcu_read_unlock_sched(void) |
865 | { | |
bde23c68 HC |
866 | rcu_lockdep_assert(!rcu_is_cpu_idle(), |
867 | "rcu_read_unlock_sched() used illegally while idle"); | |
d8ab29f8 | 868 | rcu_lock_release(&rcu_sched_lock_map); |
bc33f24b | 869 | __release(RCU_SCHED); |
d6714c22 PM |
870 | preempt_enable(); |
871 | } | |
1eba8f84 PM |
872 | |
873 | /* Used by lockdep and tracing: cannot be traced, cannot call lockdep. */ | |
7c614d64 | 874 | static inline notrace void rcu_read_unlock_sched_notrace(void) |
d6714c22 | 875 | { |
bc33f24b | 876 | __release(RCU_SCHED); |
d6714c22 PM |
877 | preempt_enable_notrace(); |
878 | } | |
1c50b728 | 879 | |
1da177e4 | 880 | /** |
ca5ecddf PM |
881 | * rcu_assign_pointer() - assign to RCU-protected pointer |
882 | * @p: pointer to assign to | |
883 | * @v: value to assign (publish) | |
c26d34a5 | 884 | * |
ca5ecddf PM |
885 | * Assigns the specified value to the specified RCU-protected |
886 | * pointer, ensuring that any concurrent RCU readers will see | |
e9023c40 | 887 | * any prior initialization. |
1da177e4 LT |
888 | * |
889 | * Inserts memory barriers on architectures that require them | |
6846c0c5 PM |
890 | * (which is most of them), and also prevents the compiler from |
891 | * reordering the code that initializes the structure after the pointer | |
892 | * assignment. More importantly, this call documents which pointers | |
893 | * will be dereferenced by RCU read-side code. | |
894 | * | |
895 | * In some special cases, you may use RCU_INIT_POINTER() instead | |
896 | * of rcu_assign_pointer(). RCU_INIT_POINTER() is a bit faster due | |
897 | * to the fact that it does not constrain either the CPU or the compiler. | |
898 | * That said, using RCU_INIT_POINTER() when you should have used | |
899 | * rcu_assign_pointer() is a very bad thing that results in | |
900 | * impossible-to-diagnose memory corruption. So please be careful. | |
901 | * See the RCU_INIT_POINTER() comment header for details. | |
1da177e4 | 902 | */ |
d99c4f6b | 903 | #define rcu_assign_pointer(p, v) \ |
ca5ecddf PM |
904 | __rcu_assign_pointer((p), (v), __rcu) |
905 | ||
906 | /** | |
907 | * RCU_INIT_POINTER() - initialize an RCU protected pointer | |
908 | * | |
6846c0c5 PM |
909 | * Initialize an RCU-protected pointer in special cases where readers |
910 | * do not need ordering constraints on the CPU or the compiler. These | |
911 | * special cases are: | |
912 | * | |
913 | * 1. This use of RCU_INIT_POINTER() is NULLing out the pointer -or- | |
914 | * 2. The caller has taken whatever steps are required to prevent | |
915 | * RCU readers from concurrently accessing this pointer -or- | |
916 | * 3. The referenced data structure has already been exposed to | |
917 | * readers either at compile time or via rcu_assign_pointer() -and- | |
918 | * a. You have not made -any- reader-visible changes to | |
919 | * this structure since then -or- | |
920 | * b. It is OK for readers accessing this structure from its | |
921 | * new location to see the old state of the structure. (For | |
922 | * example, the changes were to statistical counters or to | |
923 | * other state where exact synchronization is not required.) | |
924 | * | |
925 | * Failure to follow these rules governing use of RCU_INIT_POINTER() will | |
926 | * result in impossible-to-diagnose memory corruption. As in the structures | |
927 | * will look OK in crash dumps, but any concurrent RCU readers might | |
928 | * see pre-initialized values of the referenced data structure. So | |
929 | * please be very careful how you use RCU_INIT_POINTER()!!! | |
930 | * | |
931 | * If you are creating an RCU-protected linked structure that is accessed | |
932 | * by a single external-to-structure RCU-protected pointer, then you may | |
933 | * use RCU_INIT_POINTER() to initialize the internal RCU-protected | |
934 | * pointers, but you must use rcu_assign_pointer() to initialize the | |
935 | * external-to-structure pointer -after- you have completely initialized | |
936 | * the reader-accessible portions of the linked structure. | |
ca5ecddf PM |
937 | */ |
938 | #define RCU_INIT_POINTER(p, v) \ | |
d1b88eb9 PM |
939 | do { \ |
940 | p = (typeof(*v) __force __rcu *)(v); \ | |
941 | } while (0) | |
9ab1544e | 942 | |
172708d0 PM |
943 | /** |
944 | * RCU_POINTER_INITIALIZER() - statically initialize an RCU protected pointer | |
945 | * | |
946 | * GCC-style initialization for an RCU-protected pointer in a structure field. | |
947 | */ | |
948 | #define RCU_POINTER_INITIALIZER(p, v) \ | |
949 | .p = (typeof(*v) __force __rcu *)(v) | |
9ab1544e | 950 | |
d8169d4c JE |
951 | /* |
952 | * Does the specified offset indicate that the corresponding rcu_head | |
953 | * structure can be handled by kfree_rcu()? | |
954 | */ | |
955 | #define __is_kfree_rcu_offset(offset) ((offset) < 4096) | |
956 | ||
957 | /* | |
958 | * Helper macro for kfree_rcu() to prevent argument-expansion eyestrain. | |
959 | */ | |
960 | #define __kfree_rcu(head, offset) \ | |
961 | do { \ | |
962 | BUILD_BUG_ON(!__is_kfree_rcu_offset(offset)); \ | |
4fa3b6cb | 963 | kfree_call_rcu(head, (void (*)(struct rcu_head *))(unsigned long)(offset)); \ |
d8169d4c JE |
964 | } while (0) |
965 | ||
9ab1544e LJ |
966 | /** |
967 | * kfree_rcu() - kfree an object after a grace period. | |
968 | * @ptr: pointer to kfree | |
969 | * @rcu_head: the name of the struct rcu_head within the type of @ptr. | |
970 | * | |
971 | * Many rcu callbacks functions just call kfree() on the base structure. | |
972 | * These functions are trivial, but their size adds up, and furthermore | |
973 | * when they are used in a kernel module, that module must invoke the | |
974 | * high-latency rcu_barrier() function at module-unload time. | |
975 | * | |
976 | * The kfree_rcu() function handles this issue. Rather than encoding a | |
977 | * function address in the embedded rcu_head structure, kfree_rcu() instead | |
978 | * encodes the offset of the rcu_head structure within the base structure. | |
979 | * Because the functions are not allowed in the low-order 4096 bytes of | |
980 | * kernel virtual memory, offsets up to 4095 bytes can be accommodated. | |
981 | * If the offset is larger than 4095 bytes, a compile-time error will | |
982 | * be generated in __kfree_rcu(). If this error is triggered, you can | |
983 | * either fall back to use of call_rcu() or rearrange the structure to | |
984 | * position the rcu_head structure into the first 4096 bytes. | |
985 | * | |
986 | * Note that the allowable offset might decrease in the future, for example, | |
987 | * to allow something like kmem_cache_free_rcu(). | |
d8169d4c JE |
988 | * |
989 | * The BUILD_BUG_ON check must not involve any function calls, hence the | |
990 | * checks are done in macros here. | |
9ab1544e LJ |
991 | */ |
992 | #define kfree_rcu(ptr, rcu_head) \ | |
993 | __kfree_rcu(&((ptr)->rcu_head), offsetof(typeof(*(ptr)), rcu_head)) | |
994 | ||
1da177e4 | 995 | #endif /* __LINUX_RCUPDATE_H */ |