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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 | 55 | extern void do_trace_rcu_torture_read(char *rcutorturename, |
52494535 PM |
56 | struct rcu_head *rhp, |
57 | unsigned long secs, | |
58 | unsigned long c_old, | |
59 | unsigned long c); | |
4a298656 PM |
60 | #else |
61 | static inline void rcutorture_record_test_transition(void) | |
62 | { | |
63 | } | |
64 | static inline void rcutorture_record_progress(unsigned long vernum) | |
65 | { | |
66 | } | |
91afaf30 PM |
67 | #ifdef CONFIG_RCU_TRACE |
68 | extern void do_trace_rcu_torture_read(char *rcutorturename, | |
52494535 PM |
69 | struct rcu_head *rhp, |
70 | unsigned long secs, | |
71 | unsigned long c_old, | |
72 | unsigned long c); | |
91afaf30 | 73 | #else |
52494535 PM |
74 | #define do_trace_rcu_torture_read(rcutorturename, rhp, secs, c_old, c) \ |
75 | do { } while (0) | |
91afaf30 | 76 | #endif |
4a298656 PM |
77 | #endif |
78 | ||
e27fc964 TH |
79 | #define UINT_CMP_GE(a, b) (UINT_MAX / 2 >= (a) - (b)) |
80 | #define UINT_CMP_LT(a, b) (UINT_MAX / 2 < (a) - (b)) | |
a3dc3fb1 PM |
81 | #define ULONG_CMP_GE(a, b) (ULONG_MAX / 2 >= (a) - (b)) |
82 | #define ULONG_CMP_LT(a, b) (ULONG_MAX / 2 < (a) - (b)) | |
c0f4dfd4 | 83 | #define ulong2long(a) (*(long *)(&(a))) |
a3dc3fb1 | 84 | |
03b042bf | 85 | /* Exported common interfaces */ |
2c42818e PM |
86 | |
87 | #ifdef CONFIG_PREEMPT_RCU | |
88 | ||
89 | /** | |
90 | * call_rcu() - Queue an RCU callback for invocation after a grace period. | |
91 | * @head: structure to be used for queueing the RCU updates. | |
92 | * @func: actual callback function to be invoked after the grace period | |
93 | * | |
94 | * The callback function will be invoked some time after a full grace | |
95 | * period elapses, in other words after all pre-existing RCU read-side | |
96 | * critical sections have completed. However, the callback function | |
97 | * might well execute concurrently with RCU read-side critical sections | |
98 | * that started after call_rcu() was invoked. RCU read-side critical | |
99 | * sections are delimited by rcu_read_lock() and rcu_read_unlock(), | |
100 | * and may be nested. | |
f0a0e6f2 PM |
101 | * |
102 | * Note that all CPUs must agree that the grace period extended beyond | |
103 | * all pre-existing RCU read-side critical section. On systems with more | |
104 | * than one CPU, this means that when "func()" is invoked, each CPU is | |
105 | * guaranteed to have executed a full memory barrier since the end of its | |
106 | * last RCU read-side critical section whose beginning preceded the call | |
107 | * to call_rcu(). It also means that each CPU executing an RCU read-side | |
108 | * critical section that continues beyond the start of "func()" must have | |
109 | * executed a memory barrier after the call_rcu() but before the beginning | |
110 | * of that RCU read-side critical section. Note that these guarantees | |
111 | * include CPUs that are offline, idle, or executing in user mode, as | |
112 | * well as CPUs that are executing in the kernel. | |
113 | * | |
114 | * Furthermore, if CPU A invoked call_rcu() and CPU B invoked the | |
115 | * resulting RCU callback function "func()", then both CPU A and CPU B are | |
116 | * guaranteed to execute a full memory barrier during the time interval | |
117 | * between the call to call_rcu() and the invocation of "func()" -- even | |
118 | * if CPU A and CPU B are the same CPU (but again only if the system has | |
119 | * more than one CPU). | |
2c42818e PM |
120 | */ |
121 | extern void call_rcu(struct rcu_head *head, | |
122 | void (*func)(struct rcu_head *head)); | |
123 | ||
124 | #else /* #ifdef CONFIG_PREEMPT_RCU */ | |
125 | ||
126 | /* In classic RCU, call_rcu() is just call_rcu_sched(). */ | |
127 | #define call_rcu call_rcu_sched | |
128 | ||
129 | #endif /* #else #ifdef CONFIG_PREEMPT_RCU */ | |
130 | ||
131 | /** | |
132 | * call_rcu_bh() - Queue an RCU for invocation after a quicker grace period. | |
133 | * @head: structure to be used for queueing the RCU updates. | |
134 | * @func: actual callback function to be invoked after the grace period | |
135 | * | |
136 | * The callback function will be invoked some time after a full grace | |
137 | * period elapses, in other words after all currently executing RCU | |
138 | * read-side critical sections have completed. call_rcu_bh() assumes | |
139 | * that the read-side critical sections end on completion of a softirq | |
140 | * handler. This means that read-side critical sections in process | |
141 | * context must not be interrupted by softirqs. This interface is to be | |
142 | * used when most of the read-side critical sections are in softirq context. | |
143 | * RCU read-side critical sections are delimited by : | |
144 | * - rcu_read_lock() and rcu_read_unlock(), if in interrupt context. | |
145 | * OR | |
146 | * - rcu_read_lock_bh() and rcu_read_unlock_bh(), if in process context. | |
147 | * These may be nested. | |
f0a0e6f2 PM |
148 | * |
149 | * See the description of call_rcu() for more detailed information on | |
150 | * memory ordering guarantees. | |
2c42818e PM |
151 | */ |
152 | extern void call_rcu_bh(struct rcu_head *head, | |
153 | void (*func)(struct rcu_head *head)); | |
154 | ||
155 | /** | |
156 | * call_rcu_sched() - Queue an RCU for invocation after sched grace period. | |
157 | * @head: structure to be used for queueing the RCU updates. | |
158 | * @func: actual callback function to be invoked after the grace period | |
159 | * | |
160 | * The callback function will be invoked some time after a full grace | |
161 | * period elapses, in other words after all currently executing RCU | |
162 | * read-side critical sections have completed. call_rcu_sched() assumes | |
163 | * that the read-side critical sections end on enabling of preemption | |
164 | * or on voluntary preemption. | |
165 | * RCU read-side critical sections are delimited by : | |
166 | * - rcu_read_lock_sched() and rcu_read_unlock_sched(), | |
167 | * OR | |
168 | * anything that disables preemption. | |
169 | * These may be nested. | |
f0a0e6f2 PM |
170 | * |
171 | * See the description of call_rcu() for more detailed information on | |
172 | * memory ordering guarantees. | |
2c42818e | 173 | */ |
7b0b759b PM |
174 | extern void call_rcu_sched(struct rcu_head *head, |
175 | void (*func)(struct rcu_head *rcu)); | |
2c42818e | 176 | |
7b0b759b | 177 | extern void synchronize_sched(void); |
03b042bf | 178 | |
a3dc3fb1 PM |
179 | #ifdef CONFIG_PREEMPT_RCU |
180 | ||
7b0b759b PM |
181 | extern void __rcu_read_lock(void); |
182 | extern void __rcu_read_unlock(void); | |
2a3fa843 | 183 | extern void rcu_read_unlock_special(struct task_struct *t); |
7b0b759b PM |
184 | void synchronize_rcu(void); |
185 | ||
a3dc3fb1 PM |
186 | /* |
187 | * Defined as a macro as it is a very low level header included from | |
188 | * areas that don't even know about current. This gives the rcu_read_lock() | |
189 | * nesting depth, but makes sense only if CONFIG_PREEMPT_RCU -- in other | |
190 | * types of kernel builds, the rcu_read_lock() nesting depth is unknowable. | |
191 | */ | |
192 | #define rcu_preempt_depth() (current->rcu_read_lock_nesting) | |
193 | ||
7b0b759b PM |
194 | #else /* #ifdef CONFIG_PREEMPT_RCU */ |
195 | ||
196 | static inline void __rcu_read_lock(void) | |
197 | { | |
198 | preempt_disable(); | |
199 | } | |
200 | ||
201 | static inline void __rcu_read_unlock(void) | |
202 | { | |
203 | preempt_enable(); | |
204 | } | |
205 | ||
206 | static inline void synchronize_rcu(void) | |
207 | { | |
208 | synchronize_sched(); | |
209 | } | |
210 | ||
211 | static inline int rcu_preempt_depth(void) | |
212 | { | |
213 | return 0; | |
214 | } | |
215 | ||
216 | #endif /* #else #ifdef CONFIG_PREEMPT_RCU */ | |
217 | ||
218 | /* Internal to kernel */ | |
9dc5ad32 | 219 | extern void rcu_init(void); |
7b0b759b PM |
220 | extern void rcu_sched_qs(int cpu); |
221 | extern void rcu_bh_qs(int cpu); | |
222 | extern void rcu_check_callbacks(int cpu, int user); | |
223 | struct notifier_block; | |
9b2e4f18 PM |
224 | extern void rcu_idle_enter(void); |
225 | extern void rcu_idle_exit(void); | |
226 | extern void rcu_irq_enter(void); | |
227 | extern void rcu_irq_exit(void); | |
2b1d5024 FW |
228 | |
229 | #ifdef CONFIG_RCU_USER_QS | |
adf5091e FW |
230 | extern void rcu_user_enter(void); |
231 | extern void rcu_user_exit(void); | |
19dd1591 FW |
232 | extern void rcu_user_enter_after_irq(void); |
233 | extern void rcu_user_exit_after_irq(void); | |
2b1d5024 FW |
234 | #else |
235 | static inline void rcu_user_enter(void) { } | |
236 | static inline void rcu_user_exit(void) { } | |
237 | static inline void rcu_user_enter_after_irq(void) { } | |
238 | static inline void rcu_user_exit_after_irq(void) { } | |
4d9a5d43 FW |
239 | static inline void rcu_user_hooks_switch(struct task_struct *prev, |
240 | struct task_struct *next) { } | |
2b1d5024 FW |
241 | #endif /* CONFIG_RCU_USER_QS */ |
242 | ||
8a2ecf47 PM |
243 | /** |
244 | * RCU_NONIDLE - Indicate idle-loop code that needs RCU readers | |
245 | * @a: Code that RCU needs to pay attention to. | |
246 | * | |
247 | * RCU, RCU-bh, and RCU-sched read-side critical sections are forbidden | |
248 | * in the inner idle loop, that is, between the rcu_idle_enter() and | |
249 | * the rcu_idle_exit() -- RCU will happily ignore any such read-side | |
250 | * critical sections. However, things like powertop need tracepoints | |
251 | * in the inner idle loop. | |
252 | * | |
253 | * This macro provides the way out: RCU_NONIDLE(do_something_with_RCU()) | |
254 | * will tell RCU that it needs to pay attending, invoke its argument | |
255 | * (in this example, a call to the do_something_with_RCU() function), | |
256 | * and then tell RCU to go back to ignoring this CPU. It is permissible | |
257 | * to nest RCU_NONIDLE() wrappers, but the nesting level is currently | |
258 | * quite limited. If deeper nesting is required, it will be necessary | |
259 | * to adjust DYNTICK_TASK_NESTING_VALUE accordingly. | |
8a2ecf47 PM |
260 | */ |
261 | #define RCU_NONIDLE(a) \ | |
262 | do { \ | |
b4270ee3 | 263 | rcu_irq_enter(); \ |
8a2ecf47 | 264 | do { a; } while (0); \ |
b4270ee3 | 265 | rcu_irq_exit(); \ |
8a2ecf47 PM |
266 | } while (0) |
267 | ||
2c42818e PM |
268 | /* |
269 | * Infrastructure to implement the synchronize_() primitives in | |
270 | * TREE_RCU and rcu_barrier_() primitives in TINY_RCU. | |
271 | */ | |
272 | ||
273 | typedef void call_rcu_func_t(struct rcu_head *head, | |
274 | void (*func)(struct rcu_head *head)); | |
275 | void wait_rcu_gp(call_rcu_func_t crf); | |
276 | ||
f41d911f | 277 | #if defined(CONFIG_TREE_RCU) || defined(CONFIG_TREE_PREEMPT_RCU) |
64db4cff | 278 | #include <linux/rcutree.h> |
127781d1 | 279 | #elif defined(CONFIG_TINY_RCU) |
9b1d82fa | 280 | #include <linux/rcutiny.h> |
64db4cff PM |
281 | #else |
282 | #error "Unknown RCU implementation specified to kernel configuration" | |
6b3ef48a | 283 | #endif |
01c1c660 | 284 | |
551d55a9 MD |
285 | /* |
286 | * init_rcu_head_on_stack()/destroy_rcu_head_on_stack() are needed for dynamic | |
287 | * initialization and destruction of rcu_head on the stack. rcu_head structures | |
288 | * allocated dynamically in the heap or defined statically don't need any | |
289 | * initialization. | |
290 | */ | |
291 | #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD | |
292 | extern void init_rcu_head_on_stack(struct rcu_head *head); | |
293 | extern void destroy_rcu_head_on_stack(struct rcu_head *head); | |
294 | #else /* !CONFIG_DEBUG_OBJECTS_RCU_HEAD */ | |
4376030a MD |
295 | static inline void init_rcu_head_on_stack(struct rcu_head *head) |
296 | { | |
297 | } | |
298 | ||
299 | static inline void destroy_rcu_head_on_stack(struct rcu_head *head) | |
300 | { | |
301 | } | |
551d55a9 | 302 | #endif /* #else !CONFIG_DEBUG_OBJECTS_RCU_HEAD */ |
4376030a | 303 | |
62fde6ed PM |
304 | #if defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_SMP) |
305 | extern int rcu_is_cpu_idle(void); | |
306 | #endif /* #if defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_SMP) */ | |
307 | ||
c0d6d01b PM |
308 | #if defined(CONFIG_HOTPLUG_CPU) && defined(CONFIG_PROVE_RCU) |
309 | bool rcu_lockdep_current_cpu_online(void); | |
310 | #else /* #if defined(CONFIG_HOTPLUG_CPU) && defined(CONFIG_PROVE_RCU) */ | |
311 | static inline bool rcu_lockdep_current_cpu_online(void) | |
312 | { | |
313 | return 1; | |
314 | } | |
315 | #endif /* #else #if defined(CONFIG_HOTPLUG_CPU) && defined(CONFIG_PROVE_RCU) */ | |
316 | ||
bc33f24b | 317 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
632ee200 | 318 | |
00f49e57 FW |
319 | static inline void rcu_lock_acquire(struct lockdep_map *map) |
320 | { | |
00f49e57 FW |
321 | lock_acquire(map, 0, 0, 2, 1, NULL, _THIS_IP_); |
322 | } | |
323 | ||
324 | static inline void rcu_lock_release(struct lockdep_map *map) | |
325 | { | |
00f49e57 FW |
326 | lock_release(map, 1, _THIS_IP_); |
327 | } | |
328 | ||
bc33f24b | 329 | extern struct lockdep_map rcu_lock_map; |
632ee200 | 330 | extern struct lockdep_map rcu_bh_lock_map; |
632ee200 | 331 | extern struct lockdep_map rcu_sched_lock_map; |
bc293d62 | 332 | extern int debug_lockdep_rcu_enabled(void); |
54dbf96c | 333 | |
632ee200 | 334 | /** |
ca5ecddf | 335 | * rcu_read_lock_held() - might we be in RCU read-side critical section? |
632ee200 | 336 | * |
d20200b5 PM |
337 | * If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an RCU |
338 | * read-side critical section. In absence of CONFIG_DEBUG_LOCK_ALLOC, | |
632ee200 | 339 | * this assumes we are in an RCU read-side critical section unless it can |
ca5ecddf PM |
340 | * prove otherwise. This is useful for debug checks in functions that |
341 | * require that they be called within an RCU read-side critical section. | |
54dbf96c | 342 | * |
ca5ecddf | 343 | * Checks debug_lockdep_rcu_enabled() to prevent false positives during boot |
32c141a0 | 344 | * and while lockdep is disabled. |
3842a083 PM |
345 | * |
346 | * Note that rcu_read_lock() and the matching rcu_read_unlock() must | |
347 | * occur in the same context, for example, it is illegal to invoke | |
348 | * rcu_read_unlock() in process context if the matching rcu_read_lock() | |
349 | * was invoked from within an irq handler. | |
c0d6d01b PM |
350 | * |
351 | * Note that rcu_read_lock() is disallowed if the CPU is either idle or | |
352 | * offline from an RCU perspective, so check for those as well. | |
632ee200 PM |
353 | */ |
354 | static inline int rcu_read_lock_held(void) | |
355 | { | |
54dbf96c PM |
356 | if (!debug_lockdep_rcu_enabled()) |
357 | return 1; | |
e6b80a3b FW |
358 | if (rcu_is_cpu_idle()) |
359 | return 0; | |
c0d6d01b PM |
360 | if (!rcu_lockdep_current_cpu_online()) |
361 | return 0; | |
54dbf96c | 362 | return lock_is_held(&rcu_lock_map); |
632ee200 PM |
363 | } |
364 | ||
e3818b8d PM |
365 | /* |
366 | * rcu_read_lock_bh_held() is defined out of line to avoid #include-file | |
367 | * hell. | |
632ee200 | 368 | */ |
e3818b8d | 369 | extern int rcu_read_lock_bh_held(void); |
632ee200 PM |
370 | |
371 | /** | |
ca5ecddf | 372 | * rcu_read_lock_sched_held() - might we be in RCU-sched read-side critical section? |
632ee200 | 373 | * |
d20200b5 PM |
374 | * If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an |
375 | * RCU-sched read-side critical section. In absence of | |
376 | * CONFIG_DEBUG_LOCK_ALLOC, this assumes we are in an RCU-sched read-side | |
377 | * critical section unless it can prove otherwise. Note that disabling | |
378 | * of preemption (including disabling irqs) counts as an RCU-sched | |
ca5ecddf PM |
379 | * read-side critical section. This is useful for debug checks in functions |
380 | * that required that they be called within an RCU-sched read-side | |
381 | * critical section. | |
54dbf96c | 382 | * |
32c141a0 PM |
383 | * Check debug_lockdep_rcu_enabled() to prevent false positives during boot |
384 | * and while lockdep is disabled. | |
e6b80a3b FW |
385 | * |
386 | * Note that if the CPU is in the idle loop from an RCU point of | |
387 | * view (ie: that we are in the section between rcu_idle_enter() and | |
388 | * rcu_idle_exit()) then rcu_read_lock_held() returns false even if the CPU | |
389 | * did an rcu_read_lock(). The reason for this is that RCU ignores CPUs | |
390 | * that are in such a section, considering these as in extended quiescent | |
391 | * state, so such a CPU is effectively never in an RCU read-side critical | |
392 | * section regardless of what RCU primitives it invokes. This state of | |
393 | * affairs is required --- we need to keep an RCU-free window in idle | |
394 | * where the CPU may possibly enter into low power mode. This way we can | |
395 | * notice an extended quiescent state to other CPUs that started a grace | |
396 | * period. Otherwise we would delay any grace period as long as we run in | |
397 | * the idle task. | |
c0d6d01b PM |
398 | * |
399 | * Similarly, we avoid claiming an SRCU read lock held if the current | |
400 | * CPU is offline. | |
632ee200 | 401 | */ |
bdd4e85d | 402 | #ifdef CONFIG_PREEMPT_COUNT |
632ee200 PM |
403 | static inline int rcu_read_lock_sched_held(void) |
404 | { | |
405 | int lockdep_opinion = 0; | |
406 | ||
54dbf96c PM |
407 | if (!debug_lockdep_rcu_enabled()) |
408 | return 1; | |
e6b80a3b FW |
409 | if (rcu_is_cpu_idle()) |
410 | return 0; | |
c0d6d01b PM |
411 | if (!rcu_lockdep_current_cpu_online()) |
412 | return 0; | |
632ee200 PM |
413 | if (debug_locks) |
414 | lockdep_opinion = lock_is_held(&rcu_sched_lock_map); | |
0cff810f | 415 | return lockdep_opinion || preempt_count() != 0 || irqs_disabled(); |
632ee200 | 416 | } |
bdd4e85d | 417 | #else /* #ifdef CONFIG_PREEMPT_COUNT */ |
e6033e3b PM |
418 | static inline int rcu_read_lock_sched_held(void) |
419 | { | |
420 | return 1; | |
632ee200 | 421 | } |
bdd4e85d | 422 | #endif /* #else #ifdef CONFIG_PREEMPT_COUNT */ |
632ee200 PM |
423 | |
424 | #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ | |
425 | ||
d8ab29f8 PM |
426 | # define rcu_lock_acquire(a) do { } while (0) |
427 | # define rcu_lock_release(a) do { } while (0) | |
632ee200 PM |
428 | |
429 | static inline int rcu_read_lock_held(void) | |
430 | { | |
431 | return 1; | |
432 | } | |
433 | ||
434 | static inline int rcu_read_lock_bh_held(void) | |
435 | { | |
436 | return 1; | |
437 | } | |
438 | ||
bdd4e85d | 439 | #ifdef CONFIG_PREEMPT_COUNT |
632ee200 PM |
440 | static inline int rcu_read_lock_sched_held(void) |
441 | { | |
bbad9379 | 442 | return preempt_count() != 0 || irqs_disabled(); |
632ee200 | 443 | } |
bdd4e85d | 444 | #else /* #ifdef CONFIG_PREEMPT_COUNT */ |
e6033e3b PM |
445 | static inline int rcu_read_lock_sched_held(void) |
446 | { | |
447 | return 1; | |
632ee200 | 448 | } |
bdd4e85d | 449 | #endif /* #else #ifdef CONFIG_PREEMPT_COUNT */ |
632ee200 PM |
450 | |
451 | #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */ | |
452 | ||
453 | #ifdef CONFIG_PROVE_RCU | |
454 | ||
ee84b824 PM |
455 | extern int rcu_my_thread_group_empty(void); |
456 | ||
4221a991 TH |
457 | /** |
458 | * rcu_lockdep_assert - emit lockdep splat if specified condition not met | |
459 | * @c: condition to check | |
b3fbab05 | 460 | * @s: informative message |
4221a991 | 461 | */ |
b3fbab05 | 462 | #define rcu_lockdep_assert(c, s) \ |
2b3fc35f | 463 | do { \ |
7ccaba53 | 464 | static bool __section(.data.unlikely) __warned; \ |
2b3fc35f LJ |
465 | if (debug_lockdep_rcu_enabled() && !__warned && !(c)) { \ |
466 | __warned = true; \ | |
b3fbab05 | 467 | lockdep_rcu_suspicious(__FILE__, __LINE__, s); \ |
2b3fc35f LJ |
468 | } \ |
469 | } while (0) | |
470 | ||
50406b98 PM |
471 | #if defined(CONFIG_PROVE_RCU) && !defined(CONFIG_PREEMPT_RCU) |
472 | static inline void rcu_preempt_sleep_check(void) | |
473 | { | |
474 | rcu_lockdep_assert(!lock_is_held(&rcu_lock_map), | |
5cf05ad7 | 475 | "Illegal context switch in RCU read-side critical section"); |
50406b98 PM |
476 | } |
477 | #else /* #ifdef CONFIG_PROVE_RCU */ | |
478 | static inline void rcu_preempt_sleep_check(void) | |
479 | { | |
480 | } | |
481 | #endif /* #else #ifdef CONFIG_PROVE_RCU */ | |
482 | ||
b3fbab05 PM |
483 | #define rcu_sleep_check() \ |
484 | do { \ | |
50406b98 | 485 | rcu_preempt_sleep_check(); \ |
b3fbab05 PM |
486 | rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map), \ |
487 | "Illegal context switch in RCU-bh" \ | |
488 | " read-side critical section"); \ | |
489 | rcu_lockdep_assert(!lock_is_held(&rcu_sched_lock_map), \ | |
490 | "Illegal context switch in RCU-sched"\ | |
491 | " read-side critical section"); \ | |
492 | } while (0) | |
493 | ||
ca5ecddf PM |
494 | #else /* #ifdef CONFIG_PROVE_RCU */ |
495 | ||
b3fbab05 PM |
496 | #define rcu_lockdep_assert(c, s) do { } while (0) |
497 | #define rcu_sleep_check() do { } while (0) | |
ca5ecddf PM |
498 | |
499 | #endif /* #else #ifdef CONFIG_PROVE_RCU */ | |
500 | ||
501 | /* | |
502 | * Helper functions for rcu_dereference_check(), rcu_dereference_protected() | |
503 | * and rcu_assign_pointer(). Some of these could be folded into their | |
504 | * callers, but they are left separate in order to ease introduction of | |
505 | * multiple flavors of pointers to match the multiple flavors of RCU | |
506 | * (e.g., __rcu_bh, * __rcu_sched, and __srcu), should this make sense in | |
507 | * the future. | |
508 | */ | |
53ecfba2 PM |
509 | |
510 | #ifdef __CHECKER__ | |
511 | #define rcu_dereference_sparse(p, space) \ | |
512 | ((void)(((typeof(*p) space *)p) == p)) | |
513 | #else /* #ifdef __CHECKER__ */ | |
514 | #define rcu_dereference_sparse(p, space) | |
515 | #endif /* #else #ifdef __CHECKER__ */ | |
516 | ||
ca5ecddf PM |
517 | #define __rcu_access_pointer(p, space) \ |
518 | ({ \ | |
519 | typeof(*p) *_________p1 = (typeof(*p)*__force )ACCESS_ONCE(p); \ | |
53ecfba2 | 520 | rcu_dereference_sparse(p, space); \ |
ca5ecddf PM |
521 | ((typeof(*p) __force __kernel *)(_________p1)); \ |
522 | }) | |
523 | #define __rcu_dereference_check(p, c, space) \ | |
524 | ({ \ | |
525 | typeof(*p) *_________p1 = (typeof(*p)*__force )ACCESS_ONCE(p); \ | |
b3fbab05 PM |
526 | rcu_lockdep_assert(c, "suspicious rcu_dereference_check()" \ |
527 | " usage"); \ | |
53ecfba2 | 528 | rcu_dereference_sparse(p, space); \ |
ca5ecddf PM |
529 | smp_read_barrier_depends(); \ |
530 | ((typeof(*p) __force __kernel *)(_________p1)); \ | |
531 | }) | |
532 | #define __rcu_dereference_protected(p, c, space) \ | |
533 | ({ \ | |
b3fbab05 PM |
534 | rcu_lockdep_assert(c, "suspicious rcu_dereference_protected()" \ |
535 | " usage"); \ | |
53ecfba2 | 536 | rcu_dereference_sparse(p, space); \ |
ca5ecddf PM |
537 | ((typeof(*p) __force __kernel *)(p)); \ |
538 | }) | |
539 | ||
a4dd9925 PM |
540 | #define __rcu_access_index(p, space) \ |
541 | ({ \ | |
542 | typeof(p) _________p1 = ACCESS_ONCE(p); \ | |
543 | rcu_dereference_sparse(p, space); \ | |
544 | (_________p1); \ | |
545 | }) | |
ca5ecddf PM |
546 | #define __rcu_dereference_index_check(p, c) \ |
547 | ({ \ | |
548 | typeof(p) _________p1 = ACCESS_ONCE(p); \ | |
b3fbab05 PM |
549 | rcu_lockdep_assert(c, \ |
550 | "suspicious rcu_dereference_index_check()" \ | |
551 | " usage"); \ | |
ca5ecddf PM |
552 | smp_read_barrier_depends(); \ |
553 | (_________p1); \ | |
554 | }) | |
555 | #define __rcu_assign_pointer(p, v, space) \ | |
e9023c40 | 556 | do { \ |
d322f45c | 557 | smp_wmb(); \ |
ca5ecddf | 558 | (p) = (typeof(*v) __force space *)(v); \ |
e9023c40 | 559 | } while (0) |
ca5ecddf PM |
560 | |
561 | ||
562 | /** | |
563 | * rcu_access_pointer() - fetch RCU pointer with no dereferencing | |
564 | * @p: The pointer to read | |
565 | * | |
566 | * Return the value of the specified RCU-protected pointer, but omit the | |
567 | * smp_read_barrier_depends() and keep the ACCESS_ONCE(). This is useful | |
568 | * when the value of this pointer is accessed, but the pointer is not | |
569 | * dereferenced, for example, when testing an RCU-protected pointer against | |
570 | * NULL. Although rcu_access_pointer() may also be used in cases where | |
571 | * update-side locks prevent the value of the pointer from changing, you | |
572 | * should instead use rcu_dereference_protected() for this use case. | |
5e1ee6e1 PM |
573 | * |
574 | * It is also permissible to use rcu_access_pointer() when read-side | |
575 | * access to the pointer was removed at least one grace period ago, as | |
576 | * is the case in the context of the RCU callback that is freeing up | |
577 | * the data, or after a synchronize_rcu() returns. This can be useful | |
578 | * when tearing down multi-linked structures after a grace period | |
579 | * has elapsed. | |
ca5ecddf PM |
580 | */ |
581 | #define rcu_access_pointer(p) __rcu_access_pointer((p), __rcu) | |
582 | ||
632ee200 | 583 | /** |
ca5ecddf | 584 | * rcu_dereference_check() - rcu_dereference with debug checking |
c08c68dd DH |
585 | * @p: The pointer to read, prior to dereferencing |
586 | * @c: The conditions under which the dereference will take place | |
632ee200 | 587 | * |
c08c68dd | 588 | * Do an rcu_dereference(), but check that the conditions under which the |
ca5ecddf PM |
589 | * dereference will take place are correct. Typically the conditions |
590 | * indicate the various locking conditions that should be held at that | |
591 | * point. The check should return true if the conditions are satisfied. | |
592 | * An implicit check for being in an RCU read-side critical section | |
593 | * (rcu_read_lock()) is included. | |
c08c68dd DH |
594 | * |
595 | * For example: | |
596 | * | |
ca5ecddf | 597 | * bar = rcu_dereference_check(foo->bar, lockdep_is_held(&foo->lock)); |
c08c68dd DH |
598 | * |
599 | * could be used to indicate to lockdep that foo->bar may only be dereferenced | |
ca5ecddf | 600 | * if either rcu_read_lock() is held, or that the lock required to replace |
c08c68dd DH |
601 | * the bar struct at foo->bar is held. |
602 | * | |
603 | * Note that the list of conditions may also include indications of when a lock | |
604 | * need not be held, for example during initialisation or destruction of the | |
605 | * target struct: | |
606 | * | |
ca5ecddf | 607 | * bar = rcu_dereference_check(foo->bar, lockdep_is_held(&foo->lock) || |
c08c68dd | 608 | * atomic_read(&foo->usage) == 0); |
ca5ecddf PM |
609 | * |
610 | * Inserts memory barriers on architectures that require them | |
611 | * (currently only the Alpha), prevents the compiler from refetching | |
612 | * (and from merging fetches), and, more importantly, documents exactly | |
613 | * which pointers are protected by RCU and checks that the pointer is | |
614 | * annotated as __rcu. | |
632ee200 PM |
615 | */ |
616 | #define rcu_dereference_check(p, c) \ | |
ca5ecddf PM |
617 | __rcu_dereference_check((p), rcu_read_lock_held() || (c), __rcu) |
618 | ||
619 | /** | |
620 | * rcu_dereference_bh_check() - rcu_dereference_bh with debug checking | |
621 | * @p: The pointer to read, prior to dereferencing | |
622 | * @c: The conditions under which the dereference will take place | |
623 | * | |
624 | * This is the RCU-bh counterpart to rcu_dereference_check(). | |
625 | */ | |
626 | #define rcu_dereference_bh_check(p, c) \ | |
627 | __rcu_dereference_check((p), rcu_read_lock_bh_held() || (c), __rcu) | |
632ee200 | 628 | |
b62730ba | 629 | /** |
ca5ecddf PM |
630 | * rcu_dereference_sched_check() - rcu_dereference_sched with debug checking |
631 | * @p: The pointer to read, prior to dereferencing | |
632 | * @c: The conditions under which the dereference will take place | |
633 | * | |
634 | * This is the RCU-sched counterpart to rcu_dereference_check(). | |
635 | */ | |
636 | #define rcu_dereference_sched_check(p, c) \ | |
637 | __rcu_dereference_check((p), rcu_read_lock_sched_held() || (c), \ | |
638 | __rcu) | |
639 | ||
640 | #define rcu_dereference_raw(p) rcu_dereference_check(p, 1) /*@@@ needed? @@@*/ | |
641 | ||
12bcbe66 SR |
642 | /* |
643 | * The tracing infrastructure traces RCU (we want that), but unfortunately | |
644 | * some of the RCU checks causes tracing to lock up the system. | |
645 | * | |
646 | * The tracing version of rcu_dereference_raw() must not call | |
647 | * rcu_read_lock_held(). | |
648 | */ | |
649 | #define rcu_dereference_raw_notrace(p) __rcu_dereference_check((p), 1, __rcu) | |
650 | ||
a4dd9925 PM |
651 | /** |
652 | * rcu_access_index() - fetch RCU index with no dereferencing | |
653 | * @p: The index to read | |
654 | * | |
655 | * Return the value of the specified RCU-protected index, but omit the | |
656 | * smp_read_barrier_depends() and keep the ACCESS_ONCE(). This is useful | |
657 | * when the value of this index is accessed, but the index is not | |
658 | * dereferenced, for example, when testing an RCU-protected index against | |
659 | * -1. Although rcu_access_index() may also be used in cases where | |
660 | * update-side locks prevent the value of the index from changing, you | |
661 | * should instead use rcu_dereference_index_protected() for this use case. | |
662 | */ | |
663 | #define rcu_access_index(p) __rcu_access_index((p), __rcu) | |
664 | ||
ca5ecddf PM |
665 | /** |
666 | * rcu_dereference_index_check() - rcu_dereference for indices with debug checking | |
667 | * @p: The pointer to read, prior to dereferencing | |
668 | * @c: The conditions under which the dereference will take place | |
669 | * | |
670 | * Similar to rcu_dereference_check(), but omits the sparse checking. | |
671 | * This allows rcu_dereference_index_check() to be used on integers, | |
672 | * which can then be used as array indices. Attempting to use | |
673 | * rcu_dereference_check() on an integer will give compiler warnings | |
674 | * because the sparse address-space mechanism relies on dereferencing | |
675 | * the RCU-protected pointer. Dereferencing integers is not something | |
676 | * that even gcc will put up with. | |
677 | * | |
678 | * Note that this function does not implicitly check for RCU read-side | |
679 | * critical sections. If this function gains lots of uses, it might | |
680 | * make sense to provide versions for each flavor of RCU, but it does | |
681 | * not make sense as of early 2010. | |
682 | */ | |
683 | #define rcu_dereference_index_check(p, c) \ | |
684 | __rcu_dereference_index_check((p), (c)) | |
685 | ||
686 | /** | |
687 | * rcu_dereference_protected() - fetch RCU pointer when updates prevented | |
688 | * @p: The pointer to read, prior to dereferencing | |
689 | * @c: The conditions under which the dereference will take place | |
b62730ba PM |
690 | * |
691 | * Return the value of the specified RCU-protected pointer, but omit | |
692 | * both the smp_read_barrier_depends() and the ACCESS_ONCE(). This | |
693 | * is useful in cases where update-side locks prevent the value of the | |
694 | * pointer from changing. Please note that this primitive does -not- | |
695 | * prevent the compiler from repeating this reference or combining it | |
696 | * with other references, so it should not be used without protection | |
697 | * of appropriate locks. | |
ca5ecddf PM |
698 | * |
699 | * This function is only for update-side use. Using this function | |
700 | * when protected only by rcu_read_lock() will result in infrequent | |
701 | * but very ugly failures. | |
b62730ba PM |
702 | */ |
703 | #define rcu_dereference_protected(p, c) \ | |
ca5ecddf | 704 | __rcu_dereference_protected((p), (c), __rcu) |
b62730ba | 705 | |
bc33f24b | 706 | |
b62730ba | 707 | /** |
ca5ecddf PM |
708 | * rcu_dereference() - fetch RCU-protected pointer for dereferencing |
709 | * @p: The pointer to read, prior to dereferencing | |
b62730ba | 710 | * |
ca5ecddf | 711 | * This is a simple wrapper around rcu_dereference_check(). |
b62730ba | 712 | */ |
ca5ecddf | 713 | #define rcu_dereference(p) rcu_dereference_check(p, 0) |
b62730ba | 714 | |
1da177e4 | 715 | /** |
ca5ecddf PM |
716 | * rcu_dereference_bh() - fetch an RCU-bh-protected pointer for dereferencing |
717 | * @p: The pointer to read, prior to dereferencing | |
718 | * | |
719 | * Makes rcu_dereference_check() do the dirty work. | |
720 | */ | |
721 | #define rcu_dereference_bh(p) rcu_dereference_bh_check(p, 0) | |
722 | ||
723 | /** | |
724 | * rcu_dereference_sched() - fetch RCU-sched-protected pointer for dereferencing | |
725 | * @p: The pointer to read, prior to dereferencing | |
726 | * | |
727 | * Makes rcu_dereference_check() do the dirty work. | |
728 | */ | |
729 | #define rcu_dereference_sched(p) rcu_dereference_sched_check(p, 0) | |
730 | ||
731 | /** | |
732 | * rcu_read_lock() - mark the beginning of an RCU read-side critical section | |
1da177e4 | 733 | * |
9b06e818 | 734 | * When synchronize_rcu() is invoked on one CPU while other CPUs |
1da177e4 | 735 | * are within RCU read-side critical sections, then the |
9b06e818 | 736 | * synchronize_rcu() is guaranteed to block until after all the other |
1da177e4 LT |
737 | * CPUs exit their critical sections. Similarly, if call_rcu() is invoked |
738 | * on one CPU while other CPUs are within RCU read-side critical | |
739 | * sections, invocation of the corresponding RCU callback is deferred | |
740 | * until after the all the other CPUs exit their critical sections. | |
741 | * | |
742 | * Note, however, that RCU callbacks are permitted to run concurrently | |
77d8485a | 743 | * with new RCU read-side critical sections. One way that this can happen |
1da177e4 LT |
744 | * is via the following sequence of events: (1) CPU 0 enters an RCU |
745 | * read-side critical section, (2) CPU 1 invokes call_rcu() to register | |
746 | * an RCU callback, (3) CPU 0 exits the RCU read-side critical section, | |
747 | * (4) CPU 2 enters a RCU read-side critical section, (5) the RCU | |
748 | * callback is invoked. This is legal, because the RCU read-side critical | |
749 | * section that was running concurrently with the call_rcu() (and which | |
750 | * therefore might be referencing something that the corresponding RCU | |
751 | * callback would free up) has completed before the corresponding | |
752 | * RCU callback is invoked. | |
753 | * | |
754 | * RCU read-side critical sections may be nested. Any deferred actions | |
755 | * will be deferred until the outermost RCU read-side critical section | |
756 | * completes. | |
757 | * | |
9079fd7c PM |
758 | * You can avoid reading and understanding the next paragraph by |
759 | * following this rule: don't put anything in an rcu_read_lock() RCU | |
760 | * read-side critical section that would block in a !PREEMPT kernel. | |
761 | * But if you want the full story, read on! | |
762 | * | |
763 | * In non-preemptible RCU implementations (TREE_RCU and TINY_RCU), it | |
764 | * is illegal to block while in an RCU read-side critical section. In | |
765 | * preemptible RCU implementations (TREE_PREEMPT_RCU and TINY_PREEMPT_RCU) | |
766 | * in CONFIG_PREEMPT kernel builds, RCU read-side critical sections may | |
767 | * be preempted, but explicit blocking is illegal. Finally, in preemptible | |
90f45e4e | 768 | * RCU implementations in real-time (with -rt patchset) kernel builds, |
9079fd7c PM |
769 | * RCU read-side critical sections may be preempted and they may also |
770 | * block, but only when acquiring spinlocks that are subject to priority | |
771 | * inheritance. | |
1da177e4 | 772 | */ |
bc33f24b PM |
773 | static inline void rcu_read_lock(void) |
774 | { | |
775 | __rcu_read_lock(); | |
776 | __acquire(RCU); | |
d8ab29f8 | 777 | rcu_lock_acquire(&rcu_lock_map); |
bde23c68 HC |
778 | rcu_lockdep_assert(!rcu_is_cpu_idle(), |
779 | "rcu_read_lock() used illegally while idle"); | |
bc33f24b | 780 | } |
1da177e4 | 781 | |
1da177e4 LT |
782 | /* |
783 | * So where is rcu_write_lock()? It does not exist, as there is no | |
784 | * way for writers to lock out RCU readers. This is a feature, not | |
785 | * a bug -- this property is what provides RCU's performance benefits. | |
786 | * Of course, writers must coordinate with each other. The normal | |
787 | * spinlock primitives work well for this, but any other technique may be | |
788 | * used as well. RCU does not care how the writers keep out of each | |
789 | * others' way, as long as they do so. | |
790 | */ | |
3d76c082 PM |
791 | |
792 | /** | |
ca5ecddf | 793 | * rcu_read_unlock() - marks the end of an RCU read-side critical section. |
3d76c082 PM |
794 | * |
795 | * See rcu_read_lock() for more information. | |
796 | */ | |
bc33f24b PM |
797 | static inline void rcu_read_unlock(void) |
798 | { | |
bde23c68 HC |
799 | rcu_lockdep_assert(!rcu_is_cpu_idle(), |
800 | "rcu_read_unlock() used illegally while idle"); | |
d8ab29f8 | 801 | rcu_lock_release(&rcu_lock_map); |
bc33f24b PM |
802 | __release(RCU); |
803 | __rcu_read_unlock(); | |
804 | } | |
1da177e4 LT |
805 | |
806 | /** | |
ca5ecddf | 807 | * rcu_read_lock_bh() - mark the beginning of an RCU-bh critical section |
1da177e4 LT |
808 | * |
809 | * This is equivalent of rcu_read_lock(), but to be used when updates | |
ca5ecddf PM |
810 | * are being done using call_rcu_bh() or synchronize_rcu_bh(). Since |
811 | * both call_rcu_bh() and synchronize_rcu_bh() consider completion of a | |
812 | * softirq handler to be a quiescent state, a process in RCU read-side | |
813 | * critical section must be protected by disabling softirqs. Read-side | |
814 | * critical sections in interrupt context can use just rcu_read_lock(), | |
815 | * though this should at least be commented to avoid confusing people | |
816 | * reading the code. | |
3842a083 PM |
817 | * |
818 | * Note that rcu_read_lock_bh() and the matching rcu_read_unlock_bh() | |
819 | * must occur in the same context, for example, it is illegal to invoke | |
820 | * rcu_read_unlock_bh() from one task if the matching rcu_read_lock_bh() | |
821 | * was invoked from some other task. | |
1da177e4 | 822 | */ |
bc33f24b PM |
823 | static inline void rcu_read_lock_bh(void) |
824 | { | |
6206ab9b | 825 | local_bh_disable(); |
bc33f24b | 826 | __acquire(RCU_BH); |
d8ab29f8 | 827 | rcu_lock_acquire(&rcu_bh_lock_map); |
bde23c68 HC |
828 | rcu_lockdep_assert(!rcu_is_cpu_idle(), |
829 | "rcu_read_lock_bh() used illegally while idle"); | |
bc33f24b | 830 | } |
1da177e4 LT |
831 | |
832 | /* | |
833 | * rcu_read_unlock_bh - marks the end of a softirq-only RCU critical section | |
834 | * | |
835 | * See rcu_read_lock_bh() for more information. | |
836 | */ | |
bc33f24b PM |
837 | static inline void rcu_read_unlock_bh(void) |
838 | { | |
bde23c68 HC |
839 | rcu_lockdep_assert(!rcu_is_cpu_idle(), |
840 | "rcu_read_unlock_bh() used illegally while idle"); | |
d8ab29f8 | 841 | rcu_lock_release(&rcu_bh_lock_map); |
bc33f24b | 842 | __release(RCU_BH); |
6206ab9b | 843 | local_bh_enable(); |
bc33f24b | 844 | } |
1da177e4 | 845 | |
1c50b728 | 846 | /** |
ca5ecddf | 847 | * rcu_read_lock_sched() - mark the beginning of a RCU-sched critical section |
1c50b728 | 848 | * |
ca5ecddf PM |
849 | * This is equivalent of rcu_read_lock(), but to be used when updates |
850 | * are being done using call_rcu_sched() or synchronize_rcu_sched(). | |
851 | * Read-side critical sections can also be introduced by anything that | |
852 | * disables preemption, including local_irq_disable() and friends. | |
3842a083 PM |
853 | * |
854 | * Note that rcu_read_lock_sched() and the matching rcu_read_unlock_sched() | |
855 | * must occur in the same context, for example, it is illegal to invoke | |
856 | * rcu_read_unlock_sched() from process context if the matching | |
857 | * rcu_read_lock_sched() was invoked from an NMI handler. | |
1c50b728 | 858 | */ |
d6714c22 PM |
859 | static inline void rcu_read_lock_sched(void) |
860 | { | |
861 | preempt_disable(); | |
bc33f24b | 862 | __acquire(RCU_SCHED); |
d8ab29f8 | 863 | rcu_lock_acquire(&rcu_sched_lock_map); |
bde23c68 HC |
864 | rcu_lockdep_assert(!rcu_is_cpu_idle(), |
865 | "rcu_read_lock_sched() used illegally while idle"); | |
d6714c22 | 866 | } |
1eba8f84 PM |
867 | |
868 | /* Used by lockdep and tracing: cannot be traced, cannot call lockdep. */ | |
7c614d64 | 869 | static inline notrace void rcu_read_lock_sched_notrace(void) |
d6714c22 PM |
870 | { |
871 | preempt_disable_notrace(); | |
bc33f24b | 872 | __acquire(RCU_SCHED); |
d6714c22 | 873 | } |
1c50b728 MD |
874 | |
875 | /* | |
876 | * rcu_read_unlock_sched - marks the end of a RCU-classic critical section | |
877 | * | |
878 | * See rcu_read_lock_sched for more information. | |
879 | */ | |
d6714c22 PM |
880 | static inline void rcu_read_unlock_sched(void) |
881 | { | |
bde23c68 HC |
882 | rcu_lockdep_assert(!rcu_is_cpu_idle(), |
883 | "rcu_read_unlock_sched() used illegally while idle"); | |
d8ab29f8 | 884 | rcu_lock_release(&rcu_sched_lock_map); |
bc33f24b | 885 | __release(RCU_SCHED); |
d6714c22 PM |
886 | preempt_enable(); |
887 | } | |
1eba8f84 PM |
888 | |
889 | /* Used by lockdep and tracing: cannot be traced, cannot call lockdep. */ | |
7c614d64 | 890 | static inline notrace void rcu_read_unlock_sched_notrace(void) |
d6714c22 | 891 | { |
bc33f24b | 892 | __release(RCU_SCHED); |
d6714c22 PM |
893 | preempt_enable_notrace(); |
894 | } | |
1c50b728 | 895 | |
1da177e4 | 896 | /** |
ca5ecddf PM |
897 | * rcu_assign_pointer() - assign to RCU-protected pointer |
898 | * @p: pointer to assign to | |
899 | * @v: value to assign (publish) | |
c26d34a5 | 900 | * |
ca5ecddf PM |
901 | * Assigns the specified value to the specified RCU-protected |
902 | * pointer, ensuring that any concurrent RCU readers will see | |
e9023c40 | 903 | * any prior initialization. |
1da177e4 LT |
904 | * |
905 | * Inserts memory barriers on architectures that require them | |
6846c0c5 PM |
906 | * (which is most of them), and also prevents the compiler from |
907 | * reordering the code that initializes the structure after the pointer | |
908 | * assignment. More importantly, this call documents which pointers | |
909 | * will be dereferenced by RCU read-side code. | |
910 | * | |
911 | * In some special cases, you may use RCU_INIT_POINTER() instead | |
912 | * of rcu_assign_pointer(). RCU_INIT_POINTER() is a bit faster due | |
913 | * to the fact that it does not constrain either the CPU or the compiler. | |
914 | * That said, using RCU_INIT_POINTER() when you should have used | |
915 | * rcu_assign_pointer() is a very bad thing that results in | |
916 | * impossible-to-diagnose memory corruption. So please be careful. | |
917 | * See the RCU_INIT_POINTER() comment header for details. | |
1da177e4 | 918 | */ |
d99c4f6b | 919 | #define rcu_assign_pointer(p, v) \ |
ca5ecddf PM |
920 | __rcu_assign_pointer((p), (v), __rcu) |
921 | ||
922 | /** | |
923 | * RCU_INIT_POINTER() - initialize an RCU protected pointer | |
924 | * | |
6846c0c5 PM |
925 | * Initialize an RCU-protected pointer in special cases where readers |
926 | * do not need ordering constraints on the CPU or the compiler. These | |
927 | * special cases are: | |
928 | * | |
929 | * 1. This use of RCU_INIT_POINTER() is NULLing out the pointer -or- | |
930 | * 2. The caller has taken whatever steps are required to prevent | |
931 | * RCU readers from concurrently accessing this pointer -or- | |
932 | * 3. The referenced data structure has already been exposed to | |
933 | * readers either at compile time or via rcu_assign_pointer() -and- | |
934 | * a. You have not made -any- reader-visible changes to | |
935 | * this structure since then -or- | |
936 | * b. It is OK for readers accessing this structure from its | |
937 | * new location to see the old state of the structure. (For | |
938 | * example, the changes were to statistical counters or to | |
939 | * other state where exact synchronization is not required.) | |
940 | * | |
941 | * Failure to follow these rules governing use of RCU_INIT_POINTER() will | |
942 | * result in impossible-to-diagnose memory corruption. As in the structures | |
943 | * will look OK in crash dumps, but any concurrent RCU readers might | |
944 | * see pre-initialized values of the referenced data structure. So | |
945 | * please be very careful how you use RCU_INIT_POINTER()!!! | |
946 | * | |
947 | * If you are creating an RCU-protected linked structure that is accessed | |
948 | * by a single external-to-structure RCU-protected pointer, then you may | |
949 | * use RCU_INIT_POINTER() to initialize the internal RCU-protected | |
950 | * pointers, but you must use rcu_assign_pointer() to initialize the | |
951 | * external-to-structure pointer -after- you have completely initialized | |
952 | * the reader-accessible portions of the linked structure. | |
ca5ecddf PM |
953 | */ |
954 | #define RCU_INIT_POINTER(p, v) \ | |
d1b88eb9 PM |
955 | do { \ |
956 | p = (typeof(*v) __force __rcu *)(v); \ | |
957 | } while (0) | |
9ab1544e | 958 | |
172708d0 PM |
959 | /** |
960 | * RCU_POINTER_INITIALIZER() - statically initialize an RCU protected pointer | |
961 | * | |
962 | * GCC-style initialization for an RCU-protected pointer in a structure field. | |
963 | */ | |
964 | #define RCU_POINTER_INITIALIZER(p, v) \ | |
965 | .p = (typeof(*v) __force __rcu *)(v) | |
9ab1544e | 966 | |
d8169d4c JE |
967 | /* |
968 | * Does the specified offset indicate that the corresponding rcu_head | |
969 | * structure can be handled by kfree_rcu()? | |
970 | */ | |
971 | #define __is_kfree_rcu_offset(offset) ((offset) < 4096) | |
972 | ||
973 | /* | |
974 | * Helper macro for kfree_rcu() to prevent argument-expansion eyestrain. | |
975 | */ | |
976 | #define __kfree_rcu(head, offset) \ | |
977 | do { \ | |
978 | BUILD_BUG_ON(!__is_kfree_rcu_offset(offset)); \ | |
4fa3b6cb | 979 | kfree_call_rcu(head, (void (*)(struct rcu_head *))(unsigned long)(offset)); \ |
d8169d4c JE |
980 | } while (0) |
981 | ||
9ab1544e LJ |
982 | /** |
983 | * kfree_rcu() - kfree an object after a grace period. | |
984 | * @ptr: pointer to kfree | |
985 | * @rcu_head: the name of the struct rcu_head within the type of @ptr. | |
986 | * | |
987 | * Many rcu callbacks functions just call kfree() on the base structure. | |
988 | * These functions are trivial, but their size adds up, and furthermore | |
989 | * when they are used in a kernel module, that module must invoke the | |
990 | * high-latency rcu_barrier() function at module-unload time. | |
991 | * | |
992 | * The kfree_rcu() function handles this issue. Rather than encoding a | |
993 | * function address in the embedded rcu_head structure, kfree_rcu() instead | |
994 | * encodes the offset of the rcu_head structure within the base structure. | |
995 | * Because the functions are not allowed in the low-order 4096 bytes of | |
996 | * kernel virtual memory, offsets up to 4095 bytes can be accommodated. | |
997 | * If the offset is larger than 4095 bytes, a compile-time error will | |
998 | * be generated in __kfree_rcu(). If this error is triggered, you can | |
999 | * either fall back to use of call_rcu() or rearrange the structure to | |
1000 | * position the rcu_head structure into the first 4096 bytes. | |
1001 | * | |
1002 | * Note that the allowable offset might decrease in the future, for example, | |
1003 | * to allow something like kmem_cache_free_rcu(). | |
d8169d4c JE |
1004 | * |
1005 | * The BUILD_BUG_ON check must not involve any function calls, hence the | |
1006 | * checks are done in macros here. | |
9ab1544e LJ |
1007 | */ |
1008 | #define kfree_rcu(ptr, rcu_head) \ | |
1009 | __kfree_rcu(&((ptr)->rcu_head), offsetof(typeof(*(ptr)), rcu_head)) | |
1010 | ||
d1e43fa5 FW |
1011 | #ifdef CONFIG_RCU_NOCB_CPU |
1012 | extern bool rcu_is_nocb_cpu(int cpu); | |
1013 | #else | |
1014 | static inline bool rcu_is_nocb_cpu(int cpu) { return false; } | |
1015 | #endif /* #else #ifdef CONFIG_RCU_NOCB_CPU */ | |
1016 | ||
1017 | ||
1da177e4 | 1018 | #endif /* __LINUX_RCUPDATE_H */ |