]>
Commit | Line | Data |
---|---|---|
6053ee3b IM |
1 | /* |
2 | * kernel/mutex.c | |
3 | * | |
4 | * Mutexes: blocking mutual exclusion locks | |
5 | * | |
6 | * Started by Ingo Molnar: | |
7 | * | |
8 | * Copyright (C) 2004, 2005, 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com> | |
9 | * | |
10 | * Many thanks to Arjan van de Ven, Thomas Gleixner, Steven Rostedt and | |
11 | * David Howells for suggestions and improvements. | |
12 | * | |
0d66bf6d PZ |
13 | * - Adaptive spinning for mutexes by Peter Zijlstra. (Ported to mainline |
14 | * from the -rt tree, where it was originally implemented for rtmutexes | |
15 | * by Steven Rostedt, based on work by Gregory Haskins, Peter Morreale | |
16 | * and Sven Dietrich. | |
17 | * | |
6053ee3b IM |
18 | * Also see Documentation/mutex-design.txt. |
19 | */ | |
20 | #include <linux/mutex.h> | |
21 | #include <linux/sched.h> | |
8bd75c77 | 22 | #include <linux/sched/rt.h> |
9984de1a | 23 | #include <linux/export.h> |
6053ee3b IM |
24 | #include <linux/spinlock.h> |
25 | #include <linux/interrupt.h> | |
9a11b49a | 26 | #include <linux/debug_locks.h> |
6053ee3b IM |
27 | |
28 | /* | |
29 | * In the DEBUG case we are using the "NULL fastpath" for mutexes, | |
30 | * which forces all calls into the slowpath: | |
31 | */ | |
32 | #ifdef CONFIG_DEBUG_MUTEXES | |
33 | # include "mutex-debug.h" | |
34 | # include <asm-generic/mutex-null.h> | |
35 | #else | |
36 | # include "mutex.h" | |
37 | # include <asm/mutex.h> | |
38 | #endif | |
39 | ||
ef5d4707 IM |
40 | void |
41 | __mutex_init(struct mutex *lock, const char *name, struct lock_class_key *key) | |
6053ee3b IM |
42 | { |
43 | atomic_set(&lock->count, 1); | |
44 | spin_lock_init(&lock->wait_lock); | |
45 | INIT_LIST_HEAD(&lock->wait_list); | |
0d66bf6d | 46 | mutex_clear_owner(lock); |
6053ee3b | 47 | |
ef5d4707 | 48 | debug_mutex_init(lock, name, key); |
6053ee3b IM |
49 | } |
50 | ||
51 | EXPORT_SYMBOL(__mutex_init); | |
52 | ||
e4564f79 | 53 | #ifndef CONFIG_DEBUG_LOCK_ALLOC |
6053ee3b IM |
54 | /* |
55 | * We split the mutex lock/unlock logic into separate fastpath and | |
56 | * slowpath functions, to reduce the register pressure on the fastpath. | |
57 | * We also put the fastpath first in the kernel image, to make sure the | |
58 | * branch is predicted by the CPU as default-untaken. | |
59 | */ | |
7918baa5 | 60 | static __used noinline void __sched |
9a11b49a | 61 | __mutex_lock_slowpath(atomic_t *lock_count); |
6053ee3b | 62 | |
ef5dc121 | 63 | /** |
6053ee3b IM |
64 | * mutex_lock - acquire the mutex |
65 | * @lock: the mutex to be acquired | |
66 | * | |
67 | * Lock the mutex exclusively for this task. If the mutex is not | |
68 | * available right now, it will sleep until it can get it. | |
69 | * | |
70 | * The mutex must later on be released by the same task that | |
71 | * acquired it. Recursive locking is not allowed. The task | |
72 | * may not exit without first unlocking the mutex. Also, kernel | |
73 | * memory where the mutex resides mutex must not be freed with | |
74 | * the mutex still locked. The mutex must first be initialized | |
75 | * (or statically defined) before it can be locked. memset()-ing | |
76 | * the mutex to 0 is not allowed. | |
77 | * | |
78 | * ( The CONFIG_DEBUG_MUTEXES .config option turns on debugging | |
79 | * checks that will enforce the restrictions and will also do | |
80 | * deadlock debugging. ) | |
81 | * | |
82 | * This function is similar to (but not equivalent to) down(). | |
83 | */ | |
b09d2501 | 84 | void __sched mutex_lock(struct mutex *lock) |
6053ee3b | 85 | { |
c544bdb1 | 86 | might_sleep(); |
6053ee3b IM |
87 | /* |
88 | * The locking fastpath is the 1->0 transition from | |
89 | * 'unlocked' into 'locked' state. | |
6053ee3b IM |
90 | */ |
91 | __mutex_fastpath_lock(&lock->count, __mutex_lock_slowpath); | |
0d66bf6d | 92 | mutex_set_owner(lock); |
6053ee3b IM |
93 | } |
94 | ||
95 | EXPORT_SYMBOL(mutex_lock); | |
e4564f79 | 96 | #endif |
6053ee3b | 97 | |
41fcb9f2 WL |
98 | #ifdef CONFIG_MUTEX_SPIN_ON_OWNER |
99 | /* | |
100 | * Mutex spinning code migrated from kernel/sched/core.c | |
101 | */ | |
102 | ||
103 | static inline bool owner_running(struct mutex *lock, struct task_struct *owner) | |
104 | { | |
105 | if (lock->owner != owner) | |
106 | return false; | |
107 | ||
108 | /* | |
109 | * Ensure we emit the owner->on_cpu, dereference _after_ checking | |
110 | * lock->owner still matches owner, if that fails, owner might | |
111 | * point to free()d memory, if it still matches, the rcu_read_lock() | |
112 | * ensures the memory stays valid. | |
113 | */ | |
114 | barrier(); | |
115 | ||
116 | return owner->on_cpu; | |
117 | } | |
118 | ||
119 | /* | |
120 | * Look out! "owner" is an entirely speculative pointer | |
121 | * access and not reliable. | |
122 | */ | |
123 | static noinline | |
124 | int mutex_spin_on_owner(struct mutex *lock, struct task_struct *owner) | |
125 | { | |
126 | rcu_read_lock(); | |
127 | while (owner_running(lock, owner)) { | |
128 | if (need_resched()) | |
129 | break; | |
130 | ||
131 | arch_mutex_cpu_relax(); | |
132 | } | |
133 | rcu_read_unlock(); | |
134 | ||
135 | /* | |
136 | * We break out the loop above on need_resched() and when the | |
137 | * owner changed, which is a sign for heavy contention. Return | |
138 | * success only when lock->owner is NULL. | |
139 | */ | |
140 | return lock->owner == NULL; | |
141 | } | |
142 | #endif | |
143 | ||
7918baa5 | 144 | static __used noinline void __sched __mutex_unlock_slowpath(atomic_t *lock_count); |
6053ee3b | 145 | |
ef5dc121 | 146 | /** |
6053ee3b IM |
147 | * mutex_unlock - release the mutex |
148 | * @lock: the mutex to be released | |
149 | * | |
150 | * Unlock a mutex that has been locked by this task previously. | |
151 | * | |
152 | * This function must not be used in interrupt context. Unlocking | |
153 | * of a not locked mutex is not allowed. | |
154 | * | |
155 | * This function is similar to (but not equivalent to) up(). | |
156 | */ | |
7ad5b3a5 | 157 | void __sched mutex_unlock(struct mutex *lock) |
6053ee3b IM |
158 | { |
159 | /* | |
160 | * The unlocking fastpath is the 0->1 transition from 'locked' | |
161 | * into 'unlocked' state: | |
6053ee3b | 162 | */ |
0d66bf6d PZ |
163 | #ifndef CONFIG_DEBUG_MUTEXES |
164 | /* | |
165 | * When debugging is enabled we must not clear the owner before time, | |
166 | * the slow path will always be taken, and that clears the owner field | |
167 | * after verifying that it was indeed current. | |
168 | */ | |
169 | mutex_clear_owner(lock); | |
170 | #endif | |
6053ee3b IM |
171 | __mutex_fastpath_unlock(&lock->count, __mutex_unlock_slowpath); |
172 | } | |
173 | ||
174 | EXPORT_SYMBOL(mutex_unlock); | |
175 | ||
176 | /* | |
177 | * Lock a mutex (possibly interruptible), slowpath: | |
178 | */ | |
179 | static inline int __sched | |
e4564f79 | 180 | __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass, |
e4c70a66 | 181 | struct lockdep_map *nest_lock, unsigned long ip) |
6053ee3b IM |
182 | { |
183 | struct task_struct *task = current; | |
184 | struct mutex_waiter waiter; | |
1fb00c6c | 185 | unsigned long flags; |
6053ee3b | 186 | |
41719b03 | 187 | preempt_disable(); |
e4c70a66 | 188 | mutex_acquire_nest(&lock->dep_map, subclass, 0, nest_lock, ip); |
c0226027 FW |
189 | |
190 | #ifdef CONFIG_MUTEX_SPIN_ON_OWNER | |
0d66bf6d PZ |
191 | /* |
192 | * Optimistic spinning. | |
193 | * | |
194 | * We try to spin for acquisition when we find that there are no | |
195 | * pending waiters and the lock owner is currently running on a | |
196 | * (different) CPU. | |
197 | * | |
198 | * The rationale is that if the lock owner is running, it is likely to | |
199 | * release the lock soon. | |
200 | * | |
201 | * Since this needs the lock owner, and this mutex implementation | |
202 | * doesn't track the owner atomically in the lock field, we need to | |
203 | * track it non-atomically. | |
204 | * | |
205 | * We can't do this for DEBUG_MUTEXES because that relies on wait_lock | |
206 | * to serialize everything. | |
207 | */ | |
208 | ||
209 | for (;;) { | |
c6eb3dda | 210 | struct task_struct *owner; |
0d66bf6d | 211 | |
0d66bf6d PZ |
212 | /* |
213 | * If there's an owner, wait for it to either | |
214 | * release the lock or go to sleep. | |
215 | */ | |
216 | owner = ACCESS_ONCE(lock->owner); | |
217 | if (owner && !mutex_spin_on_owner(lock, owner)) | |
218 | break; | |
219 | ||
ac6e60ee CM |
220 | if (atomic_cmpxchg(&lock->count, 1, 0) == 1) { |
221 | lock_acquired(&lock->dep_map, ip); | |
222 | mutex_set_owner(lock); | |
223 | preempt_enable(); | |
224 | return 0; | |
225 | } | |
226 | ||
0d66bf6d PZ |
227 | /* |
228 | * When there's no owner, we might have preempted between the | |
229 | * owner acquiring the lock and setting the owner field. If | |
230 | * we're an RT task that will live-lock because we won't let | |
231 | * the owner complete. | |
232 | */ | |
233 | if (!owner && (need_resched() || rt_task(task))) | |
234 | break; | |
235 | ||
0d66bf6d PZ |
236 | /* |
237 | * The cpu_relax() call is a compiler barrier which forces | |
238 | * everything in this loop to be re-loaded. We don't need | |
239 | * memory barriers as we'll eventually observe the right | |
240 | * values at the cost of a few extra spins. | |
241 | */ | |
335d7afb | 242 | arch_mutex_cpu_relax(); |
0d66bf6d PZ |
243 | } |
244 | #endif | |
1fb00c6c | 245 | spin_lock_mutex(&lock->wait_lock, flags); |
6053ee3b | 246 | |
9a11b49a | 247 | debug_mutex_lock_common(lock, &waiter); |
c9f4f06d | 248 | debug_mutex_add_waiter(lock, &waiter, task_thread_info(task)); |
6053ee3b IM |
249 | |
250 | /* add waiting tasks to the end of the waitqueue (FIFO): */ | |
251 | list_add_tail(&waiter.list, &lock->wait_list); | |
252 | waiter.task = task; | |
253 | ||
93d81d1a | 254 | if (atomic_xchg(&lock->count, -1) == 1) |
4fe87745 PZ |
255 | goto done; |
256 | ||
e4564f79 | 257 | lock_contended(&lock->dep_map, ip); |
4fe87745 | 258 | |
6053ee3b IM |
259 | for (;;) { |
260 | /* | |
261 | * Lets try to take the lock again - this is needed even if | |
262 | * we get here for the first time (shortly after failing to | |
263 | * acquire the lock), to make sure that we get a wakeup once | |
264 | * it's unlocked. Later on, if we sleep, this is the | |
265 | * operation that gives us the lock. We xchg it to -1, so | |
266 | * that when we release the lock, we properly wake up the | |
267 | * other waiters: | |
268 | */ | |
93d81d1a | 269 | if (atomic_xchg(&lock->count, -1) == 1) |
6053ee3b IM |
270 | break; |
271 | ||
272 | /* | |
273 | * got a signal? (This code gets eliminated in the | |
274 | * TASK_UNINTERRUPTIBLE case.) | |
275 | */ | |
6ad36762 | 276 | if (unlikely(signal_pending_state(state, task))) { |
ad776537 LH |
277 | mutex_remove_waiter(lock, &waiter, |
278 | task_thread_info(task)); | |
e4564f79 | 279 | mutex_release(&lock->dep_map, 1, ip); |
1fb00c6c | 280 | spin_unlock_mutex(&lock->wait_lock, flags); |
6053ee3b IM |
281 | |
282 | debug_mutex_free_waiter(&waiter); | |
41719b03 | 283 | preempt_enable(); |
6053ee3b IM |
284 | return -EINTR; |
285 | } | |
286 | __set_task_state(task, state); | |
287 | ||
25985edc | 288 | /* didn't get the lock, go to sleep: */ |
1fb00c6c | 289 | spin_unlock_mutex(&lock->wait_lock, flags); |
bd2f5536 | 290 | schedule_preempt_disabled(); |
1fb00c6c | 291 | spin_lock_mutex(&lock->wait_lock, flags); |
6053ee3b IM |
292 | } |
293 | ||
4fe87745 | 294 | done: |
c7e78cff | 295 | lock_acquired(&lock->dep_map, ip); |
6053ee3b | 296 | /* got the lock - rejoice! */ |
0d66bf6d PZ |
297 | mutex_remove_waiter(lock, &waiter, current_thread_info()); |
298 | mutex_set_owner(lock); | |
6053ee3b IM |
299 | |
300 | /* set it to 0 if there are no waiters left: */ | |
301 | if (likely(list_empty(&lock->wait_list))) | |
302 | atomic_set(&lock->count, 0); | |
303 | ||
1fb00c6c | 304 | spin_unlock_mutex(&lock->wait_lock, flags); |
6053ee3b IM |
305 | |
306 | debug_mutex_free_waiter(&waiter); | |
41719b03 | 307 | preempt_enable(); |
6053ee3b | 308 | |
6053ee3b IM |
309 | return 0; |
310 | } | |
311 | ||
ef5d4707 IM |
312 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
313 | void __sched | |
314 | mutex_lock_nested(struct mutex *lock, unsigned int subclass) | |
315 | { | |
316 | might_sleep(); | |
e4c70a66 | 317 | __mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, subclass, NULL, _RET_IP_); |
ef5d4707 IM |
318 | } |
319 | ||
320 | EXPORT_SYMBOL_GPL(mutex_lock_nested); | |
d63a5a74 | 321 | |
e4c70a66 PZ |
322 | void __sched |
323 | _mutex_lock_nest_lock(struct mutex *lock, struct lockdep_map *nest) | |
324 | { | |
325 | might_sleep(); | |
326 | __mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, 0, nest, _RET_IP_); | |
327 | } | |
328 | ||
329 | EXPORT_SYMBOL_GPL(_mutex_lock_nest_lock); | |
330 | ||
ad776537 LH |
331 | int __sched |
332 | mutex_lock_killable_nested(struct mutex *lock, unsigned int subclass) | |
333 | { | |
334 | might_sleep(); | |
e4c70a66 | 335 | return __mutex_lock_common(lock, TASK_KILLABLE, subclass, NULL, _RET_IP_); |
ad776537 LH |
336 | } |
337 | EXPORT_SYMBOL_GPL(mutex_lock_killable_nested); | |
338 | ||
d63a5a74 N |
339 | int __sched |
340 | mutex_lock_interruptible_nested(struct mutex *lock, unsigned int subclass) | |
341 | { | |
342 | might_sleep(); | |
0d66bf6d | 343 | return __mutex_lock_common(lock, TASK_INTERRUPTIBLE, |
e4c70a66 | 344 | subclass, NULL, _RET_IP_); |
d63a5a74 N |
345 | } |
346 | ||
347 | EXPORT_SYMBOL_GPL(mutex_lock_interruptible_nested); | |
ef5d4707 IM |
348 | #endif |
349 | ||
6053ee3b IM |
350 | /* |
351 | * Release the lock, slowpath: | |
352 | */ | |
7ad5b3a5 | 353 | static inline void |
ef5d4707 | 354 | __mutex_unlock_common_slowpath(atomic_t *lock_count, int nested) |
6053ee3b | 355 | { |
02706647 | 356 | struct mutex *lock = container_of(lock_count, struct mutex, count); |
1fb00c6c | 357 | unsigned long flags; |
6053ee3b | 358 | |
1fb00c6c | 359 | spin_lock_mutex(&lock->wait_lock, flags); |
ef5d4707 | 360 | mutex_release(&lock->dep_map, nested, _RET_IP_); |
9a11b49a | 361 | debug_mutex_unlock(lock); |
6053ee3b IM |
362 | |
363 | /* | |
364 | * some architectures leave the lock unlocked in the fastpath failure | |
365 | * case, others need to leave it locked. In the later case we have to | |
366 | * unlock it here | |
367 | */ | |
368 | if (__mutex_slowpath_needs_to_unlock()) | |
369 | atomic_set(&lock->count, 1); | |
370 | ||
6053ee3b IM |
371 | if (!list_empty(&lock->wait_list)) { |
372 | /* get the first entry from the wait-list: */ | |
373 | struct mutex_waiter *waiter = | |
374 | list_entry(lock->wait_list.next, | |
375 | struct mutex_waiter, list); | |
376 | ||
377 | debug_mutex_wake_waiter(lock, waiter); | |
378 | ||
379 | wake_up_process(waiter->task); | |
380 | } | |
381 | ||
1fb00c6c | 382 | spin_unlock_mutex(&lock->wait_lock, flags); |
6053ee3b IM |
383 | } |
384 | ||
9a11b49a IM |
385 | /* |
386 | * Release the lock, slowpath: | |
387 | */ | |
7918baa5 | 388 | static __used noinline void |
9a11b49a IM |
389 | __mutex_unlock_slowpath(atomic_t *lock_count) |
390 | { | |
ef5d4707 | 391 | __mutex_unlock_common_slowpath(lock_count, 1); |
9a11b49a IM |
392 | } |
393 | ||
e4564f79 | 394 | #ifndef CONFIG_DEBUG_LOCK_ALLOC |
6053ee3b IM |
395 | /* |
396 | * Here come the less common (and hence less performance-critical) APIs: | |
397 | * mutex_lock_interruptible() and mutex_trylock(). | |
398 | */ | |
7ad5b3a5 | 399 | static noinline int __sched |
ad776537 LH |
400 | __mutex_lock_killable_slowpath(atomic_t *lock_count); |
401 | ||
7ad5b3a5 | 402 | static noinline int __sched |
9a11b49a | 403 | __mutex_lock_interruptible_slowpath(atomic_t *lock_count); |
6053ee3b | 404 | |
ef5dc121 RD |
405 | /** |
406 | * mutex_lock_interruptible - acquire the mutex, interruptible | |
6053ee3b IM |
407 | * @lock: the mutex to be acquired |
408 | * | |
409 | * Lock the mutex like mutex_lock(), and return 0 if the mutex has | |
410 | * been acquired or sleep until the mutex becomes available. If a | |
411 | * signal arrives while waiting for the lock then this function | |
412 | * returns -EINTR. | |
413 | * | |
414 | * This function is similar to (but not equivalent to) down_interruptible(). | |
415 | */ | |
7ad5b3a5 | 416 | int __sched mutex_lock_interruptible(struct mutex *lock) |
6053ee3b | 417 | { |
0d66bf6d PZ |
418 | int ret; |
419 | ||
c544bdb1 | 420 | might_sleep(); |
0d66bf6d | 421 | ret = __mutex_fastpath_lock_retval |
6053ee3b | 422 | (&lock->count, __mutex_lock_interruptible_slowpath); |
0d66bf6d PZ |
423 | if (!ret) |
424 | mutex_set_owner(lock); | |
425 | ||
426 | return ret; | |
6053ee3b IM |
427 | } |
428 | ||
429 | EXPORT_SYMBOL(mutex_lock_interruptible); | |
430 | ||
7ad5b3a5 | 431 | int __sched mutex_lock_killable(struct mutex *lock) |
ad776537 | 432 | { |
0d66bf6d PZ |
433 | int ret; |
434 | ||
ad776537 | 435 | might_sleep(); |
0d66bf6d | 436 | ret = __mutex_fastpath_lock_retval |
ad776537 | 437 | (&lock->count, __mutex_lock_killable_slowpath); |
0d66bf6d PZ |
438 | if (!ret) |
439 | mutex_set_owner(lock); | |
440 | ||
441 | return ret; | |
ad776537 LH |
442 | } |
443 | EXPORT_SYMBOL(mutex_lock_killable); | |
444 | ||
7918baa5 | 445 | static __used noinline void __sched |
e4564f79 PZ |
446 | __mutex_lock_slowpath(atomic_t *lock_count) |
447 | { | |
448 | struct mutex *lock = container_of(lock_count, struct mutex, count); | |
449 | ||
e4c70a66 | 450 | __mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, 0, NULL, _RET_IP_); |
e4564f79 PZ |
451 | } |
452 | ||
7ad5b3a5 | 453 | static noinline int __sched |
ad776537 LH |
454 | __mutex_lock_killable_slowpath(atomic_t *lock_count) |
455 | { | |
456 | struct mutex *lock = container_of(lock_count, struct mutex, count); | |
457 | ||
e4c70a66 | 458 | return __mutex_lock_common(lock, TASK_KILLABLE, 0, NULL, _RET_IP_); |
ad776537 LH |
459 | } |
460 | ||
7ad5b3a5 | 461 | static noinline int __sched |
9a11b49a | 462 | __mutex_lock_interruptible_slowpath(atomic_t *lock_count) |
6053ee3b IM |
463 | { |
464 | struct mutex *lock = container_of(lock_count, struct mutex, count); | |
465 | ||
e4c70a66 | 466 | return __mutex_lock_common(lock, TASK_INTERRUPTIBLE, 0, NULL, _RET_IP_); |
6053ee3b | 467 | } |
e4564f79 | 468 | #endif |
6053ee3b IM |
469 | |
470 | /* | |
471 | * Spinlock based trylock, we take the spinlock and check whether we | |
472 | * can get the lock: | |
473 | */ | |
474 | static inline int __mutex_trylock_slowpath(atomic_t *lock_count) | |
475 | { | |
476 | struct mutex *lock = container_of(lock_count, struct mutex, count); | |
1fb00c6c | 477 | unsigned long flags; |
6053ee3b IM |
478 | int prev; |
479 | ||
1fb00c6c | 480 | spin_lock_mutex(&lock->wait_lock, flags); |
6053ee3b IM |
481 | |
482 | prev = atomic_xchg(&lock->count, -1); | |
ef5d4707 | 483 | if (likely(prev == 1)) { |
0d66bf6d | 484 | mutex_set_owner(lock); |
ef5d4707 IM |
485 | mutex_acquire(&lock->dep_map, 0, 1, _RET_IP_); |
486 | } | |
0d66bf6d | 487 | |
6053ee3b IM |
488 | /* Set it back to 0 if there are no waiters: */ |
489 | if (likely(list_empty(&lock->wait_list))) | |
490 | atomic_set(&lock->count, 0); | |
491 | ||
1fb00c6c | 492 | spin_unlock_mutex(&lock->wait_lock, flags); |
6053ee3b IM |
493 | |
494 | return prev == 1; | |
495 | } | |
496 | ||
ef5dc121 RD |
497 | /** |
498 | * mutex_trylock - try to acquire the mutex, without waiting | |
6053ee3b IM |
499 | * @lock: the mutex to be acquired |
500 | * | |
501 | * Try to acquire the mutex atomically. Returns 1 if the mutex | |
502 | * has been acquired successfully, and 0 on contention. | |
503 | * | |
504 | * NOTE: this function follows the spin_trylock() convention, so | |
ef5dc121 | 505 | * it is negated from the down_trylock() return values! Be careful |
6053ee3b IM |
506 | * about this when converting semaphore users to mutexes. |
507 | * | |
508 | * This function must not be used in interrupt context. The | |
509 | * mutex must be released by the same task that acquired it. | |
510 | */ | |
7ad5b3a5 | 511 | int __sched mutex_trylock(struct mutex *lock) |
6053ee3b | 512 | { |
0d66bf6d PZ |
513 | int ret; |
514 | ||
515 | ret = __mutex_fastpath_trylock(&lock->count, __mutex_trylock_slowpath); | |
516 | if (ret) | |
517 | mutex_set_owner(lock); | |
518 | ||
519 | return ret; | |
6053ee3b | 520 | } |
6053ee3b | 521 | EXPORT_SYMBOL(mutex_trylock); |
a511e3f9 AM |
522 | |
523 | /** | |
524 | * atomic_dec_and_mutex_lock - return holding mutex if we dec to 0 | |
525 | * @cnt: the atomic which we are to dec | |
526 | * @lock: the mutex to return holding if we dec to 0 | |
527 | * | |
528 | * return true and hold lock if we dec to 0, return false otherwise | |
529 | */ | |
530 | int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock) | |
531 | { | |
532 | /* dec if we can't possibly hit 0 */ | |
533 | if (atomic_add_unless(cnt, -1, 1)) | |
534 | return 0; | |
535 | /* we might hit 0, so take the lock */ | |
536 | mutex_lock(lock); | |
537 | if (!atomic_dec_and_test(cnt)) { | |
538 | /* when we actually did the dec, we didn't hit 0 */ | |
539 | mutex_unlock(lock); | |
540 | return 0; | |
541 | } | |
542 | /* we hit 0, and we hold the lock */ | |
543 | return 1; | |
544 | } | |
545 | EXPORT_SYMBOL(atomic_dec_and_mutex_lock); |