Commit | Line | Data |
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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 | ||
0dc8c730 WL |
40 | /* |
41 | * A mutex count of -1 indicates that waiters are sleeping waiting for the | |
42 | * mutex. Some architectures can allow any negative number, not just -1, for | |
43 | * this purpose. | |
44 | */ | |
45 | #ifdef __ARCH_ALLOW_ANY_NEGATIVE_MUTEX_COUNT | |
46 | #define MUTEX_SHOW_NO_WAITER(mutex) (atomic_read(&(mutex)->count) >= 0) | |
47 | #else | |
48 | #define MUTEX_SHOW_NO_WAITER(mutex) (atomic_read(&(mutex)->count) != -1) | |
49 | #endif | |
50 | ||
ef5d4707 IM |
51 | void |
52 | __mutex_init(struct mutex *lock, const char *name, struct lock_class_key *key) | |
6053ee3b IM |
53 | { |
54 | atomic_set(&lock->count, 1); | |
55 | spin_lock_init(&lock->wait_lock); | |
56 | INIT_LIST_HEAD(&lock->wait_list); | |
0d66bf6d | 57 | mutex_clear_owner(lock); |
2bd2c92c WL |
58 | #ifdef CONFIG_MUTEX_SPIN_ON_OWNER |
59 | lock->spin_mlock = NULL; | |
60 | #endif | |
6053ee3b | 61 | |
ef5d4707 | 62 | debug_mutex_init(lock, name, key); |
6053ee3b IM |
63 | } |
64 | ||
65 | EXPORT_SYMBOL(__mutex_init); | |
66 | ||
e4564f79 | 67 | #ifndef CONFIG_DEBUG_LOCK_ALLOC |
6053ee3b IM |
68 | /* |
69 | * We split the mutex lock/unlock logic into separate fastpath and | |
70 | * slowpath functions, to reduce the register pressure on the fastpath. | |
71 | * We also put the fastpath first in the kernel image, to make sure the | |
72 | * branch is predicted by the CPU as default-untaken. | |
73 | */ | |
7918baa5 | 74 | static __used noinline void __sched |
9a11b49a | 75 | __mutex_lock_slowpath(atomic_t *lock_count); |
6053ee3b | 76 | |
ef5dc121 | 77 | /** |
6053ee3b IM |
78 | * mutex_lock - acquire the mutex |
79 | * @lock: the mutex to be acquired | |
80 | * | |
81 | * Lock the mutex exclusively for this task. If the mutex is not | |
82 | * available right now, it will sleep until it can get it. | |
83 | * | |
84 | * The mutex must later on be released by the same task that | |
85 | * acquired it. Recursive locking is not allowed. The task | |
86 | * may not exit without first unlocking the mutex. Also, kernel | |
87 | * memory where the mutex resides mutex must not be freed with | |
88 | * the mutex still locked. The mutex must first be initialized | |
89 | * (or statically defined) before it can be locked. memset()-ing | |
90 | * the mutex to 0 is not allowed. | |
91 | * | |
92 | * ( The CONFIG_DEBUG_MUTEXES .config option turns on debugging | |
93 | * checks that will enforce the restrictions and will also do | |
94 | * deadlock debugging. ) | |
95 | * | |
96 | * This function is similar to (but not equivalent to) down(). | |
97 | */ | |
b09d2501 | 98 | void __sched mutex_lock(struct mutex *lock) |
6053ee3b | 99 | { |
c544bdb1 | 100 | might_sleep(); |
6053ee3b IM |
101 | /* |
102 | * The locking fastpath is the 1->0 transition from | |
103 | * 'unlocked' into 'locked' state. | |
6053ee3b IM |
104 | */ |
105 | __mutex_fastpath_lock(&lock->count, __mutex_lock_slowpath); | |
0d66bf6d | 106 | mutex_set_owner(lock); |
6053ee3b IM |
107 | } |
108 | ||
109 | EXPORT_SYMBOL(mutex_lock); | |
e4564f79 | 110 | #endif |
6053ee3b | 111 | |
41fcb9f2 | 112 | #ifdef CONFIG_MUTEX_SPIN_ON_OWNER |
2bd2c92c WL |
113 | /* |
114 | * In order to avoid a stampede of mutex spinners from acquiring the mutex | |
115 | * more or less simultaneously, the spinners need to acquire a MCS lock | |
116 | * first before spinning on the owner field. | |
117 | * | |
118 | * We don't inline mspin_lock() so that perf can correctly account for the | |
119 | * time spent in this lock function. | |
120 | */ | |
121 | struct mspin_node { | |
122 | struct mspin_node *next ; | |
123 | int locked; /* 1 if lock acquired */ | |
124 | }; | |
125 | #define MLOCK(mutex) ((struct mspin_node **)&((mutex)->spin_mlock)) | |
126 | ||
127 | static noinline | |
128 | void mspin_lock(struct mspin_node **lock, struct mspin_node *node) | |
129 | { | |
130 | struct mspin_node *prev; | |
131 | ||
132 | /* Init node */ | |
133 | node->locked = 0; | |
134 | node->next = NULL; | |
135 | ||
136 | prev = xchg(lock, node); | |
137 | if (likely(prev == NULL)) { | |
138 | /* Lock acquired */ | |
139 | node->locked = 1; | |
140 | return; | |
141 | } | |
142 | ACCESS_ONCE(prev->next) = node; | |
143 | smp_wmb(); | |
144 | /* Wait until the lock holder passes the lock down */ | |
145 | while (!ACCESS_ONCE(node->locked)) | |
146 | arch_mutex_cpu_relax(); | |
147 | } | |
148 | ||
149 | static void mspin_unlock(struct mspin_node **lock, struct mspin_node *node) | |
150 | { | |
151 | struct mspin_node *next = ACCESS_ONCE(node->next); | |
152 | ||
153 | if (likely(!next)) { | |
154 | /* | |
155 | * Release the lock by setting it to NULL | |
156 | */ | |
157 | if (cmpxchg(lock, node, NULL) == node) | |
158 | return; | |
159 | /* Wait until the next pointer is set */ | |
160 | while (!(next = ACCESS_ONCE(node->next))) | |
161 | arch_mutex_cpu_relax(); | |
162 | } | |
163 | ACCESS_ONCE(next->locked) = 1; | |
164 | smp_wmb(); | |
165 | } | |
166 | ||
41fcb9f2 WL |
167 | /* |
168 | * Mutex spinning code migrated from kernel/sched/core.c | |
169 | */ | |
170 | ||
171 | static inline bool owner_running(struct mutex *lock, struct task_struct *owner) | |
172 | { | |
173 | if (lock->owner != owner) | |
174 | return false; | |
175 | ||
176 | /* | |
177 | * Ensure we emit the owner->on_cpu, dereference _after_ checking | |
178 | * lock->owner still matches owner, if that fails, owner might | |
179 | * point to free()d memory, if it still matches, the rcu_read_lock() | |
180 | * ensures the memory stays valid. | |
181 | */ | |
182 | barrier(); | |
183 | ||
184 | return owner->on_cpu; | |
185 | } | |
186 | ||
187 | /* | |
188 | * Look out! "owner" is an entirely speculative pointer | |
189 | * access and not reliable. | |
190 | */ | |
191 | static noinline | |
192 | int mutex_spin_on_owner(struct mutex *lock, struct task_struct *owner) | |
193 | { | |
194 | rcu_read_lock(); | |
195 | while (owner_running(lock, owner)) { | |
196 | if (need_resched()) | |
197 | break; | |
198 | ||
199 | arch_mutex_cpu_relax(); | |
200 | } | |
201 | rcu_read_unlock(); | |
202 | ||
203 | /* | |
204 | * We break out the loop above on need_resched() and when the | |
205 | * owner changed, which is a sign for heavy contention. Return | |
206 | * success only when lock->owner is NULL. | |
207 | */ | |
208 | return lock->owner == NULL; | |
209 | } | |
2bd2c92c WL |
210 | |
211 | /* | |
212 | * Initial check for entering the mutex spinning loop | |
213 | */ | |
214 | static inline int mutex_can_spin_on_owner(struct mutex *lock) | |
215 | { | |
216 | int retval = 1; | |
217 | ||
218 | rcu_read_lock(); | |
219 | if (lock->owner) | |
220 | retval = lock->owner->on_cpu; | |
221 | rcu_read_unlock(); | |
222 | /* | |
223 | * if lock->owner is not set, the mutex owner may have just acquired | |
224 | * it and not set the owner yet or the mutex has been released. | |
225 | */ | |
226 | return retval; | |
227 | } | |
41fcb9f2 WL |
228 | #endif |
229 | ||
7918baa5 | 230 | static __used noinline void __sched __mutex_unlock_slowpath(atomic_t *lock_count); |
6053ee3b | 231 | |
ef5dc121 | 232 | /** |
6053ee3b IM |
233 | * mutex_unlock - release the mutex |
234 | * @lock: the mutex to be released | |
235 | * | |
236 | * Unlock a mutex that has been locked by this task previously. | |
237 | * | |
238 | * This function must not be used in interrupt context. Unlocking | |
239 | * of a not locked mutex is not allowed. | |
240 | * | |
241 | * This function is similar to (but not equivalent to) up(). | |
242 | */ | |
7ad5b3a5 | 243 | void __sched mutex_unlock(struct mutex *lock) |
6053ee3b IM |
244 | { |
245 | /* | |
246 | * The unlocking fastpath is the 0->1 transition from 'locked' | |
247 | * into 'unlocked' state: | |
6053ee3b | 248 | */ |
0d66bf6d PZ |
249 | #ifndef CONFIG_DEBUG_MUTEXES |
250 | /* | |
251 | * When debugging is enabled we must not clear the owner before time, | |
252 | * the slow path will always be taken, and that clears the owner field | |
253 | * after verifying that it was indeed current. | |
254 | */ | |
255 | mutex_clear_owner(lock); | |
256 | #endif | |
6053ee3b IM |
257 | __mutex_fastpath_unlock(&lock->count, __mutex_unlock_slowpath); |
258 | } | |
259 | ||
260 | EXPORT_SYMBOL(mutex_unlock); | |
261 | ||
262 | /* | |
263 | * Lock a mutex (possibly interruptible), slowpath: | |
264 | */ | |
265 | static inline int __sched | |
e4564f79 | 266 | __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass, |
e4c70a66 | 267 | struct lockdep_map *nest_lock, unsigned long ip) |
6053ee3b IM |
268 | { |
269 | struct task_struct *task = current; | |
270 | struct mutex_waiter waiter; | |
1fb00c6c | 271 | unsigned long flags; |
6053ee3b | 272 | |
41719b03 | 273 | preempt_disable(); |
e4c70a66 | 274 | mutex_acquire_nest(&lock->dep_map, subclass, 0, nest_lock, ip); |
c0226027 FW |
275 | |
276 | #ifdef CONFIG_MUTEX_SPIN_ON_OWNER | |
0d66bf6d PZ |
277 | /* |
278 | * Optimistic spinning. | |
279 | * | |
280 | * We try to spin for acquisition when we find that there are no | |
281 | * pending waiters and the lock owner is currently running on a | |
282 | * (different) CPU. | |
283 | * | |
284 | * The rationale is that if the lock owner is running, it is likely to | |
285 | * release the lock soon. | |
286 | * | |
287 | * Since this needs the lock owner, and this mutex implementation | |
288 | * doesn't track the owner atomically in the lock field, we need to | |
289 | * track it non-atomically. | |
290 | * | |
291 | * We can't do this for DEBUG_MUTEXES because that relies on wait_lock | |
292 | * to serialize everything. | |
2bd2c92c WL |
293 | * |
294 | * The mutex spinners are queued up using MCS lock so that only one | |
295 | * spinner can compete for the mutex. However, if mutex spinning isn't | |
296 | * going to happen, there is no point in going through the lock/unlock | |
297 | * overhead. | |
0d66bf6d | 298 | */ |
2bd2c92c WL |
299 | if (!mutex_can_spin_on_owner(lock)) |
300 | goto slowpath; | |
0d66bf6d PZ |
301 | |
302 | for (;;) { | |
c6eb3dda | 303 | struct task_struct *owner; |
2bd2c92c | 304 | struct mspin_node node; |
0d66bf6d | 305 | |
0d66bf6d PZ |
306 | /* |
307 | * If there's an owner, wait for it to either | |
308 | * release the lock or go to sleep. | |
309 | */ | |
2bd2c92c | 310 | mspin_lock(MLOCK(lock), &node); |
0d66bf6d | 311 | owner = ACCESS_ONCE(lock->owner); |
2bd2c92c WL |
312 | if (owner && !mutex_spin_on_owner(lock, owner)) { |
313 | mspin_unlock(MLOCK(lock), &node); | |
0d66bf6d | 314 | break; |
2bd2c92c | 315 | } |
0d66bf6d | 316 | |
0dc8c730 WL |
317 | if ((atomic_read(&lock->count) == 1) && |
318 | (atomic_cmpxchg(&lock->count, 1, 0) == 1)) { | |
ac6e60ee CM |
319 | lock_acquired(&lock->dep_map, ip); |
320 | mutex_set_owner(lock); | |
2bd2c92c | 321 | mspin_unlock(MLOCK(lock), &node); |
ac6e60ee CM |
322 | preempt_enable(); |
323 | return 0; | |
324 | } | |
2bd2c92c | 325 | mspin_unlock(MLOCK(lock), &node); |
ac6e60ee | 326 | |
0d66bf6d PZ |
327 | /* |
328 | * When there's no owner, we might have preempted between the | |
329 | * owner acquiring the lock and setting the owner field. If | |
330 | * we're an RT task that will live-lock because we won't let | |
331 | * the owner complete. | |
332 | */ | |
333 | if (!owner && (need_resched() || rt_task(task))) | |
334 | break; | |
335 | ||
0d66bf6d PZ |
336 | /* |
337 | * The cpu_relax() call is a compiler barrier which forces | |
338 | * everything in this loop to be re-loaded. We don't need | |
339 | * memory barriers as we'll eventually observe the right | |
340 | * values at the cost of a few extra spins. | |
341 | */ | |
335d7afb | 342 | arch_mutex_cpu_relax(); |
0d66bf6d | 343 | } |
2bd2c92c | 344 | slowpath: |
0d66bf6d | 345 | #endif |
1fb00c6c | 346 | spin_lock_mutex(&lock->wait_lock, flags); |
6053ee3b | 347 | |
9a11b49a | 348 | debug_mutex_lock_common(lock, &waiter); |
c9f4f06d | 349 | debug_mutex_add_waiter(lock, &waiter, task_thread_info(task)); |
6053ee3b IM |
350 | |
351 | /* add waiting tasks to the end of the waitqueue (FIFO): */ | |
352 | list_add_tail(&waiter.list, &lock->wait_list); | |
353 | waiter.task = task; | |
354 | ||
0dc8c730 | 355 | if (MUTEX_SHOW_NO_WAITER(lock) && (atomic_xchg(&lock->count, -1) == 1)) |
4fe87745 PZ |
356 | goto done; |
357 | ||
e4564f79 | 358 | lock_contended(&lock->dep_map, ip); |
4fe87745 | 359 | |
6053ee3b IM |
360 | for (;;) { |
361 | /* | |
362 | * Lets try to take the lock again - this is needed even if | |
363 | * we get here for the first time (shortly after failing to | |
364 | * acquire the lock), to make sure that we get a wakeup once | |
365 | * it's unlocked. Later on, if we sleep, this is the | |
366 | * operation that gives us the lock. We xchg it to -1, so | |
367 | * that when we release the lock, we properly wake up the | |
368 | * other waiters: | |
369 | */ | |
0dc8c730 WL |
370 | if (MUTEX_SHOW_NO_WAITER(lock) && |
371 | (atomic_xchg(&lock->count, -1) == 1)) | |
6053ee3b IM |
372 | break; |
373 | ||
374 | /* | |
375 | * got a signal? (This code gets eliminated in the | |
376 | * TASK_UNINTERRUPTIBLE case.) | |
377 | */ | |
6ad36762 | 378 | if (unlikely(signal_pending_state(state, task))) { |
ad776537 LH |
379 | mutex_remove_waiter(lock, &waiter, |
380 | task_thread_info(task)); | |
e4564f79 | 381 | mutex_release(&lock->dep_map, 1, ip); |
1fb00c6c | 382 | spin_unlock_mutex(&lock->wait_lock, flags); |
6053ee3b IM |
383 | |
384 | debug_mutex_free_waiter(&waiter); | |
41719b03 | 385 | preempt_enable(); |
6053ee3b IM |
386 | return -EINTR; |
387 | } | |
388 | __set_task_state(task, state); | |
389 | ||
25985edc | 390 | /* didn't get the lock, go to sleep: */ |
1fb00c6c | 391 | spin_unlock_mutex(&lock->wait_lock, flags); |
bd2f5536 | 392 | schedule_preempt_disabled(); |
1fb00c6c | 393 | spin_lock_mutex(&lock->wait_lock, flags); |
6053ee3b IM |
394 | } |
395 | ||
4fe87745 | 396 | done: |
c7e78cff | 397 | lock_acquired(&lock->dep_map, ip); |
6053ee3b | 398 | /* got the lock - rejoice! */ |
0d66bf6d PZ |
399 | mutex_remove_waiter(lock, &waiter, current_thread_info()); |
400 | mutex_set_owner(lock); | |
6053ee3b IM |
401 | |
402 | /* set it to 0 if there are no waiters left: */ | |
403 | if (likely(list_empty(&lock->wait_list))) | |
404 | atomic_set(&lock->count, 0); | |
405 | ||
1fb00c6c | 406 | spin_unlock_mutex(&lock->wait_lock, flags); |
6053ee3b IM |
407 | |
408 | debug_mutex_free_waiter(&waiter); | |
41719b03 | 409 | preempt_enable(); |
6053ee3b | 410 | |
6053ee3b IM |
411 | return 0; |
412 | } | |
413 | ||
ef5d4707 IM |
414 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
415 | void __sched | |
416 | mutex_lock_nested(struct mutex *lock, unsigned int subclass) | |
417 | { | |
418 | might_sleep(); | |
e4c70a66 | 419 | __mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, subclass, NULL, _RET_IP_); |
ef5d4707 IM |
420 | } |
421 | ||
422 | EXPORT_SYMBOL_GPL(mutex_lock_nested); | |
d63a5a74 | 423 | |
e4c70a66 PZ |
424 | void __sched |
425 | _mutex_lock_nest_lock(struct mutex *lock, struct lockdep_map *nest) | |
426 | { | |
427 | might_sleep(); | |
428 | __mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, 0, nest, _RET_IP_); | |
429 | } | |
430 | ||
431 | EXPORT_SYMBOL_GPL(_mutex_lock_nest_lock); | |
432 | ||
ad776537 LH |
433 | int __sched |
434 | mutex_lock_killable_nested(struct mutex *lock, unsigned int subclass) | |
435 | { | |
436 | might_sleep(); | |
e4c70a66 | 437 | return __mutex_lock_common(lock, TASK_KILLABLE, subclass, NULL, _RET_IP_); |
ad776537 LH |
438 | } |
439 | EXPORT_SYMBOL_GPL(mutex_lock_killable_nested); | |
440 | ||
d63a5a74 N |
441 | int __sched |
442 | mutex_lock_interruptible_nested(struct mutex *lock, unsigned int subclass) | |
443 | { | |
444 | might_sleep(); | |
0d66bf6d | 445 | return __mutex_lock_common(lock, TASK_INTERRUPTIBLE, |
e4c70a66 | 446 | subclass, NULL, _RET_IP_); |
d63a5a74 N |
447 | } |
448 | ||
449 | EXPORT_SYMBOL_GPL(mutex_lock_interruptible_nested); | |
ef5d4707 IM |
450 | #endif |
451 | ||
6053ee3b IM |
452 | /* |
453 | * Release the lock, slowpath: | |
454 | */ | |
7ad5b3a5 | 455 | static inline void |
ef5d4707 | 456 | __mutex_unlock_common_slowpath(atomic_t *lock_count, int nested) |
6053ee3b | 457 | { |
02706647 | 458 | struct mutex *lock = container_of(lock_count, struct mutex, count); |
1fb00c6c | 459 | unsigned long flags; |
6053ee3b | 460 | |
1fb00c6c | 461 | spin_lock_mutex(&lock->wait_lock, flags); |
ef5d4707 | 462 | mutex_release(&lock->dep_map, nested, _RET_IP_); |
9a11b49a | 463 | debug_mutex_unlock(lock); |
6053ee3b IM |
464 | |
465 | /* | |
466 | * some architectures leave the lock unlocked in the fastpath failure | |
467 | * case, others need to leave it locked. In the later case we have to | |
468 | * unlock it here | |
469 | */ | |
470 | if (__mutex_slowpath_needs_to_unlock()) | |
471 | atomic_set(&lock->count, 1); | |
472 | ||
6053ee3b IM |
473 | if (!list_empty(&lock->wait_list)) { |
474 | /* get the first entry from the wait-list: */ | |
475 | struct mutex_waiter *waiter = | |
476 | list_entry(lock->wait_list.next, | |
477 | struct mutex_waiter, list); | |
478 | ||
479 | debug_mutex_wake_waiter(lock, waiter); | |
480 | ||
481 | wake_up_process(waiter->task); | |
482 | } | |
483 | ||
1fb00c6c | 484 | spin_unlock_mutex(&lock->wait_lock, flags); |
6053ee3b IM |
485 | } |
486 | ||
9a11b49a IM |
487 | /* |
488 | * Release the lock, slowpath: | |
489 | */ | |
7918baa5 | 490 | static __used noinline void |
9a11b49a IM |
491 | __mutex_unlock_slowpath(atomic_t *lock_count) |
492 | { | |
ef5d4707 | 493 | __mutex_unlock_common_slowpath(lock_count, 1); |
9a11b49a IM |
494 | } |
495 | ||
e4564f79 | 496 | #ifndef CONFIG_DEBUG_LOCK_ALLOC |
6053ee3b IM |
497 | /* |
498 | * Here come the less common (and hence less performance-critical) APIs: | |
499 | * mutex_lock_interruptible() and mutex_trylock(). | |
500 | */ | |
7ad5b3a5 | 501 | static noinline int __sched |
ad776537 LH |
502 | __mutex_lock_killable_slowpath(atomic_t *lock_count); |
503 | ||
7ad5b3a5 | 504 | static noinline int __sched |
9a11b49a | 505 | __mutex_lock_interruptible_slowpath(atomic_t *lock_count); |
6053ee3b | 506 | |
ef5dc121 RD |
507 | /** |
508 | * mutex_lock_interruptible - acquire the mutex, interruptible | |
6053ee3b IM |
509 | * @lock: the mutex to be acquired |
510 | * | |
511 | * Lock the mutex like mutex_lock(), and return 0 if the mutex has | |
512 | * been acquired or sleep until the mutex becomes available. If a | |
513 | * signal arrives while waiting for the lock then this function | |
514 | * returns -EINTR. | |
515 | * | |
516 | * This function is similar to (but not equivalent to) down_interruptible(). | |
517 | */ | |
7ad5b3a5 | 518 | int __sched mutex_lock_interruptible(struct mutex *lock) |
6053ee3b | 519 | { |
0d66bf6d PZ |
520 | int ret; |
521 | ||
c544bdb1 | 522 | might_sleep(); |
0d66bf6d | 523 | ret = __mutex_fastpath_lock_retval |
6053ee3b | 524 | (&lock->count, __mutex_lock_interruptible_slowpath); |
0d66bf6d PZ |
525 | if (!ret) |
526 | mutex_set_owner(lock); | |
527 | ||
528 | return ret; | |
6053ee3b IM |
529 | } |
530 | ||
531 | EXPORT_SYMBOL(mutex_lock_interruptible); | |
532 | ||
7ad5b3a5 | 533 | int __sched mutex_lock_killable(struct mutex *lock) |
ad776537 | 534 | { |
0d66bf6d PZ |
535 | int ret; |
536 | ||
ad776537 | 537 | might_sleep(); |
0d66bf6d | 538 | ret = __mutex_fastpath_lock_retval |
ad776537 | 539 | (&lock->count, __mutex_lock_killable_slowpath); |
0d66bf6d PZ |
540 | if (!ret) |
541 | mutex_set_owner(lock); | |
542 | ||
543 | return ret; | |
ad776537 LH |
544 | } |
545 | EXPORT_SYMBOL(mutex_lock_killable); | |
546 | ||
7918baa5 | 547 | static __used noinline void __sched |
e4564f79 PZ |
548 | __mutex_lock_slowpath(atomic_t *lock_count) |
549 | { | |
550 | struct mutex *lock = container_of(lock_count, struct mutex, count); | |
551 | ||
e4c70a66 | 552 | __mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, 0, NULL, _RET_IP_); |
e4564f79 PZ |
553 | } |
554 | ||
7ad5b3a5 | 555 | static noinline int __sched |
ad776537 LH |
556 | __mutex_lock_killable_slowpath(atomic_t *lock_count) |
557 | { | |
558 | struct mutex *lock = container_of(lock_count, struct mutex, count); | |
559 | ||
e4c70a66 | 560 | return __mutex_lock_common(lock, TASK_KILLABLE, 0, NULL, _RET_IP_); |
ad776537 LH |
561 | } |
562 | ||
7ad5b3a5 | 563 | static noinline int __sched |
9a11b49a | 564 | __mutex_lock_interruptible_slowpath(atomic_t *lock_count) |
6053ee3b IM |
565 | { |
566 | struct mutex *lock = container_of(lock_count, struct mutex, count); | |
567 | ||
e4c70a66 | 568 | return __mutex_lock_common(lock, TASK_INTERRUPTIBLE, 0, NULL, _RET_IP_); |
6053ee3b | 569 | } |
e4564f79 | 570 | #endif |
6053ee3b IM |
571 | |
572 | /* | |
573 | * Spinlock based trylock, we take the spinlock and check whether we | |
574 | * can get the lock: | |
575 | */ | |
576 | static inline int __mutex_trylock_slowpath(atomic_t *lock_count) | |
577 | { | |
578 | struct mutex *lock = container_of(lock_count, struct mutex, count); | |
1fb00c6c | 579 | unsigned long flags; |
6053ee3b IM |
580 | int prev; |
581 | ||
1fb00c6c | 582 | spin_lock_mutex(&lock->wait_lock, flags); |
6053ee3b IM |
583 | |
584 | prev = atomic_xchg(&lock->count, -1); | |
ef5d4707 | 585 | if (likely(prev == 1)) { |
0d66bf6d | 586 | mutex_set_owner(lock); |
ef5d4707 IM |
587 | mutex_acquire(&lock->dep_map, 0, 1, _RET_IP_); |
588 | } | |
0d66bf6d | 589 | |
6053ee3b IM |
590 | /* Set it back to 0 if there are no waiters: */ |
591 | if (likely(list_empty(&lock->wait_list))) | |
592 | atomic_set(&lock->count, 0); | |
593 | ||
1fb00c6c | 594 | spin_unlock_mutex(&lock->wait_lock, flags); |
6053ee3b IM |
595 | |
596 | return prev == 1; | |
597 | } | |
598 | ||
ef5dc121 RD |
599 | /** |
600 | * mutex_trylock - try to acquire the mutex, without waiting | |
6053ee3b IM |
601 | * @lock: the mutex to be acquired |
602 | * | |
603 | * Try to acquire the mutex atomically. Returns 1 if the mutex | |
604 | * has been acquired successfully, and 0 on contention. | |
605 | * | |
606 | * NOTE: this function follows the spin_trylock() convention, so | |
ef5dc121 | 607 | * it is negated from the down_trylock() return values! Be careful |
6053ee3b IM |
608 | * about this when converting semaphore users to mutexes. |
609 | * | |
610 | * This function must not be used in interrupt context. The | |
611 | * mutex must be released by the same task that acquired it. | |
612 | */ | |
7ad5b3a5 | 613 | int __sched mutex_trylock(struct mutex *lock) |
6053ee3b | 614 | { |
0d66bf6d PZ |
615 | int ret; |
616 | ||
617 | ret = __mutex_fastpath_trylock(&lock->count, __mutex_trylock_slowpath); | |
618 | if (ret) | |
619 | mutex_set_owner(lock); | |
620 | ||
621 | return ret; | |
6053ee3b | 622 | } |
6053ee3b | 623 | EXPORT_SYMBOL(mutex_trylock); |
a511e3f9 AM |
624 | |
625 | /** | |
626 | * atomic_dec_and_mutex_lock - return holding mutex if we dec to 0 | |
627 | * @cnt: the atomic which we are to dec | |
628 | * @lock: the mutex to return holding if we dec to 0 | |
629 | * | |
630 | * return true and hold lock if we dec to 0, return false otherwise | |
631 | */ | |
632 | int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock) | |
633 | { | |
634 | /* dec if we can't possibly hit 0 */ | |
635 | if (atomic_add_unless(cnt, -1, 1)) | |
636 | return 0; | |
637 | /* we might hit 0, so take the lock */ | |
638 | mutex_lock(lock); | |
639 | if (!atomic_dec_and_test(cnt)) { | |
640 | /* when we actually did the dec, we didn't hit 0 */ | |
641 | mutex_unlock(lock); | |
642 | return 0; | |
643 | } | |
644 | /* we hit 0, and we hold the lock */ | |
645 | return 1; | |
646 | } | |
647 | EXPORT_SYMBOL(atomic_dec_and_mutex_lock); |