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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> | |
1b375dc3 | 21 | #include <linux/ww_mutex.h> |
6053ee3b | 22 | #include <linux/sched.h> |
8bd75c77 | 23 | #include <linux/sched/rt.h> |
9984de1a | 24 | #include <linux/export.h> |
6053ee3b IM |
25 | #include <linux/spinlock.h> |
26 | #include <linux/interrupt.h> | |
9a11b49a | 27 | #include <linux/debug_locks.h> |
6053ee3b IM |
28 | |
29 | /* | |
30 | * In the DEBUG case we are using the "NULL fastpath" for mutexes, | |
31 | * which forces all calls into the slowpath: | |
32 | */ | |
33 | #ifdef CONFIG_DEBUG_MUTEXES | |
34 | # include "mutex-debug.h" | |
35 | # include <asm-generic/mutex-null.h> | |
36 | #else | |
37 | # include "mutex.h" | |
38 | # include <asm/mutex.h> | |
39 | #endif | |
40 | ||
0dc8c730 | 41 | /* |
cc189d25 WL |
42 | * A negative mutex count indicates that waiters are sleeping waiting for the |
43 | * mutex. | |
0dc8c730 | 44 | */ |
0dc8c730 | 45 | #define MUTEX_SHOW_NO_WAITER(mutex) (atomic_read(&(mutex)->count) >= 0) |
0dc8c730 | 46 | |
ef5d4707 IM |
47 | void |
48 | __mutex_init(struct mutex *lock, const char *name, struct lock_class_key *key) | |
6053ee3b IM |
49 | { |
50 | atomic_set(&lock->count, 1); | |
51 | spin_lock_init(&lock->wait_lock); | |
52 | INIT_LIST_HEAD(&lock->wait_list); | |
0d66bf6d | 53 | mutex_clear_owner(lock); |
2bd2c92c WL |
54 | #ifdef CONFIG_MUTEX_SPIN_ON_OWNER |
55 | lock->spin_mlock = NULL; | |
56 | #endif | |
6053ee3b | 57 | |
ef5d4707 | 58 | debug_mutex_init(lock, name, key); |
6053ee3b IM |
59 | } |
60 | ||
61 | EXPORT_SYMBOL(__mutex_init); | |
62 | ||
e4564f79 | 63 | #ifndef CONFIG_DEBUG_LOCK_ALLOC |
6053ee3b IM |
64 | /* |
65 | * We split the mutex lock/unlock logic into separate fastpath and | |
66 | * slowpath functions, to reduce the register pressure on the fastpath. | |
67 | * We also put the fastpath first in the kernel image, to make sure the | |
68 | * branch is predicted by the CPU as default-untaken. | |
69 | */ | |
7918baa5 | 70 | static __used noinline void __sched |
9a11b49a | 71 | __mutex_lock_slowpath(atomic_t *lock_count); |
6053ee3b | 72 | |
ef5dc121 | 73 | /** |
6053ee3b IM |
74 | * mutex_lock - acquire the mutex |
75 | * @lock: the mutex to be acquired | |
76 | * | |
77 | * Lock the mutex exclusively for this task. If the mutex is not | |
78 | * available right now, it will sleep until it can get it. | |
79 | * | |
80 | * The mutex must later on be released by the same task that | |
81 | * acquired it. Recursive locking is not allowed. The task | |
82 | * may not exit without first unlocking the mutex. Also, kernel | |
83 | * memory where the mutex resides mutex must not be freed with | |
84 | * the mutex still locked. The mutex must first be initialized | |
85 | * (or statically defined) before it can be locked. memset()-ing | |
86 | * the mutex to 0 is not allowed. | |
87 | * | |
88 | * ( The CONFIG_DEBUG_MUTEXES .config option turns on debugging | |
89 | * checks that will enforce the restrictions and will also do | |
90 | * deadlock debugging. ) | |
91 | * | |
92 | * This function is similar to (but not equivalent to) down(). | |
93 | */ | |
b09d2501 | 94 | void __sched mutex_lock(struct mutex *lock) |
6053ee3b | 95 | { |
c544bdb1 | 96 | might_sleep(); |
6053ee3b IM |
97 | /* |
98 | * The locking fastpath is the 1->0 transition from | |
99 | * 'unlocked' into 'locked' state. | |
6053ee3b IM |
100 | */ |
101 | __mutex_fastpath_lock(&lock->count, __mutex_lock_slowpath); | |
0d66bf6d | 102 | mutex_set_owner(lock); |
6053ee3b IM |
103 | } |
104 | ||
105 | EXPORT_SYMBOL(mutex_lock); | |
e4564f79 | 106 | #endif |
6053ee3b | 107 | |
41fcb9f2 | 108 | #ifdef CONFIG_MUTEX_SPIN_ON_OWNER |
2bd2c92c WL |
109 | /* |
110 | * In order to avoid a stampede of mutex spinners from acquiring the mutex | |
111 | * more or less simultaneously, the spinners need to acquire a MCS lock | |
112 | * first before spinning on the owner field. | |
113 | * | |
114 | * We don't inline mspin_lock() so that perf can correctly account for the | |
115 | * time spent in this lock function. | |
116 | */ | |
117 | struct mspin_node { | |
118 | struct mspin_node *next ; | |
119 | int locked; /* 1 if lock acquired */ | |
120 | }; | |
121 | #define MLOCK(mutex) ((struct mspin_node **)&((mutex)->spin_mlock)) | |
122 | ||
123 | static noinline | |
124 | void mspin_lock(struct mspin_node **lock, struct mspin_node *node) | |
125 | { | |
126 | struct mspin_node *prev; | |
127 | ||
128 | /* Init node */ | |
129 | node->locked = 0; | |
130 | node->next = NULL; | |
131 | ||
132 | prev = xchg(lock, node); | |
133 | if (likely(prev == NULL)) { | |
134 | /* Lock acquired */ | |
135 | node->locked = 1; | |
136 | return; | |
137 | } | |
138 | ACCESS_ONCE(prev->next) = node; | |
139 | smp_wmb(); | |
140 | /* Wait until the lock holder passes the lock down */ | |
141 | while (!ACCESS_ONCE(node->locked)) | |
142 | arch_mutex_cpu_relax(); | |
143 | } | |
144 | ||
145 | static void mspin_unlock(struct mspin_node **lock, struct mspin_node *node) | |
146 | { | |
147 | struct mspin_node *next = ACCESS_ONCE(node->next); | |
148 | ||
149 | if (likely(!next)) { | |
150 | /* | |
151 | * Release the lock by setting it to NULL | |
152 | */ | |
153 | if (cmpxchg(lock, node, NULL) == node) | |
154 | return; | |
155 | /* Wait until the next pointer is set */ | |
156 | while (!(next = ACCESS_ONCE(node->next))) | |
157 | arch_mutex_cpu_relax(); | |
158 | } | |
159 | ACCESS_ONCE(next->locked) = 1; | |
160 | smp_wmb(); | |
161 | } | |
162 | ||
41fcb9f2 WL |
163 | /* |
164 | * Mutex spinning code migrated from kernel/sched/core.c | |
165 | */ | |
166 | ||
167 | static inline bool owner_running(struct mutex *lock, struct task_struct *owner) | |
168 | { | |
169 | if (lock->owner != owner) | |
170 | return false; | |
171 | ||
172 | /* | |
173 | * Ensure we emit the owner->on_cpu, dereference _after_ checking | |
174 | * lock->owner still matches owner, if that fails, owner might | |
175 | * point to free()d memory, if it still matches, the rcu_read_lock() | |
176 | * ensures the memory stays valid. | |
177 | */ | |
178 | barrier(); | |
179 | ||
180 | return owner->on_cpu; | |
181 | } | |
182 | ||
183 | /* | |
184 | * Look out! "owner" is an entirely speculative pointer | |
185 | * access and not reliable. | |
186 | */ | |
187 | static noinline | |
188 | int mutex_spin_on_owner(struct mutex *lock, struct task_struct *owner) | |
189 | { | |
190 | rcu_read_lock(); | |
191 | while (owner_running(lock, owner)) { | |
192 | if (need_resched()) | |
193 | break; | |
194 | ||
195 | arch_mutex_cpu_relax(); | |
196 | } | |
197 | rcu_read_unlock(); | |
198 | ||
199 | /* | |
200 | * We break out the loop above on need_resched() and when the | |
201 | * owner changed, which is a sign for heavy contention. Return | |
202 | * success only when lock->owner is NULL. | |
203 | */ | |
204 | return lock->owner == NULL; | |
205 | } | |
2bd2c92c WL |
206 | |
207 | /* | |
208 | * Initial check for entering the mutex spinning loop | |
209 | */ | |
210 | static inline int mutex_can_spin_on_owner(struct mutex *lock) | |
211 | { | |
212 | int retval = 1; | |
213 | ||
214 | rcu_read_lock(); | |
215 | if (lock->owner) | |
216 | retval = lock->owner->on_cpu; | |
217 | rcu_read_unlock(); | |
218 | /* | |
219 | * if lock->owner is not set, the mutex owner may have just acquired | |
220 | * it and not set the owner yet or the mutex has been released. | |
221 | */ | |
222 | return retval; | |
223 | } | |
41fcb9f2 WL |
224 | #endif |
225 | ||
7918baa5 | 226 | static __used noinline void __sched __mutex_unlock_slowpath(atomic_t *lock_count); |
6053ee3b | 227 | |
ef5dc121 | 228 | /** |
6053ee3b IM |
229 | * mutex_unlock - release the mutex |
230 | * @lock: the mutex to be released | |
231 | * | |
232 | * Unlock a mutex that has been locked by this task previously. | |
233 | * | |
234 | * This function must not be used in interrupt context. Unlocking | |
235 | * of a not locked mutex is not allowed. | |
236 | * | |
237 | * This function is similar to (but not equivalent to) up(). | |
238 | */ | |
7ad5b3a5 | 239 | void __sched mutex_unlock(struct mutex *lock) |
6053ee3b IM |
240 | { |
241 | /* | |
242 | * The unlocking fastpath is the 0->1 transition from 'locked' | |
243 | * into 'unlocked' state: | |
6053ee3b | 244 | */ |
0d66bf6d PZ |
245 | #ifndef CONFIG_DEBUG_MUTEXES |
246 | /* | |
247 | * When debugging is enabled we must not clear the owner before time, | |
248 | * the slow path will always be taken, and that clears the owner field | |
249 | * after verifying that it was indeed current. | |
250 | */ | |
251 | mutex_clear_owner(lock); | |
252 | #endif | |
6053ee3b IM |
253 | __mutex_fastpath_unlock(&lock->count, __mutex_unlock_slowpath); |
254 | } | |
255 | ||
256 | EXPORT_SYMBOL(mutex_unlock); | |
257 | ||
040a0a37 ML |
258 | /** |
259 | * ww_mutex_unlock - release the w/w mutex | |
260 | * @lock: the mutex to be released | |
261 | * | |
262 | * Unlock a mutex that has been locked by this task previously with any of the | |
263 | * ww_mutex_lock* functions (with or without an acquire context). It is | |
264 | * forbidden to release the locks after releasing the acquire context. | |
265 | * | |
266 | * This function must not be used in interrupt context. Unlocking | |
267 | * of a unlocked mutex is not allowed. | |
268 | */ | |
269 | void __sched ww_mutex_unlock(struct ww_mutex *lock) | |
270 | { | |
271 | /* | |
272 | * The unlocking fastpath is the 0->1 transition from 'locked' | |
273 | * into 'unlocked' state: | |
274 | */ | |
275 | if (lock->ctx) { | |
276 | #ifdef CONFIG_DEBUG_MUTEXES | |
277 | DEBUG_LOCKS_WARN_ON(!lock->ctx->acquired); | |
278 | #endif | |
279 | if (lock->ctx->acquired > 0) | |
280 | lock->ctx->acquired--; | |
281 | lock->ctx = NULL; | |
282 | } | |
283 | ||
284 | #ifndef CONFIG_DEBUG_MUTEXES | |
285 | /* | |
286 | * When debugging is enabled we must not clear the owner before time, | |
287 | * the slow path will always be taken, and that clears the owner field | |
288 | * after verifying that it was indeed current. | |
289 | */ | |
290 | mutex_clear_owner(&lock->base); | |
291 | #endif | |
292 | __mutex_fastpath_unlock(&lock->base.count, __mutex_unlock_slowpath); | |
293 | } | |
294 | EXPORT_SYMBOL(ww_mutex_unlock); | |
295 | ||
296 | static inline int __sched | |
297 | __mutex_lock_check_stamp(struct mutex *lock, struct ww_acquire_ctx *ctx) | |
298 | { | |
299 | struct ww_mutex *ww = container_of(lock, struct ww_mutex, base); | |
300 | struct ww_acquire_ctx *hold_ctx = ACCESS_ONCE(ww->ctx); | |
301 | ||
302 | if (!hold_ctx) | |
303 | return 0; | |
304 | ||
305 | if (unlikely(ctx == hold_ctx)) | |
306 | return -EALREADY; | |
307 | ||
308 | if (ctx->stamp - hold_ctx->stamp <= LONG_MAX && | |
309 | (ctx->stamp != hold_ctx->stamp || ctx > hold_ctx)) { | |
310 | #ifdef CONFIG_DEBUG_MUTEXES | |
311 | DEBUG_LOCKS_WARN_ON(ctx->contending_lock); | |
312 | ctx->contending_lock = ww; | |
313 | #endif | |
314 | return -EDEADLK; | |
315 | } | |
316 | ||
317 | return 0; | |
318 | } | |
319 | ||
320 | static __always_inline void ww_mutex_lock_acquired(struct ww_mutex *ww, | |
321 | struct ww_acquire_ctx *ww_ctx) | |
322 | { | |
323 | #ifdef CONFIG_DEBUG_MUTEXES | |
324 | /* | |
325 | * If this WARN_ON triggers, you used ww_mutex_lock to acquire, | |
326 | * but released with a normal mutex_unlock in this call. | |
327 | * | |
328 | * This should never happen, always use ww_mutex_unlock. | |
329 | */ | |
330 | DEBUG_LOCKS_WARN_ON(ww->ctx); | |
331 | ||
332 | /* | |
333 | * Not quite done after calling ww_acquire_done() ? | |
334 | */ | |
335 | DEBUG_LOCKS_WARN_ON(ww_ctx->done_acquire); | |
336 | ||
337 | if (ww_ctx->contending_lock) { | |
338 | /* | |
339 | * After -EDEADLK you tried to | |
340 | * acquire a different ww_mutex? Bad! | |
341 | */ | |
342 | DEBUG_LOCKS_WARN_ON(ww_ctx->contending_lock != ww); | |
343 | ||
344 | /* | |
345 | * You called ww_mutex_lock after receiving -EDEADLK, | |
346 | * but 'forgot' to unlock everything else first? | |
347 | */ | |
348 | DEBUG_LOCKS_WARN_ON(ww_ctx->acquired > 0); | |
349 | ww_ctx->contending_lock = NULL; | |
350 | } | |
351 | ||
352 | /* | |
353 | * Naughty, using a different class will lead to undefined behavior! | |
354 | */ | |
355 | DEBUG_LOCKS_WARN_ON(ww_ctx->ww_class != ww->ww_class); | |
356 | #endif | |
357 | ww_ctx->acquired++; | |
358 | } | |
359 | ||
360 | /* | |
361 | * after acquiring lock with fastpath or when we lost out in contested | |
362 | * slowpath, set ctx and wake up any waiters so they can recheck. | |
363 | * | |
364 | * This function is never called when CONFIG_DEBUG_LOCK_ALLOC is set, | |
365 | * as the fastpath and opportunistic spinning are disabled in that case. | |
366 | */ | |
367 | static __always_inline void | |
368 | ww_mutex_set_context_fastpath(struct ww_mutex *lock, | |
369 | struct ww_acquire_ctx *ctx) | |
370 | { | |
371 | unsigned long flags; | |
372 | struct mutex_waiter *cur; | |
373 | ||
374 | ww_mutex_lock_acquired(lock, ctx); | |
375 | ||
376 | lock->ctx = ctx; | |
377 | ||
378 | /* | |
379 | * The lock->ctx update should be visible on all cores before | |
380 | * the atomic read is done, otherwise contended waiters might be | |
381 | * missed. The contended waiters will either see ww_ctx == NULL | |
382 | * and keep spinning, or it will acquire wait_lock, add itself | |
383 | * to waiter list and sleep. | |
384 | */ | |
385 | smp_mb(); /* ^^^ */ | |
386 | ||
387 | /* | |
388 | * Check if lock is contended, if not there is nobody to wake up | |
389 | */ | |
390 | if (likely(atomic_read(&lock->base.count) == 0)) | |
391 | return; | |
392 | ||
393 | /* | |
394 | * Uh oh, we raced in fastpath, wake up everyone in this case, | |
395 | * so they can see the new lock->ctx. | |
396 | */ | |
397 | spin_lock_mutex(&lock->base.wait_lock, flags); | |
398 | list_for_each_entry(cur, &lock->base.wait_list, list) { | |
399 | debug_mutex_wake_waiter(&lock->base, cur); | |
400 | wake_up_process(cur->task); | |
401 | } | |
402 | spin_unlock_mutex(&lock->base.wait_lock, flags); | |
403 | } | |
404 | ||
6053ee3b IM |
405 | /* |
406 | * Lock a mutex (possibly interruptible), slowpath: | |
407 | */ | |
040a0a37 | 408 | static __always_inline int __sched |
e4564f79 | 409 | __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass, |
040a0a37 ML |
410 | struct lockdep_map *nest_lock, unsigned long ip, |
411 | struct ww_acquire_ctx *ww_ctx) | |
6053ee3b IM |
412 | { |
413 | struct task_struct *task = current; | |
414 | struct mutex_waiter waiter; | |
1fb00c6c | 415 | unsigned long flags; |
040a0a37 | 416 | int ret; |
6053ee3b | 417 | |
41719b03 | 418 | preempt_disable(); |
e4c70a66 | 419 | mutex_acquire_nest(&lock->dep_map, subclass, 0, nest_lock, ip); |
c0226027 FW |
420 | |
421 | #ifdef CONFIG_MUTEX_SPIN_ON_OWNER | |
0d66bf6d PZ |
422 | /* |
423 | * Optimistic spinning. | |
424 | * | |
425 | * We try to spin for acquisition when we find that there are no | |
426 | * pending waiters and the lock owner is currently running on a | |
427 | * (different) CPU. | |
428 | * | |
429 | * The rationale is that if the lock owner is running, it is likely to | |
430 | * release the lock soon. | |
431 | * | |
432 | * Since this needs the lock owner, and this mutex implementation | |
433 | * doesn't track the owner atomically in the lock field, we need to | |
434 | * track it non-atomically. | |
435 | * | |
436 | * We can't do this for DEBUG_MUTEXES because that relies on wait_lock | |
437 | * to serialize everything. | |
2bd2c92c WL |
438 | * |
439 | * The mutex spinners are queued up using MCS lock so that only one | |
440 | * spinner can compete for the mutex. However, if mutex spinning isn't | |
441 | * going to happen, there is no point in going through the lock/unlock | |
442 | * overhead. | |
0d66bf6d | 443 | */ |
2bd2c92c WL |
444 | if (!mutex_can_spin_on_owner(lock)) |
445 | goto slowpath; | |
0d66bf6d PZ |
446 | |
447 | for (;;) { | |
c6eb3dda | 448 | struct task_struct *owner; |
2bd2c92c | 449 | struct mspin_node node; |
0d66bf6d | 450 | |
040a0a37 ML |
451 | if (!__builtin_constant_p(ww_ctx == NULL) && ww_ctx->acquired > 0) { |
452 | struct ww_mutex *ww; | |
453 | ||
454 | ww = container_of(lock, struct ww_mutex, base); | |
455 | /* | |
456 | * If ww->ctx is set the contents are undefined, only | |
457 | * by acquiring wait_lock there is a guarantee that | |
458 | * they are not invalid when reading. | |
459 | * | |
460 | * As such, when deadlock detection needs to be | |
461 | * performed the optimistic spinning cannot be done. | |
462 | */ | |
463 | if (ACCESS_ONCE(ww->ctx)) | |
464 | break; | |
465 | } | |
466 | ||
0d66bf6d PZ |
467 | /* |
468 | * If there's an owner, wait for it to either | |
469 | * release the lock or go to sleep. | |
470 | */ | |
2bd2c92c | 471 | mspin_lock(MLOCK(lock), &node); |
0d66bf6d | 472 | owner = ACCESS_ONCE(lock->owner); |
2bd2c92c WL |
473 | if (owner && !mutex_spin_on_owner(lock, owner)) { |
474 | mspin_unlock(MLOCK(lock), &node); | |
0d66bf6d | 475 | break; |
2bd2c92c | 476 | } |
0d66bf6d | 477 | |
0dc8c730 WL |
478 | if ((atomic_read(&lock->count) == 1) && |
479 | (atomic_cmpxchg(&lock->count, 1, 0) == 1)) { | |
ac6e60ee | 480 | lock_acquired(&lock->dep_map, ip); |
040a0a37 ML |
481 | if (!__builtin_constant_p(ww_ctx == NULL)) { |
482 | struct ww_mutex *ww; | |
483 | ww = container_of(lock, struct ww_mutex, base); | |
484 | ||
485 | ww_mutex_set_context_fastpath(ww, ww_ctx); | |
486 | } | |
487 | ||
ac6e60ee | 488 | mutex_set_owner(lock); |
2bd2c92c | 489 | mspin_unlock(MLOCK(lock), &node); |
ac6e60ee CM |
490 | preempt_enable(); |
491 | return 0; | |
492 | } | |
2bd2c92c | 493 | mspin_unlock(MLOCK(lock), &node); |
ac6e60ee | 494 | |
0d66bf6d PZ |
495 | /* |
496 | * When there's no owner, we might have preempted between the | |
497 | * owner acquiring the lock and setting the owner field. If | |
498 | * we're an RT task that will live-lock because we won't let | |
499 | * the owner complete. | |
500 | */ | |
501 | if (!owner && (need_resched() || rt_task(task))) | |
502 | break; | |
503 | ||
0d66bf6d PZ |
504 | /* |
505 | * The cpu_relax() call is a compiler barrier which forces | |
506 | * everything in this loop to be re-loaded. We don't need | |
507 | * memory barriers as we'll eventually observe the right | |
508 | * values at the cost of a few extra spins. | |
509 | */ | |
335d7afb | 510 | arch_mutex_cpu_relax(); |
0d66bf6d | 511 | } |
2bd2c92c | 512 | slowpath: |
0d66bf6d | 513 | #endif |
1fb00c6c | 514 | spin_lock_mutex(&lock->wait_lock, flags); |
6053ee3b | 515 | |
9a11b49a | 516 | debug_mutex_lock_common(lock, &waiter); |
c9f4f06d | 517 | debug_mutex_add_waiter(lock, &waiter, task_thread_info(task)); |
6053ee3b IM |
518 | |
519 | /* add waiting tasks to the end of the waitqueue (FIFO): */ | |
520 | list_add_tail(&waiter.list, &lock->wait_list); | |
521 | waiter.task = task; | |
522 | ||
0dc8c730 | 523 | if (MUTEX_SHOW_NO_WAITER(lock) && (atomic_xchg(&lock->count, -1) == 1)) |
4fe87745 PZ |
524 | goto done; |
525 | ||
e4564f79 | 526 | lock_contended(&lock->dep_map, ip); |
4fe87745 | 527 | |
6053ee3b IM |
528 | for (;;) { |
529 | /* | |
530 | * Lets try to take the lock again - this is needed even if | |
531 | * we get here for the first time (shortly after failing to | |
532 | * acquire the lock), to make sure that we get a wakeup once | |
533 | * it's unlocked. Later on, if we sleep, this is the | |
534 | * operation that gives us the lock. We xchg it to -1, so | |
535 | * that when we release the lock, we properly wake up the | |
536 | * other waiters: | |
537 | */ | |
0dc8c730 WL |
538 | if (MUTEX_SHOW_NO_WAITER(lock) && |
539 | (atomic_xchg(&lock->count, -1) == 1)) | |
6053ee3b IM |
540 | break; |
541 | ||
542 | /* | |
543 | * got a signal? (This code gets eliminated in the | |
544 | * TASK_UNINTERRUPTIBLE case.) | |
545 | */ | |
6ad36762 | 546 | if (unlikely(signal_pending_state(state, task))) { |
040a0a37 ML |
547 | ret = -EINTR; |
548 | goto err; | |
549 | } | |
6053ee3b | 550 | |
040a0a37 ML |
551 | if (!__builtin_constant_p(ww_ctx == NULL) && ww_ctx->acquired > 0) { |
552 | ret = __mutex_lock_check_stamp(lock, ww_ctx); | |
553 | if (ret) | |
554 | goto err; | |
6053ee3b | 555 | } |
040a0a37 | 556 | |
6053ee3b IM |
557 | __set_task_state(task, state); |
558 | ||
25985edc | 559 | /* didn't get the lock, go to sleep: */ |
1fb00c6c | 560 | spin_unlock_mutex(&lock->wait_lock, flags); |
bd2f5536 | 561 | schedule_preempt_disabled(); |
1fb00c6c | 562 | spin_lock_mutex(&lock->wait_lock, flags); |
6053ee3b IM |
563 | } |
564 | ||
4fe87745 | 565 | done: |
c7e78cff | 566 | lock_acquired(&lock->dep_map, ip); |
6053ee3b | 567 | /* got the lock - rejoice! */ |
0d66bf6d PZ |
568 | mutex_remove_waiter(lock, &waiter, current_thread_info()); |
569 | mutex_set_owner(lock); | |
6053ee3b | 570 | |
040a0a37 ML |
571 | if (!__builtin_constant_p(ww_ctx == NULL)) { |
572 | struct ww_mutex *ww = container_of(lock, | |
573 | struct ww_mutex, | |
574 | base); | |
575 | struct mutex_waiter *cur; | |
576 | ||
577 | /* | |
578 | * This branch gets optimized out for the common case, | |
579 | * and is only important for ww_mutex_lock. | |
580 | */ | |
581 | ||
582 | ww_mutex_lock_acquired(ww, ww_ctx); | |
583 | ww->ctx = ww_ctx; | |
584 | ||
585 | /* | |
586 | * Give any possible sleeping processes the chance to wake up, | |
587 | * so they can recheck if they have to back off. | |
588 | */ | |
589 | list_for_each_entry(cur, &lock->wait_list, list) { | |
590 | debug_mutex_wake_waiter(lock, cur); | |
591 | wake_up_process(cur->task); | |
592 | } | |
593 | } | |
594 | ||
6053ee3b IM |
595 | /* set it to 0 if there are no waiters left: */ |
596 | if (likely(list_empty(&lock->wait_list))) | |
597 | atomic_set(&lock->count, 0); | |
598 | ||
1fb00c6c | 599 | spin_unlock_mutex(&lock->wait_lock, flags); |
6053ee3b IM |
600 | |
601 | debug_mutex_free_waiter(&waiter); | |
41719b03 | 602 | preempt_enable(); |
6053ee3b | 603 | |
6053ee3b | 604 | return 0; |
040a0a37 ML |
605 | |
606 | err: | |
607 | mutex_remove_waiter(lock, &waiter, task_thread_info(task)); | |
608 | spin_unlock_mutex(&lock->wait_lock, flags); | |
609 | debug_mutex_free_waiter(&waiter); | |
610 | mutex_release(&lock->dep_map, 1, ip); | |
611 | preempt_enable(); | |
612 | return ret; | |
6053ee3b IM |
613 | } |
614 | ||
ef5d4707 IM |
615 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
616 | void __sched | |
617 | mutex_lock_nested(struct mutex *lock, unsigned int subclass) | |
618 | { | |
619 | might_sleep(); | |
040a0a37 ML |
620 | __mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, |
621 | subclass, NULL, _RET_IP_, NULL); | |
ef5d4707 IM |
622 | } |
623 | ||
624 | EXPORT_SYMBOL_GPL(mutex_lock_nested); | |
d63a5a74 | 625 | |
e4c70a66 PZ |
626 | void __sched |
627 | _mutex_lock_nest_lock(struct mutex *lock, struct lockdep_map *nest) | |
628 | { | |
629 | might_sleep(); | |
040a0a37 ML |
630 | __mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, |
631 | 0, nest, _RET_IP_, NULL); | |
e4c70a66 PZ |
632 | } |
633 | ||
634 | EXPORT_SYMBOL_GPL(_mutex_lock_nest_lock); | |
635 | ||
ad776537 LH |
636 | int __sched |
637 | mutex_lock_killable_nested(struct mutex *lock, unsigned int subclass) | |
638 | { | |
639 | might_sleep(); | |
040a0a37 ML |
640 | return __mutex_lock_common(lock, TASK_KILLABLE, |
641 | subclass, NULL, _RET_IP_, NULL); | |
ad776537 LH |
642 | } |
643 | EXPORT_SYMBOL_GPL(mutex_lock_killable_nested); | |
644 | ||
d63a5a74 N |
645 | int __sched |
646 | mutex_lock_interruptible_nested(struct mutex *lock, unsigned int subclass) | |
647 | { | |
648 | might_sleep(); | |
0d66bf6d | 649 | return __mutex_lock_common(lock, TASK_INTERRUPTIBLE, |
040a0a37 | 650 | subclass, NULL, _RET_IP_, NULL); |
d63a5a74 N |
651 | } |
652 | ||
653 | EXPORT_SYMBOL_GPL(mutex_lock_interruptible_nested); | |
040a0a37 | 654 | |
23010027 DV |
655 | static inline int |
656 | ww_mutex_deadlock_injection(struct ww_mutex *lock, struct ww_acquire_ctx *ctx) | |
657 | { | |
658 | #ifdef CONFIG_DEBUG_WW_MUTEX_SLOWPATH | |
659 | unsigned tmp; | |
660 | ||
661 | if (ctx->deadlock_inject_countdown-- == 0) { | |
662 | tmp = ctx->deadlock_inject_interval; | |
663 | if (tmp > UINT_MAX/4) | |
664 | tmp = UINT_MAX; | |
665 | else | |
666 | tmp = tmp*2 + tmp + tmp/2; | |
667 | ||
668 | ctx->deadlock_inject_interval = tmp; | |
669 | ctx->deadlock_inject_countdown = tmp; | |
670 | ctx->contending_lock = lock; | |
671 | ||
672 | ww_mutex_unlock(lock); | |
673 | ||
674 | return -EDEADLK; | |
675 | } | |
676 | #endif | |
677 | ||
678 | return 0; | |
679 | } | |
040a0a37 ML |
680 | |
681 | int __sched | |
682 | __ww_mutex_lock(struct ww_mutex *lock, struct ww_acquire_ctx *ctx) | |
683 | { | |
23010027 DV |
684 | int ret; |
685 | ||
040a0a37 | 686 | might_sleep(); |
23010027 | 687 | ret = __mutex_lock_common(&lock->base, TASK_UNINTERRUPTIBLE, |
040a0a37 | 688 | 0, &ctx->dep_map, _RET_IP_, ctx); |
85f48961 | 689 | if (!ret && ctx->acquired > 1) |
23010027 DV |
690 | return ww_mutex_deadlock_injection(lock, ctx); |
691 | ||
692 | return ret; | |
040a0a37 ML |
693 | } |
694 | EXPORT_SYMBOL_GPL(__ww_mutex_lock); | |
695 | ||
696 | int __sched | |
697 | __ww_mutex_lock_interruptible(struct ww_mutex *lock, struct ww_acquire_ctx *ctx) | |
698 | { | |
23010027 DV |
699 | int ret; |
700 | ||
040a0a37 | 701 | might_sleep(); |
23010027 DV |
702 | ret = __mutex_lock_common(&lock->base, TASK_INTERRUPTIBLE, |
703 | 0, &ctx->dep_map, _RET_IP_, ctx); | |
704 | ||
85f48961 | 705 | if (!ret && ctx->acquired > 1) |
23010027 DV |
706 | return ww_mutex_deadlock_injection(lock, ctx); |
707 | ||
708 | return ret; | |
040a0a37 ML |
709 | } |
710 | EXPORT_SYMBOL_GPL(__ww_mutex_lock_interruptible); | |
711 | ||
ef5d4707 IM |
712 | #endif |
713 | ||
6053ee3b IM |
714 | /* |
715 | * Release the lock, slowpath: | |
716 | */ | |
7ad5b3a5 | 717 | static inline void |
ef5d4707 | 718 | __mutex_unlock_common_slowpath(atomic_t *lock_count, int nested) |
6053ee3b | 719 | { |
02706647 | 720 | struct mutex *lock = container_of(lock_count, struct mutex, count); |
1fb00c6c | 721 | unsigned long flags; |
6053ee3b | 722 | |
1fb00c6c | 723 | spin_lock_mutex(&lock->wait_lock, flags); |
ef5d4707 | 724 | mutex_release(&lock->dep_map, nested, _RET_IP_); |
9a11b49a | 725 | debug_mutex_unlock(lock); |
6053ee3b IM |
726 | |
727 | /* | |
728 | * some architectures leave the lock unlocked in the fastpath failure | |
729 | * case, others need to leave it locked. In the later case we have to | |
730 | * unlock it here | |
731 | */ | |
732 | if (__mutex_slowpath_needs_to_unlock()) | |
733 | atomic_set(&lock->count, 1); | |
734 | ||
6053ee3b IM |
735 | if (!list_empty(&lock->wait_list)) { |
736 | /* get the first entry from the wait-list: */ | |
737 | struct mutex_waiter *waiter = | |
738 | list_entry(lock->wait_list.next, | |
739 | struct mutex_waiter, list); | |
740 | ||
741 | debug_mutex_wake_waiter(lock, waiter); | |
742 | ||
743 | wake_up_process(waiter->task); | |
744 | } | |
745 | ||
1fb00c6c | 746 | spin_unlock_mutex(&lock->wait_lock, flags); |
6053ee3b IM |
747 | } |
748 | ||
9a11b49a IM |
749 | /* |
750 | * Release the lock, slowpath: | |
751 | */ | |
7918baa5 | 752 | static __used noinline void |
9a11b49a IM |
753 | __mutex_unlock_slowpath(atomic_t *lock_count) |
754 | { | |
ef5d4707 | 755 | __mutex_unlock_common_slowpath(lock_count, 1); |
9a11b49a IM |
756 | } |
757 | ||
e4564f79 | 758 | #ifndef CONFIG_DEBUG_LOCK_ALLOC |
6053ee3b IM |
759 | /* |
760 | * Here come the less common (and hence less performance-critical) APIs: | |
761 | * mutex_lock_interruptible() and mutex_trylock(). | |
762 | */ | |
7ad5b3a5 | 763 | static noinline int __sched |
a41b56ef | 764 | __mutex_lock_killable_slowpath(struct mutex *lock); |
ad776537 | 765 | |
7ad5b3a5 | 766 | static noinline int __sched |
a41b56ef | 767 | __mutex_lock_interruptible_slowpath(struct mutex *lock); |
6053ee3b | 768 | |
ef5dc121 RD |
769 | /** |
770 | * mutex_lock_interruptible - acquire the mutex, interruptible | |
6053ee3b IM |
771 | * @lock: the mutex to be acquired |
772 | * | |
773 | * Lock the mutex like mutex_lock(), and return 0 if the mutex has | |
774 | * been acquired or sleep until the mutex becomes available. If a | |
775 | * signal arrives while waiting for the lock then this function | |
776 | * returns -EINTR. | |
777 | * | |
778 | * This function is similar to (but not equivalent to) down_interruptible(). | |
779 | */ | |
7ad5b3a5 | 780 | int __sched mutex_lock_interruptible(struct mutex *lock) |
6053ee3b | 781 | { |
0d66bf6d PZ |
782 | int ret; |
783 | ||
c544bdb1 | 784 | might_sleep(); |
a41b56ef ML |
785 | ret = __mutex_fastpath_lock_retval(&lock->count); |
786 | if (likely(!ret)) { | |
0d66bf6d | 787 | mutex_set_owner(lock); |
a41b56ef ML |
788 | return 0; |
789 | } else | |
790 | return __mutex_lock_interruptible_slowpath(lock); | |
6053ee3b IM |
791 | } |
792 | ||
793 | EXPORT_SYMBOL(mutex_lock_interruptible); | |
794 | ||
7ad5b3a5 | 795 | int __sched mutex_lock_killable(struct mutex *lock) |
ad776537 | 796 | { |
0d66bf6d PZ |
797 | int ret; |
798 | ||
ad776537 | 799 | might_sleep(); |
a41b56ef ML |
800 | ret = __mutex_fastpath_lock_retval(&lock->count); |
801 | if (likely(!ret)) { | |
0d66bf6d | 802 | mutex_set_owner(lock); |
a41b56ef ML |
803 | return 0; |
804 | } else | |
805 | return __mutex_lock_killable_slowpath(lock); | |
ad776537 LH |
806 | } |
807 | EXPORT_SYMBOL(mutex_lock_killable); | |
808 | ||
7918baa5 | 809 | static __used noinline void __sched |
e4564f79 PZ |
810 | __mutex_lock_slowpath(atomic_t *lock_count) |
811 | { | |
812 | struct mutex *lock = container_of(lock_count, struct mutex, count); | |
813 | ||
040a0a37 ML |
814 | __mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, 0, |
815 | NULL, _RET_IP_, NULL); | |
e4564f79 PZ |
816 | } |
817 | ||
7ad5b3a5 | 818 | static noinline int __sched |
a41b56ef | 819 | __mutex_lock_killable_slowpath(struct mutex *lock) |
ad776537 | 820 | { |
040a0a37 ML |
821 | return __mutex_lock_common(lock, TASK_KILLABLE, 0, |
822 | NULL, _RET_IP_, NULL); | |
ad776537 LH |
823 | } |
824 | ||
7ad5b3a5 | 825 | static noinline int __sched |
a41b56ef | 826 | __mutex_lock_interruptible_slowpath(struct mutex *lock) |
6053ee3b | 827 | { |
040a0a37 ML |
828 | return __mutex_lock_common(lock, TASK_INTERRUPTIBLE, 0, |
829 | NULL, _RET_IP_, NULL); | |
830 | } | |
831 | ||
832 | static noinline int __sched | |
833 | __ww_mutex_lock_slowpath(struct ww_mutex *lock, struct ww_acquire_ctx *ctx) | |
834 | { | |
835 | return __mutex_lock_common(&lock->base, TASK_UNINTERRUPTIBLE, 0, | |
836 | NULL, _RET_IP_, ctx); | |
6053ee3b | 837 | } |
040a0a37 ML |
838 | |
839 | static noinline int __sched | |
840 | __ww_mutex_lock_interruptible_slowpath(struct ww_mutex *lock, | |
841 | struct ww_acquire_ctx *ctx) | |
842 | { | |
843 | return __mutex_lock_common(&lock->base, TASK_INTERRUPTIBLE, 0, | |
844 | NULL, _RET_IP_, ctx); | |
845 | } | |
846 | ||
e4564f79 | 847 | #endif |
6053ee3b IM |
848 | |
849 | /* | |
850 | * Spinlock based trylock, we take the spinlock and check whether we | |
851 | * can get the lock: | |
852 | */ | |
853 | static inline int __mutex_trylock_slowpath(atomic_t *lock_count) | |
854 | { | |
855 | struct mutex *lock = container_of(lock_count, struct mutex, count); | |
1fb00c6c | 856 | unsigned long flags; |
6053ee3b IM |
857 | int prev; |
858 | ||
1fb00c6c | 859 | spin_lock_mutex(&lock->wait_lock, flags); |
6053ee3b IM |
860 | |
861 | prev = atomic_xchg(&lock->count, -1); | |
ef5d4707 | 862 | if (likely(prev == 1)) { |
0d66bf6d | 863 | mutex_set_owner(lock); |
ef5d4707 IM |
864 | mutex_acquire(&lock->dep_map, 0, 1, _RET_IP_); |
865 | } | |
0d66bf6d | 866 | |
6053ee3b IM |
867 | /* Set it back to 0 if there are no waiters: */ |
868 | if (likely(list_empty(&lock->wait_list))) | |
869 | atomic_set(&lock->count, 0); | |
870 | ||
1fb00c6c | 871 | spin_unlock_mutex(&lock->wait_lock, flags); |
6053ee3b IM |
872 | |
873 | return prev == 1; | |
874 | } | |
875 | ||
ef5dc121 RD |
876 | /** |
877 | * mutex_trylock - try to acquire the mutex, without waiting | |
6053ee3b IM |
878 | * @lock: the mutex to be acquired |
879 | * | |
880 | * Try to acquire the mutex atomically. Returns 1 if the mutex | |
881 | * has been acquired successfully, and 0 on contention. | |
882 | * | |
883 | * NOTE: this function follows the spin_trylock() convention, so | |
ef5dc121 | 884 | * it is negated from the down_trylock() return values! Be careful |
6053ee3b IM |
885 | * about this when converting semaphore users to mutexes. |
886 | * | |
887 | * This function must not be used in interrupt context. The | |
888 | * mutex must be released by the same task that acquired it. | |
889 | */ | |
7ad5b3a5 | 890 | int __sched mutex_trylock(struct mutex *lock) |
6053ee3b | 891 | { |
0d66bf6d PZ |
892 | int ret; |
893 | ||
894 | ret = __mutex_fastpath_trylock(&lock->count, __mutex_trylock_slowpath); | |
895 | if (ret) | |
896 | mutex_set_owner(lock); | |
897 | ||
898 | return ret; | |
6053ee3b | 899 | } |
6053ee3b | 900 | EXPORT_SYMBOL(mutex_trylock); |
a511e3f9 | 901 | |
040a0a37 ML |
902 | #ifndef CONFIG_DEBUG_LOCK_ALLOC |
903 | int __sched | |
904 | __ww_mutex_lock(struct ww_mutex *lock, struct ww_acquire_ctx *ctx) | |
905 | { | |
906 | int ret; | |
907 | ||
908 | might_sleep(); | |
909 | ||
910 | ret = __mutex_fastpath_lock_retval(&lock->base.count); | |
911 | ||
912 | if (likely(!ret)) { | |
913 | ww_mutex_set_context_fastpath(lock, ctx); | |
914 | mutex_set_owner(&lock->base); | |
915 | } else | |
916 | ret = __ww_mutex_lock_slowpath(lock, ctx); | |
917 | return ret; | |
918 | } | |
919 | EXPORT_SYMBOL(__ww_mutex_lock); | |
920 | ||
921 | int __sched | |
922 | __ww_mutex_lock_interruptible(struct ww_mutex *lock, struct ww_acquire_ctx *ctx) | |
923 | { | |
924 | int ret; | |
925 | ||
926 | might_sleep(); | |
927 | ||
928 | ret = __mutex_fastpath_lock_retval(&lock->base.count); | |
929 | ||
930 | if (likely(!ret)) { | |
931 | ww_mutex_set_context_fastpath(lock, ctx); | |
932 | mutex_set_owner(&lock->base); | |
933 | } else | |
934 | ret = __ww_mutex_lock_interruptible_slowpath(lock, ctx); | |
935 | return ret; | |
936 | } | |
937 | EXPORT_SYMBOL(__ww_mutex_lock_interruptible); | |
938 | ||
939 | #endif | |
940 | ||
a511e3f9 AM |
941 | /** |
942 | * atomic_dec_and_mutex_lock - return holding mutex if we dec to 0 | |
943 | * @cnt: the atomic which we are to dec | |
944 | * @lock: the mutex to return holding if we dec to 0 | |
945 | * | |
946 | * return true and hold lock if we dec to 0, return false otherwise | |
947 | */ | |
948 | int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock) | |
949 | { | |
950 | /* dec if we can't possibly hit 0 */ | |
951 | if (atomic_add_unless(cnt, -1, 1)) | |
952 | return 0; | |
953 | /* we might hit 0, so take the lock */ | |
954 | mutex_lock(lock); | |
955 | if (!atomic_dec_and_test(cnt)) { | |
956 | /* when we actually did the dec, we didn't hit 0 */ | |
957 | mutex_unlock(lock); | |
958 | return 0; | |
959 | } | |
960 | /* we hit 0, and we hold the lock */ | |
961 | return 1; | |
962 | } | |
963 | EXPORT_SYMBOL(atomic_dec_and_mutex_lock); |