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Commit | Line | Data |
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6053ee3b | 1 | /* |
67a6de49 | 2 | * kernel/locking/mutex.c |
6053ee3b IM |
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> |
c9122da1 | 28 | #include "mcs_spinlock.h" |
6053ee3b IM |
29 | |
30 | /* | |
31 | * In the DEBUG case we are using the "NULL fastpath" for mutexes, | |
32 | * which forces all calls into the slowpath: | |
33 | */ | |
34 | #ifdef CONFIG_DEBUG_MUTEXES | |
35 | # include "mutex-debug.h" | |
36 | # include <asm-generic/mutex-null.h> | |
6f008e72 PZ |
37 | /* |
38 | * Must be 0 for the debug case so we do not do the unlock outside of the | |
39 | * wait_lock region. debug_mutex_unlock() will do the actual unlock in this | |
40 | * case. | |
41 | */ | |
42 | # undef __mutex_slowpath_needs_to_unlock | |
43 | # define __mutex_slowpath_needs_to_unlock() 0 | |
6053ee3b IM |
44 | #else |
45 | # include "mutex.h" | |
46 | # include <asm/mutex.h> | |
47 | #endif | |
48 | ||
0dc8c730 | 49 | /* |
cc189d25 WL |
50 | * A negative mutex count indicates that waiters are sleeping waiting for the |
51 | * mutex. | |
0dc8c730 | 52 | */ |
0dc8c730 | 53 | #define MUTEX_SHOW_NO_WAITER(mutex) (atomic_read(&(mutex)->count) >= 0) |
0dc8c730 | 54 | |
ef5d4707 IM |
55 | void |
56 | __mutex_init(struct mutex *lock, const char *name, struct lock_class_key *key) | |
6053ee3b IM |
57 | { |
58 | atomic_set(&lock->count, 1); | |
59 | spin_lock_init(&lock->wait_lock); | |
60 | INIT_LIST_HEAD(&lock->wait_list); | |
0d66bf6d | 61 | mutex_clear_owner(lock); |
2bd2c92c | 62 | #ifdef CONFIG_MUTEX_SPIN_ON_OWNER |
fb0527bd | 63 | lock->osq = NULL; |
2bd2c92c | 64 | #endif |
6053ee3b | 65 | |
ef5d4707 | 66 | debug_mutex_init(lock, name, key); |
6053ee3b IM |
67 | } |
68 | ||
69 | EXPORT_SYMBOL(__mutex_init); | |
70 | ||
e4564f79 | 71 | #ifndef CONFIG_DEBUG_LOCK_ALLOC |
6053ee3b IM |
72 | /* |
73 | * We split the mutex lock/unlock logic into separate fastpath and | |
74 | * slowpath functions, to reduce the register pressure on the fastpath. | |
75 | * We also put the fastpath first in the kernel image, to make sure the | |
76 | * branch is predicted by the CPU as default-untaken. | |
77 | */ | |
22d9fd34 | 78 | __visible void __sched __mutex_lock_slowpath(atomic_t *lock_count); |
6053ee3b | 79 | |
ef5dc121 | 80 | /** |
6053ee3b IM |
81 | * mutex_lock - acquire the mutex |
82 | * @lock: the mutex to be acquired | |
83 | * | |
84 | * Lock the mutex exclusively for this task. If the mutex is not | |
85 | * available right now, it will sleep until it can get it. | |
86 | * | |
87 | * The mutex must later on be released by the same task that | |
88 | * acquired it. Recursive locking is not allowed. The task | |
89 | * may not exit without first unlocking the mutex. Also, kernel | |
90 | * memory where the mutex resides mutex must not be freed with | |
91 | * the mutex still locked. The mutex must first be initialized | |
92 | * (or statically defined) before it can be locked. memset()-ing | |
93 | * the mutex to 0 is not allowed. | |
94 | * | |
95 | * ( The CONFIG_DEBUG_MUTEXES .config option turns on debugging | |
96 | * checks that will enforce the restrictions and will also do | |
97 | * deadlock debugging. ) | |
98 | * | |
99 | * This function is similar to (but not equivalent to) down(). | |
100 | */ | |
b09d2501 | 101 | void __sched mutex_lock(struct mutex *lock) |
6053ee3b | 102 | { |
c544bdb1 | 103 | might_sleep(); |
6053ee3b IM |
104 | /* |
105 | * The locking fastpath is the 1->0 transition from | |
106 | * 'unlocked' into 'locked' state. | |
6053ee3b IM |
107 | */ |
108 | __mutex_fastpath_lock(&lock->count, __mutex_lock_slowpath); | |
0d66bf6d | 109 | mutex_set_owner(lock); |
6053ee3b IM |
110 | } |
111 | ||
112 | EXPORT_SYMBOL(mutex_lock); | |
e4564f79 | 113 | #endif |
6053ee3b | 114 | |
41fcb9f2 | 115 | #ifdef CONFIG_MUTEX_SPIN_ON_OWNER |
2bd2c92c WL |
116 | /* |
117 | * In order to avoid a stampede of mutex spinners from acquiring the mutex | |
118 | * more or less simultaneously, the spinners need to acquire a MCS lock | |
119 | * first before spinning on the owner field. | |
120 | * | |
2bd2c92c | 121 | */ |
2bd2c92c | 122 | |
41fcb9f2 WL |
123 | /* |
124 | * Mutex spinning code migrated from kernel/sched/core.c | |
125 | */ | |
126 | ||
127 | static inline bool owner_running(struct mutex *lock, struct task_struct *owner) | |
128 | { | |
129 | if (lock->owner != owner) | |
130 | return false; | |
131 | ||
132 | /* | |
133 | * Ensure we emit the owner->on_cpu, dereference _after_ checking | |
134 | * lock->owner still matches owner, if that fails, owner might | |
135 | * point to free()d memory, if it still matches, the rcu_read_lock() | |
136 | * ensures the memory stays valid. | |
137 | */ | |
138 | barrier(); | |
139 | ||
140 | return owner->on_cpu; | |
141 | } | |
142 | ||
143 | /* | |
144 | * Look out! "owner" is an entirely speculative pointer | |
145 | * access and not reliable. | |
146 | */ | |
147 | static noinline | |
148 | int mutex_spin_on_owner(struct mutex *lock, struct task_struct *owner) | |
149 | { | |
150 | rcu_read_lock(); | |
151 | while (owner_running(lock, owner)) { | |
152 | if (need_resched()) | |
153 | break; | |
154 | ||
155 | arch_mutex_cpu_relax(); | |
156 | } | |
157 | rcu_read_unlock(); | |
158 | ||
159 | /* | |
160 | * We break out the loop above on need_resched() and when the | |
161 | * owner changed, which is a sign for heavy contention. Return | |
162 | * success only when lock->owner is NULL. | |
163 | */ | |
164 | return lock->owner == NULL; | |
165 | } | |
2bd2c92c WL |
166 | |
167 | /* | |
168 | * Initial check for entering the mutex spinning loop | |
169 | */ | |
170 | static inline int mutex_can_spin_on_owner(struct mutex *lock) | |
171 | { | |
1e40c2ed | 172 | struct task_struct *owner; |
2bd2c92c WL |
173 | int retval = 1; |
174 | ||
46af29e4 JL |
175 | if (need_resched()) |
176 | return 0; | |
177 | ||
2bd2c92c | 178 | rcu_read_lock(); |
1e40c2ed PZ |
179 | owner = ACCESS_ONCE(lock->owner); |
180 | if (owner) | |
181 | retval = owner->on_cpu; | |
2bd2c92c WL |
182 | rcu_read_unlock(); |
183 | /* | |
184 | * if lock->owner is not set, the mutex owner may have just acquired | |
185 | * it and not set the owner yet or the mutex has been released. | |
186 | */ | |
187 | return retval; | |
188 | } | |
41fcb9f2 WL |
189 | #endif |
190 | ||
22d9fd34 AK |
191 | __visible __used noinline |
192 | void __sched __mutex_unlock_slowpath(atomic_t *lock_count); | |
6053ee3b | 193 | |
ef5dc121 | 194 | /** |
6053ee3b IM |
195 | * mutex_unlock - release the mutex |
196 | * @lock: the mutex to be released | |
197 | * | |
198 | * Unlock a mutex that has been locked by this task previously. | |
199 | * | |
200 | * This function must not be used in interrupt context. Unlocking | |
201 | * of a not locked mutex is not allowed. | |
202 | * | |
203 | * This function is similar to (but not equivalent to) up(). | |
204 | */ | |
7ad5b3a5 | 205 | void __sched mutex_unlock(struct mutex *lock) |
6053ee3b IM |
206 | { |
207 | /* | |
208 | * The unlocking fastpath is the 0->1 transition from 'locked' | |
209 | * into 'unlocked' state: | |
6053ee3b | 210 | */ |
0d66bf6d PZ |
211 | #ifndef CONFIG_DEBUG_MUTEXES |
212 | /* | |
213 | * When debugging is enabled we must not clear the owner before time, | |
214 | * the slow path will always be taken, and that clears the owner field | |
215 | * after verifying that it was indeed current. | |
216 | */ | |
217 | mutex_clear_owner(lock); | |
218 | #endif | |
6053ee3b IM |
219 | __mutex_fastpath_unlock(&lock->count, __mutex_unlock_slowpath); |
220 | } | |
221 | ||
222 | EXPORT_SYMBOL(mutex_unlock); | |
223 | ||
040a0a37 ML |
224 | /** |
225 | * ww_mutex_unlock - release the w/w mutex | |
226 | * @lock: the mutex to be released | |
227 | * | |
228 | * Unlock a mutex that has been locked by this task previously with any of the | |
229 | * ww_mutex_lock* functions (with or without an acquire context). It is | |
230 | * forbidden to release the locks after releasing the acquire context. | |
231 | * | |
232 | * This function must not be used in interrupt context. Unlocking | |
233 | * of a unlocked mutex is not allowed. | |
234 | */ | |
235 | void __sched ww_mutex_unlock(struct ww_mutex *lock) | |
236 | { | |
237 | /* | |
238 | * The unlocking fastpath is the 0->1 transition from 'locked' | |
239 | * into 'unlocked' state: | |
240 | */ | |
241 | if (lock->ctx) { | |
242 | #ifdef CONFIG_DEBUG_MUTEXES | |
243 | DEBUG_LOCKS_WARN_ON(!lock->ctx->acquired); | |
244 | #endif | |
245 | if (lock->ctx->acquired > 0) | |
246 | lock->ctx->acquired--; | |
247 | lock->ctx = NULL; | |
248 | } | |
249 | ||
250 | #ifndef CONFIG_DEBUG_MUTEXES | |
251 | /* | |
252 | * When debugging is enabled we must not clear the owner before time, | |
253 | * the slow path will always be taken, and that clears the owner field | |
254 | * after verifying that it was indeed current. | |
255 | */ | |
256 | mutex_clear_owner(&lock->base); | |
257 | #endif | |
258 | __mutex_fastpath_unlock(&lock->base.count, __mutex_unlock_slowpath); | |
259 | } | |
260 | EXPORT_SYMBOL(ww_mutex_unlock); | |
261 | ||
262 | static inline int __sched | |
263 | __mutex_lock_check_stamp(struct mutex *lock, struct ww_acquire_ctx *ctx) | |
264 | { | |
265 | struct ww_mutex *ww = container_of(lock, struct ww_mutex, base); | |
266 | struct ww_acquire_ctx *hold_ctx = ACCESS_ONCE(ww->ctx); | |
267 | ||
268 | if (!hold_ctx) | |
269 | return 0; | |
270 | ||
271 | if (unlikely(ctx == hold_ctx)) | |
272 | return -EALREADY; | |
273 | ||
274 | if (ctx->stamp - hold_ctx->stamp <= LONG_MAX && | |
275 | (ctx->stamp != hold_ctx->stamp || ctx > hold_ctx)) { | |
276 | #ifdef CONFIG_DEBUG_MUTEXES | |
277 | DEBUG_LOCKS_WARN_ON(ctx->contending_lock); | |
278 | ctx->contending_lock = ww; | |
279 | #endif | |
280 | return -EDEADLK; | |
281 | } | |
282 | ||
283 | return 0; | |
284 | } | |
285 | ||
286 | static __always_inline void ww_mutex_lock_acquired(struct ww_mutex *ww, | |
287 | struct ww_acquire_ctx *ww_ctx) | |
288 | { | |
289 | #ifdef CONFIG_DEBUG_MUTEXES | |
290 | /* | |
291 | * If this WARN_ON triggers, you used ww_mutex_lock to acquire, | |
292 | * but released with a normal mutex_unlock in this call. | |
293 | * | |
294 | * This should never happen, always use ww_mutex_unlock. | |
295 | */ | |
296 | DEBUG_LOCKS_WARN_ON(ww->ctx); | |
297 | ||
298 | /* | |
299 | * Not quite done after calling ww_acquire_done() ? | |
300 | */ | |
301 | DEBUG_LOCKS_WARN_ON(ww_ctx->done_acquire); | |
302 | ||
303 | if (ww_ctx->contending_lock) { | |
304 | /* | |
305 | * After -EDEADLK you tried to | |
306 | * acquire a different ww_mutex? Bad! | |
307 | */ | |
308 | DEBUG_LOCKS_WARN_ON(ww_ctx->contending_lock != ww); | |
309 | ||
310 | /* | |
311 | * You called ww_mutex_lock after receiving -EDEADLK, | |
312 | * but 'forgot' to unlock everything else first? | |
313 | */ | |
314 | DEBUG_LOCKS_WARN_ON(ww_ctx->acquired > 0); | |
315 | ww_ctx->contending_lock = NULL; | |
316 | } | |
317 | ||
318 | /* | |
319 | * Naughty, using a different class will lead to undefined behavior! | |
320 | */ | |
321 | DEBUG_LOCKS_WARN_ON(ww_ctx->ww_class != ww->ww_class); | |
322 | #endif | |
323 | ww_ctx->acquired++; | |
324 | } | |
325 | ||
326 | /* | |
327 | * after acquiring lock with fastpath or when we lost out in contested | |
328 | * slowpath, set ctx and wake up any waiters so they can recheck. | |
329 | * | |
330 | * This function is never called when CONFIG_DEBUG_LOCK_ALLOC is set, | |
331 | * as the fastpath and opportunistic spinning are disabled in that case. | |
332 | */ | |
333 | static __always_inline void | |
334 | ww_mutex_set_context_fastpath(struct ww_mutex *lock, | |
335 | struct ww_acquire_ctx *ctx) | |
336 | { | |
337 | unsigned long flags; | |
338 | struct mutex_waiter *cur; | |
339 | ||
340 | ww_mutex_lock_acquired(lock, ctx); | |
341 | ||
342 | lock->ctx = ctx; | |
343 | ||
344 | /* | |
345 | * The lock->ctx update should be visible on all cores before | |
346 | * the atomic read is done, otherwise contended waiters might be | |
347 | * missed. The contended waiters will either see ww_ctx == NULL | |
348 | * and keep spinning, or it will acquire wait_lock, add itself | |
349 | * to waiter list and sleep. | |
350 | */ | |
351 | smp_mb(); /* ^^^ */ | |
352 | ||
353 | /* | |
354 | * Check if lock is contended, if not there is nobody to wake up | |
355 | */ | |
356 | if (likely(atomic_read(&lock->base.count) == 0)) | |
357 | return; | |
358 | ||
359 | /* | |
360 | * Uh oh, we raced in fastpath, wake up everyone in this case, | |
361 | * so they can see the new lock->ctx. | |
362 | */ | |
363 | spin_lock_mutex(&lock->base.wait_lock, flags); | |
364 | list_for_each_entry(cur, &lock->base.wait_list, list) { | |
365 | debug_mutex_wake_waiter(&lock->base, cur); | |
366 | wake_up_process(cur->task); | |
367 | } | |
368 | spin_unlock_mutex(&lock->base.wait_lock, flags); | |
369 | } | |
370 | ||
6053ee3b IM |
371 | /* |
372 | * Lock a mutex (possibly interruptible), slowpath: | |
373 | */ | |
040a0a37 | 374 | static __always_inline int __sched |
e4564f79 | 375 | __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass, |
040a0a37 | 376 | struct lockdep_map *nest_lock, unsigned long ip, |
b0267507 | 377 | struct ww_acquire_ctx *ww_ctx, const bool use_ww_ctx) |
6053ee3b IM |
378 | { |
379 | struct task_struct *task = current; | |
380 | struct mutex_waiter waiter; | |
1fb00c6c | 381 | unsigned long flags; |
040a0a37 | 382 | int ret; |
6053ee3b | 383 | |
41719b03 | 384 | preempt_disable(); |
e4c70a66 | 385 | mutex_acquire_nest(&lock->dep_map, subclass, 0, nest_lock, ip); |
c0226027 FW |
386 | |
387 | #ifdef CONFIG_MUTEX_SPIN_ON_OWNER | |
0d66bf6d PZ |
388 | /* |
389 | * Optimistic spinning. | |
390 | * | |
391 | * We try to spin for acquisition when we find that there are no | |
392 | * pending waiters and the lock owner is currently running on a | |
393 | * (different) CPU. | |
394 | * | |
395 | * The rationale is that if the lock owner is running, it is likely to | |
396 | * release the lock soon. | |
397 | * | |
398 | * Since this needs the lock owner, and this mutex implementation | |
399 | * doesn't track the owner atomically in the lock field, we need to | |
400 | * track it non-atomically. | |
401 | * | |
402 | * We can't do this for DEBUG_MUTEXES because that relies on wait_lock | |
403 | * to serialize everything. | |
2bd2c92c WL |
404 | * |
405 | * The mutex spinners are queued up using MCS lock so that only one | |
406 | * spinner can compete for the mutex. However, if mutex spinning isn't | |
407 | * going to happen, there is no point in going through the lock/unlock | |
408 | * overhead. | |
0d66bf6d | 409 | */ |
2bd2c92c WL |
410 | if (!mutex_can_spin_on_owner(lock)) |
411 | goto slowpath; | |
0d66bf6d | 412 | |
fb0527bd PZ |
413 | if (!osq_lock(&lock->osq)) |
414 | goto slowpath; | |
415 | ||
0d66bf6d | 416 | for (;;) { |
c6eb3dda | 417 | struct task_struct *owner; |
0d66bf6d | 418 | |
b0267507 | 419 | if (use_ww_ctx && ww_ctx->acquired > 0) { |
040a0a37 ML |
420 | struct ww_mutex *ww; |
421 | ||
422 | ww = container_of(lock, struct ww_mutex, base); | |
423 | /* | |
424 | * If ww->ctx is set the contents are undefined, only | |
425 | * by acquiring wait_lock there is a guarantee that | |
426 | * they are not invalid when reading. | |
427 | * | |
428 | * As such, when deadlock detection needs to be | |
429 | * performed the optimistic spinning cannot be done. | |
430 | */ | |
431 | if (ACCESS_ONCE(ww->ctx)) | |
47667fa1 | 432 | break; |
040a0a37 ML |
433 | } |
434 | ||
0d66bf6d PZ |
435 | /* |
436 | * If there's an owner, wait for it to either | |
437 | * release the lock or go to sleep. | |
438 | */ | |
439 | owner = ACCESS_ONCE(lock->owner); | |
47667fa1 JL |
440 | if (owner && !mutex_spin_on_owner(lock, owner)) |
441 | break; | |
0d66bf6d | 442 | |
0dc8c730 WL |
443 | if ((atomic_read(&lock->count) == 1) && |
444 | (atomic_cmpxchg(&lock->count, 1, 0) == 1)) { | |
ac6e60ee | 445 | lock_acquired(&lock->dep_map, ip); |
b0267507 | 446 | if (use_ww_ctx) { |
040a0a37 ML |
447 | struct ww_mutex *ww; |
448 | ww = container_of(lock, struct ww_mutex, base); | |
449 | ||
450 | ww_mutex_set_context_fastpath(ww, ww_ctx); | |
451 | } | |
452 | ||
ac6e60ee | 453 | mutex_set_owner(lock); |
fb0527bd | 454 | osq_unlock(&lock->osq); |
ac6e60ee CM |
455 | preempt_enable(); |
456 | return 0; | |
457 | } | |
458 | ||
0d66bf6d PZ |
459 | /* |
460 | * When there's no owner, we might have preempted between the | |
461 | * owner acquiring the lock and setting the owner field. If | |
462 | * we're an RT task that will live-lock because we won't let | |
463 | * the owner complete. | |
464 | */ | |
465 | if (!owner && (need_resched() || rt_task(task))) | |
47667fa1 | 466 | break; |
0d66bf6d | 467 | |
0d66bf6d PZ |
468 | /* |
469 | * The cpu_relax() call is a compiler barrier which forces | |
470 | * everything in this loop to be re-loaded. We don't need | |
471 | * memory barriers as we'll eventually observe the right | |
472 | * values at the cost of a few extra spins. | |
473 | */ | |
335d7afb | 474 | arch_mutex_cpu_relax(); |
0d66bf6d | 475 | } |
fb0527bd | 476 | osq_unlock(&lock->osq); |
2bd2c92c | 477 | slowpath: |
34c6bc2c PZ |
478 | /* |
479 | * If we fell out of the spin path because of need_resched(), | |
480 | * reschedule now, before we try-lock the mutex. This avoids getting | |
481 | * scheduled out right after we obtained the mutex. | |
482 | */ | |
483 | if (need_resched()) | |
484 | schedule_preempt_disabled(); | |
0d66bf6d | 485 | #endif |
1fb00c6c | 486 | spin_lock_mutex(&lock->wait_lock, flags); |
6053ee3b | 487 | |
ec83f425 DB |
488 | /* once more, can we acquire the lock? */ |
489 | if (MUTEX_SHOW_NO_WAITER(lock) && (atomic_xchg(&lock->count, 0) == 1)) | |
490 | goto skip_wait; | |
491 | ||
9a11b49a | 492 | debug_mutex_lock_common(lock, &waiter); |
c9f4f06d | 493 | debug_mutex_add_waiter(lock, &waiter, task_thread_info(task)); |
6053ee3b IM |
494 | |
495 | /* add waiting tasks to the end of the waitqueue (FIFO): */ | |
496 | list_add_tail(&waiter.list, &lock->wait_list); | |
497 | waiter.task = task; | |
498 | ||
e4564f79 | 499 | lock_contended(&lock->dep_map, ip); |
4fe87745 | 500 | |
6053ee3b IM |
501 | for (;;) { |
502 | /* | |
503 | * Lets try to take the lock again - this is needed even if | |
504 | * we get here for the first time (shortly after failing to | |
505 | * acquire the lock), to make sure that we get a wakeup once | |
506 | * it's unlocked. Later on, if we sleep, this is the | |
507 | * operation that gives us the lock. We xchg it to -1, so | |
508 | * that when we release the lock, we properly wake up the | |
509 | * other waiters: | |
510 | */ | |
0dc8c730 | 511 | if (MUTEX_SHOW_NO_WAITER(lock) && |
ec83f425 | 512 | (atomic_xchg(&lock->count, -1) == 1)) |
6053ee3b IM |
513 | break; |
514 | ||
515 | /* | |
516 | * got a signal? (This code gets eliminated in the | |
517 | * TASK_UNINTERRUPTIBLE case.) | |
518 | */ | |
6ad36762 | 519 | if (unlikely(signal_pending_state(state, task))) { |
040a0a37 ML |
520 | ret = -EINTR; |
521 | goto err; | |
522 | } | |
6053ee3b | 523 | |
b0267507 | 524 | if (use_ww_ctx && ww_ctx->acquired > 0) { |
040a0a37 ML |
525 | ret = __mutex_lock_check_stamp(lock, ww_ctx); |
526 | if (ret) | |
527 | goto err; | |
6053ee3b | 528 | } |
040a0a37 | 529 | |
6053ee3b IM |
530 | __set_task_state(task, state); |
531 | ||
25985edc | 532 | /* didn't get the lock, go to sleep: */ |
1fb00c6c | 533 | spin_unlock_mutex(&lock->wait_lock, flags); |
bd2f5536 | 534 | schedule_preempt_disabled(); |
1fb00c6c | 535 | spin_lock_mutex(&lock->wait_lock, flags); |
6053ee3b | 536 | } |
ec83f425 DB |
537 | mutex_remove_waiter(lock, &waiter, current_thread_info()); |
538 | /* set it to 0 if there are no waiters left: */ | |
539 | if (likely(list_empty(&lock->wait_list))) | |
540 | atomic_set(&lock->count, 0); | |
541 | debug_mutex_free_waiter(&waiter); | |
6053ee3b | 542 | |
ec83f425 DB |
543 | skip_wait: |
544 | /* got the lock - cleanup and rejoice! */ | |
c7e78cff | 545 | lock_acquired(&lock->dep_map, ip); |
0d66bf6d | 546 | mutex_set_owner(lock); |
6053ee3b | 547 | |
b0267507 | 548 | if (use_ww_ctx) { |
ec83f425 | 549 | struct ww_mutex *ww = container_of(lock, struct ww_mutex, base); |
040a0a37 ML |
550 | struct mutex_waiter *cur; |
551 | ||
552 | /* | |
553 | * This branch gets optimized out for the common case, | |
554 | * and is only important for ww_mutex_lock. | |
555 | */ | |
040a0a37 ML |
556 | ww_mutex_lock_acquired(ww, ww_ctx); |
557 | ww->ctx = ww_ctx; | |
558 | ||
559 | /* | |
560 | * Give any possible sleeping processes the chance to wake up, | |
561 | * so they can recheck if they have to back off. | |
562 | */ | |
563 | list_for_each_entry(cur, &lock->wait_list, list) { | |
564 | debug_mutex_wake_waiter(lock, cur); | |
565 | wake_up_process(cur->task); | |
566 | } | |
567 | } | |
568 | ||
1fb00c6c | 569 | spin_unlock_mutex(&lock->wait_lock, flags); |
41719b03 | 570 | preempt_enable(); |
6053ee3b | 571 | return 0; |
040a0a37 ML |
572 | |
573 | err: | |
574 | mutex_remove_waiter(lock, &waiter, task_thread_info(task)); | |
575 | spin_unlock_mutex(&lock->wait_lock, flags); | |
576 | debug_mutex_free_waiter(&waiter); | |
577 | mutex_release(&lock->dep_map, 1, ip); | |
578 | preempt_enable(); | |
579 | return ret; | |
6053ee3b IM |
580 | } |
581 | ||
ef5d4707 IM |
582 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
583 | void __sched | |
584 | mutex_lock_nested(struct mutex *lock, unsigned int subclass) | |
585 | { | |
586 | might_sleep(); | |
040a0a37 | 587 | __mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, |
b0267507 | 588 | subclass, NULL, _RET_IP_, NULL, 0); |
ef5d4707 IM |
589 | } |
590 | ||
591 | EXPORT_SYMBOL_GPL(mutex_lock_nested); | |
d63a5a74 | 592 | |
e4c70a66 PZ |
593 | void __sched |
594 | _mutex_lock_nest_lock(struct mutex *lock, struct lockdep_map *nest) | |
595 | { | |
596 | might_sleep(); | |
040a0a37 | 597 | __mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, |
b0267507 | 598 | 0, nest, _RET_IP_, NULL, 0); |
e4c70a66 PZ |
599 | } |
600 | ||
601 | EXPORT_SYMBOL_GPL(_mutex_lock_nest_lock); | |
602 | ||
ad776537 LH |
603 | int __sched |
604 | mutex_lock_killable_nested(struct mutex *lock, unsigned int subclass) | |
605 | { | |
606 | might_sleep(); | |
040a0a37 | 607 | return __mutex_lock_common(lock, TASK_KILLABLE, |
b0267507 | 608 | subclass, NULL, _RET_IP_, NULL, 0); |
ad776537 LH |
609 | } |
610 | EXPORT_SYMBOL_GPL(mutex_lock_killable_nested); | |
611 | ||
d63a5a74 N |
612 | int __sched |
613 | mutex_lock_interruptible_nested(struct mutex *lock, unsigned int subclass) | |
614 | { | |
615 | might_sleep(); | |
0d66bf6d | 616 | return __mutex_lock_common(lock, TASK_INTERRUPTIBLE, |
b0267507 | 617 | subclass, NULL, _RET_IP_, NULL, 0); |
d63a5a74 N |
618 | } |
619 | ||
620 | EXPORT_SYMBOL_GPL(mutex_lock_interruptible_nested); | |
040a0a37 | 621 | |
23010027 DV |
622 | static inline int |
623 | ww_mutex_deadlock_injection(struct ww_mutex *lock, struct ww_acquire_ctx *ctx) | |
624 | { | |
625 | #ifdef CONFIG_DEBUG_WW_MUTEX_SLOWPATH | |
626 | unsigned tmp; | |
627 | ||
628 | if (ctx->deadlock_inject_countdown-- == 0) { | |
629 | tmp = ctx->deadlock_inject_interval; | |
630 | if (tmp > UINT_MAX/4) | |
631 | tmp = UINT_MAX; | |
632 | else | |
633 | tmp = tmp*2 + tmp + tmp/2; | |
634 | ||
635 | ctx->deadlock_inject_interval = tmp; | |
636 | ctx->deadlock_inject_countdown = tmp; | |
637 | ctx->contending_lock = lock; | |
638 | ||
639 | ww_mutex_unlock(lock); | |
640 | ||
641 | return -EDEADLK; | |
642 | } | |
643 | #endif | |
644 | ||
645 | return 0; | |
646 | } | |
040a0a37 ML |
647 | |
648 | int __sched | |
649 | __ww_mutex_lock(struct ww_mutex *lock, struct ww_acquire_ctx *ctx) | |
650 | { | |
23010027 DV |
651 | int ret; |
652 | ||
040a0a37 | 653 | might_sleep(); |
23010027 | 654 | ret = __mutex_lock_common(&lock->base, TASK_UNINTERRUPTIBLE, |
b0267507 | 655 | 0, &ctx->dep_map, _RET_IP_, ctx, 1); |
85f48961 | 656 | if (!ret && ctx->acquired > 1) |
23010027 DV |
657 | return ww_mutex_deadlock_injection(lock, ctx); |
658 | ||
659 | return ret; | |
040a0a37 ML |
660 | } |
661 | EXPORT_SYMBOL_GPL(__ww_mutex_lock); | |
662 | ||
663 | int __sched | |
664 | __ww_mutex_lock_interruptible(struct ww_mutex *lock, struct ww_acquire_ctx *ctx) | |
665 | { | |
23010027 DV |
666 | int ret; |
667 | ||
040a0a37 | 668 | might_sleep(); |
23010027 | 669 | ret = __mutex_lock_common(&lock->base, TASK_INTERRUPTIBLE, |
b0267507 | 670 | 0, &ctx->dep_map, _RET_IP_, ctx, 1); |
23010027 | 671 | |
85f48961 | 672 | if (!ret && ctx->acquired > 1) |
23010027 DV |
673 | return ww_mutex_deadlock_injection(lock, ctx); |
674 | ||
675 | return ret; | |
040a0a37 ML |
676 | } |
677 | EXPORT_SYMBOL_GPL(__ww_mutex_lock_interruptible); | |
678 | ||
ef5d4707 IM |
679 | #endif |
680 | ||
6053ee3b IM |
681 | /* |
682 | * Release the lock, slowpath: | |
683 | */ | |
7ad5b3a5 | 684 | static inline void |
ef5d4707 | 685 | __mutex_unlock_common_slowpath(atomic_t *lock_count, int nested) |
6053ee3b | 686 | { |
02706647 | 687 | struct mutex *lock = container_of(lock_count, struct mutex, count); |
1fb00c6c | 688 | unsigned long flags; |
6053ee3b | 689 | |
6053ee3b IM |
690 | /* |
691 | * some architectures leave the lock unlocked in the fastpath failure | |
692 | * case, others need to leave it locked. In the later case we have to | |
693 | * unlock it here | |
694 | */ | |
695 | if (__mutex_slowpath_needs_to_unlock()) | |
696 | atomic_set(&lock->count, 1); | |
697 | ||
1d8fe7dc JL |
698 | spin_lock_mutex(&lock->wait_lock, flags); |
699 | mutex_release(&lock->dep_map, nested, _RET_IP_); | |
700 | debug_mutex_unlock(lock); | |
701 | ||
6053ee3b IM |
702 | if (!list_empty(&lock->wait_list)) { |
703 | /* get the first entry from the wait-list: */ | |
704 | struct mutex_waiter *waiter = | |
705 | list_entry(lock->wait_list.next, | |
706 | struct mutex_waiter, list); | |
707 | ||
708 | debug_mutex_wake_waiter(lock, waiter); | |
709 | ||
710 | wake_up_process(waiter->task); | |
711 | } | |
712 | ||
1fb00c6c | 713 | spin_unlock_mutex(&lock->wait_lock, flags); |
6053ee3b IM |
714 | } |
715 | ||
9a11b49a IM |
716 | /* |
717 | * Release the lock, slowpath: | |
718 | */ | |
22d9fd34 | 719 | __visible void |
9a11b49a IM |
720 | __mutex_unlock_slowpath(atomic_t *lock_count) |
721 | { | |
ef5d4707 | 722 | __mutex_unlock_common_slowpath(lock_count, 1); |
9a11b49a IM |
723 | } |
724 | ||
e4564f79 | 725 | #ifndef CONFIG_DEBUG_LOCK_ALLOC |
6053ee3b IM |
726 | /* |
727 | * Here come the less common (and hence less performance-critical) APIs: | |
728 | * mutex_lock_interruptible() and mutex_trylock(). | |
729 | */ | |
7ad5b3a5 | 730 | static noinline int __sched |
a41b56ef | 731 | __mutex_lock_killable_slowpath(struct mutex *lock); |
ad776537 | 732 | |
7ad5b3a5 | 733 | static noinline int __sched |
a41b56ef | 734 | __mutex_lock_interruptible_slowpath(struct mutex *lock); |
6053ee3b | 735 | |
ef5dc121 RD |
736 | /** |
737 | * mutex_lock_interruptible - acquire the mutex, interruptible | |
6053ee3b IM |
738 | * @lock: the mutex to be acquired |
739 | * | |
740 | * Lock the mutex like mutex_lock(), and return 0 if the mutex has | |
741 | * been acquired or sleep until the mutex becomes available. If a | |
742 | * signal arrives while waiting for the lock then this function | |
743 | * returns -EINTR. | |
744 | * | |
745 | * This function is similar to (but not equivalent to) down_interruptible(). | |
746 | */ | |
7ad5b3a5 | 747 | int __sched mutex_lock_interruptible(struct mutex *lock) |
6053ee3b | 748 | { |
0d66bf6d PZ |
749 | int ret; |
750 | ||
c544bdb1 | 751 | might_sleep(); |
a41b56ef ML |
752 | ret = __mutex_fastpath_lock_retval(&lock->count); |
753 | if (likely(!ret)) { | |
0d66bf6d | 754 | mutex_set_owner(lock); |
a41b56ef ML |
755 | return 0; |
756 | } else | |
757 | return __mutex_lock_interruptible_slowpath(lock); | |
6053ee3b IM |
758 | } |
759 | ||
760 | EXPORT_SYMBOL(mutex_lock_interruptible); | |
761 | ||
7ad5b3a5 | 762 | int __sched mutex_lock_killable(struct mutex *lock) |
ad776537 | 763 | { |
0d66bf6d PZ |
764 | int ret; |
765 | ||
ad776537 | 766 | might_sleep(); |
a41b56ef ML |
767 | ret = __mutex_fastpath_lock_retval(&lock->count); |
768 | if (likely(!ret)) { | |
0d66bf6d | 769 | mutex_set_owner(lock); |
a41b56ef ML |
770 | return 0; |
771 | } else | |
772 | return __mutex_lock_killable_slowpath(lock); | |
ad776537 LH |
773 | } |
774 | EXPORT_SYMBOL(mutex_lock_killable); | |
775 | ||
22d9fd34 | 776 | __visible void __sched |
e4564f79 PZ |
777 | __mutex_lock_slowpath(atomic_t *lock_count) |
778 | { | |
779 | struct mutex *lock = container_of(lock_count, struct mutex, count); | |
780 | ||
040a0a37 | 781 | __mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, 0, |
b0267507 | 782 | NULL, _RET_IP_, NULL, 0); |
e4564f79 PZ |
783 | } |
784 | ||
7ad5b3a5 | 785 | static noinline int __sched |
a41b56ef | 786 | __mutex_lock_killable_slowpath(struct mutex *lock) |
ad776537 | 787 | { |
040a0a37 | 788 | return __mutex_lock_common(lock, TASK_KILLABLE, 0, |
b0267507 | 789 | NULL, _RET_IP_, NULL, 0); |
ad776537 LH |
790 | } |
791 | ||
7ad5b3a5 | 792 | static noinline int __sched |
a41b56ef | 793 | __mutex_lock_interruptible_slowpath(struct mutex *lock) |
6053ee3b | 794 | { |
040a0a37 | 795 | return __mutex_lock_common(lock, TASK_INTERRUPTIBLE, 0, |
b0267507 | 796 | NULL, _RET_IP_, NULL, 0); |
040a0a37 ML |
797 | } |
798 | ||
799 | static noinline int __sched | |
800 | __ww_mutex_lock_slowpath(struct ww_mutex *lock, struct ww_acquire_ctx *ctx) | |
801 | { | |
802 | return __mutex_lock_common(&lock->base, TASK_UNINTERRUPTIBLE, 0, | |
b0267507 | 803 | NULL, _RET_IP_, ctx, 1); |
6053ee3b | 804 | } |
040a0a37 ML |
805 | |
806 | static noinline int __sched | |
807 | __ww_mutex_lock_interruptible_slowpath(struct ww_mutex *lock, | |
808 | struct ww_acquire_ctx *ctx) | |
809 | { | |
810 | return __mutex_lock_common(&lock->base, TASK_INTERRUPTIBLE, 0, | |
b0267507 | 811 | NULL, _RET_IP_, ctx, 1); |
040a0a37 ML |
812 | } |
813 | ||
e4564f79 | 814 | #endif |
6053ee3b IM |
815 | |
816 | /* | |
817 | * Spinlock based trylock, we take the spinlock and check whether we | |
818 | * can get the lock: | |
819 | */ | |
820 | static inline int __mutex_trylock_slowpath(atomic_t *lock_count) | |
821 | { | |
822 | struct mutex *lock = container_of(lock_count, struct mutex, count); | |
1fb00c6c | 823 | unsigned long flags; |
6053ee3b IM |
824 | int prev; |
825 | ||
1fb00c6c | 826 | spin_lock_mutex(&lock->wait_lock, flags); |
6053ee3b IM |
827 | |
828 | prev = atomic_xchg(&lock->count, -1); | |
ef5d4707 | 829 | if (likely(prev == 1)) { |
0d66bf6d | 830 | mutex_set_owner(lock); |
ef5d4707 IM |
831 | mutex_acquire(&lock->dep_map, 0, 1, _RET_IP_); |
832 | } | |
0d66bf6d | 833 | |
6053ee3b IM |
834 | /* Set it back to 0 if there are no waiters: */ |
835 | if (likely(list_empty(&lock->wait_list))) | |
836 | atomic_set(&lock->count, 0); | |
837 | ||
1fb00c6c | 838 | spin_unlock_mutex(&lock->wait_lock, flags); |
6053ee3b IM |
839 | |
840 | return prev == 1; | |
841 | } | |
842 | ||
ef5dc121 RD |
843 | /** |
844 | * mutex_trylock - try to acquire the mutex, without waiting | |
6053ee3b IM |
845 | * @lock: the mutex to be acquired |
846 | * | |
847 | * Try to acquire the mutex atomically. Returns 1 if the mutex | |
848 | * has been acquired successfully, and 0 on contention. | |
849 | * | |
850 | * NOTE: this function follows the spin_trylock() convention, so | |
ef5dc121 | 851 | * it is negated from the down_trylock() return values! Be careful |
6053ee3b IM |
852 | * about this when converting semaphore users to mutexes. |
853 | * | |
854 | * This function must not be used in interrupt context. The | |
855 | * mutex must be released by the same task that acquired it. | |
856 | */ | |
7ad5b3a5 | 857 | int __sched mutex_trylock(struct mutex *lock) |
6053ee3b | 858 | { |
0d66bf6d PZ |
859 | int ret; |
860 | ||
861 | ret = __mutex_fastpath_trylock(&lock->count, __mutex_trylock_slowpath); | |
862 | if (ret) | |
863 | mutex_set_owner(lock); | |
864 | ||
865 | return ret; | |
6053ee3b | 866 | } |
6053ee3b | 867 | EXPORT_SYMBOL(mutex_trylock); |
a511e3f9 | 868 | |
040a0a37 ML |
869 | #ifndef CONFIG_DEBUG_LOCK_ALLOC |
870 | int __sched | |
871 | __ww_mutex_lock(struct ww_mutex *lock, struct ww_acquire_ctx *ctx) | |
872 | { | |
873 | int ret; | |
874 | ||
875 | might_sleep(); | |
876 | ||
877 | ret = __mutex_fastpath_lock_retval(&lock->base.count); | |
878 | ||
879 | if (likely(!ret)) { | |
880 | ww_mutex_set_context_fastpath(lock, ctx); | |
881 | mutex_set_owner(&lock->base); | |
882 | } else | |
883 | ret = __ww_mutex_lock_slowpath(lock, ctx); | |
884 | return ret; | |
885 | } | |
886 | EXPORT_SYMBOL(__ww_mutex_lock); | |
887 | ||
888 | int __sched | |
889 | __ww_mutex_lock_interruptible(struct ww_mutex *lock, struct ww_acquire_ctx *ctx) | |
890 | { | |
891 | int ret; | |
892 | ||
893 | might_sleep(); | |
894 | ||
895 | ret = __mutex_fastpath_lock_retval(&lock->base.count); | |
896 | ||
897 | if (likely(!ret)) { | |
898 | ww_mutex_set_context_fastpath(lock, ctx); | |
899 | mutex_set_owner(&lock->base); | |
900 | } else | |
901 | ret = __ww_mutex_lock_interruptible_slowpath(lock, ctx); | |
902 | return ret; | |
903 | } | |
904 | EXPORT_SYMBOL(__ww_mutex_lock_interruptible); | |
905 | ||
906 | #endif | |
907 | ||
a511e3f9 AM |
908 | /** |
909 | * atomic_dec_and_mutex_lock - return holding mutex if we dec to 0 | |
910 | * @cnt: the atomic which we are to dec | |
911 | * @lock: the mutex to return holding if we dec to 0 | |
912 | * | |
913 | * return true and hold lock if we dec to 0, return false otherwise | |
914 | */ | |
915 | int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock) | |
916 | { | |
917 | /* dec if we can't possibly hit 0 */ | |
918 | if (atomic_add_unless(cnt, -1, 1)) | |
919 | return 0; | |
920 | /* we might hit 0, so take the lock */ | |
921 | mutex_lock(lock); | |
922 | if (!atomic_dec_and_test(cnt)) { | |
923 | /* when we actually did the dec, we didn't hit 0 */ | |
924 | mutex_unlock(lock); | |
925 | return 0; | |
926 | } | |
927 | /* we hit 0, and we hold the lock */ | |
928 | return 1; | |
929 | } | |
930 | EXPORT_SYMBOL(atomic_dec_and_mutex_lock); |