Commit | Line | Data |
---|---|---|
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 | ||
ef5d4707 IM |
49 | void |
50 | __mutex_init(struct mutex *lock, const char *name, struct lock_class_key *key) | |
6053ee3b IM |
51 | { |
52 | atomic_set(&lock->count, 1); | |
53 | spin_lock_init(&lock->wait_lock); | |
54 | INIT_LIST_HEAD(&lock->wait_list); | |
0d66bf6d | 55 | mutex_clear_owner(lock); |
2bd2c92c | 56 | #ifdef CONFIG_MUTEX_SPIN_ON_OWNER |
4d9d951e | 57 | osq_lock_init(&lock->osq); |
2bd2c92c | 58 | #endif |
6053ee3b | 59 | |
ef5d4707 | 60 | debug_mutex_init(lock, name, key); |
6053ee3b IM |
61 | } |
62 | ||
63 | EXPORT_SYMBOL(__mutex_init); | |
64 | ||
e4564f79 | 65 | #ifndef CONFIG_DEBUG_LOCK_ALLOC |
6053ee3b IM |
66 | /* |
67 | * We split the mutex lock/unlock logic into separate fastpath and | |
68 | * slowpath functions, to reduce the register pressure on the fastpath. | |
69 | * We also put the fastpath first in the kernel image, to make sure the | |
70 | * branch is predicted by the CPU as default-untaken. | |
71 | */ | |
22d9fd34 | 72 | __visible void __sched __mutex_lock_slowpath(atomic_t *lock_count); |
6053ee3b | 73 | |
ef5dc121 | 74 | /** |
6053ee3b IM |
75 | * mutex_lock - acquire the mutex |
76 | * @lock: the mutex to be acquired | |
77 | * | |
78 | * Lock the mutex exclusively for this task. If the mutex is not | |
79 | * available right now, it will sleep until it can get it. | |
80 | * | |
81 | * The mutex must later on be released by the same task that | |
82 | * acquired it. Recursive locking is not allowed. The task | |
83 | * may not exit without first unlocking the mutex. Also, kernel | |
84 | * memory where the mutex resides mutex must not be freed with | |
85 | * the mutex still locked. The mutex must first be initialized | |
86 | * (or statically defined) before it can be locked. memset()-ing | |
87 | * the mutex to 0 is not allowed. | |
88 | * | |
89 | * ( The CONFIG_DEBUG_MUTEXES .config option turns on debugging | |
90 | * checks that will enforce the restrictions and will also do | |
91 | * deadlock debugging. ) | |
92 | * | |
93 | * This function is similar to (but not equivalent to) down(). | |
94 | */ | |
b09d2501 | 95 | void __sched mutex_lock(struct mutex *lock) |
6053ee3b | 96 | { |
c544bdb1 | 97 | might_sleep(); |
6053ee3b IM |
98 | /* |
99 | * The locking fastpath is the 1->0 transition from | |
100 | * 'unlocked' into 'locked' state. | |
6053ee3b IM |
101 | */ |
102 | __mutex_fastpath_lock(&lock->count, __mutex_lock_slowpath); | |
0d66bf6d | 103 | mutex_set_owner(lock); |
6053ee3b IM |
104 | } |
105 | ||
106 | EXPORT_SYMBOL(mutex_lock); | |
e4564f79 | 107 | #endif |
6053ee3b | 108 | |
41fcb9f2 | 109 | #ifdef CONFIG_MUTEX_SPIN_ON_OWNER |
2bd2c92c WL |
110 | /* |
111 | * In order to avoid a stampede of mutex spinners from acquiring the mutex | |
112 | * more or less simultaneously, the spinners need to acquire a MCS lock | |
113 | * first before spinning on the owner field. | |
114 | * | |
2bd2c92c | 115 | */ |
2bd2c92c | 116 | |
41fcb9f2 WL |
117 | /* |
118 | * Mutex spinning code migrated from kernel/sched/core.c | |
119 | */ | |
120 | ||
121 | static inline bool owner_running(struct mutex *lock, struct task_struct *owner) | |
122 | { | |
123 | if (lock->owner != owner) | |
124 | return false; | |
125 | ||
126 | /* | |
127 | * Ensure we emit the owner->on_cpu, dereference _after_ checking | |
128 | * lock->owner still matches owner, if that fails, owner might | |
129 | * point to free()d memory, if it still matches, the rcu_read_lock() | |
130 | * ensures the memory stays valid. | |
131 | */ | |
132 | barrier(); | |
133 | ||
134 | return owner->on_cpu; | |
135 | } | |
136 | ||
137 | /* | |
138 | * Look out! "owner" is an entirely speculative pointer | |
139 | * access and not reliable. | |
140 | */ | |
141 | static noinline | |
142 | int mutex_spin_on_owner(struct mutex *lock, struct task_struct *owner) | |
143 | { | |
144 | rcu_read_lock(); | |
145 | while (owner_running(lock, owner)) { | |
146 | if (need_resched()) | |
147 | break; | |
148 | ||
3a6bfbc9 | 149 | cpu_relax_lowlatency(); |
41fcb9f2 WL |
150 | } |
151 | rcu_read_unlock(); | |
152 | ||
153 | /* | |
154 | * We break out the loop above on need_resched() and when the | |
155 | * owner changed, which is a sign for heavy contention. Return | |
156 | * success only when lock->owner is NULL. | |
157 | */ | |
158 | return lock->owner == NULL; | |
159 | } | |
2bd2c92c WL |
160 | |
161 | /* | |
162 | * Initial check for entering the mutex spinning loop | |
163 | */ | |
164 | static inline int mutex_can_spin_on_owner(struct mutex *lock) | |
165 | { | |
1e40c2ed | 166 | struct task_struct *owner; |
2bd2c92c WL |
167 | int retval = 1; |
168 | ||
46af29e4 JL |
169 | if (need_resched()) |
170 | return 0; | |
171 | ||
2bd2c92c | 172 | rcu_read_lock(); |
1e40c2ed PZ |
173 | owner = ACCESS_ONCE(lock->owner); |
174 | if (owner) | |
175 | retval = owner->on_cpu; | |
2bd2c92c WL |
176 | rcu_read_unlock(); |
177 | /* | |
178 | * if lock->owner is not set, the mutex owner may have just acquired | |
179 | * it and not set the owner yet or the mutex has been released. | |
180 | */ | |
181 | return retval; | |
182 | } | |
41fcb9f2 WL |
183 | #endif |
184 | ||
22d9fd34 AK |
185 | __visible __used noinline |
186 | void __sched __mutex_unlock_slowpath(atomic_t *lock_count); | |
6053ee3b | 187 | |
ef5dc121 | 188 | /** |
6053ee3b IM |
189 | * mutex_unlock - release the mutex |
190 | * @lock: the mutex to be released | |
191 | * | |
192 | * Unlock a mutex that has been locked by this task previously. | |
193 | * | |
194 | * This function must not be used in interrupt context. Unlocking | |
195 | * of a not locked mutex is not allowed. | |
196 | * | |
197 | * This function is similar to (but not equivalent to) up(). | |
198 | */ | |
7ad5b3a5 | 199 | void __sched mutex_unlock(struct mutex *lock) |
6053ee3b IM |
200 | { |
201 | /* | |
202 | * The unlocking fastpath is the 0->1 transition from 'locked' | |
203 | * into 'unlocked' state: | |
6053ee3b | 204 | */ |
0d66bf6d PZ |
205 | #ifndef CONFIG_DEBUG_MUTEXES |
206 | /* | |
207 | * When debugging is enabled we must not clear the owner before time, | |
208 | * the slow path will always be taken, and that clears the owner field | |
209 | * after verifying that it was indeed current. | |
210 | */ | |
211 | mutex_clear_owner(lock); | |
212 | #endif | |
6053ee3b IM |
213 | __mutex_fastpath_unlock(&lock->count, __mutex_unlock_slowpath); |
214 | } | |
215 | ||
216 | EXPORT_SYMBOL(mutex_unlock); | |
217 | ||
040a0a37 ML |
218 | /** |
219 | * ww_mutex_unlock - release the w/w mutex | |
220 | * @lock: the mutex to be released | |
221 | * | |
222 | * Unlock a mutex that has been locked by this task previously with any of the | |
223 | * ww_mutex_lock* functions (with or without an acquire context). It is | |
224 | * forbidden to release the locks after releasing the acquire context. | |
225 | * | |
226 | * This function must not be used in interrupt context. Unlocking | |
227 | * of a unlocked mutex is not allowed. | |
228 | */ | |
229 | void __sched ww_mutex_unlock(struct ww_mutex *lock) | |
230 | { | |
231 | /* | |
232 | * The unlocking fastpath is the 0->1 transition from 'locked' | |
233 | * into 'unlocked' state: | |
234 | */ | |
235 | if (lock->ctx) { | |
236 | #ifdef CONFIG_DEBUG_MUTEXES | |
237 | DEBUG_LOCKS_WARN_ON(!lock->ctx->acquired); | |
238 | #endif | |
239 | if (lock->ctx->acquired > 0) | |
240 | lock->ctx->acquired--; | |
241 | lock->ctx = NULL; | |
242 | } | |
243 | ||
244 | #ifndef CONFIG_DEBUG_MUTEXES | |
245 | /* | |
246 | * When debugging is enabled we must not clear the owner before time, | |
247 | * the slow path will always be taken, and that clears the owner field | |
248 | * after verifying that it was indeed current. | |
249 | */ | |
250 | mutex_clear_owner(&lock->base); | |
251 | #endif | |
252 | __mutex_fastpath_unlock(&lock->base.count, __mutex_unlock_slowpath); | |
253 | } | |
254 | EXPORT_SYMBOL(ww_mutex_unlock); | |
255 | ||
256 | static inline int __sched | |
257 | __mutex_lock_check_stamp(struct mutex *lock, struct ww_acquire_ctx *ctx) | |
258 | { | |
259 | struct ww_mutex *ww = container_of(lock, struct ww_mutex, base); | |
260 | struct ww_acquire_ctx *hold_ctx = ACCESS_ONCE(ww->ctx); | |
261 | ||
262 | if (!hold_ctx) | |
263 | return 0; | |
264 | ||
265 | if (unlikely(ctx == hold_ctx)) | |
266 | return -EALREADY; | |
267 | ||
268 | if (ctx->stamp - hold_ctx->stamp <= LONG_MAX && | |
269 | (ctx->stamp != hold_ctx->stamp || ctx > hold_ctx)) { | |
270 | #ifdef CONFIG_DEBUG_MUTEXES | |
271 | DEBUG_LOCKS_WARN_ON(ctx->contending_lock); | |
272 | ctx->contending_lock = ww; | |
273 | #endif | |
274 | return -EDEADLK; | |
275 | } | |
276 | ||
277 | return 0; | |
278 | } | |
279 | ||
280 | static __always_inline void ww_mutex_lock_acquired(struct ww_mutex *ww, | |
281 | struct ww_acquire_ctx *ww_ctx) | |
282 | { | |
283 | #ifdef CONFIG_DEBUG_MUTEXES | |
284 | /* | |
285 | * If this WARN_ON triggers, you used ww_mutex_lock to acquire, | |
286 | * but released with a normal mutex_unlock in this call. | |
287 | * | |
288 | * This should never happen, always use ww_mutex_unlock. | |
289 | */ | |
290 | DEBUG_LOCKS_WARN_ON(ww->ctx); | |
291 | ||
292 | /* | |
293 | * Not quite done after calling ww_acquire_done() ? | |
294 | */ | |
295 | DEBUG_LOCKS_WARN_ON(ww_ctx->done_acquire); | |
296 | ||
297 | if (ww_ctx->contending_lock) { | |
298 | /* | |
299 | * After -EDEADLK you tried to | |
300 | * acquire a different ww_mutex? Bad! | |
301 | */ | |
302 | DEBUG_LOCKS_WARN_ON(ww_ctx->contending_lock != ww); | |
303 | ||
304 | /* | |
305 | * You called ww_mutex_lock after receiving -EDEADLK, | |
306 | * but 'forgot' to unlock everything else first? | |
307 | */ | |
308 | DEBUG_LOCKS_WARN_ON(ww_ctx->acquired > 0); | |
309 | ww_ctx->contending_lock = NULL; | |
310 | } | |
311 | ||
312 | /* | |
313 | * Naughty, using a different class will lead to undefined behavior! | |
314 | */ | |
315 | DEBUG_LOCKS_WARN_ON(ww_ctx->ww_class != ww->ww_class); | |
316 | #endif | |
317 | ww_ctx->acquired++; | |
318 | } | |
319 | ||
320 | /* | |
321 | * after acquiring lock with fastpath or when we lost out in contested | |
322 | * slowpath, set ctx and wake up any waiters so they can recheck. | |
323 | * | |
324 | * This function is never called when CONFIG_DEBUG_LOCK_ALLOC is set, | |
325 | * as the fastpath and opportunistic spinning are disabled in that case. | |
326 | */ | |
327 | static __always_inline void | |
328 | ww_mutex_set_context_fastpath(struct ww_mutex *lock, | |
329 | struct ww_acquire_ctx *ctx) | |
330 | { | |
331 | unsigned long flags; | |
332 | struct mutex_waiter *cur; | |
333 | ||
334 | ww_mutex_lock_acquired(lock, ctx); | |
335 | ||
336 | lock->ctx = ctx; | |
337 | ||
338 | /* | |
339 | * The lock->ctx update should be visible on all cores before | |
340 | * the atomic read is done, otherwise contended waiters might be | |
341 | * missed. The contended waiters will either see ww_ctx == NULL | |
342 | * and keep spinning, or it will acquire wait_lock, add itself | |
343 | * to waiter list and sleep. | |
344 | */ | |
345 | smp_mb(); /* ^^^ */ | |
346 | ||
347 | /* | |
348 | * Check if lock is contended, if not there is nobody to wake up | |
349 | */ | |
350 | if (likely(atomic_read(&lock->base.count) == 0)) | |
351 | return; | |
352 | ||
353 | /* | |
354 | * Uh oh, we raced in fastpath, wake up everyone in this case, | |
355 | * so they can see the new lock->ctx. | |
356 | */ | |
357 | spin_lock_mutex(&lock->base.wait_lock, flags); | |
358 | list_for_each_entry(cur, &lock->base.wait_list, list) { | |
359 | debug_mutex_wake_waiter(&lock->base, cur); | |
360 | wake_up_process(cur->task); | |
361 | } | |
362 | spin_unlock_mutex(&lock->base.wait_lock, flags); | |
363 | } | |
364 | ||
6053ee3b IM |
365 | /* |
366 | * Lock a mutex (possibly interruptible), slowpath: | |
367 | */ | |
040a0a37 | 368 | static __always_inline int __sched |
e4564f79 | 369 | __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass, |
040a0a37 | 370 | struct lockdep_map *nest_lock, unsigned long ip, |
b0267507 | 371 | struct ww_acquire_ctx *ww_ctx, const bool use_ww_ctx) |
6053ee3b IM |
372 | { |
373 | struct task_struct *task = current; | |
374 | struct mutex_waiter waiter; | |
1fb00c6c | 375 | unsigned long flags; |
040a0a37 | 376 | int ret; |
6053ee3b | 377 | |
41719b03 | 378 | preempt_disable(); |
e4c70a66 | 379 | mutex_acquire_nest(&lock->dep_map, subclass, 0, nest_lock, ip); |
c0226027 FW |
380 | |
381 | #ifdef CONFIG_MUTEX_SPIN_ON_OWNER | |
0d66bf6d PZ |
382 | /* |
383 | * Optimistic spinning. | |
384 | * | |
0c3c0f0d JL |
385 | * We try to spin for acquisition when we find that the lock owner |
386 | * is currently running on a (different) CPU and while we don't | |
387 | * need to reschedule. The rationale is that if the lock owner is | |
388 | * running, it is likely to release the lock soon. | |
0d66bf6d PZ |
389 | * |
390 | * Since this needs the lock owner, and this mutex implementation | |
391 | * doesn't track the owner atomically in the lock field, we need to | |
392 | * track it non-atomically. | |
393 | * | |
394 | * We can't do this for DEBUG_MUTEXES because that relies on wait_lock | |
395 | * to serialize everything. | |
2bd2c92c WL |
396 | * |
397 | * The mutex spinners are queued up using MCS lock so that only one | |
398 | * spinner can compete for the mutex. However, if mutex spinning isn't | |
399 | * going to happen, there is no point in going through the lock/unlock | |
400 | * overhead. | |
0d66bf6d | 401 | */ |
2bd2c92c WL |
402 | if (!mutex_can_spin_on_owner(lock)) |
403 | goto slowpath; | |
0d66bf6d | 404 | |
fb0527bd PZ |
405 | if (!osq_lock(&lock->osq)) |
406 | goto slowpath; | |
407 | ||
0d66bf6d | 408 | for (;;) { |
c6eb3dda | 409 | struct task_struct *owner; |
0d66bf6d | 410 | |
b0267507 | 411 | if (use_ww_ctx && ww_ctx->acquired > 0) { |
040a0a37 ML |
412 | struct ww_mutex *ww; |
413 | ||
414 | ww = container_of(lock, struct ww_mutex, base); | |
415 | /* | |
416 | * If ww->ctx is set the contents are undefined, only | |
417 | * by acquiring wait_lock there is a guarantee that | |
418 | * they are not invalid when reading. | |
419 | * | |
420 | * As such, when deadlock detection needs to be | |
421 | * performed the optimistic spinning cannot be done. | |
422 | */ | |
423 | if (ACCESS_ONCE(ww->ctx)) | |
47667fa1 | 424 | break; |
040a0a37 ML |
425 | } |
426 | ||
0d66bf6d PZ |
427 | /* |
428 | * If there's an owner, wait for it to either | |
429 | * release the lock or go to sleep. | |
430 | */ | |
431 | owner = ACCESS_ONCE(lock->owner); | |
47667fa1 JL |
432 | if (owner && !mutex_spin_on_owner(lock, owner)) |
433 | break; | |
0d66bf6d | 434 | |
0d968dd8 JL |
435 | /* Try to acquire the mutex if it is unlocked. */ |
436 | if (!mutex_is_locked(lock) && | |
0dc8c730 | 437 | (atomic_cmpxchg(&lock->count, 1, 0) == 1)) { |
ac6e60ee | 438 | lock_acquired(&lock->dep_map, ip); |
b0267507 | 439 | if (use_ww_ctx) { |
040a0a37 ML |
440 | struct ww_mutex *ww; |
441 | ww = container_of(lock, struct ww_mutex, base); | |
442 | ||
443 | ww_mutex_set_context_fastpath(ww, ww_ctx); | |
444 | } | |
445 | ||
ac6e60ee | 446 | mutex_set_owner(lock); |
fb0527bd | 447 | osq_unlock(&lock->osq); |
ac6e60ee CM |
448 | preempt_enable(); |
449 | return 0; | |
450 | } | |
451 | ||
0d66bf6d PZ |
452 | /* |
453 | * When there's no owner, we might have preempted between the | |
454 | * owner acquiring the lock and setting the owner field. If | |
455 | * we're an RT task that will live-lock because we won't let | |
456 | * the owner complete. | |
457 | */ | |
458 | if (!owner && (need_resched() || rt_task(task))) | |
47667fa1 | 459 | break; |
0d66bf6d | 460 | |
0d66bf6d PZ |
461 | /* |
462 | * The cpu_relax() call is a compiler barrier which forces | |
463 | * everything in this loop to be re-loaded. We don't need | |
464 | * memory barriers as we'll eventually observe the right | |
465 | * values at the cost of a few extra spins. | |
466 | */ | |
3a6bfbc9 | 467 | cpu_relax_lowlatency(); |
0d66bf6d | 468 | } |
fb0527bd | 469 | osq_unlock(&lock->osq); |
2bd2c92c | 470 | slowpath: |
34c6bc2c PZ |
471 | /* |
472 | * If we fell out of the spin path because of need_resched(), | |
473 | * reschedule now, before we try-lock the mutex. This avoids getting | |
474 | * scheduled out right after we obtained the mutex. | |
475 | */ | |
476 | if (need_resched()) | |
477 | schedule_preempt_disabled(); | |
0d66bf6d | 478 | #endif |
1fb00c6c | 479 | spin_lock_mutex(&lock->wait_lock, flags); |
6053ee3b | 480 | |
1e820c96 JL |
481 | /* |
482 | * Once more, try to acquire the lock. Only try-lock the mutex if | |
0d968dd8 | 483 | * it is unlocked to reduce unnecessary xchg() operations. |
1e820c96 | 484 | */ |
0d968dd8 | 485 | if (!mutex_is_locked(lock) && (atomic_xchg(&lock->count, 0) == 1)) |
ec83f425 DB |
486 | goto skip_wait; |
487 | ||
9a11b49a | 488 | debug_mutex_lock_common(lock, &waiter); |
c9f4f06d | 489 | debug_mutex_add_waiter(lock, &waiter, task_thread_info(task)); |
6053ee3b IM |
490 | |
491 | /* add waiting tasks to the end of the waitqueue (FIFO): */ | |
492 | list_add_tail(&waiter.list, &lock->wait_list); | |
493 | waiter.task = task; | |
494 | ||
e4564f79 | 495 | lock_contended(&lock->dep_map, ip); |
4fe87745 | 496 | |
6053ee3b IM |
497 | for (;;) { |
498 | /* | |
499 | * Lets try to take the lock again - this is needed even if | |
500 | * we get here for the first time (shortly after failing to | |
501 | * acquire the lock), to make sure that we get a wakeup once | |
502 | * it's unlocked. Later on, if we sleep, this is the | |
503 | * operation that gives us the lock. We xchg it to -1, so | |
504 | * that when we release the lock, we properly wake up the | |
1e820c96 JL |
505 | * other waiters. We only attempt the xchg if the count is |
506 | * non-negative in order to avoid unnecessary xchg operations: | |
6053ee3b | 507 | */ |
1e820c96 | 508 | if (atomic_read(&lock->count) >= 0 && |
ec83f425 | 509 | (atomic_xchg(&lock->count, -1) == 1)) |
6053ee3b IM |
510 | break; |
511 | ||
512 | /* | |
513 | * got a signal? (This code gets eliminated in the | |
514 | * TASK_UNINTERRUPTIBLE case.) | |
515 | */ | |
6ad36762 | 516 | if (unlikely(signal_pending_state(state, task))) { |
040a0a37 ML |
517 | ret = -EINTR; |
518 | goto err; | |
519 | } | |
6053ee3b | 520 | |
b0267507 | 521 | if (use_ww_ctx && ww_ctx->acquired > 0) { |
040a0a37 ML |
522 | ret = __mutex_lock_check_stamp(lock, ww_ctx); |
523 | if (ret) | |
524 | goto err; | |
6053ee3b | 525 | } |
040a0a37 | 526 | |
6053ee3b IM |
527 | __set_task_state(task, state); |
528 | ||
25985edc | 529 | /* didn't get the lock, go to sleep: */ |
1fb00c6c | 530 | spin_unlock_mutex(&lock->wait_lock, flags); |
bd2f5536 | 531 | schedule_preempt_disabled(); |
1fb00c6c | 532 | spin_lock_mutex(&lock->wait_lock, flags); |
6053ee3b | 533 | } |
ec83f425 DB |
534 | mutex_remove_waiter(lock, &waiter, current_thread_info()); |
535 | /* set it to 0 if there are no waiters left: */ | |
536 | if (likely(list_empty(&lock->wait_list))) | |
537 | atomic_set(&lock->count, 0); | |
538 | debug_mutex_free_waiter(&waiter); | |
6053ee3b | 539 | |
ec83f425 DB |
540 | skip_wait: |
541 | /* got the lock - cleanup and rejoice! */ | |
c7e78cff | 542 | lock_acquired(&lock->dep_map, ip); |
0d66bf6d | 543 | mutex_set_owner(lock); |
6053ee3b | 544 | |
b0267507 | 545 | if (use_ww_ctx) { |
ec83f425 | 546 | struct ww_mutex *ww = container_of(lock, struct ww_mutex, base); |
040a0a37 ML |
547 | struct mutex_waiter *cur; |
548 | ||
549 | /* | |
550 | * This branch gets optimized out for the common case, | |
551 | * and is only important for ww_mutex_lock. | |
552 | */ | |
040a0a37 ML |
553 | ww_mutex_lock_acquired(ww, ww_ctx); |
554 | ww->ctx = ww_ctx; | |
555 | ||
556 | /* | |
557 | * Give any possible sleeping processes the chance to wake up, | |
558 | * so they can recheck if they have to back off. | |
559 | */ | |
560 | list_for_each_entry(cur, &lock->wait_list, list) { | |
561 | debug_mutex_wake_waiter(lock, cur); | |
562 | wake_up_process(cur->task); | |
563 | } | |
564 | } | |
565 | ||
1fb00c6c | 566 | spin_unlock_mutex(&lock->wait_lock, flags); |
41719b03 | 567 | preempt_enable(); |
6053ee3b | 568 | return 0; |
040a0a37 ML |
569 | |
570 | err: | |
571 | mutex_remove_waiter(lock, &waiter, task_thread_info(task)); | |
572 | spin_unlock_mutex(&lock->wait_lock, flags); | |
573 | debug_mutex_free_waiter(&waiter); | |
574 | mutex_release(&lock->dep_map, 1, ip); | |
575 | preempt_enable(); | |
576 | return ret; | |
6053ee3b IM |
577 | } |
578 | ||
ef5d4707 IM |
579 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
580 | void __sched | |
581 | mutex_lock_nested(struct mutex *lock, unsigned int subclass) | |
582 | { | |
583 | might_sleep(); | |
040a0a37 | 584 | __mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, |
b0267507 | 585 | subclass, NULL, _RET_IP_, NULL, 0); |
ef5d4707 IM |
586 | } |
587 | ||
588 | EXPORT_SYMBOL_GPL(mutex_lock_nested); | |
d63a5a74 | 589 | |
e4c70a66 PZ |
590 | void __sched |
591 | _mutex_lock_nest_lock(struct mutex *lock, struct lockdep_map *nest) | |
592 | { | |
593 | might_sleep(); | |
040a0a37 | 594 | __mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, |
b0267507 | 595 | 0, nest, _RET_IP_, NULL, 0); |
e4c70a66 PZ |
596 | } |
597 | ||
598 | EXPORT_SYMBOL_GPL(_mutex_lock_nest_lock); | |
599 | ||
ad776537 LH |
600 | int __sched |
601 | mutex_lock_killable_nested(struct mutex *lock, unsigned int subclass) | |
602 | { | |
603 | might_sleep(); | |
040a0a37 | 604 | return __mutex_lock_common(lock, TASK_KILLABLE, |
b0267507 | 605 | subclass, NULL, _RET_IP_, NULL, 0); |
ad776537 LH |
606 | } |
607 | EXPORT_SYMBOL_GPL(mutex_lock_killable_nested); | |
608 | ||
d63a5a74 N |
609 | int __sched |
610 | mutex_lock_interruptible_nested(struct mutex *lock, unsigned int subclass) | |
611 | { | |
612 | might_sleep(); | |
0d66bf6d | 613 | return __mutex_lock_common(lock, TASK_INTERRUPTIBLE, |
b0267507 | 614 | subclass, NULL, _RET_IP_, NULL, 0); |
d63a5a74 N |
615 | } |
616 | ||
617 | EXPORT_SYMBOL_GPL(mutex_lock_interruptible_nested); | |
040a0a37 | 618 | |
23010027 DV |
619 | static inline int |
620 | ww_mutex_deadlock_injection(struct ww_mutex *lock, struct ww_acquire_ctx *ctx) | |
621 | { | |
622 | #ifdef CONFIG_DEBUG_WW_MUTEX_SLOWPATH | |
623 | unsigned tmp; | |
624 | ||
625 | if (ctx->deadlock_inject_countdown-- == 0) { | |
626 | tmp = ctx->deadlock_inject_interval; | |
627 | if (tmp > UINT_MAX/4) | |
628 | tmp = UINT_MAX; | |
629 | else | |
630 | tmp = tmp*2 + tmp + tmp/2; | |
631 | ||
632 | ctx->deadlock_inject_interval = tmp; | |
633 | ctx->deadlock_inject_countdown = tmp; | |
634 | ctx->contending_lock = lock; | |
635 | ||
636 | ww_mutex_unlock(lock); | |
637 | ||
638 | return -EDEADLK; | |
639 | } | |
640 | #endif | |
641 | ||
642 | return 0; | |
643 | } | |
040a0a37 ML |
644 | |
645 | int __sched | |
646 | __ww_mutex_lock(struct ww_mutex *lock, struct ww_acquire_ctx *ctx) | |
647 | { | |
23010027 DV |
648 | int ret; |
649 | ||
040a0a37 | 650 | might_sleep(); |
23010027 | 651 | ret = __mutex_lock_common(&lock->base, TASK_UNINTERRUPTIBLE, |
b0267507 | 652 | 0, &ctx->dep_map, _RET_IP_, ctx, 1); |
85f48961 | 653 | if (!ret && ctx->acquired > 1) |
23010027 DV |
654 | return ww_mutex_deadlock_injection(lock, ctx); |
655 | ||
656 | return ret; | |
040a0a37 ML |
657 | } |
658 | EXPORT_SYMBOL_GPL(__ww_mutex_lock); | |
659 | ||
660 | int __sched | |
661 | __ww_mutex_lock_interruptible(struct ww_mutex *lock, struct ww_acquire_ctx *ctx) | |
662 | { | |
23010027 DV |
663 | int ret; |
664 | ||
040a0a37 | 665 | might_sleep(); |
23010027 | 666 | ret = __mutex_lock_common(&lock->base, TASK_INTERRUPTIBLE, |
b0267507 | 667 | 0, &ctx->dep_map, _RET_IP_, ctx, 1); |
23010027 | 668 | |
85f48961 | 669 | if (!ret && ctx->acquired > 1) |
23010027 DV |
670 | return ww_mutex_deadlock_injection(lock, ctx); |
671 | ||
672 | return ret; | |
040a0a37 ML |
673 | } |
674 | EXPORT_SYMBOL_GPL(__ww_mutex_lock_interruptible); | |
675 | ||
ef5d4707 IM |
676 | #endif |
677 | ||
6053ee3b IM |
678 | /* |
679 | * Release the lock, slowpath: | |
680 | */ | |
7ad5b3a5 | 681 | static inline void |
242489cf | 682 | __mutex_unlock_common_slowpath(struct mutex *lock, int nested) |
6053ee3b | 683 | { |
1fb00c6c | 684 | unsigned long flags; |
6053ee3b | 685 | |
6053ee3b IM |
686 | /* |
687 | * some architectures leave the lock unlocked in the fastpath failure | |
688 | * case, others need to leave it locked. In the later case we have to | |
689 | * unlock it here | |
690 | */ | |
691 | if (__mutex_slowpath_needs_to_unlock()) | |
692 | atomic_set(&lock->count, 1); | |
693 | ||
1d8fe7dc JL |
694 | spin_lock_mutex(&lock->wait_lock, flags); |
695 | mutex_release(&lock->dep_map, nested, _RET_IP_); | |
696 | debug_mutex_unlock(lock); | |
697 | ||
6053ee3b IM |
698 | if (!list_empty(&lock->wait_list)) { |
699 | /* get the first entry from the wait-list: */ | |
700 | struct mutex_waiter *waiter = | |
701 | list_entry(lock->wait_list.next, | |
702 | struct mutex_waiter, list); | |
703 | ||
704 | debug_mutex_wake_waiter(lock, waiter); | |
705 | ||
706 | wake_up_process(waiter->task); | |
707 | } | |
708 | ||
1fb00c6c | 709 | spin_unlock_mutex(&lock->wait_lock, flags); |
6053ee3b IM |
710 | } |
711 | ||
9a11b49a IM |
712 | /* |
713 | * Release the lock, slowpath: | |
714 | */ | |
22d9fd34 | 715 | __visible void |
9a11b49a IM |
716 | __mutex_unlock_slowpath(atomic_t *lock_count) |
717 | { | |
242489cf DB |
718 | struct mutex *lock = container_of(lock_count, struct mutex, count); |
719 | ||
720 | __mutex_unlock_common_slowpath(lock, 1); | |
9a11b49a IM |
721 | } |
722 | ||
e4564f79 | 723 | #ifndef CONFIG_DEBUG_LOCK_ALLOC |
6053ee3b IM |
724 | /* |
725 | * Here come the less common (and hence less performance-critical) APIs: | |
726 | * mutex_lock_interruptible() and mutex_trylock(). | |
727 | */ | |
7ad5b3a5 | 728 | static noinline int __sched |
a41b56ef | 729 | __mutex_lock_killable_slowpath(struct mutex *lock); |
ad776537 | 730 | |
7ad5b3a5 | 731 | static noinline int __sched |
a41b56ef | 732 | __mutex_lock_interruptible_slowpath(struct mutex *lock); |
6053ee3b | 733 | |
ef5dc121 RD |
734 | /** |
735 | * mutex_lock_interruptible - acquire the mutex, interruptible | |
6053ee3b IM |
736 | * @lock: the mutex to be acquired |
737 | * | |
738 | * Lock the mutex like mutex_lock(), and return 0 if the mutex has | |
739 | * been acquired or sleep until the mutex becomes available. If a | |
740 | * signal arrives while waiting for the lock then this function | |
741 | * returns -EINTR. | |
742 | * | |
743 | * This function is similar to (but not equivalent to) down_interruptible(). | |
744 | */ | |
7ad5b3a5 | 745 | int __sched mutex_lock_interruptible(struct mutex *lock) |
6053ee3b | 746 | { |
0d66bf6d PZ |
747 | int ret; |
748 | ||
c544bdb1 | 749 | might_sleep(); |
a41b56ef ML |
750 | ret = __mutex_fastpath_lock_retval(&lock->count); |
751 | if (likely(!ret)) { | |
0d66bf6d | 752 | mutex_set_owner(lock); |
a41b56ef ML |
753 | return 0; |
754 | } else | |
755 | return __mutex_lock_interruptible_slowpath(lock); | |
6053ee3b IM |
756 | } |
757 | ||
758 | EXPORT_SYMBOL(mutex_lock_interruptible); | |
759 | ||
7ad5b3a5 | 760 | int __sched mutex_lock_killable(struct mutex *lock) |
ad776537 | 761 | { |
0d66bf6d PZ |
762 | int ret; |
763 | ||
ad776537 | 764 | might_sleep(); |
a41b56ef ML |
765 | ret = __mutex_fastpath_lock_retval(&lock->count); |
766 | if (likely(!ret)) { | |
0d66bf6d | 767 | mutex_set_owner(lock); |
a41b56ef ML |
768 | return 0; |
769 | } else | |
770 | return __mutex_lock_killable_slowpath(lock); | |
ad776537 LH |
771 | } |
772 | EXPORT_SYMBOL(mutex_lock_killable); | |
773 | ||
22d9fd34 | 774 | __visible void __sched |
e4564f79 PZ |
775 | __mutex_lock_slowpath(atomic_t *lock_count) |
776 | { | |
777 | struct mutex *lock = container_of(lock_count, struct mutex, count); | |
778 | ||
040a0a37 | 779 | __mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, 0, |
b0267507 | 780 | NULL, _RET_IP_, NULL, 0); |
e4564f79 PZ |
781 | } |
782 | ||
7ad5b3a5 | 783 | static noinline int __sched |
a41b56ef | 784 | __mutex_lock_killable_slowpath(struct mutex *lock) |
ad776537 | 785 | { |
040a0a37 | 786 | return __mutex_lock_common(lock, TASK_KILLABLE, 0, |
b0267507 | 787 | NULL, _RET_IP_, NULL, 0); |
ad776537 LH |
788 | } |
789 | ||
7ad5b3a5 | 790 | static noinline int __sched |
a41b56ef | 791 | __mutex_lock_interruptible_slowpath(struct mutex *lock) |
6053ee3b | 792 | { |
040a0a37 | 793 | return __mutex_lock_common(lock, TASK_INTERRUPTIBLE, 0, |
b0267507 | 794 | NULL, _RET_IP_, NULL, 0); |
040a0a37 ML |
795 | } |
796 | ||
797 | static noinline int __sched | |
798 | __ww_mutex_lock_slowpath(struct ww_mutex *lock, struct ww_acquire_ctx *ctx) | |
799 | { | |
800 | return __mutex_lock_common(&lock->base, TASK_UNINTERRUPTIBLE, 0, | |
b0267507 | 801 | NULL, _RET_IP_, ctx, 1); |
6053ee3b | 802 | } |
040a0a37 ML |
803 | |
804 | static noinline int __sched | |
805 | __ww_mutex_lock_interruptible_slowpath(struct ww_mutex *lock, | |
806 | struct ww_acquire_ctx *ctx) | |
807 | { | |
808 | return __mutex_lock_common(&lock->base, TASK_INTERRUPTIBLE, 0, | |
b0267507 | 809 | NULL, _RET_IP_, ctx, 1); |
040a0a37 ML |
810 | } |
811 | ||
e4564f79 | 812 | #endif |
6053ee3b IM |
813 | |
814 | /* | |
815 | * Spinlock based trylock, we take the spinlock and check whether we | |
816 | * can get the lock: | |
817 | */ | |
818 | static inline int __mutex_trylock_slowpath(atomic_t *lock_count) | |
819 | { | |
820 | struct mutex *lock = container_of(lock_count, struct mutex, count); | |
1fb00c6c | 821 | unsigned long flags; |
6053ee3b IM |
822 | int prev; |
823 | ||
72d5305d JL |
824 | /* No need to trylock if the mutex is locked. */ |
825 | if (mutex_is_locked(lock)) | |
826 | return 0; | |
827 | ||
1fb00c6c | 828 | spin_lock_mutex(&lock->wait_lock, flags); |
6053ee3b IM |
829 | |
830 | prev = atomic_xchg(&lock->count, -1); | |
ef5d4707 | 831 | if (likely(prev == 1)) { |
0d66bf6d | 832 | mutex_set_owner(lock); |
ef5d4707 IM |
833 | mutex_acquire(&lock->dep_map, 0, 1, _RET_IP_); |
834 | } | |
0d66bf6d | 835 | |
6053ee3b IM |
836 | /* Set it back to 0 if there are no waiters: */ |
837 | if (likely(list_empty(&lock->wait_list))) | |
838 | atomic_set(&lock->count, 0); | |
839 | ||
1fb00c6c | 840 | spin_unlock_mutex(&lock->wait_lock, flags); |
6053ee3b IM |
841 | |
842 | return prev == 1; | |
843 | } | |
844 | ||
ef5dc121 RD |
845 | /** |
846 | * mutex_trylock - try to acquire the mutex, without waiting | |
6053ee3b IM |
847 | * @lock: the mutex to be acquired |
848 | * | |
849 | * Try to acquire the mutex atomically. Returns 1 if the mutex | |
850 | * has been acquired successfully, and 0 on contention. | |
851 | * | |
852 | * NOTE: this function follows the spin_trylock() convention, so | |
ef5dc121 | 853 | * it is negated from the down_trylock() return values! Be careful |
6053ee3b IM |
854 | * about this when converting semaphore users to mutexes. |
855 | * | |
856 | * This function must not be used in interrupt context. The | |
857 | * mutex must be released by the same task that acquired it. | |
858 | */ | |
7ad5b3a5 | 859 | int __sched mutex_trylock(struct mutex *lock) |
6053ee3b | 860 | { |
0d66bf6d PZ |
861 | int ret; |
862 | ||
863 | ret = __mutex_fastpath_trylock(&lock->count, __mutex_trylock_slowpath); | |
864 | if (ret) | |
865 | mutex_set_owner(lock); | |
866 | ||
867 | return ret; | |
6053ee3b | 868 | } |
6053ee3b | 869 | EXPORT_SYMBOL(mutex_trylock); |
a511e3f9 | 870 | |
040a0a37 ML |
871 | #ifndef CONFIG_DEBUG_LOCK_ALLOC |
872 | int __sched | |
873 | __ww_mutex_lock(struct ww_mutex *lock, struct ww_acquire_ctx *ctx) | |
874 | { | |
875 | int ret; | |
876 | ||
877 | might_sleep(); | |
878 | ||
879 | ret = __mutex_fastpath_lock_retval(&lock->base.count); | |
880 | ||
881 | if (likely(!ret)) { | |
882 | ww_mutex_set_context_fastpath(lock, ctx); | |
883 | mutex_set_owner(&lock->base); | |
884 | } else | |
885 | ret = __ww_mutex_lock_slowpath(lock, ctx); | |
886 | return ret; | |
887 | } | |
888 | EXPORT_SYMBOL(__ww_mutex_lock); | |
889 | ||
890 | int __sched | |
891 | __ww_mutex_lock_interruptible(struct ww_mutex *lock, struct ww_acquire_ctx *ctx) | |
892 | { | |
893 | int ret; | |
894 | ||
895 | might_sleep(); | |
896 | ||
897 | ret = __mutex_fastpath_lock_retval(&lock->base.count); | |
898 | ||
899 | if (likely(!ret)) { | |
900 | ww_mutex_set_context_fastpath(lock, ctx); | |
901 | mutex_set_owner(&lock->base); | |
902 | } else | |
903 | ret = __ww_mutex_lock_interruptible_slowpath(lock, ctx); | |
904 | return ret; | |
905 | } | |
906 | EXPORT_SYMBOL(__ww_mutex_lock_interruptible); | |
907 | ||
908 | #endif | |
909 | ||
a511e3f9 AM |
910 | /** |
911 | * atomic_dec_and_mutex_lock - return holding mutex if we dec to 0 | |
912 | * @cnt: the atomic which we are to dec | |
913 | * @lock: the mutex to return holding if we dec to 0 | |
914 | * | |
915 | * return true and hold lock if we dec to 0, return false otherwise | |
916 | */ | |
917 | int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock) | |
918 | { | |
919 | /* dec if we can't possibly hit 0 */ | |
920 | if (atomic_add_unless(cnt, -1, 1)) | |
921 | return 0; | |
922 | /* we might hit 0, so take the lock */ | |
923 | mutex_lock(lock); | |
924 | if (!atomic_dec_and_test(cnt)) { | |
925 | /* when we actually did the dec, we didn't hit 0 */ | |
926 | mutex_unlock(lock); | |
927 | return 0; | |
928 | } | |
929 | /* we hit 0, and we hold the lock */ | |
930 | return 1; | |
931 | } | |
932 | EXPORT_SYMBOL(atomic_dec_and_mutex_lock); |