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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 | * | |
214e0aed | 18 | * Also see Documentation/locking/mutex-design.txt. |
6053ee3b IM |
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> |
7a215f89 | 28 | #include <linux/osq_lock.h> |
6053ee3b | 29 | |
6053ee3b IM |
30 | #ifdef CONFIG_DEBUG_MUTEXES |
31 | # include "mutex-debug.h" | |
6053ee3b IM |
32 | #else |
33 | # include "mutex.h" | |
6053ee3b IM |
34 | #endif |
35 | ||
ef5d4707 IM |
36 | void |
37 | __mutex_init(struct mutex *lock, const char *name, struct lock_class_key *key) | |
6053ee3b | 38 | { |
3ca0ff57 | 39 | atomic_long_set(&lock->owner, 0); |
6053ee3b IM |
40 | spin_lock_init(&lock->wait_lock); |
41 | INIT_LIST_HEAD(&lock->wait_list); | |
2bd2c92c | 42 | #ifdef CONFIG_MUTEX_SPIN_ON_OWNER |
4d9d951e | 43 | osq_lock_init(&lock->osq); |
2bd2c92c | 44 | #endif |
6053ee3b | 45 | |
ef5d4707 | 46 | debug_mutex_init(lock, name, key); |
6053ee3b | 47 | } |
6053ee3b IM |
48 | EXPORT_SYMBOL(__mutex_init); |
49 | ||
3ca0ff57 PZ |
50 | /* |
51 | * @owner: contains: 'struct task_struct *' to the current lock owner, | |
52 | * NULL means not owned. Since task_struct pointers are aligned at | |
e274795e | 53 | * at least L1_CACHE_BYTES, we have low bits to store extra state. |
3ca0ff57 PZ |
54 | * |
55 | * Bit0 indicates a non-empty waiter list; unlock must issue a wakeup. | |
9d659ae1 | 56 | * Bit1 indicates unlock needs to hand the lock to the top-waiter |
e274795e | 57 | * Bit2 indicates handoff has been done and we're waiting for pickup. |
3ca0ff57 PZ |
58 | */ |
59 | #define MUTEX_FLAG_WAITERS 0x01 | |
9d659ae1 | 60 | #define MUTEX_FLAG_HANDOFF 0x02 |
e274795e | 61 | #define MUTEX_FLAG_PICKUP 0x04 |
3ca0ff57 | 62 | |
e274795e | 63 | #define MUTEX_FLAGS 0x07 |
3ca0ff57 PZ |
64 | |
65 | static inline struct task_struct *__owner_task(unsigned long owner) | |
66 | { | |
67 | return (struct task_struct *)(owner & ~MUTEX_FLAGS); | |
68 | } | |
69 | ||
70 | static inline unsigned long __owner_flags(unsigned long owner) | |
71 | { | |
72 | return owner & MUTEX_FLAGS; | |
73 | } | |
74 | ||
75 | /* | |
e274795e | 76 | * Trylock variant that retuns the owning task on failure. |
3ca0ff57 | 77 | */ |
e274795e | 78 | static inline struct task_struct *__mutex_trylock_or_owner(struct mutex *lock) |
3ca0ff57 PZ |
79 | { |
80 | unsigned long owner, curr = (unsigned long)current; | |
81 | ||
82 | owner = atomic_long_read(&lock->owner); | |
83 | for (;;) { /* must loop, can race against a flag */ | |
9d659ae1 | 84 | unsigned long old, flags = __owner_flags(owner); |
e274795e | 85 | unsigned long task = owner & ~MUTEX_FLAGS; |
9d659ae1 | 86 | |
e274795e PZ |
87 | if (task) { |
88 | if (likely(task != curr)) | |
89 | break; | |
3ca0ff57 | 90 | |
e274795e PZ |
91 | if (likely(!(flags & MUTEX_FLAG_PICKUP))) |
92 | break; | |
9d659ae1 | 93 | |
e274795e PZ |
94 | flags &= ~MUTEX_FLAG_PICKUP; |
95 | } else { | |
96 | #ifdef CONFIG_DEBUG_MUTEXES | |
97 | DEBUG_LOCKS_WARN_ON(flags & MUTEX_FLAG_PICKUP); | |
98 | #endif | |
9d659ae1 PZ |
99 | } |
100 | ||
101 | /* | |
102 | * We set the HANDOFF bit, we must make sure it doesn't live | |
103 | * past the point where we acquire it. This would be possible | |
104 | * if we (accidentally) set the bit on an unlocked mutex. | |
105 | */ | |
e274795e | 106 | flags &= ~MUTEX_FLAG_HANDOFF; |
3ca0ff57 | 107 | |
9d659ae1 | 108 | old = atomic_long_cmpxchg_acquire(&lock->owner, owner, curr | flags); |
3ca0ff57 | 109 | if (old == owner) |
e274795e | 110 | return NULL; |
3ca0ff57 PZ |
111 | |
112 | owner = old; | |
113 | } | |
e274795e PZ |
114 | |
115 | return __owner_task(owner); | |
116 | } | |
117 | ||
118 | /* | |
119 | * Actual trylock that will work on any unlocked state. | |
120 | */ | |
121 | static inline bool __mutex_trylock(struct mutex *lock) | |
122 | { | |
123 | return !__mutex_trylock_or_owner(lock); | |
3ca0ff57 PZ |
124 | } |
125 | ||
126 | #ifndef CONFIG_DEBUG_LOCK_ALLOC | |
127 | /* | |
128 | * Lockdep annotations are contained to the slow paths for simplicity. | |
129 | * There is nothing that would stop spreading the lockdep annotations outwards | |
130 | * except more code. | |
131 | */ | |
132 | ||
133 | /* | |
134 | * Optimistic trylock that only works in the uncontended case. Make sure to | |
135 | * follow with a __mutex_trylock() before failing. | |
136 | */ | |
137 | static __always_inline bool __mutex_trylock_fast(struct mutex *lock) | |
138 | { | |
139 | unsigned long curr = (unsigned long)current; | |
140 | ||
141 | if (!atomic_long_cmpxchg_acquire(&lock->owner, 0UL, curr)) | |
142 | return true; | |
143 | ||
144 | return false; | |
145 | } | |
146 | ||
147 | static __always_inline bool __mutex_unlock_fast(struct mutex *lock) | |
148 | { | |
149 | unsigned long curr = (unsigned long)current; | |
150 | ||
151 | if (atomic_long_cmpxchg_release(&lock->owner, curr, 0UL) == curr) | |
152 | return true; | |
153 | ||
154 | return false; | |
155 | } | |
156 | #endif | |
157 | ||
158 | static inline void __mutex_set_flag(struct mutex *lock, unsigned long flag) | |
159 | { | |
160 | atomic_long_or(flag, &lock->owner); | |
161 | } | |
162 | ||
163 | static inline void __mutex_clear_flag(struct mutex *lock, unsigned long flag) | |
164 | { | |
165 | atomic_long_andnot(flag, &lock->owner); | |
166 | } | |
167 | ||
9d659ae1 PZ |
168 | static inline bool __mutex_waiter_is_first(struct mutex *lock, struct mutex_waiter *waiter) |
169 | { | |
170 | return list_first_entry(&lock->wait_list, struct mutex_waiter, list) == waiter; | |
171 | } | |
172 | ||
173 | /* | |
174 | * Give up ownership to a specific task, when @task = NULL, this is equivalent | |
e274795e PZ |
175 | * to a regular unlock. Sets PICKUP on a handoff, clears HANDOF, preserves |
176 | * WAITERS. Provides RELEASE semantics like a regular unlock, the | |
177 | * __mutex_trylock() provides a matching ACQUIRE semantics for the handoff. | |
9d659ae1 PZ |
178 | */ |
179 | static void __mutex_handoff(struct mutex *lock, struct task_struct *task) | |
180 | { | |
181 | unsigned long owner = atomic_long_read(&lock->owner); | |
182 | ||
183 | for (;;) { | |
184 | unsigned long old, new; | |
185 | ||
186 | #ifdef CONFIG_DEBUG_MUTEXES | |
187 | DEBUG_LOCKS_WARN_ON(__owner_task(owner) != current); | |
e274795e | 188 | DEBUG_LOCKS_WARN_ON(owner & MUTEX_FLAG_PICKUP); |
9d659ae1 PZ |
189 | #endif |
190 | ||
191 | new = (owner & MUTEX_FLAG_WAITERS); | |
192 | new |= (unsigned long)task; | |
e274795e PZ |
193 | if (task) |
194 | new |= MUTEX_FLAG_PICKUP; | |
9d659ae1 PZ |
195 | |
196 | old = atomic_long_cmpxchg_release(&lock->owner, owner, new); | |
197 | if (old == owner) | |
198 | break; | |
199 | ||
200 | owner = old; | |
201 | } | |
202 | } | |
203 | ||
e4564f79 | 204 | #ifndef CONFIG_DEBUG_LOCK_ALLOC |
6053ee3b IM |
205 | /* |
206 | * We split the mutex lock/unlock logic into separate fastpath and | |
207 | * slowpath functions, to reduce the register pressure on the fastpath. | |
208 | * We also put the fastpath first in the kernel image, to make sure the | |
209 | * branch is predicted by the CPU as default-untaken. | |
210 | */ | |
3ca0ff57 | 211 | static void __sched __mutex_lock_slowpath(struct mutex *lock); |
6053ee3b | 212 | |
ef5dc121 | 213 | /** |
6053ee3b IM |
214 | * mutex_lock - acquire the mutex |
215 | * @lock: the mutex to be acquired | |
216 | * | |
217 | * Lock the mutex exclusively for this task. If the mutex is not | |
218 | * available right now, it will sleep until it can get it. | |
219 | * | |
220 | * The mutex must later on be released by the same task that | |
221 | * acquired it. Recursive locking is not allowed. The task | |
222 | * may not exit without first unlocking the mutex. Also, kernel | |
139b6fd2 | 223 | * memory where the mutex resides must not be freed with |
6053ee3b IM |
224 | * the mutex still locked. The mutex must first be initialized |
225 | * (or statically defined) before it can be locked. memset()-ing | |
226 | * the mutex to 0 is not allowed. | |
227 | * | |
228 | * ( The CONFIG_DEBUG_MUTEXES .config option turns on debugging | |
229 | * checks that will enforce the restrictions and will also do | |
230 | * deadlock debugging. ) | |
231 | * | |
232 | * This function is similar to (but not equivalent to) down(). | |
233 | */ | |
b09d2501 | 234 | void __sched mutex_lock(struct mutex *lock) |
6053ee3b | 235 | { |
c544bdb1 | 236 | might_sleep(); |
6053ee3b | 237 | |
3ca0ff57 PZ |
238 | if (!__mutex_trylock_fast(lock)) |
239 | __mutex_lock_slowpath(lock); | |
240 | } | |
6053ee3b | 241 | EXPORT_SYMBOL(mutex_lock); |
e4564f79 | 242 | #endif |
6053ee3b | 243 | |
427b1820 PZ |
244 | static __always_inline void |
245 | ww_mutex_lock_acquired(struct ww_mutex *ww, struct ww_acquire_ctx *ww_ctx) | |
76916515 DB |
246 | { |
247 | #ifdef CONFIG_DEBUG_MUTEXES | |
248 | /* | |
249 | * If this WARN_ON triggers, you used ww_mutex_lock to acquire, | |
250 | * but released with a normal mutex_unlock in this call. | |
251 | * | |
252 | * This should never happen, always use ww_mutex_unlock. | |
253 | */ | |
254 | DEBUG_LOCKS_WARN_ON(ww->ctx); | |
255 | ||
256 | /* | |
257 | * Not quite done after calling ww_acquire_done() ? | |
258 | */ | |
259 | DEBUG_LOCKS_WARN_ON(ww_ctx->done_acquire); | |
260 | ||
261 | if (ww_ctx->contending_lock) { | |
262 | /* | |
263 | * After -EDEADLK you tried to | |
264 | * acquire a different ww_mutex? Bad! | |
265 | */ | |
266 | DEBUG_LOCKS_WARN_ON(ww_ctx->contending_lock != ww); | |
267 | ||
268 | /* | |
269 | * You called ww_mutex_lock after receiving -EDEADLK, | |
270 | * but 'forgot' to unlock everything else first? | |
271 | */ | |
272 | DEBUG_LOCKS_WARN_ON(ww_ctx->acquired > 0); | |
273 | ww_ctx->contending_lock = NULL; | |
274 | } | |
275 | ||
276 | /* | |
277 | * Naughty, using a different class will lead to undefined behavior! | |
278 | */ | |
279 | DEBUG_LOCKS_WARN_ON(ww_ctx->ww_class != ww->ww_class); | |
280 | #endif | |
281 | ww_ctx->acquired++; | |
282 | } | |
283 | ||
3822da3e NH |
284 | static inline bool __sched |
285 | __ww_ctx_stamp_after(struct ww_acquire_ctx *a, struct ww_acquire_ctx *b) | |
286 | { | |
287 | return a->stamp - b->stamp <= LONG_MAX && | |
288 | (a->stamp != b->stamp || a > b); | |
289 | } | |
290 | ||
659cf9f5 NH |
291 | /* |
292 | * Wake up any waiters that may have to back off when the lock is held by the | |
293 | * given context. | |
294 | * | |
295 | * Due to the invariants on the wait list, this can only affect the first | |
296 | * waiter with a context. | |
297 | * | |
298 | * The current task must not be on the wait list. | |
299 | */ | |
300 | static void __sched | |
301 | __ww_mutex_wakeup_for_backoff(struct mutex *lock, struct ww_acquire_ctx *ww_ctx) | |
302 | { | |
303 | struct mutex_waiter *cur; | |
304 | ||
305 | lockdep_assert_held(&lock->wait_lock); | |
306 | ||
307 | list_for_each_entry(cur, &lock->wait_list, list) { | |
308 | if (!cur->ww_ctx) | |
309 | continue; | |
310 | ||
311 | if (cur->ww_ctx->acquired > 0 && | |
312 | __ww_ctx_stamp_after(cur->ww_ctx, ww_ctx)) { | |
313 | debug_mutex_wake_waiter(lock, cur); | |
314 | wake_up_process(cur->task); | |
315 | } | |
316 | ||
317 | break; | |
318 | } | |
319 | } | |
320 | ||
76916515 | 321 | /* |
4bd19084 | 322 | * After acquiring lock with fastpath or when we lost out in contested |
76916515 | 323 | * slowpath, set ctx and wake up any waiters so they can recheck. |
76916515 DB |
324 | */ |
325 | static __always_inline void | |
427b1820 | 326 | ww_mutex_set_context_fastpath(struct ww_mutex *lock, struct ww_acquire_ctx *ctx) |
76916515 | 327 | { |
76916515 DB |
328 | ww_mutex_lock_acquired(lock, ctx); |
329 | ||
330 | lock->ctx = ctx; | |
331 | ||
332 | /* | |
333 | * The lock->ctx update should be visible on all cores before | |
334 | * the atomic read is done, otherwise contended waiters might be | |
335 | * missed. The contended waiters will either see ww_ctx == NULL | |
336 | * and keep spinning, or it will acquire wait_lock, add itself | |
337 | * to waiter list and sleep. | |
338 | */ | |
339 | smp_mb(); /* ^^^ */ | |
340 | ||
341 | /* | |
342 | * Check if lock is contended, if not there is nobody to wake up | |
343 | */ | |
3ca0ff57 | 344 | if (likely(!(atomic_long_read(&lock->base.owner) & MUTEX_FLAG_WAITERS))) |
76916515 DB |
345 | return; |
346 | ||
347 | /* | |
348 | * Uh oh, we raced in fastpath, wake up everyone in this case, | |
349 | * so they can see the new lock->ctx. | |
350 | */ | |
b9c16a0e | 351 | spin_lock(&lock->base.wait_lock); |
659cf9f5 | 352 | __ww_mutex_wakeup_for_backoff(&lock->base, ctx); |
b9c16a0e | 353 | spin_unlock(&lock->base.wait_lock); |
76916515 DB |
354 | } |
355 | ||
4bd19084 | 356 | /* |
659cf9f5 NH |
357 | * After acquiring lock in the slowpath set ctx. |
358 | * | |
359 | * Unlike for the fast path, the caller ensures that waiters are woken up where | |
360 | * necessary. | |
4bd19084 DB |
361 | * |
362 | * Callers must hold the mutex wait_lock. | |
363 | */ | |
364 | static __always_inline void | |
427b1820 | 365 | ww_mutex_set_context_slowpath(struct ww_mutex *lock, struct ww_acquire_ctx *ctx) |
4bd19084 | 366 | { |
4bd19084 DB |
367 | ww_mutex_lock_acquired(lock, ctx); |
368 | lock->ctx = ctx; | |
4bd19084 | 369 | } |
76916515 | 370 | |
41fcb9f2 | 371 | #ifdef CONFIG_MUTEX_SPIN_ON_OWNER |
c516df97 NH |
372 | |
373 | static inline | |
374 | bool ww_mutex_spin_on_owner(struct mutex *lock, struct ww_acquire_ctx *ww_ctx, | |
375 | struct mutex_waiter *waiter) | |
376 | { | |
377 | struct ww_mutex *ww; | |
378 | ||
379 | ww = container_of(lock, struct ww_mutex, base); | |
4bd19084 DB |
380 | |
381 | /* | |
c516df97 NH |
382 | * If ww->ctx is set the contents are undefined, only |
383 | * by acquiring wait_lock there is a guarantee that | |
384 | * they are not invalid when reading. | |
385 | * | |
386 | * As such, when deadlock detection needs to be | |
387 | * performed the optimistic spinning cannot be done. | |
388 | * | |
389 | * Check this in every inner iteration because we may | |
390 | * be racing against another thread's ww_mutex_lock. | |
4bd19084 | 391 | */ |
c516df97 NH |
392 | if (ww_ctx->acquired > 0 && READ_ONCE(ww->ctx)) |
393 | return false; | |
394 | ||
395 | /* | |
396 | * If we aren't on the wait list yet, cancel the spin | |
397 | * if there are waiters. We want to avoid stealing the | |
398 | * lock from a waiter with an earlier stamp, since the | |
399 | * other thread may already own a lock that we also | |
400 | * need. | |
401 | */ | |
402 | if (!waiter && (atomic_long_read(&lock->owner) & MUTEX_FLAG_WAITERS)) | |
403 | return false; | |
404 | ||
405 | /* | |
406 | * Similarly, stop spinning if we are no longer the | |
407 | * first waiter. | |
408 | */ | |
409 | if (waiter && !__mutex_waiter_is_first(lock, waiter)) | |
410 | return false; | |
411 | ||
412 | return true; | |
4bd19084 | 413 | } |
76916515 | 414 | |
41fcb9f2 | 415 | /* |
25f13b40 NH |
416 | * Look out! "owner" is an entirely speculative pointer access and not |
417 | * reliable. | |
418 | * | |
419 | * "noinline" so that this function shows up on perf profiles. | |
41fcb9f2 WL |
420 | */ |
421 | static noinline | |
25f13b40 | 422 | bool mutex_spin_on_owner(struct mutex *lock, struct task_struct *owner, |
c516df97 | 423 | struct ww_acquire_ctx *ww_ctx, struct mutex_waiter *waiter) |
41fcb9f2 | 424 | { |
01ac33c1 | 425 | bool ret = true; |
be1f7bf2 | 426 | |
41fcb9f2 | 427 | rcu_read_lock(); |
3ca0ff57 | 428 | while (__mutex_owner(lock) == owner) { |
be1f7bf2 JL |
429 | /* |
430 | * Ensure we emit the owner->on_cpu, dereference _after_ | |
01ac33c1 JL |
431 | * checking lock->owner still matches owner. If that fails, |
432 | * owner might point to freed memory. If it still matches, | |
be1f7bf2 JL |
433 | * the rcu_read_lock() ensures the memory stays valid. |
434 | */ | |
435 | barrier(); | |
436 | ||
05ffc951 PX |
437 | /* |
438 | * Use vcpu_is_preempted to detect lock holder preemption issue. | |
439 | */ | |
440 | if (!owner->on_cpu || need_resched() || | |
441 | vcpu_is_preempted(task_cpu(owner))) { | |
be1f7bf2 JL |
442 | ret = false; |
443 | break; | |
444 | } | |
41fcb9f2 | 445 | |
c516df97 NH |
446 | if (ww_ctx && !ww_mutex_spin_on_owner(lock, ww_ctx, waiter)) { |
447 | ret = false; | |
448 | break; | |
25f13b40 NH |
449 | } |
450 | ||
f2f09a4c | 451 | cpu_relax(); |
41fcb9f2 WL |
452 | } |
453 | rcu_read_unlock(); | |
454 | ||
be1f7bf2 | 455 | return ret; |
41fcb9f2 | 456 | } |
2bd2c92c WL |
457 | |
458 | /* | |
459 | * Initial check for entering the mutex spinning loop | |
460 | */ | |
461 | static inline int mutex_can_spin_on_owner(struct mutex *lock) | |
462 | { | |
1e40c2ed | 463 | struct task_struct *owner; |
2bd2c92c WL |
464 | int retval = 1; |
465 | ||
46af29e4 JL |
466 | if (need_resched()) |
467 | return 0; | |
468 | ||
2bd2c92c | 469 | rcu_read_lock(); |
3ca0ff57 | 470 | owner = __mutex_owner(lock); |
05ffc951 PX |
471 | |
472 | /* | |
473 | * As lock holder preemption issue, we both skip spinning if task is not | |
474 | * on cpu or its cpu is preempted | |
475 | */ | |
1e40c2ed | 476 | if (owner) |
05ffc951 | 477 | retval = owner->on_cpu && !vcpu_is_preempted(task_cpu(owner)); |
2bd2c92c | 478 | rcu_read_unlock(); |
3ca0ff57 | 479 | |
2bd2c92c | 480 | /* |
3ca0ff57 PZ |
481 | * If lock->owner is not set, the mutex has been released. Return true |
482 | * such that we'll trylock in the spin path, which is a faster option | |
483 | * than the blocking slow path. | |
2bd2c92c WL |
484 | */ |
485 | return retval; | |
486 | } | |
76916515 | 487 | |
76916515 DB |
488 | /* |
489 | * Optimistic spinning. | |
490 | * | |
491 | * We try to spin for acquisition when we find that the lock owner | |
492 | * is currently running on a (different) CPU and while we don't | |
493 | * need to reschedule. The rationale is that if the lock owner is | |
494 | * running, it is likely to release the lock soon. | |
495 | * | |
76916515 DB |
496 | * The mutex spinners are queued up using MCS lock so that only one |
497 | * spinner can compete for the mutex. However, if mutex spinning isn't | |
498 | * going to happen, there is no point in going through the lock/unlock | |
499 | * overhead. | |
500 | * | |
501 | * Returns true when the lock was taken, otherwise false, indicating | |
502 | * that we need to jump to the slowpath and sleep. | |
b341afb3 WL |
503 | * |
504 | * The waiter flag is set to true if the spinner is a waiter in the wait | |
505 | * queue. The waiter-spinner will spin on the lock directly and concurrently | |
506 | * with the spinner at the head of the OSQ, if present, until the owner is | |
507 | * changed to itself. | |
76916515 | 508 | */ |
427b1820 PZ |
509 | static __always_inline bool |
510 | mutex_optimistic_spin(struct mutex *lock, struct ww_acquire_ctx *ww_ctx, | |
c516df97 | 511 | const bool use_ww_ctx, struct mutex_waiter *waiter) |
76916515 | 512 | { |
b341afb3 WL |
513 | if (!waiter) { |
514 | /* | |
515 | * The purpose of the mutex_can_spin_on_owner() function is | |
516 | * to eliminate the overhead of osq_lock() and osq_unlock() | |
517 | * in case spinning isn't possible. As a waiter-spinner | |
518 | * is not going to take OSQ lock anyway, there is no need | |
519 | * to call mutex_can_spin_on_owner(). | |
520 | */ | |
521 | if (!mutex_can_spin_on_owner(lock)) | |
522 | goto fail; | |
76916515 | 523 | |
b341afb3 WL |
524 | /* |
525 | * In order to avoid a stampede of mutex spinners trying to | |
526 | * acquire the mutex all at once, the spinners need to take a | |
527 | * MCS (queued) lock first before spinning on the owner field. | |
528 | */ | |
529 | if (!osq_lock(&lock->osq)) | |
530 | goto fail; | |
531 | } | |
76916515 | 532 | |
b341afb3 | 533 | for (;;) { |
76916515 DB |
534 | struct task_struct *owner; |
535 | ||
e274795e PZ |
536 | /* Try to acquire the mutex... */ |
537 | owner = __mutex_trylock_or_owner(lock); | |
538 | if (!owner) | |
539 | break; | |
76916515 DB |
540 | |
541 | /* | |
e274795e | 542 | * There's an owner, wait for it to either |
76916515 DB |
543 | * release the lock or go to sleep. |
544 | */ | |
c516df97 | 545 | if (!mutex_spin_on_owner(lock, owner, ww_ctx, waiter)) |
e274795e | 546 | goto fail_unlock; |
b341afb3 | 547 | |
76916515 DB |
548 | /* |
549 | * The cpu_relax() call is a compiler barrier which forces | |
550 | * everything in this loop to be re-loaded. We don't need | |
551 | * memory barriers as we'll eventually observe the right | |
552 | * values at the cost of a few extra spins. | |
553 | */ | |
f2f09a4c | 554 | cpu_relax(); |
76916515 DB |
555 | } |
556 | ||
b341afb3 WL |
557 | if (!waiter) |
558 | osq_unlock(&lock->osq); | |
559 | ||
560 | return true; | |
561 | ||
562 | ||
563 | fail_unlock: | |
564 | if (!waiter) | |
565 | osq_unlock(&lock->osq); | |
566 | ||
567 | fail: | |
76916515 DB |
568 | /* |
569 | * If we fell out of the spin path because of need_resched(), | |
570 | * reschedule now, before we try-lock the mutex. This avoids getting | |
571 | * scheduled out right after we obtained the mutex. | |
572 | */ | |
6f942a1f PZ |
573 | if (need_resched()) { |
574 | /* | |
575 | * We _should_ have TASK_RUNNING here, but just in case | |
576 | * we do not, make it so, otherwise we might get stuck. | |
577 | */ | |
578 | __set_current_state(TASK_RUNNING); | |
76916515 | 579 | schedule_preempt_disabled(); |
6f942a1f | 580 | } |
76916515 DB |
581 | |
582 | return false; | |
583 | } | |
584 | #else | |
427b1820 PZ |
585 | static __always_inline bool |
586 | mutex_optimistic_spin(struct mutex *lock, struct ww_acquire_ctx *ww_ctx, | |
c516df97 | 587 | const bool use_ww_ctx, struct mutex_waiter *waiter) |
76916515 DB |
588 | { |
589 | return false; | |
590 | } | |
41fcb9f2 WL |
591 | #endif |
592 | ||
3ca0ff57 | 593 | static noinline void __sched __mutex_unlock_slowpath(struct mutex *lock, unsigned long ip); |
6053ee3b | 594 | |
ef5dc121 | 595 | /** |
6053ee3b IM |
596 | * mutex_unlock - release the mutex |
597 | * @lock: the mutex to be released | |
598 | * | |
599 | * Unlock a mutex that has been locked by this task previously. | |
600 | * | |
601 | * This function must not be used in interrupt context. Unlocking | |
602 | * of a not locked mutex is not allowed. | |
603 | * | |
604 | * This function is similar to (but not equivalent to) up(). | |
605 | */ | |
7ad5b3a5 | 606 | void __sched mutex_unlock(struct mutex *lock) |
6053ee3b | 607 | { |
3ca0ff57 PZ |
608 | #ifndef CONFIG_DEBUG_LOCK_ALLOC |
609 | if (__mutex_unlock_fast(lock)) | |
610 | return; | |
0d66bf6d | 611 | #endif |
3ca0ff57 | 612 | __mutex_unlock_slowpath(lock, _RET_IP_); |
6053ee3b | 613 | } |
6053ee3b IM |
614 | EXPORT_SYMBOL(mutex_unlock); |
615 | ||
040a0a37 ML |
616 | /** |
617 | * ww_mutex_unlock - release the w/w mutex | |
618 | * @lock: the mutex to be released | |
619 | * | |
620 | * Unlock a mutex that has been locked by this task previously with any of the | |
621 | * ww_mutex_lock* functions (with or without an acquire context). It is | |
622 | * forbidden to release the locks after releasing the acquire context. | |
623 | * | |
624 | * This function must not be used in interrupt context. Unlocking | |
625 | * of a unlocked mutex is not allowed. | |
626 | */ | |
627 | void __sched ww_mutex_unlock(struct ww_mutex *lock) | |
628 | { | |
629 | /* | |
630 | * The unlocking fastpath is the 0->1 transition from 'locked' | |
631 | * into 'unlocked' state: | |
632 | */ | |
633 | if (lock->ctx) { | |
634 | #ifdef CONFIG_DEBUG_MUTEXES | |
635 | DEBUG_LOCKS_WARN_ON(!lock->ctx->acquired); | |
636 | #endif | |
637 | if (lock->ctx->acquired > 0) | |
638 | lock->ctx->acquired--; | |
639 | lock->ctx = NULL; | |
640 | } | |
641 | ||
3ca0ff57 | 642 | mutex_unlock(&lock->base); |
040a0a37 ML |
643 | } |
644 | EXPORT_SYMBOL(ww_mutex_unlock); | |
645 | ||
646 | static inline int __sched | |
200b1874 NH |
647 | __ww_mutex_lock_check_stamp(struct mutex *lock, struct mutex_waiter *waiter, |
648 | struct ww_acquire_ctx *ctx) | |
040a0a37 ML |
649 | { |
650 | struct ww_mutex *ww = container_of(lock, struct ww_mutex, base); | |
4d3199e4 | 651 | struct ww_acquire_ctx *hold_ctx = READ_ONCE(ww->ctx); |
200b1874 | 652 | struct mutex_waiter *cur; |
040a0a37 | 653 | |
200b1874 NH |
654 | if (hold_ctx && __ww_ctx_stamp_after(ctx, hold_ctx)) |
655 | goto deadlock; | |
040a0a37 | 656 | |
200b1874 NH |
657 | /* |
658 | * If there is a waiter in front of us that has a context, then its | |
659 | * stamp is earlier than ours and we must back off. | |
660 | */ | |
661 | cur = waiter; | |
662 | list_for_each_entry_continue_reverse(cur, &lock->wait_list, list) { | |
663 | if (cur->ww_ctx) | |
664 | goto deadlock; | |
040a0a37 ML |
665 | } |
666 | ||
667 | return 0; | |
200b1874 NH |
668 | |
669 | deadlock: | |
670 | #ifdef CONFIG_DEBUG_MUTEXES | |
671 | DEBUG_LOCKS_WARN_ON(ctx->contending_lock); | |
672 | ctx->contending_lock = ww; | |
673 | #endif | |
674 | return -EDEADLK; | |
040a0a37 ML |
675 | } |
676 | ||
6baa5c60 NH |
677 | static inline int __sched |
678 | __ww_mutex_add_waiter(struct mutex_waiter *waiter, | |
679 | struct mutex *lock, | |
680 | struct ww_acquire_ctx *ww_ctx) | |
681 | { | |
682 | struct mutex_waiter *cur; | |
683 | struct list_head *pos; | |
684 | ||
685 | if (!ww_ctx) { | |
686 | list_add_tail(&waiter->list, &lock->wait_list); | |
040a0a37 | 687 | return 0; |
6baa5c60 | 688 | } |
040a0a37 | 689 | |
6baa5c60 NH |
690 | /* |
691 | * Add the waiter before the first waiter with a higher stamp. | |
692 | * Waiters without a context are skipped to avoid starving | |
693 | * them. | |
694 | */ | |
695 | pos = &lock->wait_list; | |
696 | list_for_each_entry_reverse(cur, &lock->wait_list, list) { | |
697 | if (!cur->ww_ctx) | |
698 | continue; | |
699 | ||
700 | if (__ww_ctx_stamp_after(ww_ctx, cur->ww_ctx)) { | |
701 | /* Back off immediately if necessary. */ | |
702 | if (ww_ctx->acquired > 0) { | |
040a0a37 | 703 | #ifdef CONFIG_DEBUG_MUTEXES |
6baa5c60 NH |
704 | struct ww_mutex *ww; |
705 | ||
706 | ww = container_of(lock, struct ww_mutex, base); | |
707 | DEBUG_LOCKS_WARN_ON(ww_ctx->contending_lock); | |
708 | ww_ctx->contending_lock = ww; | |
040a0a37 | 709 | #endif |
6baa5c60 NH |
710 | return -EDEADLK; |
711 | } | |
712 | ||
713 | break; | |
714 | } | |
715 | ||
716 | pos = &cur->list; | |
200b1874 NH |
717 | |
718 | /* | |
719 | * Wake up the waiter so that it gets a chance to back | |
720 | * off. | |
721 | */ | |
722 | if (cur->ww_ctx->acquired > 0) { | |
723 | debug_mutex_wake_waiter(lock, cur); | |
724 | wake_up_process(cur->task); | |
725 | } | |
040a0a37 ML |
726 | } |
727 | ||
6baa5c60 | 728 | list_add_tail(&waiter->list, pos); |
040a0a37 ML |
729 | return 0; |
730 | } | |
731 | ||
6053ee3b IM |
732 | /* |
733 | * Lock a mutex (possibly interruptible), slowpath: | |
734 | */ | |
040a0a37 | 735 | static __always_inline int __sched |
e4564f79 | 736 | __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass, |
040a0a37 | 737 | struct lockdep_map *nest_lock, unsigned long ip, |
b0267507 | 738 | struct ww_acquire_ctx *ww_ctx, const bool use_ww_ctx) |
6053ee3b | 739 | { |
6053ee3b | 740 | struct mutex_waiter waiter; |
9d659ae1 | 741 | bool first = false; |
a40ca565 | 742 | struct ww_mutex *ww; |
040a0a37 | 743 | int ret; |
6053ee3b | 744 | |
427b1820 | 745 | might_sleep(); |
ea9e0fb8 | 746 | |
427b1820 | 747 | ww = container_of(lock, struct ww_mutex, base); |
ea9e0fb8 | 748 | if (use_ww_ctx && ww_ctx) { |
0422e83d CW |
749 | if (unlikely(ww_ctx == READ_ONCE(ww->ctx))) |
750 | return -EALREADY; | |
751 | } | |
752 | ||
41719b03 | 753 | preempt_disable(); |
e4c70a66 | 754 | mutex_acquire_nest(&lock->dep_map, subclass, 0, nest_lock, ip); |
c0226027 | 755 | |
e274795e | 756 | if (__mutex_trylock(lock) || |
c516df97 | 757 | mutex_optimistic_spin(lock, ww_ctx, use_ww_ctx, NULL)) { |
76916515 | 758 | /* got the lock, yay! */ |
3ca0ff57 | 759 | lock_acquired(&lock->dep_map, ip); |
ea9e0fb8 | 760 | if (use_ww_ctx && ww_ctx) |
3ca0ff57 | 761 | ww_mutex_set_context_fastpath(ww, ww_ctx); |
76916515 DB |
762 | preempt_enable(); |
763 | return 0; | |
0d66bf6d | 764 | } |
76916515 | 765 | |
b9c16a0e | 766 | spin_lock(&lock->wait_lock); |
1e820c96 | 767 | /* |
3ca0ff57 | 768 | * After waiting to acquire the wait_lock, try again. |
1e820c96 | 769 | */ |
659cf9f5 NH |
770 | if (__mutex_trylock(lock)) { |
771 | if (use_ww_ctx && ww_ctx) | |
772 | __ww_mutex_wakeup_for_backoff(lock, ww_ctx); | |
773 | ||
ec83f425 | 774 | goto skip_wait; |
659cf9f5 | 775 | } |
ec83f425 | 776 | |
9a11b49a | 777 | debug_mutex_lock_common(lock, &waiter); |
d269a8b8 | 778 | debug_mutex_add_waiter(lock, &waiter, current); |
6053ee3b | 779 | |
6baa5c60 NH |
780 | lock_contended(&lock->dep_map, ip); |
781 | ||
782 | if (!use_ww_ctx) { | |
783 | /* add waiting tasks to the end of the waitqueue (FIFO): */ | |
784 | list_add_tail(&waiter.list, &lock->wait_list); | |
977625a6 NH |
785 | |
786 | #ifdef CONFIG_DEBUG_MUTEXES | |
787 | waiter.ww_ctx = MUTEX_POISON_WW_CTX; | |
788 | #endif | |
6baa5c60 NH |
789 | } else { |
790 | /* Add in stamp order, waking up waiters that must back off. */ | |
791 | ret = __ww_mutex_add_waiter(&waiter, lock, ww_ctx); | |
792 | if (ret) | |
793 | goto err_early_backoff; | |
794 | ||
795 | waiter.ww_ctx = ww_ctx; | |
796 | } | |
797 | ||
d269a8b8 | 798 | waiter.task = current; |
6053ee3b | 799 | |
9d659ae1 | 800 | if (__mutex_waiter_is_first(lock, &waiter)) |
3ca0ff57 PZ |
801 | __mutex_set_flag(lock, MUTEX_FLAG_WAITERS); |
802 | ||
642fa448 | 803 | set_current_state(state); |
6053ee3b | 804 | for (;;) { |
5bbd7e64 PZ |
805 | /* |
806 | * Once we hold wait_lock, we're serialized against | |
807 | * mutex_unlock() handing the lock off to us, do a trylock | |
808 | * before testing the error conditions to make sure we pick up | |
809 | * the handoff. | |
810 | */ | |
e274795e | 811 | if (__mutex_trylock(lock)) |
5bbd7e64 | 812 | goto acquired; |
6053ee3b IM |
813 | |
814 | /* | |
5bbd7e64 PZ |
815 | * Check for signals and wound conditions while holding |
816 | * wait_lock. This ensures the lock cancellation is ordered | |
817 | * against mutex_unlock() and wake-ups do not go missing. | |
6053ee3b | 818 | */ |
d269a8b8 | 819 | if (unlikely(signal_pending_state(state, current))) { |
040a0a37 ML |
820 | ret = -EINTR; |
821 | goto err; | |
822 | } | |
6053ee3b | 823 | |
ea9e0fb8 | 824 | if (use_ww_ctx && ww_ctx && ww_ctx->acquired > 0) { |
200b1874 | 825 | ret = __ww_mutex_lock_check_stamp(lock, &waiter, ww_ctx); |
040a0a37 ML |
826 | if (ret) |
827 | goto err; | |
6053ee3b | 828 | } |
040a0a37 | 829 | |
b9c16a0e | 830 | spin_unlock(&lock->wait_lock); |
bd2f5536 | 831 | schedule_preempt_disabled(); |
9d659ae1 | 832 | |
6baa5c60 NH |
833 | /* |
834 | * ww_mutex needs to always recheck its position since its waiter | |
835 | * list is not FIFO ordered. | |
836 | */ | |
837 | if ((use_ww_ctx && ww_ctx) || !first) { | |
838 | first = __mutex_waiter_is_first(lock, &waiter); | |
839 | if (first) | |
840 | __mutex_set_flag(lock, MUTEX_FLAG_HANDOFF); | |
9d659ae1 | 841 | } |
5bbd7e64 | 842 | |
642fa448 | 843 | set_current_state(state); |
5bbd7e64 PZ |
844 | /* |
845 | * Here we order against unlock; we must either see it change | |
846 | * state back to RUNNING and fall through the next schedule(), | |
847 | * or we must see its unlock and acquire. | |
848 | */ | |
e274795e | 849 | if (__mutex_trylock(lock) || |
c516df97 | 850 | (first && mutex_optimistic_spin(lock, ww_ctx, use_ww_ctx, &waiter))) |
5bbd7e64 PZ |
851 | break; |
852 | ||
b9c16a0e | 853 | spin_lock(&lock->wait_lock); |
6053ee3b | 854 | } |
b9c16a0e | 855 | spin_lock(&lock->wait_lock); |
5bbd7e64 | 856 | acquired: |
642fa448 | 857 | __set_current_state(TASK_RUNNING); |
51587bcf | 858 | |
d269a8b8 | 859 | mutex_remove_waiter(lock, &waiter, current); |
ec83f425 | 860 | if (likely(list_empty(&lock->wait_list))) |
9d659ae1 | 861 | __mutex_clear_flag(lock, MUTEX_FLAGS); |
3ca0ff57 | 862 | |
ec83f425 | 863 | debug_mutex_free_waiter(&waiter); |
6053ee3b | 864 | |
ec83f425 DB |
865 | skip_wait: |
866 | /* got the lock - cleanup and rejoice! */ | |
c7e78cff | 867 | lock_acquired(&lock->dep_map, ip); |
6053ee3b | 868 | |
ea9e0fb8 | 869 | if (use_ww_ctx && ww_ctx) |
4bd19084 | 870 | ww_mutex_set_context_slowpath(ww, ww_ctx); |
040a0a37 | 871 | |
b9c16a0e | 872 | spin_unlock(&lock->wait_lock); |
41719b03 | 873 | preempt_enable(); |
6053ee3b | 874 | return 0; |
040a0a37 ML |
875 | |
876 | err: | |
642fa448 | 877 | __set_current_state(TASK_RUNNING); |
d269a8b8 | 878 | mutex_remove_waiter(lock, &waiter, current); |
6baa5c60 | 879 | err_early_backoff: |
b9c16a0e | 880 | spin_unlock(&lock->wait_lock); |
040a0a37 ML |
881 | debug_mutex_free_waiter(&waiter); |
882 | mutex_release(&lock->dep_map, 1, ip); | |
883 | preempt_enable(); | |
884 | return ret; | |
6053ee3b IM |
885 | } |
886 | ||
427b1820 PZ |
887 | static int __sched |
888 | __mutex_lock(struct mutex *lock, long state, unsigned int subclass, | |
889 | struct lockdep_map *nest_lock, unsigned long ip) | |
890 | { | |
891 | return __mutex_lock_common(lock, state, subclass, nest_lock, ip, NULL, false); | |
892 | } | |
893 | ||
894 | static int __sched | |
895 | __ww_mutex_lock(struct mutex *lock, long state, unsigned int subclass, | |
896 | struct lockdep_map *nest_lock, unsigned long ip, | |
897 | struct ww_acquire_ctx *ww_ctx) | |
898 | { | |
899 | return __mutex_lock_common(lock, state, subclass, nest_lock, ip, ww_ctx, true); | |
900 | } | |
901 | ||
ef5d4707 IM |
902 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
903 | void __sched | |
904 | mutex_lock_nested(struct mutex *lock, unsigned int subclass) | |
905 | { | |
427b1820 | 906 | __mutex_lock(lock, TASK_UNINTERRUPTIBLE, subclass, NULL, _RET_IP_); |
ef5d4707 IM |
907 | } |
908 | ||
909 | EXPORT_SYMBOL_GPL(mutex_lock_nested); | |
d63a5a74 | 910 | |
e4c70a66 PZ |
911 | void __sched |
912 | _mutex_lock_nest_lock(struct mutex *lock, struct lockdep_map *nest) | |
913 | { | |
427b1820 | 914 | __mutex_lock(lock, TASK_UNINTERRUPTIBLE, 0, nest, _RET_IP_); |
e4c70a66 | 915 | } |
e4c70a66 PZ |
916 | EXPORT_SYMBOL_GPL(_mutex_lock_nest_lock); |
917 | ||
ad776537 LH |
918 | int __sched |
919 | mutex_lock_killable_nested(struct mutex *lock, unsigned int subclass) | |
920 | { | |
427b1820 | 921 | return __mutex_lock(lock, TASK_KILLABLE, subclass, NULL, _RET_IP_); |
ad776537 LH |
922 | } |
923 | EXPORT_SYMBOL_GPL(mutex_lock_killable_nested); | |
924 | ||
d63a5a74 N |
925 | int __sched |
926 | mutex_lock_interruptible_nested(struct mutex *lock, unsigned int subclass) | |
927 | { | |
427b1820 | 928 | return __mutex_lock(lock, TASK_INTERRUPTIBLE, subclass, NULL, _RET_IP_); |
d63a5a74 | 929 | } |
d63a5a74 | 930 | EXPORT_SYMBOL_GPL(mutex_lock_interruptible_nested); |
040a0a37 | 931 | |
1460cb65 TH |
932 | void __sched |
933 | mutex_lock_io_nested(struct mutex *lock, unsigned int subclass) | |
934 | { | |
935 | int token; | |
936 | ||
937 | might_sleep(); | |
938 | ||
939 | token = io_schedule_prepare(); | |
940 | __mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, | |
941 | subclass, NULL, _RET_IP_, NULL, 0); | |
942 | io_schedule_finish(token); | |
943 | } | |
944 | EXPORT_SYMBOL_GPL(mutex_lock_io_nested); | |
945 | ||
23010027 DV |
946 | static inline int |
947 | ww_mutex_deadlock_injection(struct ww_mutex *lock, struct ww_acquire_ctx *ctx) | |
948 | { | |
949 | #ifdef CONFIG_DEBUG_WW_MUTEX_SLOWPATH | |
950 | unsigned tmp; | |
951 | ||
952 | if (ctx->deadlock_inject_countdown-- == 0) { | |
953 | tmp = ctx->deadlock_inject_interval; | |
954 | if (tmp > UINT_MAX/4) | |
955 | tmp = UINT_MAX; | |
956 | else | |
957 | tmp = tmp*2 + tmp + tmp/2; | |
958 | ||
959 | ctx->deadlock_inject_interval = tmp; | |
960 | ctx->deadlock_inject_countdown = tmp; | |
961 | ctx->contending_lock = lock; | |
962 | ||
963 | ww_mutex_unlock(lock); | |
964 | ||
965 | return -EDEADLK; | |
966 | } | |
967 | #endif | |
968 | ||
969 | return 0; | |
970 | } | |
040a0a37 ML |
971 | |
972 | int __sched | |
c5470b22 | 973 | ww_mutex_lock(struct ww_mutex *lock, struct ww_acquire_ctx *ctx) |
040a0a37 | 974 | { |
23010027 DV |
975 | int ret; |
976 | ||
040a0a37 | 977 | might_sleep(); |
427b1820 PZ |
978 | ret = __ww_mutex_lock(&lock->base, TASK_UNINTERRUPTIBLE, |
979 | 0, ctx ? &ctx->dep_map : NULL, _RET_IP_, | |
980 | ctx); | |
ea9e0fb8 | 981 | if (!ret && ctx && ctx->acquired > 1) |
23010027 DV |
982 | return ww_mutex_deadlock_injection(lock, ctx); |
983 | ||
984 | return ret; | |
040a0a37 | 985 | } |
c5470b22 | 986 | EXPORT_SYMBOL_GPL(ww_mutex_lock); |
040a0a37 ML |
987 | |
988 | int __sched | |
c5470b22 | 989 | ww_mutex_lock_interruptible(struct ww_mutex *lock, struct ww_acquire_ctx *ctx) |
040a0a37 | 990 | { |
23010027 DV |
991 | int ret; |
992 | ||
040a0a37 | 993 | might_sleep(); |
427b1820 PZ |
994 | ret = __ww_mutex_lock(&lock->base, TASK_INTERRUPTIBLE, |
995 | 0, ctx ? &ctx->dep_map : NULL, _RET_IP_, | |
996 | ctx); | |
23010027 | 997 | |
ea9e0fb8 | 998 | if (!ret && ctx && ctx->acquired > 1) |
23010027 DV |
999 | return ww_mutex_deadlock_injection(lock, ctx); |
1000 | ||
1001 | return ret; | |
040a0a37 | 1002 | } |
c5470b22 | 1003 | EXPORT_SYMBOL_GPL(ww_mutex_lock_interruptible); |
040a0a37 | 1004 | |
ef5d4707 IM |
1005 | #endif |
1006 | ||
6053ee3b IM |
1007 | /* |
1008 | * Release the lock, slowpath: | |
1009 | */ | |
3ca0ff57 | 1010 | static noinline void __sched __mutex_unlock_slowpath(struct mutex *lock, unsigned long ip) |
6053ee3b | 1011 | { |
9d659ae1 | 1012 | struct task_struct *next = NULL; |
194a6b5b | 1013 | DEFINE_WAKE_Q(wake_q); |
b9c16a0e | 1014 | unsigned long owner; |
6053ee3b | 1015 | |
3ca0ff57 PZ |
1016 | mutex_release(&lock->dep_map, 1, ip); |
1017 | ||
6053ee3b | 1018 | /* |
9d659ae1 PZ |
1019 | * Release the lock before (potentially) taking the spinlock such that |
1020 | * other contenders can get on with things ASAP. | |
1021 | * | |
1022 | * Except when HANDOFF, in that case we must not clear the owner field, | |
1023 | * but instead set it to the top waiter. | |
6053ee3b | 1024 | */ |
9d659ae1 PZ |
1025 | owner = atomic_long_read(&lock->owner); |
1026 | for (;;) { | |
1027 | unsigned long old; | |
1028 | ||
1029 | #ifdef CONFIG_DEBUG_MUTEXES | |
1030 | DEBUG_LOCKS_WARN_ON(__owner_task(owner) != current); | |
e274795e | 1031 | DEBUG_LOCKS_WARN_ON(owner & MUTEX_FLAG_PICKUP); |
9d659ae1 PZ |
1032 | #endif |
1033 | ||
1034 | if (owner & MUTEX_FLAG_HANDOFF) | |
1035 | break; | |
1036 | ||
1037 | old = atomic_long_cmpxchg_release(&lock->owner, owner, | |
1038 | __owner_flags(owner)); | |
1039 | if (old == owner) { | |
1040 | if (owner & MUTEX_FLAG_WAITERS) | |
1041 | break; | |
1042 | ||
1043 | return; | |
1044 | } | |
1045 | ||
1046 | owner = old; | |
1047 | } | |
6053ee3b | 1048 | |
b9c16a0e | 1049 | spin_lock(&lock->wait_lock); |
1d8fe7dc | 1050 | debug_mutex_unlock(lock); |
6053ee3b IM |
1051 | if (!list_empty(&lock->wait_list)) { |
1052 | /* get the first entry from the wait-list: */ | |
1053 | struct mutex_waiter *waiter = | |
9d659ae1 PZ |
1054 | list_first_entry(&lock->wait_list, |
1055 | struct mutex_waiter, list); | |
1056 | ||
1057 | next = waiter->task; | |
6053ee3b IM |
1058 | |
1059 | debug_mutex_wake_waiter(lock, waiter); | |
9d659ae1 | 1060 | wake_q_add(&wake_q, next); |
6053ee3b IM |
1061 | } |
1062 | ||
9d659ae1 PZ |
1063 | if (owner & MUTEX_FLAG_HANDOFF) |
1064 | __mutex_handoff(lock, next); | |
1065 | ||
b9c16a0e | 1066 | spin_unlock(&lock->wait_lock); |
9d659ae1 | 1067 | |
1329ce6f | 1068 | wake_up_q(&wake_q); |
6053ee3b IM |
1069 | } |
1070 | ||
e4564f79 | 1071 | #ifndef CONFIG_DEBUG_LOCK_ALLOC |
6053ee3b IM |
1072 | /* |
1073 | * Here come the less common (and hence less performance-critical) APIs: | |
1074 | * mutex_lock_interruptible() and mutex_trylock(). | |
1075 | */ | |
7ad5b3a5 | 1076 | static noinline int __sched |
a41b56ef | 1077 | __mutex_lock_killable_slowpath(struct mutex *lock); |
ad776537 | 1078 | |
7ad5b3a5 | 1079 | static noinline int __sched |
a41b56ef | 1080 | __mutex_lock_interruptible_slowpath(struct mutex *lock); |
6053ee3b | 1081 | |
ef5dc121 RD |
1082 | /** |
1083 | * mutex_lock_interruptible - acquire the mutex, interruptible | |
6053ee3b IM |
1084 | * @lock: the mutex to be acquired |
1085 | * | |
1086 | * Lock the mutex like mutex_lock(), and return 0 if the mutex has | |
1087 | * been acquired or sleep until the mutex becomes available. If a | |
1088 | * signal arrives while waiting for the lock then this function | |
1089 | * returns -EINTR. | |
1090 | * | |
1091 | * This function is similar to (but not equivalent to) down_interruptible(). | |
1092 | */ | |
7ad5b3a5 | 1093 | int __sched mutex_lock_interruptible(struct mutex *lock) |
6053ee3b | 1094 | { |
c544bdb1 | 1095 | might_sleep(); |
3ca0ff57 PZ |
1096 | |
1097 | if (__mutex_trylock_fast(lock)) | |
a41b56ef | 1098 | return 0; |
3ca0ff57 PZ |
1099 | |
1100 | return __mutex_lock_interruptible_slowpath(lock); | |
6053ee3b IM |
1101 | } |
1102 | ||
1103 | EXPORT_SYMBOL(mutex_lock_interruptible); | |
1104 | ||
7ad5b3a5 | 1105 | int __sched mutex_lock_killable(struct mutex *lock) |
ad776537 LH |
1106 | { |
1107 | might_sleep(); | |
3ca0ff57 PZ |
1108 | |
1109 | if (__mutex_trylock_fast(lock)) | |
a41b56ef | 1110 | return 0; |
3ca0ff57 PZ |
1111 | |
1112 | return __mutex_lock_killable_slowpath(lock); | |
ad776537 LH |
1113 | } |
1114 | EXPORT_SYMBOL(mutex_lock_killable); | |
1115 | ||
1460cb65 TH |
1116 | void __sched mutex_lock_io(struct mutex *lock) |
1117 | { | |
1118 | int token; | |
1119 | ||
1120 | token = io_schedule_prepare(); | |
1121 | mutex_lock(lock); | |
1122 | io_schedule_finish(token); | |
1123 | } | |
1124 | EXPORT_SYMBOL_GPL(mutex_lock_io); | |
1125 | ||
3ca0ff57 PZ |
1126 | static noinline void __sched |
1127 | __mutex_lock_slowpath(struct mutex *lock) | |
e4564f79 | 1128 | { |
427b1820 | 1129 | __mutex_lock(lock, TASK_UNINTERRUPTIBLE, 0, NULL, _RET_IP_); |
e4564f79 PZ |
1130 | } |
1131 | ||
7ad5b3a5 | 1132 | static noinline int __sched |
a41b56ef | 1133 | __mutex_lock_killable_slowpath(struct mutex *lock) |
ad776537 | 1134 | { |
427b1820 | 1135 | return __mutex_lock(lock, TASK_KILLABLE, 0, NULL, _RET_IP_); |
ad776537 LH |
1136 | } |
1137 | ||
7ad5b3a5 | 1138 | static noinline int __sched |
a41b56ef | 1139 | __mutex_lock_interruptible_slowpath(struct mutex *lock) |
6053ee3b | 1140 | { |
427b1820 | 1141 | return __mutex_lock(lock, TASK_INTERRUPTIBLE, 0, NULL, _RET_IP_); |
040a0a37 ML |
1142 | } |
1143 | ||
1144 | static noinline int __sched | |
1145 | __ww_mutex_lock_slowpath(struct ww_mutex *lock, struct ww_acquire_ctx *ctx) | |
1146 | { | |
427b1820 PZ |
1147 | return __ww_mutex_lock(&lock->base, TASK_UNINTERRUPTIBLE, 0, NULL, |
1148 | _RET_IP_, ctx); | |
6053ee3b | 1149 | } |
040a0a37 ML |
1150 | |
1151 | static noinline int __sched | |
1152 | __ww_mutex_lock_interruptible_slowpath(struct ww_mutex *lock, | |
1153 | struct ww_acquire_ctx *ctx) | |
1154 | { | |
427b1820 PZ |
1155 | return __ww_mutex_lock(&lock->base, TASK_INTERRUPTIBLE, 0, NULL, |
1156 | _RET_IP_, ctx); | |
040a0a37 ML |
1157 | } |
1158 | ||
e4564f79 | 1159 | #endif |
6053ee3b | 1160 | |
ef5dc121 RD |
1161 | /** |
1162 | * mutex_trylock - try to acquire the mutex, without waiting | |
6053ee3b IM |
1163 | * @lock: the mutex to be acquired |
1164 | * | |
1165 | * Try to acquire the mutex atomically. Returns 1 if the mutex | |
1166 | * has been acquired successfully, and 0 on contention. | |
1167 | * | |
1168 | * NOTE: this function follows the spin_trylock() convention, so | |
ef5dc121 | 1169 | * it is negated from the down_trylock() return values! Be careful |
6053ee3b IM |
1170 | * about this when converting semaphore users to mutexes. |
1171 | * | |
1172 | * This function must not be used in interrupt context. The | |
1173 | * mutex must be released by the same task that acquired it. | |
1174 | */ | |
7ad5b3a5 | 1175 | int __sched mutex_trylock(struct mutex *lock) |
6053ee3b | 1176 | { |
e274795e | 1177 | bool locked = __mutex_trylock(lock); |
0d66bf6d | 1178 | |
3ca0ff57 PZ |
1179 | if (locked) |
1180 | mutex_acquire(&lock->dep_map, 0, 1, _RET_IP_); | |
0d66bf6d | 1181 | |
3ca0ff57 | 1182 | return locked; |
6053ee3b | 1183 | } |
6053ee3b | 1184 | EXPORT_SYMBOL(mutex_trylock); |
a511e3f9 | 1185 | |
040a0a37 ML |
1186 | #ifndef CONFIG_DEBUG_LOCK_ALLOC |
1187 | int __sched | |
c5470b22 | 1188 | ww_mutex_lock(struct ww_mutex *lock, struct ww_acquire_ctx *ctx) |
040a0a37 | 1189 | { |
040a0a37 ML |
1190 | might_sleep(); |
1191 | ||
3ca0ff57 | 1192 | if (__mutex_trylock_fast(&lock->base)) { |
ea9e0fb8 NH |
1193 | if (ctx) |
1194 | ww_mutex_set_context_fastpath(lock, ctx); | |
3ca0ff57 PZ |
1195 | return 0; |
1196 | } | |
1197 | ||
1198 | return __ww_mutex_lock_slowpath(lock, ctx); | |
040a0a37 | 1199 | } |
c5470b22 | 1200 | EXPORT_SYMBOL(ww_mutex_lock); |
040a0a37 ML |
1201 | |
1202 | int __sched | |
c5470b22 | 1203 | ww_mutex_lock_interruptible(struct ww_mutex *lock, struct ww_acquire_ctx *ctx) |
040a0a37 | 1204 | { |
040a0a37 ML |
1205 | might_sleep(); |
1206 | ||
3ca0ff57 | 1207 | if (__mutex_trylock_fast(&lock->base)) { |
ea9e0fb8 NH |
1208 | if (ctx) |
1209 | ww_mutex_set_context_fastpath(lock, ctx); | |
3ca0ff57 PZ |
1210 | return 0; |
1211 | } | |
1212 | ||
1213 | return __ww_mutex_lock_interruptible_slowpath(lock, ctx); | |
040a0a37 | 1214 | } |
c5470b22 | 1215 | EXPORT_SYMBOL(ww_mutex_lock_interruptible); |
040a0a37 ML |
1216 | |
1217 | #endif | |
1218 | ||
a511e3f9 AM |
1219 | /** |
1220 | * atomic_dec_and_mutex_lock - return holding mutex if we dec to 0 | |
1221 | * @cnt: the atomic which we are to dec | |
1222 | * @lock: the mutex to return holding if we dec to 0 | |
1223 | * | |
1224 | * return true and hold lock if we dec to 0, return false otherwise | |
1225 | */ | |
1226 | int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock) | |
1227 | { | |
1228 | /* dec if we can't possibly hit 0 */ | |
1229 | if (atomic_add_unless(cnt, -1, 1)) | |
1230 | return 0; | |
1231 | /* we might hit 0, so take the lock */ | |
1232 | mutex_lock(lock); | |
1233 | if (!atomic_dec_and_test(cnt)) { | |
1234 | /* when we actually did the dec, we didn't hit 0 */ | |
1235 | mutex_unlock(lock); | |
1236 | return 0; | |
1237 | } | |
1238 | /* we hit 0, and we hold the lock */ | |
1239 | return 1; | |
1240 | } | |
1241 | EXPORT_SYMBOL(atomic_dec_and_mutex_lock); |