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 | * | |
214e0aed | 18 | * Also see Documentation/locking/mutex-design.txt. |
6053ee3b IM |
19 | */ |
20 | #include <linux/mutex.h> | |
1b375dc3 | 21 | #include <linux/ww_mutex.h> |
174cd4b1 | 22 | #include <linux/sched/signal.h> |
8bd75c77 | 23 | #include <linux/sched/rt.h> |
84f001e1 | 24 | #include <linux/sched/wake_q.h> |
b17b0153 | 25 | #include <linux/sched/debug.h> |
9984de1a | 26 | #include <linux/export.h> |
6053ee3b IM |
27 | #include <linux/spinlock.h> |
28 | #include <linux/interrupt.h> | |
9a11b49a | 29 | #include <linux/debug_locks.h> |
7a215f89 | 30 | #include <linux/osq_lock.h> |
6053ee3b | 31 | |
6053ee3b IM |
32 | #ifdef CONFIG_DEBUG_MUTEXES |
33 | # include "mutex-debug.h" | |
6053ee3b IM |
34 | #else |
35 | # include "mutex.h" | |
6053ee3b IM |
36 | #endif |
37 | ||
ef5d4707 IM |
38 | void |
39 | __mutex_init(struct mutex *lock, const char *name, struct lock_class_key *key) | |
6053ee3b | 40 | { |
3ca0ff57 | 41 | atomic_long_set(&lock->owner, 0); |
6053ee3b IM |
42 | spin_lock_init(&lock->wait_lock); |
43 | INIT_LIST_HEAD(&lock->wait_list); | |
2bd2c92c | 44 | #ifdef CONFIG_MUTEX_SPIN_ON_OWNER |
4d9d951e | 45 | osq_lock_init(&lock->osq); |
2bd2c92c | 46 | #endif |
6053ee3b | 47 | |
ef5d4707 | 48 | debug_mutex_init(lock, name, key); |
6053ee3b | 49 | } |
6053ee3b IM |
50 | EXPORT_SYMBOL(__mutex_init); |
51 | ||
3ca0ff57 PZ |
52 | /* |
53 | * @owner: contains: 'struct task_struct *' to the current lock owner, | |
54 | * NULL means not owned. Since task_struct pointers are aligned at | |
e274795e | 55 | * at least L1_CACHE_BYTES, we have low bits to store extra state. |
3ca0ff57 PZ |
56 | * |
57 | * Bit0 indicates a non-empty waiter list; unlock must issue a wakeup. | |
9d659ae1 | 58 | * Bit1 indicates unlock needs to hand the lock to the top-waiter |
e274795e | 59 | * Bit2 indicates handoff has been done and we're waiting for pickup. |
3ca0ff57 PZ |
60 | */ |
61 | #define MUTEX_FLAG_WAITERS 0x01 | |
9d659ae1 | 62 | #define MUTEX_FLAG_HANDOFF 0x02 |
e274795e | 63 | #define MUTEX_FLAG_PICKUP 0x04 |
3ca0ff57 | 64 | |
e274795e | 65 | #define MUTEX_FLAGS 0x07 |
3ca0ff57 PZ |
66 | |
67 | static inline struct task_struct *__owner_task(unsigned long owner) | |
68 | { | |
69 | return (struct task_struct *)(owner & ~MUTEX_FLAGS); | |
70 | } | |
71 | ||
72 | static inline unsigned long __owner_flags(unsigned long owner) | |
73 | { | |
74 | return owner & MUTEX_FLAGS; | |
75 | } | |
76 | ||
77 | /* | |
e274795e | 78 | * Trylock variant that retuns the owning task on failure. |
3ca0ff57 | 79 | */ |
e274795e | 80 | static inline struct task_struct *__mutex_trylock_or_owner(struct mutex *lock) |
3ca0ff57 PZ |
81 | { |
82 | unsigned long owner, curr = (unsigned long)current; | |
83 | ||
84 | owner = atomic_long_read(&lock->owner); | |
85 | for (;;) { /* must loop, can race against a flag */ | |
9d659ae1 | 86 | unsigned long old, flags = __owner_flags(owner); |
e274795e | 87 | unsigned long task = owner & ~MUTEX_FLAGS; |
9d659ae1 | 88 | |
e274795e PZ |
89 | if (task) { |
90 | if (likely(task != curr)) | |
91 | break; | |
3ca0ff57 | 92 | |
e274795e PZ |
93 | if (likely(!(flags & MUTEX_FLAG_PICKUP))) |
94 | break; | |
9d659ae1 | 95 | |
e274795e PZ |
96 | flags &= ~MUTEX_FLAG_PICKUP; |
97 | } else { | |
98 | #ifdef CONFIG_DEBUG_MUTEXES | |
99 | DEBUG_LOCKS_WARN_ON(flags & MUTEX_FLAG_PICKUP); | |
100 | #endif | |
9d659ae1 PZ |
101 | } |
102 | ||
103 | /* | |
104 | * We set the HANDOFF bit, we must make sure it doesn't live | |
105 | * past the point where we acquire it. This would be possible | |
106 | * if we (accidentally) set the bit on an unlocked mutex. | |
107 | */ | |
e274795e | 108 | flags &= ~MUTEX_FLAG_HANDOFF; |
3ca0ff57 | 109 | |
9d659ae1 | 110 | old = atomic_long_cmpxchg_acquire(&lock->owner, owner, curr | flags); |
3ca0ff57 | 111 | if (old == owner) |
e274795e | 112 | return NULL; |
3ca0ff57 PZ |
113 | |
114 | owner = old; | |
115 | } | |
e274795e PZ |
116 | |
117 | return __owner_task(owner); | |
118 | } | |
119 | ||
120 | /* | |
121 | * Actual trylock that will work on any unlocked state. | |
122 | */ | |
123 | static inline bool __mutex_trylock(struct mutex *lock) | |
124 | { | |
125 | return !__mutex_trylock_or_owner(lock); | |
3ca0ff57 PZ |
126 | } |
127 | ||
128 | #ifndef CONFIG_DEBUG_LOCK_ALLOC | |
129 | /* | |
130 | * Lockdep annotations are contained to the slow paths for simplicity. | |
131 | * There is nothing that would stop spreading the lockdep annotations outwards | |
132 | * except more code. | |
133 | */ | |
134 | ||
135 | /* | |
136 | * Optimistic trylock that only works in the uncontended case. Make sure to | |
137 | * follow with a __mutex_trylock() before failing. | |
138 | */ | |
139 | static __always_inline bool __mutex_trylock_fast(struct mutex *lock) | |
140 | { | |
141 | unsigned long curr = (unsigned long)current; | |
142 | ||
143 | if (!atomic_long_cmpxchg_acquire(&lock->owner, 0UL, curr)) | |
144 | return true; | |
145 | ||
146 | return false; | |
147 | } | |
148 | ||
149 | static __always_inline bool __mutex_unlock_fast(struct mutex *lock) | |
150 | { | |
151 | unsigned long curr = (unsigned long)current; | |
152 | ||
153 | if (atomic_long_cmpxchg_release(&lock->owner, curr, 0UL) == curr) | |
154 | return true; | |
155 | ||
156 | return false; | |
157 | } | |
158 | #endif | |
159 | ||
160 | static inline void __mutex_set_flag(struct mutex *lock, unsigned long flag) | |
161 | { | |
162 | atomic_long_or(flag, &lock->owner); | |
163 | } | |
164 | ||
165 | static inline void __mutex_clear_flag(struct mutex *lock, unsigned long flag) | |
166 | { | |
167 | atomic_long_andnot(flag, &lock->owner); | |
168 | } | |
169 | ||
9d659ae1 PZ |
170 | static inline bool __mutex_waiter_is_first(struct mutex *lock, struct mutex_waiter *waiter) |
171 | { | |
172 | return list_first_entry(&lock->wait_list, struct mutex_waiter, list) == waiter; | |
173 | } | |
174 | ||
175 | /* | |
176 | * Give up ownership to a specific task, when @task = NULL, this is equivalent | |
e274795e PZ |
177 | * to a regular unlock. Sets PICKUP on a handoff, clears HANDOF, preserves |
178 | * WAITERS. Provides RELEASE semantics like a regular unlock, the | |
179 | * __mutex_trylock() provides a matching ACQUIRE semantics for the handoff. | |
9d659ae1 PZ |
180 | */ |
181 | static void __mutex_handoff(struct mutex *lock, struct task_struct *task) | |
182 | { | |
183 | unsigned long owner = atomic_long_read(&lock->owner); | |
184 | ||
185 | for (;;) { | |
186 | unsigned long old, new; | |
187 | ||
188 | #ifdef CONFIG_DEBUG_MUTEXES | |
189 | DEBUG_LOCKS_WARN_ON(__owner_task(owner) != current); | |
e274795e | 190 | DEBUG_LOCKS_WARN_ON(owner & MUTEX_FLAG_PICKUP); |
9d659ae1 PZ |
191 | #endif |
192 | ||
193 | new = (owner & MUTEX_FLAG_WAITERS); | |
194 | new |= (unsigned long)task; | |
e274795e PZ |
195 | if (task) |
196 | new |= MUTEX_FLAG_PICKUP; | |
9d659ae1 PZ |
197 | |
198 | old = atomic_long_cmpxchg_release(&lock->owner, owner, new); | |
199 | if (old == owner) | |
200 | break; | |
201 | ||
202 | owner = old; | |
203 | } | |
204 | } | |
205 | ||
e4564f79 | 206 | #ifndef CONFIG_DEBUG_LOCK_ALLOC |
6053ee3b IM |
207 | /* |
208 | * We split the mutex lock/unlock logic into separate fastpath and | |
209 | * slowpath functions, to reduce the register pressure on the fastpath. | |
210 | * We also put the fastpath first in the kernel image, to make sure the | |
211 | * branch is predicted by the CPU as default-untaken. | |
212 | */ | |
3ca0ff57 | 213 | static void __sched __mutex_lock_slowpath(struct mutex *lock); |
6053ee3b | 214 | |
ef5dc121 | 215 | /** |
6053ee3b IM |
216 | * mutex_lock - acquire the mutex |
217 | * @lock: the mutex to be acquired | |
218 | * | |
219 | * Lock the mutex exclusively for this task. If the mutex is not | |
220 | * available right now, it will sleep until it can get it. | |
221 | * | |
222 | * The mutex must later on be released by the same task that | |
223 | * acquired it. Recursive locking is not allowed. The task | |
224 | * may not exit without first unlocking the mutex. Also, kernel | |
139b6fd2 | 225 | * memory where the mutex resides must not be freed with |
6053ee3b IM |
226 | * the mutex still locked. The mutex must first be initialized |
227 | * (or statically defined) before it can be locked. memset()-ing | |
228 | * the mutex to 0 is not allowed. | |
229 | * | |
7b4ff1ad MCC |
230 | * (The CONFIG_DEBUG_MUTEXES .config option turns on debugging |
231 | * checks that will enforce the restrictions and will also do | |
232 | * deadlock debugging) | |
6053ee3b IM |
233 | * |
234 | * This function is similar to (but not equivalent to) down(). | |
235 | */ | |
b09d2501 | 236 | void __sched mutex_lock(struct mutex *lock) |
6053ee3b | 237 | { |
c544bdb1 | 238 | might_sleep(); |
6053ee3b | 239 | |
3ca0ff57 PZ |
240 | if (!__mutex_trylock_fast(lock)) |
241 | __mutex_lock_slowpath(lock); | |
242 | } | |
6053ee3b | 243 | EXPORT_SYMBOL(mutex_lock); |
e4564f79 | 244 | #endif |
6053ee3b | 245 | |
427b1820 PZ |
246 | static __always_inline void |
247 | ww_mutex_lock_acquired(struct ww_mutex *ww, struct ww_acquire_ctx *ww_ctx) | |
76916515 DB |
248 | { |
249 | #ifdef CONFIG_DEBUG_MUTEXES | |
250 | /* | |
251 | * If this WARN_ON triggers, you used ww_mutex_lock to acquire, | |
252 | * but released with a normal mutex_unlock in this call. | |
253 | * | |
254 | * This should never happen, always use ww_mutex_unlock. | |
255 | */ | |
256 | DEBUG_LOCKS_WARN_ON(ww->ctx); | |
257 | ||
258 | /* | |
259 | * Not quite done after calling ww_acquire_done() ? | |
260 | */ | |
261 | DEBUG_LOCKS_WARN_ON(ww_ctx->done_acquire); | |
262 | ||
263 | if (ww_ctx->contending_lock) { | |
264 | /* | |
265 | * After -EDEADLK you tried to | |
266 | * acquire a different ww_mutex? Bad! | |
267 | */ | |
268 | DEBUG_LOCKS_WARN_ON(ww_ctx->contending_lock != ww); | |
269 | ||
270 | /* | |
271 | * You called ww_mutex_lock after receiving -EDEADLK, | |
272 | * but 'forgot' to unlock everything else first? | |
273 | */ | |
274 | DEBUG_LOCKS_WARN_ON(ww_ctx->acquired > 0); | |
275 | ww_ctx->contending_lock = NULL; | |
276 | } | |
277 | ||
278 | /* | |
279 | * Naughty, using a different class will lead to undefined behavior! | |
280 | */ | |
281 | DEBUG_LOCKS_WARN_ON(ww_ctx->ww_class != ww->ww_class); | |
282 | #endif | |
283 | ww_ctx->acquired++; | |
284 | } | |
285 | ||
3822da3e NH |
286 | static inline bool __sched |
287 | __ww_ctx_stamp_after(struct ww_acquire_ctx *a, struct ww_acquire_ctx *b) | |
288 | { | |
289 | return a->stamp - b->stamp <= LONG_MAX && | |
290 | (a->stamp != b->stamp || a > b); | |
291 | } | |
292 | ||
659cf9f5 NH |
293 | /* |
294 | * Wake up any waiters that may have to back off when the lock is held by the | |
295 | * given context. | |
296 | * | |
297 | * Due to the invariants on the wait list, this can only affect the first | |
298 | * waiter with a context. | |
299 | * | |
300 | * The current task must not be on the wait list. | |
301 | */ | |
302 | static void __sched | |
303 | __ww_mutex_wakeup_for_backoff(struct mutex *lock, struct ww_acquire_ctx *ww_ctx) | |
304 | { | |
305 | struct mutex_waiter *cur; | |
306 | ||
307 | lockdep_assert_held(&lock->wait_lock); | |
308 | ||
309 | list_for_each_entry(cur, &lock->wait_list, list) { | |
310 | if (!cur->ww_ctx) | |
311 | continue; | |
312 | ||
313 | if (cur->ww_ctx->acquired > 0 && | |
314 | __ww_ctx_stamp_after(cur->ww_ctx, ww_ctx)) { | |
315 | debug_mutex_wake_waiter(lock, cur); | |
316 | wake_up_process(cur->task); | |
317 | } | |
318 | ||
319 | break; | |
320 | } | |
321 | } | |
322 | ||
76916515 | 323 | /* |
4bd19084 | 324 | * After acquiring lock with fastpath or when we lost out in contested |
76916515 | 325 | * slowpath, set ctx and wake up any waiters so they can recheck. |
76916515 DB |
326 | */ |
327 | static __always_inline void | |
427b1820 | 328 | ww_mutex_set_context_fastpath(struct ww_mutex *lock, struct ww_acquire_ctx *ctx) |
76916515 | 329 | { |
76916515 DB |
330 | ww_mutex_lock_acquired(lock, ctx); |
331 | ||
332 | lock->ctx = ctx; | |
333 | ||
334 | /* | |
335 | * The lock->ctx update should be visible on all cores before | |
336 | * the atomic read is done, otherwise contended waiters might be | |
337 | * missed. The contended waiters will either see ww_ctx == NULL | |
338 | * and keep spinning, or it will acquire wait_lock, add itself | |
339 | * to waiter list and sleep. | |
340 | */ | |
341 | smp_mb(); /* ^^^ */ | |
342 | ||
343 | /* | |
344 | * Check if lock is contended, if not there is nobody to wake up | |
345 | */ | |
3ca0ff57 | 346 | if (likely(!(atomic_long_read(&lock->base.owner) & MUTEX_FLAG_WAITERS))) |
76916515 DB |
347 | return; |
348 | ||
349 | /* | |
350 | * Uh oh, we raced in fastpath, wake up everyone in this case, | |
351 | * so they can see the new lock->ctx. | |
352 | */ | |
b9c16a0e | 353 | spin_lock(&lock->base.wait_lock); |
659cf9f5 | 354 | __ww_mutex_wakeup_for_backoff(&lock->base, ctx); |
b9c16a0e | 355 | spin_unlock(&lock->base.wait_lock); |
76916515 DB |
356 | } |
357 | ||
4bd19084 | 358 | /* |
659cf9f5 NH |
359 | * After acquiring lock in the slowpath set ctx. |
360 | * | |
361 | * Unlike for the fast path, the caller ensures that waiters are woken up where | |
362 | * necessary. | |
4bd19084 DB |
363 | * |
364 | * Callers must hold the mutex wait_lock. | |
365 | */ | |
366 | static __always_inline void | |
427b1820 | 367 | ww_mutex_set_context_slowpath(struct ww_mutex *lock, struct ww_acquire_ctx *ctx) |
4bd19084 | 368 | { |
4bd19084 DB |
369 | ww_mutex_lock_acquired(lock, ctx); |
370 | lock->ctx = ctx; | |
4bd19084 | 371 | } |
76916515 | 372 | |
41fcb9f2 | 373 | #ifdef CONFIG_MUTEX_SPIN_ON_OWNER |
c516df97 NH |
374 | |
375 | static inline | |
376 | bool ww_mutex_spin_on_owner(struct mutex *lock, struct ww_acquire_ctx *ww_ctx, | |
377 | struct mutex_waiter *waiter) | |
378 | { | |
379 | struct ww_mutex *ww; | |
380 | ||
381 | ww = container_of(lock, struct ww_mutex, base); | |
4bd19084 DB |
382 | |
383 | /* | |
c516df97 NH |
384 | * If ww->ctx is set the contents are undefined, only |
385 | * by acquiring wait_lock there is a guarantee that | |
386 | * they are not invalid when reading. | |
387 | * | |
388 | * As such, when deadlock detection needs to be | |
389 | * performed the optimistic spinning cannot be done. | |
390 | * | |
391 | * Check this in every inner iteration because we may | |
392 | * be racing against another thread's ww_mutex_lock. | |
4bd19084 | 393 | */ |
c516df97 NH |
394 | if (ww_ctx->acquired > 0 && READ_ONCE(ww->ctx)) |
395 | return false; | |
396 | ||
397 | /* | |
398 | * If we aren't on the wait list yet, cancel the spin | |
399 | * if there are waiters. We want to avoid stealing the | |
400 | * lock from a waiter with an earlier stamp, since the | |
401 | * other thread may already own a lock that we also | |
402 | * need. | |
403 | */ | |
404 | if (!waiter && (atomic_long_read(&lock->owner) & MUTEX_FLAG_WAITERS)) | |
405 | return false; | |
406 | ||
407 | /* | |
408 | * Similarly, stop spinning if we are no longer the | |
409 | * first waiter. | |
410 | */ | |
411 | if (waiter && !__mutex_waiter_is_first(lock, waiter)) | |
412 | return false; | |
413 | ||
414 | return true; | |
4bd19084 | 415 | } |
76916515 | 416 | |
41fcb9f2 | 417 | /* |
25f13b40 NH |
418 | * Look out! "owner" is an entirely speculative pointer access and not |
419 | * reliable. | |
420 | * | |
421 | * "noinline" so that this function shows up on perf profiles. | |
41fcb9f2 WL |
422 | */ |
423 | static noinline | |
25f13b40 | 424 | bool mutex_spin_on_owner(struct mutex *lock, struct task_struct *owner, |
c516df97 | 425 | struct ww_acquire_ctx *ww_ctx, struct mutex_waiter *waiter) |
41fcb9f2 | 426 | { |
01ac33c1 | 427 | bool ret = true; |
be1f7bf2 | 428 | |
41fcb9f2 | 429 | rcu_read_lock(); |
3ca0ff57 | 430 | while (__mutex_owner(lock) == owner) { |
be1f7bf2 JL |
431 | /* |
432 | * Ensure we emit the owner->on_cpu, dereference _after_ | |
01ac33c1 JL |
433 | * checking lock->owner still matches owner. If that fails, |
434 | * owner might point to freed memory. If it still matches, | |
be1f7bf2 JL |
435 | * the rcu_read_lock() ensures the memory stays valid. |
436 | */ | |
437 | barrier(); | |
438 | ||
05ffc951 PX |
439 | /* |
440 | * Use vcpu_is_preempted to detect lock holder preemption issue. | |
441 | */ | |
442 | if (!owner->on_cpu || need_resched() || | |
443 | vcpu_is_preempted(task_cpu(owner))) { | |
be1f7bf2 JL |
444 | ret = false; |
445 | break; | |
446 | } | |
41fcb9f2 | 447 | |
c516df97 NH |
448 | if (ww_ctx && !ww_mutex_spin_on_owner(lock, ww_ctx, waiter)) { |
449 | ret = false; | |
450 | break; | |
25f13b40 NH |
451 | } |
452 | ||
f2f09a4c | 453 | cpu_relax(); |
41fcb9f2 WL |
454 | } |
455 | rcu_read_unlock(); | |
456 | ||
be1f7bf2 | 457 | return ret; |
41fcb9f2 | 458 | } |
2bd2c92c WL |
459 | |
460 | /* | |
461 | * Initial check for entering the mutex spinning loop | |
462 | */ | |
463 | static inline int mutex_can_spin_on_owner(struct mutex *lock) | |
464 | { | |
1e40c2ed | 465 | struct task_struct *owner; |
2bd2c92c WL |
466 | int retval = 1; |
467 | ||
46af29e4 JL |
468 | if (need_resched()) |
469 | return 0; | |
470 | ||
2bd2c92c | 471 | rcu_read_lock(); |
3ca0ff57 | 472 | owner = __mutex_owner(lock); |
05ffc951 PX |
473 | |
474 | /* | |
475 | * As lock holder preemption issue, we both skip spinning if task is not | |
476 | * on cpu or its cpu is preempted | |
477 | */ | |
1e40c2ed | 478 | if (owner) |
05ffc951 | 479 | retval = owner->on_cpu && !vcpu_is_preempted(task_cpu(owner)); |
2bd2c92c | 480 | rcu_read_unlock(); |
3ca0ff57 | 481 | |
2bd2c92c | 482 | /* |
3ca0ff57 PZ |
483 | * If lock->owner is not set, the mutex has been released. Return true |
484 | * such that we'll trylock in the spin path, which is a faster option | |
485 | * than the blocking slow path. | |
2bd2c92c WL |
486 | */ |
487 | return retval; | |
488 | } | |
76916515 | 489 | |
76916515 DB |
490 | /* |
491 | * Optimistic spinning. | |
492 | * | |
493 | * We try to spin for acquisition when we find that the lock owner | |
494 | * is currently running on a (different) CPU and while we don't | |
495 | * need to reschedule. The rationale is that if the lock owner is | |
496 | * running, it is likely to release the lock soon. | |
497 | * | |
76916515 DB |
498 | * The mutex spinners are queued up using MCS lock so that only one |
499 | * spinner can compete for the mutex. However, if mutex spinning isn't | |
500 | * going to happen, there is no point in going through the lock/unlock | |
501 | * overhead. | |
502 | * | |
503 | * Returns true when the lock was taken, otherwise false, indicating | |
504 | * that we need to jump to the slowpath and sleep. | |
b341afb3 WL |
505 | * |
506 | * The waiter flag is set to true if the spinner is a waiter in the wait | |
507 | * queue. The waiter-spinner will spin on the lock directly and concurrently | |
508 | * with the spinner at the head of the OSQ, if present, until the owner is | |
509 | * changed to itself. | |
76916515 | 510 | */ |
427b1820 PZ |
511 | static __always_inline bool |
512 | mutex_optimistic_spin(struct mutex *lock, struct ww_acquire_ctx *ww_ctx, | |
c516df97 | 513 | const bool use_ww_ctx, struct mutex_waiter *waiter) |
76916515 | 514 | { |
b341afb3 WL |
515 | if (!waiter) { |
516 | /* | |
517 | * The purpose of the mutex_can_spin_on_owner() function is | |
518 | * to eliminate the overhead of osq_lock() and osq_unlock() | |
519 | * in case spinning isn't possible. As a waiter-spinner | |
520 | * is not going to take OSQ lock anyway, there is no need | |
521 | * to call mutex_can_spin_on_owner(). | |
522 | */ | |
523 | if (!mutex_can_spin_on_owner(lock)) | |
524 | goto fail; | |
76916515 | 525 | |
b341afb3 WL |
526 | /* |
527 | * In order to avoid a stampede of mutex spinners trying to | |
528 | * acquire the mutex all at once, the spinners need to take a | |
529 | * MCS (queued) lock first before spinning on the owner field. | |
530 | */ | |
531 | if (!osq_lock(&lock->osq)) | |
532 | goto fail; | |
533 | } | |
76916515 | 534 | |
b341afb3 | 535 | for (;;) { |
76916515 DB |
536 | struct task_struct *owner; |
537 | ||
e274795e PZ |
538 | /* Try to acquire the mutex... */ |
539 | owner = __mutex_trylock_or_owner(lock); | |
540 | if (!owner) | |
541 | break; | |
76916515 DB |
542 | |
543 | /* | |
e274795e | 544 | * There's an owner, wait for it to either |
76916515 DB |
545 | * release the lock or go to sleep. |
546 | */ | |
c516df97 | 547 | if (!mutex_spin_on_owner(lock, owner, ww_ctx, waiter)) |
e274795e | 548 | goto fail_unlock; |
b341afb3 | 549 | |
76916515 DB |
550 | /* |
551 | * The cpu_relax() call is a compiler barrier which forces | |
552 | * everything in this loop to be re-loaded. We don't need | |
553 | * memory barriers as we'll eventually observe the right | |
554 | * values at the cost of a few extra spins. | |
555 | */ | |
f2f09a4c | 556 | cpu_relax(); |
76916515 DB |
557 | } |
558 | ||
b341afb3 WL |
559 | if (!waiter) |
560 | osq_unlock(&lock->osq); | |
561 | ||
562 | return true; | |
563 | ||
564 | ||
565 | fail_unlock: | |
566 | if (!waiter) | |
567 | osq_unlock(&lock->osq); | |
568 | ||
569 | fail: | |
76916515 DB |
570 | /* |
571 | * If we fell out of the spin path because of need_resched(), | |
572 | * reschedule now, before we try-lock the mutex. This avoids getting | |
573 | * scheduled out right after we obtained the mutex. | |
574 | */ | |
6f942a1f PZ |
575 | if (need_resched()) { |
576 | /* | |
577 | * We _should_ have TASK_RUNNING here, but just in case | |
578 | * we do not, make it so, otherwise we might get stuck. | |
579 | */ | |
580 | __set_current_state(TASK_RUNNING); | |
76916515 | 581 | schedule_preempt_disabled(); |
6f942a1f | 582 | } |
76916515 DB |
583 | |
584 | return false; | |
585 | } | |
586 | #else | |
427b1820 PZ |
587 | static __always_inline bool |
588 | mutex_optimistic_spin(struct mutex *lock, struct ww_acquire_ctx *ww_ctx, | |
c516df97 | 589 | const bool use_ww_ctx, struct mutex_waiter *waiter) |
76916515 DB |
590 | { |
591 | return false; | |
592 | } | |
41fcb9f2 WL |
593 | #endif |
594 | ||
3ca0ff57 | 595 | static noinline void __sched __mutex_unlock_slowpath(struct mutex *lock, unsigned long ip); |
6053ee3b | 596 | |
ef5dc121 | 597 | /** |
6053ee3b IM |
598 | * mutex_unlock - release the mutex |
599 | * @lock: the mutex to be released | |
600 | * | |
601 | * Unlock a mutex that has been locked by this task previously. | |
602 | * | |
603 | * This function must not be used in interrupt context. Unlocking | |
604 | * of a not locked mutex is not allowed. | |
605 | * | |
606 | * This function is similar to (but not equivalent to) up(). | |
607 | */ | |
7ad5b3a5 | 608 | void __sched mutex_unlock(struct mutex *lock) |
6053ee3b | 609 | { |
3ca0ff57 PZ |
610 | #ifndef CONFIG_DEBUG_LOCK_ALLOC |
611 | if (__mutex_unlock_fast(lock)) | |
612 | return; | |
0d66bf6d | 613 | #endif |
3ca0ff57 | 614 | __mutex_unlock_slowpath(lock, _RET_IP_); |
6053ee3b | 615 | } |
6053ee3b IM |
616 | EXPORT_SYMBOL(mutex_unlock); |
617 | ||
040a0a37 ML |
618 | /** |
619 | * ww_mutex_unlock - release the w/w mutex | |
620 | * @lock: the mutex to be released | |
621 | * | |
622 | * Unlock a mutex that has been locked by this task previously with any of the | |
623 | * ww_mutex_lock* functions (with or without an acquire context). It is | |
624 | * forbidden to release the locks after releasing the acquire context. | |
625 | * | |
626 | * This function must not be used in interrupt context. Unlocking | |
627 | * of a unlocked mutex is not allowed. | |
628 | */ | |
629 | void __sched ww_mutex_unlock(struct ww_mutex *lock) | |
630 | { | |
631 | /* | |
632 | * The unlocking fastpath is the 0->1 transition from 'locked' | |
633 | * into 'unlocked' state: | |
634 | */ | |
635 | if (lock->ctx) { | |
636 | #ifdef CONFIG_DEBUG_MUTEXES | |
637 | DEBUG_LOCKS_WARN_ON(!lock->ctx->acquired); | |
638 | #endif | |
639 | if (lock->ctx->acquired > 0) | |
640 | lock->ctx->acquired--; | |
641 | lock->ctx = NULL; | |
642 | } | |
643 | ||
3ca0ff57 | 644 | mutex_unlock(&lock->base); |
040a0a37 ML |
645 | } |
646 | EXPORT_SYMBOL(ww_mutex_unlock); | |
647 | ||
648 | static inline int __sched | |
200b1874 NH |
649 | __ww_mutex_lock_check_stamp(struct mutex *lock, struct mutex_waiter *waiter, |
650 | struct ww_acquire_ctx *ctx) | |
040a0a37 ML |
651 | { |
652 | struct ww_mutex *ww = container_of(lock, struct ww_mutex, base); | |
4d3199e4 | 653 | struct ww_acquire_ctx *hold_ctx = READ_ONCE(ww->ctx); |
200b1874 | 654 | struct mutex_waiter *cur; |
040a0a37 | 655 | |
200b1874 NH |
656 | if (hold_ctx && __ww_ctx_stamp_after(ctx, hold_ctx)) |
657 | goto deadlock; | |
040a0a37 | 658 | |
200b1874 NH |
659 | /* |
660 | * If there is a waiter in front of us that has a context, then its | |
661 | * stamp is earlier than ours and we must back off. | |
662 | */ | |
663 | cur = waiter; | |
664 | list_for_each_entry_continue_reverse(cur, &lock->wait_list, list) { | |
665 | if (cur->ww_ctx) | |
666 | goto deadlock; | |
040a0a37 ML |
667 | } |
668 | ||
669 | return 0; | |
200b1874 NH |
670 | |
671 | deadlock: | |
672 | #ifdef CONFIG_DEBUG_MUTEXES | |
673 | DEBUG_LOCKS_WARN_ON(ctx->contending_lock); | |
674 | ctx->contending_lock = ww; | |
675 | #endif | |
676 | return -EDEADLK; | |
040a0a37 ML |
677 | } |
678 | ||
6baa5c60 NH |
679 | static inline int __sched |
680 | __ww_mutex_add_waiter(struct mutex_waiter *waiter, | |
681 | struct mutex *lock, | |
682 | struct ww_acquire_ctx *ww_ctx) | |
683 | { | |
684 | struct mutex_waiter *cur; | |
685 | struct list_head *pos; | |
686 | ||
687 | if (!ww_ctx) { | |
688 | list_add_tail(&waiter->list, &lock->wait_list); | |
040a0a37 | 689 | return 0; |
6baa5c60 | 690 | } |
040a0a37 | 691 | |
6baa5c60 NH |
692 | /* |
693 | * Add the waiter before the first waiter with a higher stamp. | |
694 | * Waiters without a context are skipped to avoid starving | |
695 | * them. | |
696 | */ | |
697 | pos = &lock->wait_list; | |
698 | list_for_each_entry_reverse(cur, &lock->wait_list, list) { | |
699 | if (!cur->ww_ctx) | |
700 | continue; | |
701 | ||
702 | if (__ww_ctx_stamp_after(ww_ctx, cur->ww_ctx)) { | |
703 | /* Back off immediately if necessary. */ | |
704 | if (ww_ctx->acquired > 0) { | |
040a0a37 | 705 | #ifdef CONFIG_DEBUG_MUTEXES |
6baa5c60 NH |
706 | struct ww_mutex *ww; |
707 | ||
708 | ww = container_of(lock, struct ww_mutex, base); | |
709 | DEBUG_LOCKS_WARN_ON(ww_ctx->contending_lock); | |
710 | ww_ctx->contending_lock = ww; | |
040a0a37 | 711 | #endif |
6baa5c60 NH |
712 | return -EDEADLK; |
713 | } | |
714 | ||
715 | break; | |
716 | } | |
717 | ||
718 | pos = &cur->list; | |
200b1874 NH |
719 | |
720 | /* | |
721 | * Wake up the waiter so that it gets a chance to back | |
722 | * off. | |
723 | */ | |
724 | if (cur->ww_ctx->acquired > 0) { | |
725 | debug_mutex_wake_waiter(lock, cur); | |
726 | wake_up_process(cur->task); | |
727 | } | |
040a0a37 ML |
728 | } |
729 | ||
6baa5c60 | 730 | list_add_tail(&waiter->list, pos); |
040a0a37 ML |
731 | return 0; |
732 | } | |
733 | ||
6053ee3b IM |
734 | /* |
735 | * Lock a mutex (possibly interruptible), slowpath: | |
736 | */ | |
040a0a37 | 737 | static __always_inline int __sched |
e4564f79 | 738 | __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass, |
040a0a37 | 739 | struct lockdep_map *nest_lock, unsigned long ip, |
b0267507 | 740 | struct ww_acquire_ctx *ww_ctx, const bool use_ww_ctx) |
6053ee3b | 741 | { |
6053ee3b | 742 | struct mutex_waiter waiter; |
9d659ae1 | 743 | bool first = false; |
a40ca565 | 744 | struct ww_mutex *ww; |
040a0a37 | 745 | int ret; |
6053ee3b | 746 | |
427b1820 | 747 | might_sleep(); |
ea9e0fb8 | 748 | |
427b1820 | 749 | ww = container_of(lock, struct ww_mutex, base); |
ea9e0fb8 | 750 | if (use_ww_ctx && ww_ctx) { |
0422e83d CW |
751 | if (unlikely(ww_ctx == READ_ONCE(ww->ctx))) |
752 | return -EALREADY; | |
753 | } | |
754 | ||
41719b03 | 755 | preempt_disable(); |
e4c70a66 | 756 | mutex_acquire_nest(&lock->dep_map, subclass, 0, nest_lock, ip); |
c0226027 | 757 | |
e274795e | 758 | if (__mutex_trylock(lock) || |
c516df97 | 759 | mutex_optimistic_spin(lock, ww_ctx, use_ww_ctx, NULL)) { |
76916515 | 760 | /* got the lock, yay! */ |
3ca0ff57 | 761 | lock_acquired(&lock->dep_map, ip); |
ea9e0fb8 | 762 | if (use_ww_ctx && ww_ctx) |
3ca0ff57 | 763 | ww_mutex_set_context_fastpath(ww, ww_ctx); |
76916515 DB |
764 | preempt_enable(); |
765 | return 0; | |
0d66bf6d | 766 | } |
76916515 | 767 | |
b9c16a0e | 768 | spin_lock(&lock->wait_lock); |
1e820c96 | 769 | /* |
3ca0ff57 | 770 | * After waiting to acquire the wait_lock, try again. |
1e820c96 | 771 | */ |
659cf9f5 NH |
772 | if (__mutex_trylock(lock)) { |
773 | if (use_ww_ctx && ww_ctx) | |
774 | __ww_mutex_wakeup_for_backoff(lock, ww_ctx); | |
775 | ||
ec83f425 | 776 | goto skip_wait; |
659cf9f5 | 777 | } |
ec83f425 | 778 | |
9a11b49a | 779 | debug_mutex_lock_common(lock, &waiter); |
d269a8b8 | 780 | debug_mutex_add_waiter(lock, &waiter, current); |
6053ee3b | 781 | |
6baa5c60 NH |
782 | lock_contended(&lock->dep_map, ip); |
783 | ||
784 | if (!use_ww_ctx) { | |
785 | /* add waiting tasks to the end of the waitqueue (FIFO): */ | |
786 | list_add_tail(&waiter.list, &lock->wait_list); | |
977625a6 NH |
787 | |
788 | #ifdef CONFIG_DEBUG_MUTEXES | |
789 | waiter.ww_ctx = MUTEX_POISON_WW_CTX; | |
790 | #endif | |
6baa5c60 NH |
791 | } else { |
792 | /* Add in stamp order, waking up waiters that must back off. */ | |
793 | ret = __ww_mutex_add_waiter(&waiter, lock, ww_ctx); | |
794 | if (ret) | |
795 | goto err_early_backoff; | |
796 | ||
797 | waiter.ww_ctx = ww_ctx; | |
798 | } | |
799 | ||
d269a8b8 | 800 | waiter.task = current; |
6053ee3b | 801 | |
9d659ae1 | 802 | if (__mutex_waiter_is_first(lock, &waiter)) |
3ca0ff57 PZ |
803 | __mutex_set_flag(lock, MUTEX_FLAG_WAITERS); |
804 | ||
642fa448 | 805 | set_current_state(state); |
6053ee3b | 806 | for (;;) { |
5bbd7e64 PZ |
807 | /* |
808 | * Once we hold wait_lock, we're serialized against | |
809 | * mutex_unlock() handing the lock off to us, do a trylock | |
810 | * before testing the error conditions to make sure we pick up | |
811 | * the handoff. | |
812 | */ | |
e274795e | 813 | if (__mutex_trylock(lock)) |
5bbd7e64 | 814 | goto acquired; |
6053ee3b IM |
815 | |
816 | /* | |
5bbd7e64 PZ |
817 | * Check for signals and wound conditions while holding |
818 | * wait_lock. This ensures the lock cancellation is ordered | |
819 | * against mutex_unlock() and wake-ups do not go missing. | |
6053ee3b | 820 | */ |
d269a8b8 | 821 | if (unlikely(signal_pending_state(state, current))) { |
040a0a37 ML |
822 | ret = -EINTR; |
823 | goto err; | |
824 | } | |
6053ee3b | 825 | |
ea9e0fb8 | 826 | if (use_ww_ctx && ww_ctx && ww_ctx->acquired > 0) { |
200b1874 | 827 | ret = __ww_mutex_lock_check_stamp(lock, &waiter, ww_ctx); |
040a0a37 ML |
828 | if (ret) |
829 | goto err; | |
6053ee3b | 830 | } |
040a0a37 | 831 | |
b9c16a0e | 832 | spin_unlock(&lock->wait_lock); |
bd2f5536 | 833 | schedule_preempt_disabled(); |
9d659ae1 | 834 | |
6baa5c60 NH |
835 | /* |
836 | * ww_mutex needs to always recheck its position since its waiter | |
837 | * list is not FIFO ordered. | |
838 | */ | |
839 | if ((use_ww_ctx && ww_ctx) || !first) { | |
840 | first = __mutex_waiter_is_first(lock, &waiter); | |
841 | if (first) | |
842 | __mutex_set_flag(lock, MUTEX_FLAG_HANDOFF); | |
9d659ae1 | 843 | } |
5bbd7e64 | 844 | |
642fa448 | 845 | set_current_state(state); |
5bbd7e64 PZ |
846 | /* |
847 | * Here we order against unlock; we must either see it change | |
848 | * state back to RUNNING and fall through the next schedule(), | |
849 | * or we must see its unlock and acquire. | |
850 | */ | |
e274795e | 851 | if (__mutex_trylock(lock) || |
c516df97 | 852 | (first && mutex_optimistic_spin(lock, ww_ctx, use_ww_ctx, &waiter))) |
5bbd7e64 PZ |
853 | break; |
854 | ||
b9c16a0e | 855 | spin_lock(&lock->wait_lock); |
6053ee3b | 856 | } |
b9c16a0e | 857 | spin_lock(&lock->wait_lock); |
5bbd7e64 | 858 | acquired: |
642fa448 | 859 | __set_current_state(TASK_RUNNING); |
51587bcf | 860 | |
d269a8b8 | 861 | mutex_remove_waiter(lock, &waiter, current); |
ec83f425 | 862 | if (likely(list_empty(&lock->wait_list))) |
9d659ae1 | 863 | __mutex_clear_flag(lock, MUTEX_FLAGS); |
3ca0ff57 | 864 | |
ec83f425 | 865 | debug_mutex_free_waiter(&waiter); |
6053ee3b | 866 | |
ec83f425 DB |
867 | skip_wait: |
868 | /* got the lock - cleanup and rejoice! */ | |
c7e78cff | 869 | lock_acquired(&lock->dep_map, ip); |
6053ee3b | 870 | |
ea9e0fb8 | 871 | if (use_ww_ctx && ww_ctx) |
4bd19084 | 872 | ww_mutex_set_context_slowpath(ww, ww_ctx); |
040a0a37 | 873 | |
b9c16a0e | 874 | spin_unlock(&lock->wait_lock); |
41719b03 | 875 | preempt_enable(); |
6053ee3b | 876 | return 0; |
040a0a37 ML |
877 | |
878 | err: | |
642fa448 | 879 | __set_current_state(TASK_RUNNING); |
d269a8b8 | 880 | mutex_remove_waiter(lock, &waiter, current); |
6baa5c60 | 881 | err_early_backoff: |
b9c16a0e | 882 | spin_unlock(&lock->wait_lock); |
040a0a37 ML |
883 | debug_mutex_free_waiter(&waiter); |
884 | mutex_release(&lock->dep_map, 1, ip); | |
885 | preempt_enable(); | |
886 | return ret; | |
6053ee3b IM |
887 | } |
888 | ||
427b1820 PZ |
889 | static int __sched |
890 | __mutex_lock(struct mutex *lock, long state, unsigned int subclass, | |
891 | struct lockdep_map *nest_lock, unsigned long ip) | |
892 | { | |
893 | return __mutex_lock_common(lock, state, subclass, nest_lock, ip, NULL, false); | |
894 | } | |
895 | ||
896 | static int __sched | |
897 | __ww_mutex_lock(struct mutex *lock, long state, unsigned int subclass, | |
898 | struct lockdep_map *nest_lock, unsigned long ip, | |
899 | struct ww_acquire_ctx *ww_ctx) | |
900 | { | |
901 | return __mutex_lock_common(lock, state, subclass, nest_lock, ip, ww_ctx, true); | |
902 | } | |
903 | ||
ef5d4707 IM |
904 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
905 | void __sched | |
906 | mutex_lock_nested(struct mutex *lock, unsigned int subclass) | |
907 | { | |
427b1820 | 908 | __mutex_lock(lock, TASK_UNINTERRUPTIBLE, subclass, NULL, _RET_IP_); |
ef5d4707 IM |
909 | } |
910 | ||
911 | EXPORT_SYMBOL_GPL(mutex_lock_nested); | |
d63a5a74 | 912 | |
e4c70a66 PZ |
913 | void __sched |
914 | _mutex_lock_nest_lock(struct mutex *lock, struct lockdep_map *nest) | |
915 | { | |
427b1820 | 916 | __mutex_lock(lock, TASK_UNINTERRUPTIBLE, 0, nest, _RET_IP_); |
e4c70a66 | 917 | } |
e4c70a66 PZ |
918 | EXPORT_SYMBOL_GPL(_mutex_lock_nest_lock); |
919 | ||
ad776537 LH |
920 | int __sched |
921 | mutex_lock_killable_nested(struct mutex *lock, unsigned int subclass) | |
922 | { | |
427b1820 | 923 | return __mutex_lock(lock, TASK_KILLABLE, subclass, NULL, _RET_IP_); |
ad776537 LH |
924 | } |
925 | EXPORT_SYMBOL_GPL(mutex_lock_killable_nested); | |
926 | ||
d63a5a74 N |
927 | int __sched |
928 | mutex_lock_interruptible_nested(struct mutex *lock, unsigned int subclass) | |
929 | { | |
427b1820 | 930 | return __mutex_lock(lock, TASK_INTERRUPTIBLE, subclass, NULL, _RET_IP_); |
d63a5a74 | 931 | } |
d63a5a74 | 932 | EXPORT_SYMBOL_GPL(mutex_lock_interruptible_nested); |
040a0a37 | 933 | |
1460cb65 TH |
934 | void __sched |
935 | mutex_lock_io_nested(struct mutex *lock, unsigned int subclass) | |
936 | { | |
937 | int token; | |
938 | ||
939 | might_sleep(); | |
940 | ||
941 | token = io_schedule_prepare(); | |
942 | __mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, | |
943 | subclass, NULL, _RET_IP_, NULL, 0); | |
944 | io_schedule_finish(token); | |
945 | } | |
946 | EXPORT_SYMBOL_GPL(mutex_lock_io_nested); | |
947 | ||
23010027 DV |
948 | static inline int |
949 | ww_mutex_deadlock_injection(struct ww_mutex *lock, struct ww_acquire_ctx *ctx) | |
950 | { | |
951 | #ifdef CONFIG_DEBUG_WW_MUTEX_SLOWPATH | |
952 | unsigned tmp; | |
953 | ||
954 | if (ctx->deadlock_inject_countdown-- == 0) { | |
955 | tmp = ctx->deadlock_inject_interval; | |
956 | if (tmp > UINT_MAX/4) | |
957 | tmp = UINT_MAX; | |
958 | else | |
959 | tmp = tmp*2 + tmp + tmp/2; | |
960 | ||
961 | ctx->deadlock_inject_interval = tmp; | |
962 | ctx->deadlock_inject_countdown = tmp; | |
963 | ctx->contending_lock = lock; | |
964 | ||
965 | ww_mutex_unlock(lock); | |
966 | ||
967 | return -EDEADLK; | |
968 | } | |
969 | #endif | |
970 | ||
971 | return 0; | |
972 | } | |
040a0a37 ML |
973 | |
974 | int __sched | |
c5470b22 | 975 | ww_mutex_lock(struct ww_mutex *lock, struct ww_acquire_ctx *ctx) |
040a0a37 | 976 | { |
23010027 DV |
977 | int ret; |
978 | ||
040a0a37 | 979 | might_sleep(); |
427b1820 PZ |
980 | ret = __ww_mutex_lock(&lock->base, TASK_UNINTERRUPTIBLE, |
981 | 0, ctx ? &ctx->dep_map : NULL, _RET_IP_, | |
982 | ctx); | |
ea9e0fb8 | 983 | if (!ret && ctx && ctx->acquired > 1) |
23010027 DV |
984 | return ww_mutex_deadlock_injection(lock, ctx); |
985 | ||
986 | return ret; | |
040a0a37 | 987 | } |
c5470b22 | 988 | EXPORT_SYMBOL_GPL(ww_mutex_lock); |
040a0a37 ML |
989 | |
990 | int __sched | |
c5470b22 | 991 | ww_mutex_lock_interruptible(struct ww_mutex *lock, struct ww_acquire_ctx *ctx) |
040a0a37 | 992 | { |
23010027 DV |
993 | int ret; |
994 | ||
040a0a37 | 995 | might_sleep(); |
427b1820 PZ |
996 | ret = __ww_mutex_lock(&lock->base, TASK_INTERRUPTIBLE, |
997 | 0, ctx ? &ctx->dep_map : NULL, _RET_IP_, | |
998 | ctx); | |
23010027 | 999 | |
ea9e0fb8 | 1000 | if (!ret && ctx && ctx->acquired > 1) |
23010027 DV |
1001 | return ww_mutex_deadlock_injection(lock, ctx); |
1002 | ||
1003 | return ret; | |
040a0a37 | 1004 | } |
c5470b22 | 1005 | EXPORT_SYMBOL_GPL(ww_mutex_lock_interruptible); |
040a0a37 | 1006 | |
ef5d4707 IM |
1007 | #endif |
1008 | ||
6053ee3b IM |
1009 | /* |
1010 | * Release the lock, slowpath: | |
1011 | */ | |
3ca0ff57 | 1012 | static noinline void __sched __mutex_unlock_slowpath(struct mutex *lock, unsigned long ip) |
6053ee3b | 1013 | { |
9d659ae1 | 1014 | struct task_struct *next = NULL; |
194a6b5b | 1015 | DEFINE_WAKE_Q(wake_q); |
b9c16a0e | 1016 | unsigned long owner; |
6053ee3b | 1017 | |
3ca0ff57 PZ |
1018 | mutex_release(&lock->dep_map, 1, ip); |
1019 | ||
6053ee3b | 1020 | /* |
9d659ae1 PZ |
1021 | * Release the lock before (potentially) taking the spinlock such that |
1022 | * other contenders can get on with things ASAP. | |
1023 | * | |
1024 | * Except when HANDOFF, in that case we must not clear the owner field, | |
1025 | * but instead set it to the top waiter. | |
6053ee3b | 1026 | */ |
9d659ae1 PZ |
1027 | owner = atomic_long_read(&lock->owner); |
1028 | for (;;) { | |
1029 | unsigned long old; | |
1030 | ||
1031 | #ifdef CONFIG_DEBUG_MUTEXES | |
1032 | DEBUG_LOCKS_WARN_ON(__owner_task(owner) != current); | |
e274795e | 1033 | DEBUG_LOCKS_WARN_ON(owner & MUTEX_FLAG_PICKUP); |
9d659ae1 PZ |
1034 | #endif |
1035 | ||
1036 | if (owner & MUTEX_FLAG_HANDOFF) | |
1037 | break; | |
1038 | ||
1039 | old = atomic_long_cmpxchg_release(&lock->owner, owner, | |
1040 | __owner_flags(owner)); | |
1041 | if (old == owner) { | |
1042 | if (owner & MUTEX_FLAG_WAITERS) | |
1043 | break; | |
1044 | ||
1045 | return; | |
1046 | } | |
1047 | ||
1048 | owner = old; | |
1049 | } | |
6053ee3b | 1050 | |
b9c16a0e | 1051 | spin_lock(&lock->wait_lock); |
1d8fe7dc | 1052 | debug_mutex_unlock(lock); |
6053ee3b IM |
1053 | if (!list_empty(&lock->wait_list)) { |
1054 | /* get the first entry from the wait-list: */ | |
1055 | struct mutex_waiter *waiter = | |
9d659ae1 PZ |
1056 | list_first_entry(&lock->wait_list, |
1057 | struct mutex_waiter, list); | |
1058 | ||
1059 | next = waiter->task; | |
6053ee3b IM |
1060 | |
1061 | debug_mutex_wake_waiter(lock, waiter); | |
9d659ae1 | 1062 | wake_q_add(&wake_q, next); |
6053ee3b IM |
1063 | } |
1064 | ||
9d659ae1 PZ |
1065 | if (owner & MUTEX_FLAG_HANDOFF) |
1066 | __mutex_handoff(lock, next); | |
1067 | ||
b9c16a0e | 1068 | spin_unlock(&lock->wait_lock); |
9d659ae1 | 1069 | |
1329ce6f | 1070 | wake_up_q(&wake_q); |
6053ee3b IM |
1071 | } |
1072 | ||
e4564f79 | 1073 | #ifndef CONFIG_DEBUG_LOCK_ALLOC |
6053ee3b IM |
1074 | /* |
1075 | * Here come the less common (and hence less performance-critical) APIs: | |
1076 | * mutex_lock_interruptible() and mutex_trylock(). | |
1077 | */ | |
7ad5b3a5 | 1078 | static noinline int __sched |
a41b56ef | 1079 | __mutex_lock_killable_slowpath(struct mutex *lock); |
ad776537 | 1080 | |
7ad5b3a5 | 1081 | static noinline int __sched |
a41b56ef | 1082 | __mutex_lock_interruptible_slowpath(struct mutex *lock); |
6053ee3b | 1083 | |
ef5dc121 | 1084 | /** |
45dbac0e MW |
1085 | * mutex_lock_interruptible() - Acquire the mutex, interruptible by signals. |
1086 | * @lock: The mutex to be acquired. | |
6053ee3b | 1087 | * |
45dbac0e MW |
1088 | * Lock the mutex like mutex_lock(). If a signal is delivered while the |
1089 | * process is sleeping, this function will return without acquiring the | |
1090 | * mutex. | |
6053ee3b | 1091 | * |
45dbac0e MW |
1092 | * Context: Process context. |
1093 | * Return: 0 if the lock was successfully acquired or %-EINTR if a | |
1094 | * signal arrived. | |
6053ee3b | 1095 | */ |
7ad5b3a5 | 1096 | int __sched mutex_lock_interruptible(struct mutex *lock) |
6053ee3b | 1097 | { |
c544bdb1 | 1098 | might_sleep(); |
3ca0ff57 PZ |
1099 | |
1100 | if (__mutex_trylock_fast(lock)) | |
a41b56ef | 1101 | return 0; |
3ca0ff57 PZ |
1102 | |
1103 | return __mutex_lock_interruptible_slowpath(lock); | |
6053ee3b IM |
1104 | } |
1105 | ||
1106 | EXPORT_SYMBOL(mutex_lock_interruptible); | |
1107 | ||
45dbac0e MW |
1108 | /** |
1109 | * mutex_lock_killable() - Acquire the mutex, interruptible by fatal signals. | |
1110 | * @lock: The mutex to be acquired. | |
1111 | * | |
1112 | * Lock the mutex like mutex_lock(). If a signal which will be fatal to | |
1113 | * the current process is delivered while the process is sleeping, this | |
1114 | * function will return without acquiring the mutex. | |
1115 | * | |
1116 | * Context: Process context. | |
1117 | * Return: 0 if the lock was successfully acquired or %-EINTR if a | |
1118 | * fatal signal arrived. | |
1119 | */ | |
7ad5b3a5 | 1120 | int __sched mutex_lock_killable(struct mutex *lock) |
ad776537 LH |
1121 | { |
1122 | might_sleep(); | |
3ca0ff57 PZ |
1123 | |
1124 | if (__mutex_trylock_fast(lock)) | |
a41b56ef | 1125 | return 0; |
3ca0ff57 PZ |
1126 | |
1127 | return __mutex_lock_killable_slowpath(lock); | |
ad776537 LH |
1128 | } |
1129 | EXPORT_SYMBOL(mutex_lock_killable); | |
1130 | ||
45dbac0e MW |
1131 | /** |
1132 | * mutex_lock_io() - Acquire the mutex and mark the process as waiting for I/O | |
1133 | * @lock: The mutex to be acquired. | |
1134 | * | |
1135 | * Lock the mutex like mutex_lock(). While the task is waiting for this | |
1136 | * mutex, it will be accounted as being in the IO wait state by the | |
1137 | * scheduler. | |
1138 | * | |
1139 | * Context: Process context. | |
1140 | */ | |
1460cb65 TH |
1141 | void __sched mutex_lock_io(struct mutex *lock) |
1142 | { | |
1143 | int token; | |
1144 | ||
1145 | token = io_schedule_prepare(); | |
1146 | mutex_lock(lock); | |
1147 | io_schedule_finish(token); | |
1148 | } | |
1149 | EXPORT_SYMBOL_GPL(mutex_lock_io); | |
1150 | ||
3ca0ff57 PZ |
1151 | static noinline void __sched |
1152 | __mutex_lock_slowpath(struct mutex *lock) | |
e4564f79 | 1153 | { |
427b1820 | 1154 | __mutex_lock(lock, TASK_UNINTERRUPTIBLE, 0, NULL, _RET_IP_); |
e4564f79 PZ |
1155 | } |
1156 | ||
7ad5b3a5 | 1157 | static noinline int __sched |
a41b56ef | 1158 | __mutex_lock_killable_slowpath(struct mutex *lock) |
ad776537 | 1159 | { |
427b1820 | 1160 | return __mutex_lock(lock, TASK_KILLABLE, 0, NULL, _RET_IP_); |
ad776537 LH |
1161 | } |
1162 | ||
7ad5b3a5 | 1163 | static noinline int __sched |
a41b56ef | 1164 | __mutex_lock_interruptible_slowpath(struct mutex *lock) |
6053ee3b | 1165 | { |
427b1820 | 1166 | return __mutex_lock(lock, TASK_INTERRUPTIBLE, 0, NULL, _RET_IP_); |
040a0a37 ML |
1167 | } |
1168 | ||
1169 | static noinline int __sched | |
1170 | __ww_mutex_lock_slowpath(struct ww_mutex *lock, struct ww_acquire_ctx *ctx) | |
1171 | { | |
427b1820 PZ |
1172 | return __ww_mutex_lock(&lock->base, TASK_UNINTERRUPTIBLE, 0, NULL, |
1173 | _RET_IP_, ctx); | |
6053ee3b | 1174 | } |
040a0a37 ML |
1175 | |
1176 | static noinline int __sched | |
1177 | __ww_mutex_lock_interruptible_slowpath(struct ww_mutex *lock, | |
1178 | struct ww_acquire_ctx *ctx) | |
1179 | { | |
427b1820 PZ |
1180 | return __ww_mutex_lock(&lock->base, TASK_INTERRUPTIBLE, 0, NULL, |
1181 | _RET_IP_, ctx); | |
040a0a37 ML |
1182 | } |
1183 | ||
e4564f79 | 1184 | #endif |
6053ee3b | 1185 | |
ef5dc121 RD |
1186 | /** |
1187 | * mutex_trylock - try to acquire the mutex, without waiting | |
6053ee3b IM |
1188 | * @lock: the mutex to be acquired |
1189 | * | |
1190 | * Try to acquire the mutex atomically. Returns 1 if the mutex | |
1191 | * has been acquired successfully, and 0 on contention. | |
1192 | * | |
1193 | * NOTE: this function follows the spin_trylock() convention, so | |
ef5dc121 | 1194 | * it is negated from the down_trylock() return values! Be careful |
6053ee3b IM |
1195 | * about this when converting semaphore users to mutexes. |
1196 | * | |
1197 | * This function must not be used in interrupt context. The | |
1198 | * mutex must be released by the same task that acquired it. | |
1199 | */ | |
7ad5b3a5 | 1200 | int __sched mutex_trylock(struct mutex *lock) |
6053ee3b | 1201 | { |
e274795e | 1202 | bool locked = __mutex_trylock(lock); |
0d66bf6d | 1203 | |
3ca0ff57 PZ |
1204 | if (locked) |
1205 | mutex_acquire(&lock->dep_map, 0, 1, _RET_IP_); | |
0d66bf6d | 1206 | |
3ca0ff57 | 1207 | return locked; |
6053ee3b | 1208 | } |
6053ee3b | 1209 | EXPORT_SYMBOL(mutex_trylock); |
a511e3f9 | 1210 | |
040a0a37 ML |
1211 | #ifndef CONFIG_DEBUG_LOCK_ALLOC |
1212 | int __sched | |
c5470b22 | 1213 | ww_mutex_lock(struct ww_mutex *lock, struct ww_acquire_ctx *ctx) |
040a0a37 | 1214 | { |
040a0a37 ML |
1215 | might_sleep(); |
1216 | ||
3ca0ff57 | 1217 | if (__mutex_trylock_fast(&lock->base)) { |
ea9e0fb8 NH |
1218 | if (ctx) |
1219 | ww_mutex_set_context_fastpath(lock, ctx); | |
3ca0ff57 PZ |
1220 | return 0; |
1221 | } | |
1222 | ||
1223 | return __ww_mutex_lock_slowpath(lock, ctx); | |
040a0a37 | 1224 | } |
c5470b22 | 1225 | EXPORT_SYMBOL(ww_mutex_lock); |
040a0a37 ML |
1226 | |
1227 | int __sched | |
c5470b22 | 1228 | ww_mutex_lock_interruptible(struct ww_mutex *lock, struct ww_acquire_ctx *ctx) |
040a0a37 | 1229 | { |
040a0a37 ML |
1230 | might_sleep(); |
1231 | ||
3ca0ff57 | 1232 | if (__mutex_trylock_fast(&lock->base)) { |
ea9e0fb8 NH |
1233 | if (ctx) |
1234 | ww_mutex_set_context_fastpath(lock, ctx); | |
3ca0ff57 PZ |
1235 | return 0; |
1236 | } | |
1237 | ||
1238 | return __ww_mutex_lock_interruptible_slowpath(lock, ctx); | |
040a0a37 | 1239 | } |
c5470b22 | 1240 | EXPORT_SYMBOL(ww_mutex_lock_interruptible); |
040a0a37 ML |
1241 | |
1242 | #endif | |
1243 | ||
a511e3f9 AM |
1244 | /** |
1245 | * atomic_dec_and_mutex_lock - return holding mutex if we dec to 0 | |
1246 | * @cnt: the atomic which we are to dec | |
1247 | * @lock: the mutex to return holding if we dec to 0 | |
1248 | * | |
1249 | * return true and hold lock if we dec to 0, return false otherwise | |
1250 | */ | |
1251 | int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock) | |
1252 | { | |
1253 | /* dec if we can't possibly hit 0 */ | |
1254 | if (atomic_add_unless(cnt, -1, 1)) | |
1255 | return 0; | |
1256 | /* we might hit 0, so take the lock */ | |
1257 | mutex_lock(lock); | |
1258 | if (!atomic_dec_and_test(cnt)) { | |
1259 | /* when we actually did the dec, we didn't hit 0 */ | |
1260 | mutex_unlock(lock); | |
1261 | return 0; | |
1262 | } | |
1263 | /* we hit 0, and we hold the lock */ | |
1264 | return 1; | |
1265 | } | |
1266 | EXPORT_SYMBOL(atomic_dec_and_mutex_lock); |