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1 : : // SPDX-License-Identifier: GPL-2.0-only
2 : : /*
3 : : * kernel/locking/mutex.c
4 : : *
5 : : * Mutexes: blocking mutual exclusion locks
6 : : *
7 : : * Started by Ingo Molnar:
8 : : *
9 : : * Copyright (C) 2004, 2005, 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
10 : : *
11 : : * Many thanks to Arjan van de Ven, Thomas Gleixner, Steven Rostedt and
12 : : * David Howells for suggestions and improvements.
13 : : *
14 : : * - Adaptive spinning for mutexes by Peter Zijlstra. (Ported to mainline
15 : : * from the -rt tree, where it was originally implemented for rtmutexes
16 : : * by Steven Rostedt, based on work by Gregory Haskins, Peter Morreale
17 : : * and Sven Dietrich.
18 : : *
19 : : * Also see Documentation/locking/mutex-design.rst.
20 : : */
21 : : #include <linux/mutex.h>
22 : : #include <linux/ww_mutex.h>
23 : : #include <linux/sched/signal.h>
24 : : #include <linux/sched/rt.h>
25 : : #include <linux/sched/wake_q.h>
26 : : #include <linux/sched/debug.h>
27 : : #include <linux/export.h>
28 : : #include <linux/spinlock.h>
29 : : #include <linux/interrupt.h>
30 : : #include <linux/debug_locks.h>
31 : : #include <linux/osq_lock.h>
32 : :
33 : : #ifdef CONFIG_DEBUG_MUTEXES
34 : : # include "mutex-debug.h"
35 : : #else
36 : : # include "mutex.h"
37 : : #endif
38 : :
39 : : void
40 : 23383086 : __mutex_init(struct mutex *lock, const char *name, struct lock_class_key *key)
41 : : {
42 : : atomic_long_set(&lock->owner, 0);
43 : 23383086 : spin_lock_init(&lock->wait_lock);
44 : 23383086 : INIT_LIST_HEAD(&lock->wait_list);
45 : : #ifdef CONFIG_MUTEX_SPIN_ON_OWNER
46 : : osq_lock_init(&lock->osq);
47 : : #endif
48 : :
49 : : debug_mutex_init(lock, name, key);
50 : 23383086 : }
51 : : EXPORT_SYMBOL(__mutex_init);
52 : :
53 : : /*
54 : : * @owner: contains: 'struct task_struct *' to the current lock owner,
55 : : * NULL means not owned. Since task_struct pointers are aligned at
56 : : * at least L1_CACHE_BYTES, we have low bits to store extra state.
57 : : *
58 : : * Bit0 indicates a non-empty waiter list; unlock must issue a wakeup.
59 : : * Bit1 indicates unlock needs to hand the lock to the top-waiter
60 : : * Bit2 indicates handoff has been done and we're waiting for pickup.
61 : : */
62 : : #define MUTEX_FLAG_WAITERS 0x01
63 : : #define MUTEX_FLAG_HANDOFF 0x02
64 : : #define MUTEX_FLAG_PICKUP 0x04
65 : :
66 : : #define MUTEX_FLAGS 0x07
67 : :
68 : : /*
69 : : * Internal helper function; C doesn't allow us to hide it :/
70 : : *
71 : : * DO NOT USE (outside of mutex code).
72 : : */
73 : : static inline struct task_struct *__mutex_owner(struct mutex *lock)
74 : : {
75 : 91439185 : return (struct task_struct *)(atomic_long_read(&lock->owner) & ~MUTEX_FLAGS);
76 : : }
77 : :
78 : : static inline struct task_struct *__owner_task(unsigned long owner)
79 : : {
80 : 783495 : return (struct task_struct *)(owner & ~MUTEX_FLAGS);
81 : : }
82 : :
83 : 532006 : bool mutex_is_locked(struct mutex *lock)
84 : : {
85 : 532006 : return __mutex_owner(lock) != NULL;
86 : : }
87 : : EXPORT_SYMBOL(mutex_is_locked);
88 : :
89 : : __must_check enum mutex_trylock_recursive_enum
90 : 0 : mutex_trylock_recursive(struct mutex *lock)
91 : : {
92 [ # # ]: 0 : if (unlikely(__mutex_owner(lock) == current))
93 : : return MUTEX_TRYLOCK_RECURSIVE;
94 : :
95 : 0 : return mutex_trylock(lock);
96 : : }
97 : : EXPORT_SYMBOL(mutex_trylock_recursive);
98 : :
99 : : static inline unsigned long __owner_flags(unsigned long owner)
100 : : {
101 : 2093108 : return owner & MUTEX_FLAGS;
102 : : }
103 : :
104 : : /*
105 : : * Trylock variant that retuns the owning task on failure.
106 : : */
107 : 2008047 : static inline struct task_struct *__mutex_trylock_or_owner(struct mutex *lock)
108 : : {
109 : 2008047 : unsigned long owner, curr = (unsigned long)current;
110 : :
111 : 2008047 : owner = atomic_long_read(&lock->owner);
112 : : for (;;) { /* must loop, can race against a flag */
113 : : unsigned long old, flags = __owner_flags(owner);
114 : 2032597 : unsigned long task = owner & ~MUTEX_FLAGS;
115 : :
116 [ + + ]: 2032597 : if (task) {
117 [ + + ]: 784656 : if (likely(task != curr))
118 : : break;
119 : :
120 [ + - ]: 1161 : if (likely(!(flags & MUTEX_FLAG_PICKUP)))
121 : : break;
122 : :
123 : 1161 : flags &= ~MUTEX_FLAG_PICKUP;
124 : : } else {
125 : : #ifdef CONFIG_DEBUG_MUTEXES
126 : : DEBUG_LOCKS_WARN_ON(flags & MUTEX_FLAG_PICKUP);
127 : : #endif
128 : : }
129 : :
130 : : /*
131 : : * We set the HANDOFF bit, we must make sure it doesn't live
132 : : * past the point where we acquire it. This would be possible
133 : : * if we (accidentally) set the bit on an unlocked mutex.
134 : : */
135 : 1249102 : flags &= ~MUTEX_FLAG_HANDOFF;
136 : :
137 : 2498103 : old = atomic_long_cmpxchg_acquire(&lock->owner, owner, curr | flags);
138 [ + + ]: 1249001 : if (old == owner)
139 : : return NULL;
140 : :
141 : : owner = old;
142 : : }
143 : :
144 : 783495 : return __owner_task(owner);
145 : : }
146 : :
147 : : /*
148 : : * Actual trylock that will work on any unlocked state.
149 : : */
150 : 1104515 : static inline bool __mutex_trylock(struct mutex *lock)
151 : : {
152 : 1241303 : return !__mutex_trylock_or_owner(lock);
153 : : }
154 : :
155 : : #ifndef CONFIG_DEBUG_LOCK_ALLOC
156 : : /*
157 : : * Lockdep annotations are contained to the slow paths for simplicity.
158 : : * There is nothing that would stop spreading the lockdep annotations outwards
159 : : * except more code.
160 : : */
161 : :
162 : : /*
163 : : * Optimistic trylock that only works in the uncontended case. Make sure to
164 : : * follow with a __mutex_trylock() before failing.
165 : : */
166 : : static __always_inline bool __mutex_trylock_fast(struct mutex *lock)
167 : : {
168 : 81047343 : unsigned long curr = (unsigned long)current;
169 : 81058055 : unsigned long zero = 0UL;
170 : :
171 [ # # # # : 81058055 : if (atomic_long_try_cmpxchg_acquire(&lock->owner, &zero, curr))
+ + + + +
+ ]
172 : : return true;
173 : :
174 : : return false;
175 : : }
176 : :
177 : : static __always_inline bool __mutex_unlock_fast(struct mutex *lock)
178 : : {
179 : 81196198 : unsigned long curr = (unsigned long)current;
180 : :
181 [ + + ]: 81195531 : if (atomic_long_cmpxchg_release(&lock->owner, curr, 0UL) == curr)
182 : : return true;
183 : :
184 : : return false;
185 : : }
186 : : #endif
187 : :
188 : 5120 : static inline void __mutex_set_flag(struct mutex *lock, unsigned long flag)
189 : : {
190 : 8977 : atomic_long_or(flag, &lock->owner);
191 : 5120 : }
192 : :
193 : 3857 : static inline void __mutex_clear_flag(struct mutex *lock, unsigned long flag)
194 : : {
195 : 3857 : atomic_long_andnot(flag, &lock->owner);
196 : 3857 : }
197 : :
198 : 5120 : static inline bool __mutex_waiter_is_first(struct mutex *lock, struct mutex_waiter *waiter)
199 : : {
200 : 10249 : return list_first_entry(&lock->wait_list, struct mutex_waiter, list) == waiter;
201 : : }
202 : :
203 : : /*
204 : : * Add @waiter to a given location in the lock wait_list and set the
205 : : * FLAG_WAITERS flag if it's the first waiter.
206 : : */
207 : : static void __sched
208 : 5129 : __mutex_add_waiter(struct mutex *lock, struct mutex_waiter *waiter,
209 : : struct list_head *list)
210 : : {
211 : : debug_mutex_add_waiter(lock, waiter, current);
212 : :
213 : 5129 : list_add_tail(&waiter->list, list);
214 [ + + ]: 5129 : if (__mutex_waiter_is_first(lock, waiter))
215 : : __mutex_set_flag(lock, MUTEX_FLAG_WAITERS);
216 : 5129 : }
217 : :
218 : : /*
219 : : * Give up ownership to a specific task, when @task = NULL, this is equivalent
220 : : * to a regular unlock. Sets PICKUP on a handoff, clears HANDOF, preserves
221 : : * WAITERS. Provides RELEASE semantics like a regular unlock, the
222 : : * __mutex_trylock() provides a matching ACQUIRE semantics for the handoff.
223 : : */
224 : 1161 : static void __mutex_handoff(struct mutex *lock, struct task_struct *task)
225 : : {
226 : 1161 : unsigned long owner = atomic_long_read(&lock->owner);
227 : :
228 : : for (;;) {
229 : : unsigned long old, new;
230 : :
231 : : #ifdef CONFIG_DEBUG_MUTEXES
232 : : DEBUG_LOCKS_WARN_ON(__owner_task(owner) != current);
233 : : DEBUG_LOCKS_WARN_ON(owner & MUTEX_FLAG_PICKUP);
234 : : #endif
235 : :
236 : 1161 : new = (owner & MUTEX_FLAG_WAITERS);
237 : 1161 : new |= (unsigned long)task;
238 [ + - ]: 1161 : if (task)
239 : 1161 : new |= MUTEX_FLAG_PICKUP;
240 : :
241 : 2322 : old = atomic_long_cmpxchg_release(&lock->owner, owner, new);
242 [ - + ]: 1161 : if (old == owner)
243 : : break;
244 : :
245 : : owner = old;
246 : : }
247 : 1161 : }
248 : :
249 : : #ifndef CONFIG_DEBUG_LOCK_ALLOC
250 : : /*
251 : : * We split the mutex lock/unlock logic into separate fastpath and
252 : : * slowpath functions, to reduce the register pressure on the fastpath.
253 : : * We also put the fastpath first in the kernel image, to make sure the
254 : : * branch is predicted by the CPU as default-untaken.
255 : : */
256 : : static void __sched __mutex_lock_slowpath(struct mutex *lock);
257 : :
258 : : /**
259 : : * mutex_lock - acquire the mutex
260 : : * @lock: the mutex to be acquired
261 : : *
262 : : * Lock the mutex exclusively for this task. If the mutex is not
263 : : * available right now, it will sleep until it can get it.
264 : : *
265 : : * The mutex must later on be released by the same task that
266 : : * acquired it. Recursive locking is not allowed. The task
267 : : * may not exit without first unlocking the mutex. Also, kernel
268 : : * memory where the mutex resides must not be freed with
269 : : * the mutex still locked. The mutex must first be initialized
270 : : * (or statically defined) before it can be locked. memset()-ing
271 : : * the mutex to 0 is not allowed.
272 : : *
273 : : * (The CONFIG_DEBUG_MUTEXES .config option turns on debugging
274 : : * checks that will enforce the restrictions and will also do
275 : : * deadlock debugging)
276 : : *
277 : : * This function is similar to (but not equivalent to) down().
278 : : */
279 : 79441084 : void __sched mutex_lock(struct mutex *lock)
280 : : {
281 : 79441084 : might_sleep();
282 : :
283 [ + + ]: 79448123 : if (!__mutex_trylock_fast(lock))
284 : 1087258 : __mutex_lock_slowpath(lock);
285 : 79448603 : }
286 : : EXPORT_SYMBOL(mutex_lock);
287 : : #endif
288 : :
289 : : /*
290 : : * Wait-Die:
291 : : * The newer transactions are killed when:
292 : : * It (the new transaction) makes a request for a lock being held
293 : : * by an older transaction.
294 : : *
295 : : * Wound-Wait:
296 : : * The newer transactions are wounded when:
297 : : * An older transaction makes a request for a lock being held by
298 : : * the newer transaction.
299 : : */
300 : :
301 : : /*
302 : : * Associate the ww_mutex @ww with the context @ww_ctx under which we acquired
303 : : * it.
304 : : */
305 : : static __always_inline void
306 : : ww_mutex_lock_acquired(struct ww_mutex *ww, struct ww_acquire_ctx *ww_ctx)
307 : : {
308 : : #ifdef CONFIG_DEBUG_MUTEXES
309 : : /*
310 : : * If this WARN_ON triggers, you used ww_mutex_lock to acquire,
311 : : * but released with a normal mutex_unlock in this call.
312 : : *
313 : : * This should never happen, always use ww_mutex_unlock.
314 : : */
315 : : DEBUG_LOCKS_WARN_ON(ww->ctx);
316 : :
317 : : /*
318 : : * Not quite done after calling ww_acquire_done() ?
319 : : */
320 : : DEBUG_LOCKS_WARN_ON(ww_ctx->done_acquire);
321 : :
322 : : if (ww_ctx->contending_lock) {
323 : : /*
324 : : * After -EDEADLK you tried to
325 : : * acquire a different ww_mutex? Bad!
326 : : */
327 : : DEBUG_LOCKS_WARN_ON(ww_ctx->contending_lock != ww);
328 : :
329 : : /*
330 : : * You called ww_mutex_lock after receiving -EDEADLK,
331 : : * but 'forgot' to unlock everything else first?
332 : : */
333 : : DEBUG_LOCKS_WARN_ON(ww_ctx->acquired > 0);
334 : : ww_ctx->contending_lock = NULL;
335 : : }
336 : :
337 : : /*
338 : : * Naughty, using a different class will lead to undefined behavior!
339 : : */
340 : : DEBUG_LOCKS_WARN_ON(ww_ctx->ww_class != ww->ww_class);
341 : : #endif
342 : 0 : ww_ctx->acquired++;
343 : 0 : ww->ctx = ww_ctx;
344 : : }
345 : :
346 : : /*
347 : : * Determine if context @a is 'after' context @b. IOW, @a is a younger
348 : : * transaction than @b and depending on algorithm either needs to wait for
349 : : * @b or die.
350 : : */
351 : : static inline bool __sched
352 : : __ww_ctx_stamp_after(struct ww_acquire_ctx *a, struct ww_acquire_ctx *b)
353 : : {
354 : :
355 : 0 : return (signed long)(a->stamp - b->stamp) > 0;
356 : : }
357 : :
358 : : /*
359 : : * Wait-Die; wake a younger waiter context (when locks held) such that it can
360 : : * die.
361 : : *
362 : : * Among waiters with context, only the first one can have other locks acquired
363 : : * already (ctx->acquired > 0), because __ww_mutex_add_waiter() and
364 : : * __ww_mutex_check_kill() wake any but the earliest context.
365 : : */
366 : : static bool __sched
367 : 0 : __ww_mutex_die(struct mutex *lock, struct mutex_waiter *waiter,
368 : : struct ww_acquire_ctx *ww_ctx)
369 : : {
370 [ # # ]: 0 : if (!ww_ctx->is_wait_die)
371 : : return false;
372 : :
373 [ # # # # ]: 0 : if (waiter->ww_ctx->acquired > 0 &&
374 : : __ww_ctx_stamp_after(waiter->ww_ctx, ww_ctx)) {
375 : : debug_mutex_wake_waiter(lock, waiter);
376 : 0 : wake_up_process(waiter->task);
377 : : }
378 : :
379 : : return true;
380 : : }
381 : :
382 : : /*
383 : : * Wound-Wait; wound a younger @hold_ctx if it holds the lock.
384 : : *
385 : : * Wound the lock holder if there are waiters with older transactions than
386 : : * the lock holders. Even if multiple waiters may wound the lock holder,
387 : : * it's sufficient that only one does.
388 : : */
389 : 0 : static bool __ww_mutex_wound(struct mutex *lock,
390 : : struct ww_acquire_ctx *ww_ctx,
391 : : struct ww_acquire_ctx *hold_ctx)
392 : : {
393 : : struct task_struct *owner = __mutex_owner(lock);
394 : :
395 : : lockdep_assert_held(&lock->wait_lock);
396 : :
397 : : /*
398 : : * Possible through __ww_mutex_add_waiter() when we race with
399 : : * ww_mutex_set_context_fastpath(). In that case we'll get here again
400 : : * through __ww_mutex_check_waiters().
401 : : */
402 [ # # ]: 0 : if (!hold_ctx)
403 : : return false;
404 : :
405 : : /*
406 : : * Can have !owner because of __mutex_unlock_slowpath(), but if owner,
407 : : * it cannot go away because we'll have FLAG_WAITERS set and hold
408 : : * wait_lock.
409 : : */
410 [ # # ]: 0 : if (!owner)
411 : : return false;
412 : :
413 [ # # # # ]: 0 : if (ww_ctx->acquired > 0 && __ww_ctx_stamp_after(hold_ctx, ww_ctx)) {
414 : 0 : hold_ctx->wounded = 1;
415 : :
416 : : /*
417 : : * wake_up_process() paired with set_current_state()
418 : : * inserts sufficient barriers to make sure @owner either sees
419 : : * it's wounded in __ww_mutex_check_kill() or has a
420 : : * wakeup pending to re-read the wounded state.
421 : : */
422 [ # # ]: 0 : if (owner != current)
423 : 0 : wake_up_process(owner);
424 : :
425 : : return true;
426 : : }
427 : :
428 : : return false;
429 : : }
430 : :
431 : : /*
432 : : * We just acquired @lock under @ww_ctx, if there are later contexts waiting
433 : : * behind us on the wait-list, check if they need to die, or wound us.
434 : : *
435 : : * See __ww_mutex_add_waiter() for the list-order construction; basically the
436 : : * list is ordered by stamp, smallest (oldest) first.
437 : : *
438 : : * This relies on never mixing wait-die/wound-wait on the same wait-list;
439 : : * which is currently ensured by that being a ww_class property.
440 : : *
441 : : * The current task must not be on the wait list.
442 : : */
443 : : static void __sched
444 : 0 : __ww_mutex_check_waiters(struct mutex *lock, struct ww_acquire_ctx *ww_ctx)
445 : : {
446 : : struct mutex_waiter *cur;
447 : :
448 : : lockdep_assert_held(&lock->wait_lock);
449 : :
450 [ # # ]: 0 : list_for_each_entry(cur, &lock->wait_list, list) {
451 [ # # ]: 0 : if (!cur->ww_ctx)
452 : 0 : continue;
453 : :
454 [ # # # # ]: 0 : if (__ww_mutex_die(lock, cur, ww_ctx) ||
455 : 0 : __ww_mutex_wound(lock, cur->ww_ctx, ww_ctx))
456 : : break;
457 : : }
458 : 0 : }
459 : :
460 : : /*
461 : : * After acquiring lock with fastpath, where we do not hold wait_lock, set ctx
462 : : * and wake up any waiters so they can recheck.
463 : : */
464 : : static __always_inline void
465 : : ww_mutex_set_context_fastpath(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
466 : : {
467 : : ww_mutex_lock_acquired(lock, ctx);
468 : :
469 : : /*
470 : : * The lock->ctx update should be visible on all cores before
471 : : * the WAITERS check is done, otherwise contended waiters might be
472 : : * missed. The contended waiters will either see ww_ctx == NULL
473 : : * and keep spinning, or it will acquire wait_lock, add itself
474 : : * to waiter list and sleep.
475 : : */
476 : 0 : smp_mb(); /* See comments above and below. */
477 : :
478 : : /*
479 : : * [W] ww->ctx = ctx [W] MUTEX_FLAG_WAITERS
480 : : * MB MB
481 : : * [R] MUTEX_FLAG_WAITERS [R] ww->ctx
482 : : *
483 : : * The memory barrier above pairs with the memory barrier in
484 : : * __ww_mutex_add_waiter() and makes sure we either observe ww->ctx
485 : : * and/or !empty list.
486 : : */
487 [ # # # # : 0 : if (likely(!(atomic_long_read(&lock->base.owner) & MUTEX_FLAG_WAITERS)))
# # ]
488 : : return;
489 : :
490 : : /*
491 : : * Uh oh, we raced in fastpath, check if any of the waiters need to
492 : : * die or wound us.
493 : : */
494 : : spin_lock(&lock->base.wait_lock);
495 : 0 : __ww_mutex_check_waiters(&lock->base, ctx);
496 : : spin_unlock(&lock->base.wait_lock);
497 : : }
498 : :
499 : : #ifdef CONFIG_MUTEX_SPIN_ON_OWNER
500 : :
501 : : static inline
502 : : bool ww_mutex_spin_on_owner(struct mutex *lock, struct ww_acquire_ctx *ww_ctx,
503 : : struct mutex_waiter *waiter)
504 : : {
505 : : struct ww_mutex *ww;
506 : :
507 : : ww = container_of(lock, struct ww_mutex, base);
508 : :
509 : : /*
510 : : * If ww->ctx is set the contents are undefined, only
511 : : * by acquiring wait_lock there is a guarantee that
512 : : * they are not invalid when reading.
513 : : *
514 : : * As such, when deadlock detection needs to be
515 : : * performed the optimistic spinning cannot be done.
516 : : *
517 : : * Check this in every inner iteration because we may
518 : : * be racing against another thread's ww_mutex_lock.
519 : : */
520 [ # # # # ]: 0 : if (ww_ctx->acquired > 0 && READ_ONCE(ww->ctx))
521 : : return false;
522 : :
523 : : /*
524 : : * If we aren't on the wait list yet, cancel the spin
525 : : * if there are waiters. We want to avoid stealing the
526 : : * lock from a waiter with an earlier stamp, since the
527 : : * other thread may already own a lock that we also
528 : : * need.
529 : : */
530 [ # # # # ]: 0 : if (!waiter && (atomic_long_read(&lock->owner) & MUTEX_FLAG_WAITERS))
531 : : return false;
532 : :
533 : : /*
534 : : * Similarly, stop spinning if we are no longer the
535 : : * first waiter.
536 : : */
537 [ # # # # ]: 0 : if (waiter && !__mutex_waiter_is_first(lock, waiter))
538 : : return false;
539 : :
540 : : return true;
541 : : }
542 : :
543 : : /*
544 : : * Look out! "owner" is an entirely speculative pointer access and not
545 : : * reliable.
546 : : *
547 : : * "noinline" so that this function shows up on perf profiles.
548 : : */
549 : : static noinline
550 : 260328 : bool mutex_spin_on_owner(struct mutex *lock, struct task_struct *owner,
551 : : struct ww_acquire_ctx *ww_ctx, struct mutex_waiter *waiter)
552 : : {
553 : : bool ret = true;
554 : :
555 : : rcu_read_lock();
556 [ + + ]: 90396613 : while (__mutex_owner(lock) == owner) {
557 : : /*
558 : : * Ensure we emit the owner->on_cpu, dereference _after_
559 : : * checking lock->owner still matches owner. If that fails,
560 : : * owner might point to freed memory. If it still matches,
561 : : * the rcu_read_lock() ensures the memory stays valid.
562 : : */
563 : 90138878 : barrier();
564 : :
565 : : /*
566 : : * Use vcpu_is_preempted to detect lock holder preemption issue.
567 : : */
568 [ + + + + ]: 180275184 : if (!owner->on_cpu || need_resched() ||
569 : : vcpu_is_preempted(task_cpu(owner))) {
570 : : ret = false;
571 : : break;
572 : : }
573 : :
574 [ - + # # ]: 90137355 : if (ww_ctx && !ww_mutex_spin_on_owner(lock, ww_ctx, waiter)) {
575 : : ret = false;
576 : : break;
577 : : }
578 : :
579 : 90137355 : cpu_relax();
580 : : }
581 : : rcu_read_unlock();
582 : :
583 : 260328 : return ret;
584 : : }
585 : :
586 : : /*
587 : : * Initial check for entering the mutex spinning loop
588 : : */
589 : 510513 : static inline int mutex_can_spin_on_owner(struct mutex *lock)
590 : : {
591 : : struct task_struct *owner;
592 : : int retval = 1;
593 : :
594 [ + + ]: 510620 : if (need_resched())
595 : : return 0;
596 : :
597 : : rcu_read_lock();
598 : : owner = __mutex_owner(lock);
599 : :
600 : : /*
601 : : * As lock holder preemption issue, we both skip spinning if task is not
602 : : * on cpu or its cpu is preempted
603 : : */
604 [ + + ]: 510566 : if (owner)
605 [ + + ]: 696500 : retval = owner->on_cpu && !vcpu_is_preempted(task_cpu(owner));
606 : : rcu_read_unlock();
607 : :
608 : : /*
609 : : * If lock->owner is not set, the mutex has been released. Return true
610 : : * such that we'll trylock in the spin path, which is a faster option
611 : : * than the blocking slow path.
612 : : */
613 : 510968 : return retval;
614 : : }
615 : :
616 : : /*
617 : : * Optimistic spinning.
618 : : *
619 : : * We try to spin for acquisition when we find that the lock owner
620 : : * is currently running on a (different) CPU and while we don't
621 : : * need to reschedule. The rationale is that if the lock owner is
622 : : * running, it is likely to release the lock soon.
623 : : *
624 : : * The mutex spinners are queued up using MCS lock so that only one
625 : : * spinner can compete for the mutex. However, if mutex spinning isn't
626 : : * going to happen, there is no point in going through the lock/unlock
627 : : * overhead.
628 : : *
629 : : * Returns true when the lock was taken, otherwise false, indicating
630 : : * that we need to jump to the slowpath and sleep.
631 : : *
632 : : * The waiter flag is set to true if the spinner is a waiter in the wait
633 : : * queue. The waiter-spinner will spin on the lock directly and concurrently
634 : : * with the spinner at the head of the OSQ, if present, until the owner is
635 : : * changed to itself.
636 : : */
637 : : static __always_inline bool
638 : : mutex_optimistic_spin(struct mutex *lock, struct ww_acquire_ctx *ww_ctx,
639 : : const bool use_ww_ctx, struct mutex_waiter *waiter)
640 : : {
641 : : if (!waiter) {
642 : : /*
643 : : * The purpose of the mutex_can_spin_on_owner() function is
644 : : * to eliminate the overhead of osq_lock() and osq_unlock()
645 : : * in case spinning isn't possible. As a waiter-spinner
646 : : * is not going to take OSQ lock anyway, there is no need
647 : : * to call mutex_can_spin_on_owner().
648 : : */
649 [ # # + + ]: 510749 : if (!mutex_can_spin_on_owner(lock))
650 : : goto fail;
651 : :
652 : : /*
653 : : * In order to avoid a stampede of mutex spinners trying to
654 : : * acquire the mutex all at once, the spinners need to take a
655 : : * MCS (queued) lock first before spinning on the owner field.
656 : : */
657 [ # # + + ]: 507413 : if (!osq_lock(&lock->osq))
658 : : goto fail;
659 : : }
660 : :
661 : : for (;;) {
662 : : struct task_struct *owner;
663 : :
664 : : /* Try to acquire the mutex... */
665 : 766635 : owner = __mutex_trylock_or_owner(lock);
666 [ # # # # : 766629 : if (!owner)
+ + + + ]
667 : : break;
668 : :
669 : : /*
670 : : * There's an owner, wait for it to either
671 : : * release the lock or go to sleep.
672 : : */
673 [ # # # # : 260327 : if (!mutex_spin_on_owner(lock, owner, ww_ctx, waiter))
+ + + + ]
674 : : goto fail_unlock;
675 : :
676 : : /*
677 : : * The cpu_relax() call is a compiler barrier which forces
678 : : * everything in this loop to be re-loaded. We don't need
679 : : * memory barriers as we'll eventually observe the right
680 : : * values at the cost of a few extra spins.
681 : : */
682 : 257736 : cpu_relax();
683 : : }
684 : :
685 : : if (!waiter)
686 : 505761 : osq_unlock(&lock->osq);
687 : :
688 : : return true;
689 : :
690 : :
691 : : fail_unlock:
692 : : if (!waiter)
693 : 1846 : osq_unlock(&lock->osq);
694 : :
695 : : fail:
696 : : /*
697 : : * If we fell out of the spin path because of need_resched(),
698 : : * reschedule now, before we try-lock the mutex. This avoids getting
699 : : * scheduled out right after we obtained the mutex.
700 : : */
701 [ # # # # : 6437 : if (need_resched()) {
+ + + + ]
702 : : /*
703 : : * We _should_ have TASK_RUNNING here, but just in case
704 : : * we do not, make it so, otherwise we might get stuck.
705 : : */
706 : 1110 : __set_current_state(TASK_RUNNING);
707 : 1110 : schedule_preempt_disabled();
708 : : }
709 : :
710 : : return false;
711 : : }
712 : : #else
713 : : static __always_inline bool
714 : : mutex_optimistic_spin(struct mutex *lock, struct ww_acquire_ctx *ww_ctx,
715 : : const bool use_ww_ctx, struct mutex_waiter *waiter)
716 : : {
717 : : return false;
718 : : }
719 : : #endif
720 : :
721 : : static noinline void __sched __mutex_unlock_slowpath(struct mutex *lock, unsigned long ip);
722 : :
723 : : /**
724 : : * mutex_unlock - release the mutex
725 : : * @lock: the mutex to be released
726 : : *
727 : : * Unlock a mutex that has been locked by this task previously.
728 : : *
729 : : * This function must not be used in interrupt context. Unlocking
730 : : * of a not locked mutex is not allowed.
731 : : *
732 : : * This function is similar to (but not equivalent to) up().
733 : : */
734 : 81196198 : void __sched mutex_unlock(struct mutex *lock)
735 : : {
736 : : #ifndef CONFIG_DEBUG_LOCK_ALLOC
737 [ + + ]: 81197081 : if (__mutex_unlock_fast(lock))
738 : 81197074 : return;
739 : : #endif
740 : 61670 : __mutex_unlock_slowpath(lock, _RET_IP_);
741 : : }
742 : : EXPORT_SYMBOL(mutex_unlock);
743 : :
744 : : /**
745 : : * ww_mutex_unlock - release the w/w mutex
746 : : * @lock: the mutex to be released
747 : : *
748 : : * Unlock a mutex that has been locked by this task previously with any of the
749 : : * ww_mutex_lock* functions (with or without an acquire context). It is
750 : : * forbidden to release the locks after releasing the acquire context.
751 : : *
752 : : * This function must not be used in interrupt context. Unlocking
753 : : * of a unlocked mutex is not allowed.
754 : : */
755 : 621 : void __sched ww_mutex_unlock(struct ww_mutex *lock)
756 : : {
757 : : /*
758 : : * The unlocking fastpath is the 0->1 transition from 'locked'
759 : : * into 'unlocked' state:
760 : : */
761 [ - + ]: 621 : if (lock->ctx) {
762 : : #ifdef CONFIG_DEBUG_MUTEXES
763 : : DEBUG_LOCKS_WARN_ON(!lock->ctx->acquired);
764 : : #endif
765 [ # # ]: 0 : if (lock->ctx->acquired > 0)
766 : 0 : lock->ctx->acquired--;
767 : 0 : lock->ctx = NULL;
768 : : }
769 : :
770 : 621 : mutex_unlock(&lock->base);
771 : 621 : }
772 : : EXPORT_SYMBOL(ww_mutex_unlock);
773 : :
774 : :
775 : : static __always_inline int __sched
776 : : __ww_mutex_kill(struct mutex *lock, struct ww_acquire_ctx *ww_ctx)
777 : : {
778 [ # # # # : 0 : if (ww_ctx->acquired > 0) {
# # # # ]
779 : : #ifdef CONFIG_DEBUG_MUTEXES
780 : : struct ww_mutex *ww;
781 : :
782 : : ww = container_of(lock, struct ww_mutex, base);
783 : : DEBUG_LOCKS_WARN_ON(ww_ctx->contending_lock);
784 : : ww_ctx->contending_lock = ww;
785 : : #endif
786 : : return -EDEADLK;
787 : : }
788 : :
789 : : return 0;
790 : : }
791 : :
792 : :
793 : : /*
794 : : * Check the wound condition for the current lock acquire.
795 : : *
796 : : * Wound-Wait: If we're wounded, kill ourself.
797 : : *
798 : : * Wait-Die: If we're trying to acquire a lock already held by an older
799 : : * context, kill ourselves.
800 : : *
801 : : * Since __ww_mutex_add_waiter() orders the wait-list on stamp, we only have to
802 : : * look at waiters before us in the wait-list.
803 : : */
804 : : static inline int __sched
805 : 0 : __ww_mutex_check_kill(struct mutex *lock, struct mutex_waiter *waiter,
806 : : struct ww_acquire_ctx *ctx)
807 : : {
808 : : struct ww_mutex *ww = container_of(lock, struct ww_mutex, base);
809 : 0 : struct ww_acquire_ctx *hold_ctx = READ_ONCE(ww->ctx);
810 : : struct mutex_waiter *cur;
811 : :
812 [ # # ]: 0 : if (ctx->acquired == 0)
813 : : return 0;
814 : :
815 [ # # ]: 0 : if (!ctx->is_wait_die) {
816 [ # # ]: 0 : if (ctx->wounded)
817 : 0 : return __ww_mutex_kill(lock, ctx);
818 : :
819 : : return 0;
820 : : }
821 : :
822 [ # # # # ]: 0 : if (hold_ctx && __ww_ctx_stamp_after(ctx, hold_ctx))
823 : 0 : return __ww_mutex_kill(lock, ctx);
824 : :
825 : : /*
826 : : * If there is a waiter in front of us that has a context, then its
827 : : * stamp is earlier than ours and we must kill ourself.
828 : : */
829 : : cur = waiter;
830 [ # # ]: 0 : list_for_each_entry_continue_reverse(cur, &lock->wait_list, list) {
831 [ # # ]: 0 : if (!cur->ww_ctx)
832 : 0 : continue;
833 : :
834 : 0 : return __ww_mutex_kill(lock, ctx);
835 : : }
836 : :
837 : : return 0;
838 : : }
839 : :
840 : : /*
841 : : * Add @waiter to the wait-list, keep the wait-list ordered by stamp, smallest
842 : : * first. Such that older contexts are preferred to acquire the lock over
843 : : * younger contexts.
844 : : *
845 : : * Waiters without context are interspersed in FIFO order.
846 : : *
847 : : * Furthermore, for Wait-Die kill ourself immediately when possible (there are
848 : : * older contexts already waiting) to avoid unnecessary waiting and for
849 : : * Wound-Wait ensure we wound the owning context when it is younger.
850 : : */
851 : : static inline int __sched
852 : 0 : __ww_mutex_add_waiter(struct mutex_waiter *waiter,
853 : : struct mutex *lock,
854 : : struct ww_acquire_ctx *ww_ctx)
855 : : {
856 : : struct mutex_waiter *cur;
857 : : struct list_head *pos;
858 : : bool is_wait_die;
859 : :
860 [ # # ]: 0 : if (!ww_ctx) {
861 : 0 : __mutex_add_waiter(lock, waiter, &lock->wait_list);
862 : 0 : return 0;
863 : : }
864 : :
865 : 0 : is_wait_die = ww_ctx->is_wait_die;
866 : :
867 : : /*
868 : : * Add the waiter before the first waiter with a higher stamp.
869 : : * Waiters without a context are skipped to avoid starving
870 : : * them. Wait-Die waiters may die here. Wound-Wait waiters
871 : : * never die here, but they are sorted in stamp order and
872 : : * may wound the lock holder.
873 : : */
874 : 0 : pos = &lock->wait_list;
875 [ # # ]: 0 : list_for_each_entry_reverse(cur, &lock->wait_list, list) {
876 [ # # ]: 0 : if (!cur->ww_ctx)
877 : 0 : continue;
878 : :
879 [ # # ]: 0 : if (__ww_ctx_stamp_after(ww_ctx, cur->ww_ctx)) {
880 : : /*
881 : : * Wait-Die: if we find an older context waiting, there
882 : : * is no point in queueing behind it, as we'd have to
883 : : * die the moment it would acquire the lock.
884 : : */
885 [ # # ]: 0 : if (is_wait_die) {
886 : : int ret = __ww_mutex_kill(lock, ww_ctx);
887 : :
888 [ # # ]: 0 : if (ret)
889 : : return ret;
890 : : }
891 : :
892 : : break;
893 : : }
894 : :
895 : : pos = &cur->list;
896 : :
897 : : /* Wait-Die: ensure younger waiters die. */
898 : 0 : __ww_mutex_die(lock, cur, ww_ctx);
899 : : }
900 : :
901 : 0 : __mutex_add_waiter(lock, waiter, pos);
902 : :
903 : : /*
904 : : * Wound-Wait: if we're blocking on a mutex owned by a younger context,
905 : : * wound that such that we might proceed.
906 : : */
907 [ # # ]: 0 : if (!is_wait_die) {
908 : : struct ww_mutex *ww = container_of(lock, struct ww_mutex, base);
909 : :
910 : : /*
911 : : * See ww_mutex_set_context_fastpath(). Orders setting
912 : : * MUTEX_FLAG_WAITERS vs the ww->ctx load,
913 : : * such that either we or the fastpath will wound @ww->ctx.
914 : : */
915 : 0 : smp_mb();
916 : 0 : __ww_mutex_wound(lock, ww_ctx, ww->ctx);
917 : : }
918 : :
919 : : return 0;
920 : : }
921 : :
922 : : /*
923 : : * Lock a mutex (possibly interruptible), slowpath:
924 : : */
925 : : static __always_inline int __sched
926 : : __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
927 : : struct lockdep_map *nest_lock, unsigned long ip,
928 : : struct ww_acquire_ctx *ww_ctx, const bool use_ww_ctx)
929 : : {
930 : : struct mutex_waiter waiter;
931 : : bool first = false;
932 : : struct ww_mutex *ww;
933 : : int ret;
934 : :
935 : 1087746 : might_sleep();
936 : :
937 : : #ifdef CONFIG_DEBUG_MUTEXES
938 : : DEBUG_LOCKS_WARN_ON(lock->magic != lock);
939 : : #endif
940 : :
941 : : ww = container_of(lock, struct ww_mutex, base);
942 [ # # ]: 0 : if (use_ww_ctx && ww_ctx) {
943 [ # # ]: 0 : if (unlikely(ww_ctx == READ_ONCE(ww->ctx)))
944 : : return -EALREADY;
945 : :
946 : : /*
947 : : * Reset the wounded flag after a kill. No other process can
948 : : * race and wound us here since they can't have a valid owner
949 : : * pointer if we don't have any locks held.
950 : : */
951 [ # # ]: 0 : if (ww_ctx->acquired == 0)
952 : 0 : ww_ctx->wounded = 0;
953 : : }
954 : :
955 : 1087967 : preempt_disable();
956 : : mutex_acquire_nest(&lock->dep_map, subclass, 0, nest_lock, ip);
957 : :
958 [ # # # # : 1598443 : if (__mutex_trylock(lock) ||
+ + + + ]
959 : : mutex_optimistic_spin(lock, ww_ctx, use_ww_ctx, NULL)) {
960 : : /* got the lock, yay! */
961 : : lock_acquired(&lock->dep_map, ip);
962 [ # # ]: 0 : if (use_ww_ctx && ww_ctx)
963 : : ww_mutex_set_context_fastpath(ww, ww_ctx);
964 : 1081664 : preempt_enable();
965 : : return 0;
966 : : }
967 : :
968 : : spin_lock(&lock->wait_lock);
969 : : /*
970 : : * After waiting to acquire the wait_lock, try again.
971 : : */
972 [ # # + + ]: 5700 : if (__mutex_trylock(lock)) {
973 [ # # ]: 0 : if (use_ww_ctx && ww_ctx)
974 : 0 : __ww_mutex_check_waiters(lock, ww_ctx);
975 : :
976 : : goto skip_wait;
977 : : }
978 : :
979 : : debug_mutex_lock_common(lock, &waiter);
980 : :
981 : : lock_contended(&lock->dep_map, ip);
982 : :
983 : : if (!use_ww_ctx) {
984 : : /* add waiting tasks to the end of the waitqueue (FIFO): */
985 : 5129 : __mutex_add_waiter(lock, &waiter, &lock->wait_list);
986 : :
987 : :
988 : : #ifdef CONFIG_DEBUG_MUTEXES
989 : : waiter.ww_ctx = MUTEX_POISON_WW_CTX;
990 : : #endif
991 : : } else {
992 : : /*
993 : : * Add in stamp order, waking up waiters that must kill
994 : : * themselves.
995 : : */
996 : 0 : ret = __ww_mutex_add_waiter(&waiter, lock, ww_ctx);
997 [ # # ]: 0 : if (ret)
998 : : goto err_early_kill;
999 : :
1000 : 0 : waiter.ww_ctx = ww_ctx;
1001 : : }
1002 : :
1003 : 5129 : waiter.task = current;
1004 : :
1005 : 10258 : set_current_state(state);
1006 : : for (;;) {
1007 : : /*
1008 : : * Once we hold wait_lock, we're serialized against
1009 : : * mutex_unlock() handing the lock off to us, do a trylock
1010 : : * before testing the error conditions to make sure we pick up
1011 : : * the handoff.
1012 : : */
1013 [ # # + + ]: 5876 : if (__mutex_trylock(lock))
1014 : : goto acquired;
1015 : :
1016 : : /*
1017 : : * Check for signals and kill conditions while holding
1018 : : * wait_lock. This ensures the lock cancellation is ordered
1019 : : * against mutex_unlock() and wake-ups do not go missing.
1020 : : */
1021 [ # # + - ]: 5813 : if (signal_pending_state(state, current)) {
1022 : : ret = -EINTR;
1023 : : goto err;
1024 : : }
1025 : :
1026 [ # # ]: 0 : if (use_ww_ctx && ww_ctx) {
1027 : 0 : ret = __ww_mutex_check_kill(lock, &waiter, ww_ctx);
1028 [ # # ]: 0 : if (ret)
1029 : : goto err;
1030 : : }
1031 : :
1032 : : spin_unlock(&lock->wait_lock);
1033 : 5813 : schedule_preempt_disabled();
1034 : :
1035 : : /*
1036 : : * ww_mutex needs to always recheck its position since its waiter
1037 : : * list is not FIFO ordered.
1038 : : */
1039 [ # # # # : 5813 : if ((use_ww_ctx && ww_ctx) || !first) {
+ + ]
1040 : 5120 : first = __mutex_waiter_is_first(lock, &waiter);
1041 [ # # + - ]: 5120 : if (first)
1042 : 5120 : __mutex_set_flag(lock, MUTEX_FLAG_HANDOFF);
1043 : : }
1044 : :
1045 : 11626 : set_current_state(state);
1046 : : /*
1047 : : * Here we order against unlock; we must either see it change
1048 : : * state back to RUNNING and fall through the next schedule(),
1049 : : * or we must see its unlock and acquire.
1050 : : */
1051 [ # # # # : 5813 : if (__mutex_trylock(lock) ||
+ + + - ]
1052 [ # # + + ]: 1288 : (first && mutex_optimistic_spin(lock, ww_ctx, use_ww_ctx, &waiter)))
1053 : : break;
1054 : :
1055 : : spin_lock(&lock->wait_lock);
1056 : : }
1057 : : spin_lock(&lock->wait_lock);
1058 : : acquired:
1059 : 5129 : __set_current_state(TASK_RUNNING);
1060 : :
1061 [ # # ]: 0 : if (use_ww_ctx && ww_ctx) {
1062 : : /*
1063 : : * Wound-Wait; we stole the lock (!first_waiter), check the
1064 : : * waiters as anyone might want to wound us.
1065 : : */
1066 [ # # # # ]: 0 : if (!ww_ctx->is_wait_die &&
1067 : 0 : !__mutex_waiter_is_first(lock, &waiter))
1068 : 0 : __ww_mutex_check_waiters(lock, ww_ctx);
1069 : : }
1070 : :
1071 : 5129 : mutex_remove_waiter(lock, &waiter, current);
1072 [ # # + + ]: 5129 : if (likely(list_empty(&lock->wait_list)))
1073 : 3857 : __mutex_clear_flag(lock, MUTEX_FLAGS);
1074 : :
1075 : : debug_mutex_free_waiter(&waiter);
1076 : :
1077 : : skip_wait:
1078 : : /* got the lock - cleanup and rejoice! */
1079 : : lock_acquired(&lock->dep_map, ip);
1080 : :
1081 [ # # ]: 0 : if (use_ww_ctx && ww_ctx)
1082 : : ww_mutex_lock_acquired(ww, ww_ctx);
1083 : :
1084 : : spin_unlock(&lock->wait_lock);
1085 : 5700 : preempt_enable();
1086 : : return 0;
1087 : :
1088 : : err:
1089 : 0 : __set_current_state(TASK_RUNNING);
1090 : 0 : mutex_remove_waiter(lock, &waiter, current);
1091 : : err_early_kill:
1092 : : spin_unlock(&lock->wait_lock);
1093 : : debug_mutex_free_waiter(&waiter);
1094 : : mutex_release(&lock->dep_map, 1, ip);
1095 : 0 : preempt_enable();
1096 : : return ret;
1097 : : }
1098 : :
1099 : : static int __sched
1100 : 1087746 : __mutex_lock(struct mutex *lock, long state, unsigned int subclass,
1101 : : struct lockdep_map *nest_lock, unsigned long ip)
1102 : : {
1103 : 1088071 : return __mutex_lock_common(lock, state, subclass, nest_lock, ip, NULL, false);
1104 : : }
1105 : :
1106 : : static int __sched
1107 : 0 : __ww_mutex_lock(struct mutex *lock, long state, unsigned int subclass,
1108 : : struct lockdep_map *nest_lock, unsigned long ip,
1109 : : struct ww_acquire_ctx *ww_ctx)
1110 : : {
1111 : 0 : return __mutex_lock_common(lock, state, subclass, nest_lock, ip, ww_ctx, true);
1112 : : }
1113 : :
1114 : : #ifdef CONFIG_DEBUG_LOCK_ALLOC
1115 : : void __sched
1116 : : mutex_lock_nested(struct mutex *lock, unsigned int subclass)
1117 : : {
1118 : : __mutex_lock(lock, TASK_UNINTERRUPTIBLE, subclass, NULL, _RET_IP_);
1119 : : }
1120 : :
1121 : : EXPORT_SYMBOL_GPL(mutex_lock_nested);
1122 : :
1123 : : void __sched
1124 : : _mutex_lock_nest_lock(struct mutex *lock, struct lockdep_map *nest)
1125 : : {
1126 : : __mutex_lock(lock, TASK_UNINTERRUPTIBLE, 0, nest, _RET_IP_);
1127 : : }
1128 : : EXPORT_SYMBOL_GPL(_mutex_lock_nest_lock);
1129 : :
1130 : : int __sched
1131 : : mutex_lock_killable_nested(struct mutex *lock, unsigned int subclass)
1132 : : {
1133 : : return __mutex_lock(lock, TASK_KILLABLE, subclass, NULL, _RET_IP_);
1134 : : }
1135 : : EXPORT_SYMBOL_GPL(mutex_lock_killable_nested);
1136 : :
1137 : : int __sched
1138 : : mutex_lock_interruptible_nested(struct mutex *lock, unsigned int subclass)
1139 : : {
1140 : : return __mutex_lock(lock, TASK_INTERRUPTIBLE, subclass, NULL, _RET_IP_);
1141 : : }
1142 : : EXPORT_SYMBOL_GPL(mutex_lock_interruptible_nested);
1143 : :
1144 : : void __sched
1145 : : mutex_lock_io_nested(struct mutex *lock, unsigned int subclass)
1146 : : {
1147 : : int token;
1148 : :
1149 : : might_sleep();
1150 : :
1151 : : token = io_schedule_prepare();
1152 : : __mutex_lock_common(lock, TASK_UNINTERRUPTIBLE,
1153 : : subclass, NULL, _RET_IP_, NULL, 0);
1154 : : io_schedule_finish(token);
1155 : : }
1156 : : EXPORT_SYMBOL_GPL(mutex_lock_io_nested);
1157 : :
1158 : : static inline int
1159 : : ww_mutex_deadlock_injection(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
1160 : : {
1161 : : #ifdef CONFIG_DEBUG_WW_MUTEX_SLOWPATH
1162 : : unsigned tmp;
1163 : :
1164 : : if (ctx->deadlock_inject_countdown-- == 0) {
1165 : : tmp = ctx->deadlock_inject_interval;
1166 : : if (tmp > UINT_MAX/4)
1167 : : tmp = UINT_MAX;
1168 : : else
1169 : : tmp = tmp*2 + tmp + tmp/2;
1170 : :
1171 : : ctx->deadlock_inject_interval = tmp;
1172 : : ctx->deadlock_inject_countdown = tmp;
1173 : : ctx->contending_lock = lock;
1174 : :
1175 : : ww_mutex_unlock(lock);
1176 : :
1177 : : return -EDEADLK;
1178 : : }
1179 : : #endif
1180 : :
1181 : : return 0;
1182 : : }
1183 : :
1184 : : int __sched
1185 : : ww_mutex_lock(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
1186 : : {
1187 : : int ret;
1188 : :
1189 : : might_sleep();
1190 : : ret = __ww_mutex_lock(&lock->base, TASK_UNINTERRUPTIBLE,
1191 : : 0, ctx ? &ctx->dep_map : NULL, _RET_IP_,
1192 : : ctx);
1193 : : if (!ret && ctx && ctx->acquired > 1)
1194 : : return ww_mutex_deadlock_injection(lock, ctx);
1195 : :
1196 : : return ret;
1197 : : }
1198 : : EXPORT_SYMBOL_GPL(ww_mutex_lock);
1199 : :
1200 : : int __sched
1201 : : ww_mutex_lock_interruptible(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
1202 : : {
1203 : : int ret;
1204 : :
1205 : : might_sleep();
1206 : : ret = __ww_mutex_lock(&lock->base, TASK_INTERRUPTIBLE,
1207 : : 0, ctx ? &ctx->dep_map : NULL, _RET_IP_,
1208 : : ctx);
1209 : :
1210 : : if (!ret && ctx && ctx->acquired > 1)
1211 : : return ww_mutex_deadlock_injection(lock, ctx);
1212 : :
1213 : : return ret;
1214 : : }
1215 : : EXPORT_SYMBOL_GPL(ww_mutex_lock_interruptible);
1216 : :
1217 : : #endif
1218 : :
1219 : : /*
1220 : : * Release the lock, slowpath:
1221 : : */
1222 : 61670 : static noinline void __sched __mutex_unlock_slowpath(struct mutex *lock, unsigned long ip)
1223 : : {
1224 : : struct task_struct *next = NULL;
1225 : 61670 : DEFINE_WAKE_Q(wake_q);
1226 : : unsigned long owner;
1227 : :
1228 : : mutex_release(&lock->dep_map, 1, ip);
1229 : :
1230 : : /*
1231 : : * Release the lock before (potentially) taking the spinlock such that
1232 : : * other contenders can get on with things ASAP.
1233 : : *
1234 : : * Except when HANDOFF, in that case we must not clear the owner field,
1235 : : * but instead set it to the top waiter.
1236 : : */
1237 : 61670 : owner = atomic_long_read(&lock->owner);
1238 : : for (;;) {
1239 : : unsigned long old;
1240 : :
1241 : : #ifdef CONFIG_DEBUG_MUTEXES
1242 : : DEBUG_LOCKS_WARN_ON(__owner_task(owner) != current);
1243 : : DEBUG_LOCKS_WARN_ON(owner & MUTEX_FLAG_PICKUP);
1244 : : #endif
1245 : :
1246 [ + + ]: 61672 : if (owner & MUTEX_FLAG_HANDOFF)
1247 : : break;
1248 : :
1249 : 181532 : old = atomic_long_cmpxchg_release(&lock->owner, owner,
1250 : : __owner_flags(owner));
1251 [ + + ]: 60510 : if (old == owner) {
1252 [ + - ]: 60508 : if (owner & MUTEX_FLAG_WAITERS)
1253 : : break;
1254 : :
1255 : 0 : return;
1256 : : }
1257 : :
1258 : : owner = old;
1259 : : }
1260 : :
1261 : : spin_lock(&lock->wait_lock);
1262 : : debug_mutex_unlock(lock);
1263 [ + - ]: 123340 : if (!list_empty(&lock->wait_list)) {
1264 : : /* get the first entry from the wait-list: */
1265 : : struct mutex_waiter *waiter =
1266 : 61670 : list_first_entry(&lock->wait_list,
1267 : : struct mutex_waiter, list);
1268 : :
1269 : 61670 : next = waiter->task;
1270 : :
1271 : : debug_mutex_wake_waiter(lock, waiter);
1272 : 61670 : wake_q_add(&wake_q, next);
1273 : : }
1274 : :
1275 [ + + ]: 61670 : if (owner & MUTEX_FLAG_HANDOFF)
1276 : 1161 : __mutex_handoff(lock, next);
1277 : :
1278 : : spin_unlock(&lock->wait_lock);
1279 : :
1280 : 61669 : wake_up_q(&wake_q);
1281 : : }
1282 : :
1283 : : #ifndef CONFIG_DEBUG_LOCK_ALLOC
1284 : : /*
1285 : : * Here come the less common (and hence less performance-critical) APIs:
1286 : : * mutex_lock_interruptible() and mutex_trylock().
1287 : : */
1288 : : static noinline int __sched
1289 : : __mutex_lock_killable_slowpath(struct mutex *lock);
1290 : :
1291 : : static noinline int __sched
1292 : : __mutex_lock_interruptible_slowpath(struct mutex *lock);
1293 : :
1294 : : /**
1295 : : * mutex_lock_interruptible() - Acquire the mutex, interruptible by signals.
1296 : : * @lock: The mutex to be acquired.
1297 : : *
1298 : : * Lock the mutex like mutex_lock(). If a signal is delivered while the
1299 : : * process is sleeping, this function will return without acquiring the
1300 : : * mutex.
1301 : : *
1302 : : * Context: Process context.
1303 : : * Return: 0 if the lock was successfully acquired or %-EINTR if a
1304 : : * signal arrived.
1305 : : */
1306 : 1127297 : int __sched mutex_lock_interruptible(struct mutex *lock)
1307 : : {
1308 : 1127297 : might_sleep();
1309 : :
1310 [ + + ]: 1127312 : if (__mutex_trylock_fast(lock))
1311 : : return 0;
1312 : :
1313 : 95 : return __mutex_lock_interruptible_slowpath(lock);
1314 : : }
1315 : :
1316 : : EXPORT_SYMBOL(mutex_lock_interruptible);
1317 : :
1318 : : /**
1319 : : * mutex_lock_killable() - Acquire the mutex, interruptible by fatal signals.
1320 : : * @lock: The mutex to be acquired.
1321 : : *
1322 : : * Lock the mutex like mutex_lock(). If a signal which will be fatal to
1323 : : * the current process is delivered while the process is sleeping, this
1324 : : * function will return without acquiring the mutex.
1325 : : *
1326 : : * Context: Process context.
1327 : : * Return: 0 if the lock was successfully acquired or %-EINTR if a
1328 : : * fatal signal arrived.
1329 : : */
1330 : 471053 : int __sched mutex_lock_killable(struct mutex *lock)
1331 : : {
1332 : 471053 : might_sleep();
1333 : :
1334 [ + + ]: 471016 : if (__mutex_trylock_fast(lock))
1335 : : return 0;
1336 : :
1337 : 243 : return __mutex_lock_killable_slowpath(lock);
1338 : : }
1339 : : EXPORT_SYMBOL(mutex_lock_killable);
1340 : :
1341 : : /**
1342 : : * mutex_lock_io() - Acquire the mutex and mark the process as waiting for I/O
1343 : : * @lock: The mutex to be acquired.
1344 : : *
1345 : : * Lock the mutex like mutex_lock(). While the task is waiting for this
1346 : : * mutex, it will be accounted as being in the IO wait state by the
1347 : : * scheduler.
1348 : : *
1349 : : * Context: Process context.
1350 : : */
1351 : 207 : void __sched mutex_lock_io(struct mutex *lock)
1352 : : {
1353 : : int token;
1354 : :
1355 : 207 : token = io_schedule_prepare();
1356 : 207 : mutex_lock(lock);
1357 : 207 : io_schedule_finish(token);
1358 : 207 : }
1359 : : EXPORT_SYMBOL_GPL(mutex_lock_io);
1360 : :
1361 : : static noinline void __sched
1362 : 1087240 : __mutex_lock_slowpath(struct mutex *lock)
1363 : : {
1364 : 1087240 : __mutex_lock(lock, TASK_UNINTERRUPTIBLE, 0, NULL, _RET_IP_);
1365 : 1087736 : }
1366 : :
1367 : : static noinline int __sched
1368 : 243 : __mutex_lock_killable_slowpath(struct mutex *lock)
1369 : : {
1370 : 243 : return __mutex_lock(lock, TASK_KILLABLE, 0, NULL, _RET_IP_);
1371 : : }
1372 : :
1373 : : static noinline int __sched
1374 : 95 : __mutex_lock_interruptible_slowpath(struct mutex *lock)
1375 : : {
1376 : 95 : return __mutex_lock(lock, TASK_INTERRUPTIBLE, 0, NULL, _RET_IP_);
1377 : : }
1378 : :
1379 : : static noinline int __sched
1380 : 0 : __ww_mutex_lock_slowpath(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
1381 : : {
1382 : 0 : return __ww_mutex_lock(&lock->base, TASK_UNINTERRUPTIBLE, 0, NULL,
1383 : 0 : _RET_IP_, ctx);
1384 : : }
1385 : :
1386 : : static noinline int __sched
1387 : 0 : __ww_mutex_lock_interruptible_slowpath(struct ww_mutex *lock,
1388 : : struct ww_acquire_ctx *ctx)
1389 : : {
1390 : 0 : return __ww_mutex_lock(&lock->base, TASK_INTERRUPTIBLE, 0, NULL,
1391 : 0 : _RET_IP_, ctx);
1392 : : }
1393 : :
1394 : : #endif
1395 : :
1396 : : /**
1397 : : * mutex_trylock - try to acquire the mutex, without waiting
1398 : : * @lock: the mutex to be acquired
1399 : : *
1400 : : * Try to acquire the mutex atomically. Returns 1 if the mutex
1401 : : * has been acquired successfully, and 0 on contention.
1402 : : *
1403 : : * NOTE: this function follows the spin_trylock() convention, so
1404 : : * it is negated from the down_trylock() return values! Be careful
1405 : : * about this when converting semaphore users to mutexes.
1406 : : *
1407 : : * This function must not be used in interrupt context. The
1408 : : * mutex must be released by the same task that acquired it.
1409 : : */
1410 : 136788 : int __sched mutex_trylock(struct mutex *lock)
1411 : : {
1412 : : bool locked;
1413 : :
1414 : : #ifdef CONFIG_DEBUG_MUTEXES
1415 : : DEBUG_LOCKS_WARN_ON(lock->magic != lock);
1416 : : #endif
1417 : :
1418 : : locked = __mutex_trylock(lock);
1419 : : if (locked)
1420 : : mutex_acquire(&lock->dep_map, 0, 1, _RET_IP_);
1421 : :
1422 : 136788 : return locked;
1423 : : }
1424 : : EXPORT_SYMBOL(mutex_trylock);
1425 : :
1426 : : #ifndef CONFIG_DEBUG_LOCK_ALLOC
1427 : : int __sched
1428 : 0 : ww_mutex_lock(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
1429 : : {
1430 : 0 : might_sleep();
1431 : :
1432 [ # # ]: 0 : if (__mutex_trylock_fast(&lock->base)) {
1433 [ # # ]: 0 : if (ctx)
1434 : : ww_mutex_set_context_fastpath(lock, ctx);
1435 : : return 0;
1436 : : }
1437 : :
1438 : 0 : return __ww_mutex_lock_slowpath(lock, ctx);
1439 : : }
1440 : : EXPORT_SYMBOL(ww_mutex_lock);
1441 : :
1442 : : int __sched
1443 : 0 : ww_mutex_lock_interruptible(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
1444 : : {
1445 : 0 : might_sleep();
1446 : :
1447 [ # # ]: 0 : if (__mutex_trylock_fast(&lock->base)) {
1448 [ # # ]: 0 : if (ctx)
1449 : : ww_mutex_set_context_fastpath(lock, ctx);
1450 : : return 0;
1451 : : }
1452 : :
1453 : 0 : return __ww_mutex_lock_interruptible_slowpath(lock, ctx);
1454 : : }
1455 : : EXPORT_SYMBOL(ww_mutex_lock_interruptible);
1456 : :
1457 : : #endif
1458 : :
1459 : : /**
1460 : : * atomic_dec_and_mutex_lock - return holding mutex if we dec to 0
1461 : : * @cnt: the atomic which we are to dec
1462 : : * @lock: the mutex to return holding if we dec to 0
1463 : : *
1464 : : * return true and hold lock if we dec to 0, return false otherwise
1465 : : */
1466 : 0 : int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock)
1467 : : {
1468 : : /* dec if we can't possibly hit 0 */
1469 [ # # ]: 0 : if (atomic_add_unless(cnt, -1, 1))
1470 : : return 0;
1471 : : /* we might hit 0, so take the lock */
1472 : 0 : mutex_lock(lock);
1473 [ # # ]: 0 : if (!atomic_dec_and_test(cnt)) {
1474 : : /* when we actually did the dec, we didn't hit 0 */
1475 : 0 : mutex_unlock(lock);
1476 : 0 : return 0;
1477 : : }
1478 : : /* we hit 0, and we hold the lock */
1479 : : return 1;
1480 : : }
1481 : : EXPORT_SYMBOL(atomic_dec_and_mutex_lock);
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