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