Release 4.7 kernel/locking/mutex.c

/*
 * kernel/locking/mutex.c
 *
 * Mutexes: blocking mutual exclusion locks
 *
 * Started by Ingo Molnar:
 *
 *  Copyright (C) 2004, 2005, 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
 *
 * Many thanks to Arjan van de Ven, Thomas Gleixner, Steven Rostedt and
 * David Howells for suggestions and improvements.
 *
 *  - Adaptive spinning for mutexes by Peter Zijlstra. (Ported to mainline
 *    from the -rt tree, where it was originally implemented for rtmutexes
 *    by Steven Rostedt, based on work by Gregory Haskins, Peter Morreale
 *    and Sven Dietrich.
 *
 * Also see Documentation/locking/mutex-design.txt.
 */
#include <linux/mutex.h>
#include <linux/ww_mutex.h>
#include <linux/sched.h>
#include <linux/sched/rt.h>
#include <linux/export.h>
#include <linux/spinlock.h>
#include <linux/interrupt.h>
#include <linux/debug_locks.h>
#include <linux/osq_lock.h>

/*
 * In the DEBUG case we are using the "NULL fastpath" for mutexes,
 * which forces all calls into the slowpath:
 */
#ifdef CONFIG_DEBUG_MUTEXES
# include "mutex-debug.h"
# include <asm-generic/mutex-null.h>
/*
 * Must be 0 for the debug case so we do not do the unlock outside of the
 * wait_lock region. debug_mutex_unlock() will do the actual unlock in this
 * case.
 */

# undef __mutex_slowpath_needs_to_unlock

# define  __mutex_slowpath_needs_to_unlock()	0
#else
# include "mutex.h"
# include <asm/mutex.h>
#endif


void

__mutex_init(struct mutex *lock, const char *name, struct lock_class_key *key)
{
	atomic_set(&lock->count, 1);
	spin_lock_init(&lock->wait_lock);
	INIT_LIST_HEAD(&lock->wait_list);
	mutex_clear_owner(lock);
#ifdef CONFIG_MUTEX_SPIN_ON_OWNER
	osq_lock_init(&lock->osq);
#endif

	debug_mutex_init(lock, name, key);
}

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EXPORT_SYMBOL(__mutex_init);

#ifndef CONFIG_DEBUG_LOCK_ALLOC
/*
 * We split the mutex lock/unlock logic into separate fastpath and
 * slowpath functions, to reduce the register pressure on the fastpath.
 * We also put the fastpath first in the kernel image, to make sure the
 * branch is predicted by the CPU as default-untaken.
 */
__visible void __sched __mutex_lock_slowpath(atomic_t *lock_count);

/**
 * mutex_lock - acquire the mutex
 * @lock: the mutex to be acquired
 *
 * Lock the mutex exclusively for this task. If the mutex is not
 * available right now, it will sleep until it can get it.
 *
 * The mutex must later on be released by the same task that
 * acquired it. Recursive locking is not allowed. The task
 * may not exit without first unlocking the mutex. Also, kernel
 * memory where the mutex resides must not be freed with
 * the mutex still locked. The mutex must first be initialized
 * (or statically defined) before it can be locked. memset()-ing
 * the mutex to 0 is not allowed.
 *
 * ( The CONFIG_DEBUG_MUTEXES .config option turns on debugging
 *   checks that will enforce the restrictions and will also do
 *   deadlock debugging. )
 *
 * This function is similar to (but not equivalent to) down().
 */


void __sched mutex_lock(struct mutex *lock)
{
	might_sleep();
	/*
         * The locking fastpath is the 1->0 transition from
         * 'unlocked' into 'locked' state.
         */
	__mutex_fastpath_lock(&lock->count, __mutex_lock_slowpath);
	mutex_set_owner(lock);
}

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EXPORT_SYMBOL(mutex_lock);
#endif



static __always_inline void ww_mutex_lock_acquired(struct ww_mutex *ww,
						   struct ww_acquire_ctx *ww_ctx)
{
#ifdef CONFIG_DEBUG_MUTEXES
	/*
         * If this WARN_ON triggers, you used ww_mutex_lock to acquire,
         * but released with a normal mutex_unlock in this call.
         *
         * This should never happen, always use ww_mutex_unlock.
         */
	DEBUG_LOCKS_WARN_ON(ww->ctx);

	/*
         * Not quite done after calling ww_acquire_done() ?
         */
	DEBUG_LOCKS_WARN_ON(ww_ctx->done_acquire);

	if (ww_ctx->contending_lock) {
		/*
                 * After -EDEADLK you tried to
                 * acquire a different ww_mutex? Bad!
                 */
		DEBUG_LOCKS_WARN_ON(ww_ctx->contending_lock != ww);

		/*
                 * You called ww_mutex_lock after receiving -EDEADLK,
                 * but 'forgot' to unlock everything else first?
                 */
		DEBUG_LOCKS_WARN_ON(ww_ctx->acquired > 0);
		ww_ctx->contending_lock = NULL;
	}

	/*
         * Naughty, using a different class will lead to undefined behavior!
         */
	DEBUG_LOCKS_WARN_ON(ww_ctx->ww_class != ww->ww_class);
#endif
	ww_ctx->acquired++;
}

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/*
 * After acquiring lock with fastpath or when we lost out in contested
 * slowpath, set ctx and wake up any waiters so they can recheck.
 *
 * This function is never called when CONFIG_DEBUG_LOCK_ALLOC is set,
 * as the fastpath and opportunistic spinning are disabled in that case.
 */

static __always_inline void

ww_mutex_set_context_fastpath(struct ww_mutex *lock,
			       struct ww_acquire_ctx *ctx)
{
	unsigned long flags;
	struct mutex_waiter *cur;

	ww_mutex_lock_acquired(lock, ctx);

	lock->ctx = ctx;

	/*
         * The lock->ctx update should be visible on all cores before
         * the atomic read is done, otherwise contended waiters might be
         * missed. The contended waiters will either see ww_ctx == NULL
         * and keep spinning, or it will acquire wait_lock, add itself
         * to waiter list and sleep.
         */
	smp_mb(); /* ^^^ */

	/*
         * Check if lock is contended, if not there is nobody to wake up
         */
	if (likely(atomic_read(&lock->base.count) == 0))
		return;

	/*
         * Uh oh, we raced in fastpath, wake up everyone in this case,
         * so they can see the new lock->ctx.
         */
	spin_lock_mutex(&lock->base.wait_lock, flags);
	list_for_each_entry(cur, &lock->base.wait_list, list) {
		debug_mutex_wake_waiter(&lock->base, cur);
		wake_up_process(cur->task);
	}
	spin_unlock_mutex(&lock->base.wait_lock, flags);
}

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/*
 * After acquiring lock in the slowpath set ctx and wake up any
 * waiters so they can recheck.
 *
 * Callers must hold the mutex wait_lock.
 */

static __always_inline void

ww_mutex_set_context_slowpath(struct ww_mutex *lock,
			      struct ww_acquire_ctx *ctx)
{
	struct mutex_waiter *cur;

	ww_mutex_lock_acquired(lock, ctx);
	lock->ctx = ctx;

	/*
         * Give any possible sleeping processes the chance to wake up,
         * so they can recheck if they have to back off.
         */
	list_for_each_entry(cur, &lock->base.wait_list, list) {
		debug_mutex_wake_waiter(&lock->base, cur);
		wake_up_process(cur->task);
	}
}

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#ifdef CONFIG_MUTEX_SPIN_ON_OWNER
/*
 * Look out! "owner" is an entirely speculative pointer
 * access and not reliable.
 */

static noinline

bool mutex_spin_on_owner(struct mutex *lock, struct task_struct *owner)
{
	bool ret = true;

	rcu_read_lock();
	while (lock->owner == owner) {
		/*
                 * Ensure we emit the owner->on_cpu, dereference _after_
                 * checking lock->owner still matches owner. If that fails,
                 * owner might point to freed memory. If it still matches,
                 * the rcu_read_lock() ensures the memory stays valid.
                 */
		barrier();

		if (!owner->on_cpu || need_resched()) {
			ret = false;
			break;
		}

		cpu_relax_lowlatency();
	}
	rcu_read_unlock();

	return ret;
}

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/*
 * Initial check for entering the mutex spinning loop
 */


static inline int mutex_can_spin_on_owner(struct mutex *lock)
{
	struct task_struct *owner;
	int retval = 1;

	if (need_resched())
		return 0;

	rcu_read_lock();
	owner = READ_ONCE(lock->owner);
	if (owner)
		retval = owner->on_cpu;
	rcu_read_unlock();
	/*
         * if lock->owner is not set, the mutex owner may have just acquired
         * it and not set the owner yet or the mutex has been released.
         */
	return retval;
}

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/*
 * Atomically try to take the lock when it is available
 */


static inline bool mutex_try_to_acquire(struct mutex *lock)
{
	return !mutex_is_locked(lock) &&
		(atomic_cmpxchg_acquire(&lock->count, 1, 0) == 1);
}

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/*
 * Optimistic spinning.
 *
 * We try to spin for acquisition when we find that the lock owner
 * is currently running on a (different) CPU and while we don't
 * need to reschedule. The rationale is that if the lock owner is
 * running, it is likely to release the lock soon.
 *
 * Since this needs the lock owner, and this mutex implementation
 * doesn't track the owner atomically in the lock field, we need to
 * track it non-atomically.
 *
 * We can't do this for DEBUG_MUTEXES because that relies on wait_lock
 * to serialize everything.
 *
 * The mutex spinners are queued up using MCS lock so that only one
 * spinner can compete for the mutex. However, if mutex spinning isn't
 * going to happen, there is no point in going through the lock/unlock
 * overhead.
 *
 * Returns true when the lock was taken, otherwise false, indicating
 * that we need to jump to the slowpath and sleep.
 */


static bool mutex_optimistic_spin(struct mutex *lock,
				  struct ww_acquire_ctx *ww_ctx, const bool use_ww_ctx)
{
	struct task_struct *task = current;

	if (!mutex_can_spin_on_owner(lock))
		goto done;

	/*
         * In order to avoid a stampede of mutex spinners trying to
         * acquire the mutex all at once, the spinners need to take a
         * MCS (queued) lock first before spinning on the owner field.
         */
	if (!osq_lock(&lock->osq))
		goto done;

	while (true) {
		struct task_struct *owner;

		if (use_ww_ctx && ww_ctx->acquired > 0) {
			struct ww_mutex *ww;

			ww = container_of(lock, struct ww_mutex, base);
			/*
                         * If ww->ctx is set the contents are undefined, only
                         * by acquiring wait_lock there is a guarantee that
                         * they are not invalid when reading.
                         *
                         * As such, when deadlock detection needs to be
                         * performed the optimistic spinning cannot be done.
                         */
			if (READ_ONCE(ww->ctx))
				break;
		}

		/*
                 * If there's an owner, wait for it to either
                 * release the lock or go to sleep.
                 */
		owner = READ_ONCE(lock->owner);
		if (owner && !mutex_spin_on_owner(lock, owner))
			break;

		/* Try to acquire the mutex if it is unlocked. */
		if (mutex_try_to_acquire(lock)) {
			lock_acquired(&lock->dep_map, ip);

			if (use_ww_ctx) {
				struct ww_mutex *ww;
				ww = container_of(lock, struct ww_mutex, base);

				ww_mutex_set_context_fastpath(ww, ww_ctx);
			}

			mutex_set_owner(lock);
			osq_unlock(&lock->osq);
			return true;
		}

		/*
                 * When there's no owner, we might have preempted between the
                 * owner acquiring the lock and setting the owner field. If
                 * we're an RT task that will live-lock because we won't let
                 * the owner complete.
                 */
		if (!owner && (need_resched() || rt_task(task)))
			break;

		/*
                 * The cpu_relax() call is a compiler barrier which forces
                 * everything in this loop to be re-loaded. We don't need
                 * memory barriers as we'll eventually observe the right
                 * values at the cost of a few extra spins.
                 */
		cpu_relax_lowlatency();
	}

	osq_unlock(&lock->osq);
done:
	/*
         * If we fell out of the spin path because of need_resched(),
         * reschedule now, before we try-lock the mutex. This avoids getting
         * scheduled out right after we obtained the mutex.
         */
	if (need_resched()) {
		/*
                 * We _should_ have TASK_RUNNING here, but just in case
                 * we do not, make it so, otherwise we might get stuck.
                 */
		__set_current_state(TASK_RUNNING);
		schedule_preempt_disabled();
	}

	return false;
}
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#else


static bool mutex_optimistic_spin(struct mutex *lock,
				  struct ww_acquire_ctx *ww_ctx, const bool use_ww_ctx)
{
	return false;
}
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#endif

__visible __used noinline
void __sched __mutex_unlock_slowpath(atomic_t *lock_count);

/**
 * mutex_unlock - release the mutex
 * @lock: the mutex to be released
 *
 * Unlock a mutex that has been locked by this task previously.
 *
 * This function must not be used in interrupt context. Unlocking
 * of a not locked mutex is not allowed.
 *
 * This function is similar to (but not equivalent to) up().
 */


void __sched mutex_unlock(struct mutex *lock)
{
	/*
         * The unlocking fastpath is the 0->1 transition from 'locked'
         * into 'unlocked' state:
         */
#ifndef CONFIG_DEBUG_MUTEXES
	/*
         * When debugging is enabled we must not clear the owner before time,
         * the slow path will always be taken, and that clears the owner field
         * after verifying that it was indeed current.
         */
	mutex_clear_owner(lock);
#endif
	__mutex_fastpath_unlock(&lock->count, __mutex_unlock_slowpath);
}

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EXPORT_SYMBOL(mutex_unlock);

/**
 * ww_mutex_unlock - release the w/w mutex
 * @lock: the mutex to be released
 *
 * Unlock a mutex that has been locked by this task previously with any of the
 * ww_mutex_lock* functions (with or without an acquire context). It is
 * forbidden to release the locks after releasing the acquire context.
 *
 * This function must not be used in interrupt context. Unlocking
 * of a unlocked mutex is not allowed.
 */


void __sched ww_mutex_unlock(struct ww_mutex *lock)
{
	/*
         * The unlocking fastpath is the 0->1 transition from 'locked'
         * into 'unlocked' state:
         */
	if (lock->ctx) {
#ifdef CONFIG_DEBUG_MUTEXES
		DEBUG_LOCKS_WARN_ON(!lock->ctx->acquired);
#endif
		if (lock->ctx->acquired > 0)
			lock->ctx->acquired--;
		lock->ctx = NULL;
	}

#ifndef CONFIG_DEBUG_MUTEXES
	/*
         * When debugging is enabled we must not clear the owner before time,
         * the slow path will always be taken, and that clears the owner field
         * after verifying that it was indeed current.
         */
	mutex_clear_owner(&lock->base);
#endif
	__mutex_fastpath_unlock(&lock->base.count, __mutex_unlock_slowpath);
}
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EXPORT_SYMBOL(ww_mutex_unlock);


static inline int __sched

__ww_mutex_lock_check_stamp(struct mutex *lock, struct ww_acquire_ctx *ctx)
{
	struct ww_mutex *ww = container_of(lock, struct ww_mutex, base);
	struct ww_acquire_ctx *hold_ctx = READ_ONCE(ww->ctx);

	if (!hold_ctx)
		return 0;

	if (ctx->stamp - hold_ctx->stamp <= LONG_MAX &&
	    (ctx->stamp != hold_ctx->stamp || ctx > hold_ctx)) {
#ifdef CONFIG_DEBUG_MUTEXES
		DEBUG_LOCKS_WARN_ON(ctx->contending_lock);
		ctx->contending_lock = ww;
#endif
		return -EDEADLK;
	}

	return 0;
}

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/*
 * Lock a mutex (possibly interruptible), slowpath:
 */

static __always_inline int __sched

__mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
		    struct lockdep_map *nest_lock, unsigned long ip,
		    struct ww_acquire_ctx *ww_ctx, const bool use_ww_ctx)
{
	struct task_struct *task = current;
	struct mutex_waiter waiter;
	unsigned long flags;
	int ret;

	if (use_ww_ctx) {
		struct ww_mutex *ww = container_of(lock, struct ww_mutex, base);
		if (unlikely(ww_ctx == READ_ONCE(ww->ctx)))
			return -EALREADY;
	}

	preempt_disable();
	mutex_acquire_nest(&lock->dep_map, subclass, 0, nest_lock, ip);

	if (mutex_optimistic_spin(lock, ww_ctx, use_ww_ctx)) {
		/* got the lock, yay! */
		preempt_enable();
		return 0;
	}

	spin_lock_mutex(&lock->wait_lock, flags);

	/*
         * Once more, try to acquire the lock. Only try-lock the mutex if
         * it is unlocked to reduce unnecessary xchg() operations.
         */
	if (!mutex_is_locked(lock) &&
	    (atomic_xchg_acquire(&lock->count, 0) == 1))
		goto skip_wait;

	debug_mutex_lock_common(lock, &waiter);
	debug_mutex_add_waiter(lock, &waiter, task);

	/* add waiting tasks to the end of the waitqueue (FIFO): */
	list_add_tail(&waiter.list, &lock->wait_list);
	waiter.task = task;

	lock_contended(&lock->dep_map, ip);

	for (;;) {
		/*
                 * Lets try to take the lock again - this is needed even if
                 * we get here for the first time (shortly after failing to
                 * acquire the lock), to make sure that we get a wakeup once
                 * it's unlocked. Later on, if we sleep, this is the
                 * operation that gives us the lock. We xchg it to -1, so
                 * that when we release the lock, we properly wake up the
                 * other waiters. We only attempt the xchg if the count is
                 * non-negative in order to avoid unnecessary xchg operations:
                 */
		if (atomic_read(&lock->count) >= 0 &&
		    (atomic_xchg_acquire(&lock->count, -1) == 1))
			break;

		/*
                 * got a signal? (This code gets eliminated in the
                 * TASK_UNINTERRUPTIBLE case.)
                 */
		if (unlikely(signal_pending_state(state, task))) {
			ret = -EINTR;
			goto err;
		}

		if (use_ww_ctx && ww_ctx->acquired > 0) {
			ret = __ww_mutex_lock_check_stamp(lock, ww_ctx);
			if (ret)
				goto err;
		}

		__set_task_state(task, state);

		/* didn't get the lock, go to sleep: */
		spin_unlock_mutex(&lock->wait_lock, flags);
		schedule_preempt_disabled();
		spin_lock_mutex(&lock->wait_lock, flags);
	}
	__set_task_state(task, TASK_RUNNING);

	mutex_remove_waiter(lock, &waiter, task);
	/* set it to 0 if there are no waiters left: */
	if (likely(list_empty(&lock->wait_list)))
		atomic_set(&lock->count, 0);
	debug_mutex_free_waiter(&waiter);

skip_wait:
	/* got the lock - cleanup and rejoice! */
	lock_acquired(&lock->dep_map, ip);
	mutex_set_owner(lock);

	if (use_ww_ctx) {
		struct ww_mutex *ww = container_of(lock, struct ww_mutex, base);
		ww_mutex_set_context_slowpath(ww, ww_ctx);
	}

	spin_unlock_mutex(&lock->wait_lock, flags);
	preempt_enable();
	return 0;

err:
	mutex_remove_waiter(lock, &waiter, task);
	spin_unlock_mutex(&lock->wait_lock, flags);
	debug_mutex_free_waiter(&waiter);
	mutex_release(&lock->dep_map, 1, ip);
	preempt_enable();
	return ret;
}

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1
3.45%
thomas gleixner
thomas gleixner
1
0.20%
1
3.45%
lucas de marchi
lucas de marchi
1
0.20%
1
3.45%
linus torvalds
linus torvalds
1
0.20%
1
3.45%
Total
491
100.00%
29
100.00%

#ifdef CONFIG_DEBUG_LOCK_ALLOC

void __sched

mutex_lock_nested(struct mutex *lock, unsigned int subclass)
{
	might_sleep();
	__mutex_lock_common(lock, TASK_UNINTERRUPTIBLE,
			    subclass, NULL, _RET_IP_, NULL, 0);
}

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ingo molnar
ingo molnar
27
77.14%
1
20.00%
peter zijlstra
peter zijlstra
4
11.43%
2
40.00%
tetsuo handa
tetsuo handa
2
5.71%
1
20.00%
maarten lankhorst
maarten lankhorst
2
5.71%
1
20.00%
Total
35
100.00%
5
100.00%


EXPORT_SYMBOL_GPL(mutex_lock_nested);


void __sched

_mutex_lock_nest_lock(struct mutex *lock, struct lockdep_map *nest)
{
	might_sleep();
	__mutex_lock_common(lock, TASK_UNINTERRUPTIBLE,
			    0, nest, _RET_IP_, NULL, 0);
}

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peter zijlstra
peter zijlstra
32
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1
33.33%
maarten lankhorst
maarten lankhorst
2
5.56%
1
33.33%
tetsuo handa
tetsuo handa
2
5.56%
1
33.33%
Total
36
100.00%
3
100.00%


EXPORT_SYMBOL_GPL(_mutex_lock_nest_lock);


int __sched

mutex_lock_killable_nested(struct mutex *lock, unsigned int subclass)
{
	might_sleep();
	return __mutex_lock_common(lock, TASK_KILLABLE,
				   subclass, NULL, _RET_IP_, NULL, 0);
}
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liam r. howlett
liam r. howlett
20
55.56%
1
25.00%
maarten lankhorst
maarten lankhorst
12
33.33%
1
25.00%
neil brown
neil brown
2
5.56%
1
25.00%
tetsuo handa
tetsuo handa
2
5.56%
1
25.00%
Total
36
100.00%
4
100.00%


EXPORT_SYMBOL_GPL(mutex_lock_killable_nested);


int __sched

mutex_lock_interruptible_nested(struct mutex *lock, unsigned int subclass)
{
	might_sleep();
	return __mutex_lock_common(lock, TASK_INTERRUPTIBLE,
				   subclass, NULL, _RET_IP_, NULL, 0);
}

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maarten lankhorst
maarten lankhorst
34
94.44%
1
50.00%
tetsuo handa
tetsuo handa
2
5.56%
1
50.00%
Total
36
100.00%
2
100.00%


EXPORT_SYMBOL_GPL(mutex_lock_interruptible_nested);


static inline int

ww_mutex_deadlock_injection(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
{
#ifdef CONFIG_DEBUG_WW_MUTEX_SLOWPATH
	unsigned tmp;

	if (ctx->deadlock_inject_countdown-- == 0) {
		tmp = ctx->deadlock_inject_interval;
		if (tmp > UINT_MAX/4)
			tmp = UINT_MAX;
		else
			tmp = tmp*2 + tmp + tmp/2;

		ctx->deadlock_inject_interval = tmp;
		ctx->deadlock_inject_countdown = tmp;
		ctx->contending_lock = lock;

		ww_mutex_unlock(lock);

		return -EDEADLK;
	}
#endif

	return 0;
}

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daniel vetter
daniel vetter
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1
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97
100.00%
1
100.00%


int __sched

__ww_mutex_lock(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
{
	int ret;

	might_sleep();
	ret =  __mutex_lock_common(&lock->base, TASK_UNINTERRUPTIBLE,
				   0, &ctx->dep_map, _RET_IP_, ctx, 1);
	if (!ret && ctx->acquired > 1)
		return ww_mutex_deadlock_injection(lock, ctx);

	return ret;
}
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maarten lankhorst
maarten lankhorst
34
49.28%
2
33.33%
daniel vetter
daniel vetter
26
37.68%
1
16.67%
liam r. howlett
liam r. howlett
6
8.70%
1
16.67%
tetsuo handa
tetsuo handa
2
2.90%
1
16.67%
peter zijlstra
peter zijlstra
1
1.45%
1
16.67%
Total
69
100.00%
6
100.00%


EXPORT_SYMBOL_GPL(__ww_mutex_lock);


int __sched

__ww_mutex_lock_interruptible(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
{
	int ret;

	might_sleep();
	ret = __mutex_lock_common(&lock->base, TASK_INTERRUPTIBLE,
				  0, &ctx->dep_map, _RET_IP_, ctx, 1);

	if (!ret && ctx->acquired > 1)
		return ww_mutex_deadlock_injection(lock, ctx);

	return ret;
}
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daniel vetter
daniel vetter
26
37.68%
1
12.50%
neil brown
neil brown
19
27.54%
1
12.50%
maarten lankhorst
maarten lankhorst
17
24.64%
2
25.00%
peter zijlstra
peter zijlstra
3
4.35%
2
25.00%
tetsuo handa
tetsuo handa
2
2.90%
1
12.50%
liam r. howlett
liam r. howlett
2
2.90%
1
12.50%
Total
69
100.00%
8
100.00%


EXPORT_SYMBOL_GPL(__ww_mutex_lock_interruptible);

#endif

/*
 * Release the lock, slowpath:
 */

static inline void

__mutex_unlock_common_slowpath(struct mutex *lock, int nested)
{
	unsigned long flags;
	WAKE_Q(wake_q);

	/*
         * As a performance measurement, release the lock before doing other
         * wakeup related duties to follow. This allows other tasks to acquire
         * the lock sooner, while still handling cleanups in past unlock calls.
         * This can be done as we do not enforce strict equivalence between the
         * mutex counter and wait_list.
         *
         *
         * Some architectures leave the lock unlocked in the fastpath failure
         * case, others need to leave it locked. In the later case we have to
         * unlock it here - as the lock counter is currently 0 or negative.
         */
	if (__mutex_slowpath_needs_to_unlock())
		atomic_set(&lock->count, 1);

	spin_lock_mutex(&lock->wait_lock, flags);
	mutex_release(&lock->dep_map, nested, _RET_IP_);
	debug_mutex_unlock(lock);

	if (!list_empty(&lock->wait_list)) {
		/* get the first entry from the wait-list: */
		struct mutex_waiter *waiter =
				list_entry(lock->wait_list.next,
					   struct mutex_waiter, list);

		debug_mutex_wake_waiter(lock, waiter);
		wake_q_add(&wake_q, waiter->task);
	}

	spin_unlock_mutex(&lock->wait_lock, flags);
	wake_up_q(&wake_q);
}

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ingo molnar
99
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4
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davidlohr bueso
davidlohr bueso
19
14.29%
3
37.50%
jason low
jason low
15
11.28%
1
12.50%
Total
133
100.00%
8
100.00%

/*
 * Release the lock, slowpath:
 */

__visible void

__mutex_unlock_slowpath(atomic_t *lock_count)
{
	struct mutex *lock = container_of(lock_count, struct mutex, count);

	__mutex_unlock_common_slowpath(lock, 1);
}

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davidlohr bueso
davidlohr bueso
16
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1
25.00%
ingo molnar
ingo molnar
15
46.88%
2
50.00%
andi kleen
andi kleen
1
3.12%
1
25.00%
Total
32
100.00%
4
100.00%

#ifndef CONFIG_DEBUG_LOCK_ALLOC
/*
 * Here come the less common (and hence less performance-critical) APIs:
 * mutex_lock_interruptible() and mutex_trylock().
 */
static noinline int __sched
__mutex_lock_killable_slowpath(struct mutex *lock);

static noinline int __sched
__mutex_lock_interruptible_slowpath(struct mutex *lock);

/**
 * mutex_lock_interruptible - acquire the mutex, interruptible
 * @lock: the mutex to be acquired
 *
 * Lock the mutex like mutex_lock(), and return 0 if the mutex has
 * been acquired or sleep until the mutex becomes available. If a
 * signal arrives while waiting for the lock then this function
 * returns -EINTR.
 *
 * This function is similar to (but not equivalent to) down_interruptible().
 */


int __sched mutex_lock_interruptible(struct mutex *lock)
{
	int ret;

	might_sleep();
	ret =  __mutex_fastpath_lock_retval(&lock->count);
	if (likely(!ret)) {
		mutex_set_owner(lock);
		return 0;
	} else
		return __mutex_lock_interruptible_slowpath(lock);
}

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ingo molnar
ingo molnar
22
42.31%
2
50.00%
peter zijlstra
peter zijlstra
17
32.69%
1
25.00%
maarten lankhorst
maarten lankhorst
13
25.00%
1
25.00%
Total
52
100.00%
4
100.00%


EXPORT_SYMBOL(mutex_lock_interruptible);



int __sched mutex_lock_killable(struct mutex *lock)
{
	int ret;

	might_sleep();
	ret = __mutex_fastpath_lock_retval(&lock->count);
	if (likely(!ret)) {
		mutex_set_owner(lock);
		return 0;
	} else
		return __mutex_lock_killable_slowpath(lock);
}
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liam r. howlett
liam r. howlett
22
42.31%
1
33.33%
peter zijlstra
peter zijlstra
17
32.69%
1
33.33%
maarten lankhorst
maarten lankhorst
13
25.00%
1
33.33%
Total
52
100.00%
3
100.00%


EXPORT_SYMBOL(mutex_lock_killable);


__visible void __sched

__mutex_lock_slowpath(atomic_t *lock_count)
{
	struct mutex *lock = container_of(lock_count, struct mutex, count);

	__mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, 0,
			    NULL, _RET_IP_, NULL, 0);
}

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peter zijlstra
peter zijlstra
37
86.05%
2
33.33%
tetsuo handa
tetsuo handa
2
4.65%
1
16.67%
maarten lankhorst
maarten lankhorst
2
4.65%
1
16.67%
harvey harrison
harvey harrison
1
2.33%
1
16.67%
andi kleen
andi kleen
1
2.33%
1
16.67%
Total
43
100.00%
6
100.00%


static noinline int __sched

__mutex_lock_killable_slowpath(struct mutex *lock)
{
	return __mutex_lock_common(lock, TASK_KILLABLE, 0,
				   NULL, _RET_IP_, NULL, 0);
}

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liam r. howlett
liam r. howlett
19
61.29%
1
12.50%
maarten lankhorst
maarten lankhorst
4
12.90%
2
25.00%
peter zijlstra
peter zijlstra
3
9.68%
2
25.00%
ingo molnar
ingo molnar
2
6.45%
1
12.50%
tetsuo handa
tetsuo handa
2
6.45%
1
12.50%
harvey harrison
harvey harrison
1
3.23%
1
12.50%
Total
31
100.00%
8
100.00%


static noinline int __sched

__mutex_lock_interruptible_slowpath(struct mutex *lock)
{
	return __mutex_lock_common(lock, TASK_INTERRUPTIBLE, 0,
				   NULL, _RET_IP_, NULL, 0);
}

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ingo molnar
ingo molnar
14
45.16%
2
25.00%
maarten lankhorst
maarten lankhorst
7
22.58%
2
25.00%
peter zijlstra
peter zijlstra
4
12.90%
2
25.00%
liam r. howlett
liam r. howlett
4
12.90%
1
12.50%
tetsuo handa
tetsuo handa
2
6.45%
1
12.50%
Total
31
100.00%
8
100.00%


static noinline int __sched

__ww_mutex_lock_slowpath(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
{
	return __mutex_lock_common(&lock->base, TASK_UNINTERRUPTIBLE, 0,
				   NULL, _RET_IP_, ctx, 1);
}

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maarten lankhorst
maarten lankhorst
37
94.87%
1
50.00%
tetsuo handa
tetsuo handa
2
5.13%
1
50.00%
Total
39
100.00%
2
100.00%


static noinline int __sched

__ww_mutex_lock_interruptible_slowpath(struct ww_mutex *lock,
					    struct ww_acquire_ctx *ctx)
{
	return __mutex_lock_common(&lock->base, TASK_INTERRUPTIBLE, 0,
				   NULL, _RET_IP_, ctx, 1);
}

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maarten lankhorst
maarten lankhorst
34
87.18%
1
33.33%
ingo molnar
ingo molnar
3
7.69%
1
33.33%
tetsuo handa
tetsuo handa
2
5.13%
1
33.33%
Total
39
100.00%
3
100.00%

#endif

/*
 * Spinlock based trylock, we take the spinlock and check whether we
 * can get the lock:
 */


static inline int __mutex_trylock_slowpath(atomic_t *lock_count)
{
	struct mutex *lock = container_of(lock_count, struct mutex, count);
	unsigned long flags;
	int prev;

	/* No need to trylock if the mutex is locked. */
	if (mutex_is_locked(lock))
		return 0;

	spin_lock_mutex(&lock->wait_lock, flags);

	prev = atomic_xchg_acquire(&lock->count, -1);
	if (likely(prev == 1)) {
		mutex_set_owner(lock);
		mutex_acquire(&lock->dep_map, 0, 1, _RET_IP_);
	}

	/* Set it back to 0 if there are no waiters: */
	if (likely(list_empty(&lock->wait_list)))
		atomic_set(&lock->count, 0);

	spin_unlock_mutex(&lock->wait_lock, flags);

	return prev == 1;
}

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ingo molnar
ingo molnar
123
90.44%
3
50.00%
jason low
jason low
11
8.09%
1
16.67%
davidlohr bueso
davidlohr bueso
1
0.74%
1
16.67%
peter zijlstra
peter zijlstra
1
0.74%
1
16.67%
Total
136
100.00%
6
100.00%

/**
 * mutex_trylock - try to acquire the mutex, without waiting
 * @lock: the mutex to be acquired
 *
 * Try to acquire the mutex atomically. Returns 1 if the mutex
 * has been acquired successfully, and 0 on contention.
 *
 * NOTE: this function follows the spin_trylock() convention, so
 * it is negated from the down_trylock() return values! Be careful
 * about this when converting semaphore users to mutexes.
 *
 * This function must not be used in interrupt context. The
 * mutex must be released by the same task that acquired it.
 */


int __sched mutex_trylock(struct mutex *lock)
{
	int ret;

	ret = __mutex_fastpath_trylock(&lock->count, __mutex_trylock_slowpath);
	if (ret)
		mutex_set_owner(lock);

	return ret;
}
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ingo molnar
ingo molnar
21
55.26%
2
66.67%
peter zijlstra
peter zijlstra
17
44.74%
1
33.33%
Total
38
100.00%
3
100.00%


EXPORT_SYMBOL(mutex_trylock);

#ifndef CONFIG_DEBUG_LOCK_ALLOC

int __sched

__ww_mutex_lock(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
{
	int ret;

	might_sleep();

	ret = __mutex_fastpath_lock_retval(&lock->base.count);

	if (likely(!ret)) {
		ww_mutex_set_context_fastpath(lock, ctx);
		mutex_set_owner(&lock->base);
	} else
		ret = __ww_mutex_lock_slowpath(lock, ctx);
	return ret;
}
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maarten lankhorst
maarten lankhorst
72
100.00%
1
100.00%
Total
72
100.00%
1
100.00%


EXPORT_SYMBOL(__ww_mutex_lock);


int __sched

__ww_mutex_lock_interruptible(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
{
	int ret;

	might_sleep();

	ret = __mutex_fastpath_lock_retval(&lock->base.count);

	if (likely(!ret)) {
		ww_mutex_set_context_fastpath(lock, ctx);
		mutex_set_owner(&lock->base);
	} else
		ret = __ww_mutex_lock_interruptible_slowpath(lock, ctx);
	return ret;
}
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maarten lankhorst
maarten lankhorst
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1
100.00%
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72
100.00%
1
100.00%


EXPORT_SYMBOL(__ww_mutex_lock_interruptible);

#endif

/**
 * atomic_dec_and_mutex_lock - return holding mutex if we dec to 0
 * @cnt: the atomic which we are to dec
 * @lock: the mutex to return holding if we dec to 0
 *
 * return true and hold lock if we dec to 0, return false otherwise
 */


int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock)
{
	/* dec if we can't possibly hit 0 */
	if (atomic_add_unless(cnt, -1, 1))
		return 0;
	/* we might hit 0, so take the lock */
	mutex_lock(lock);
	if (!atomic_dec_and_test(cnt)) {
		/* when we actually did the dec, we didn't hit 0 */
		mutex_unlock(lock);
		return 0;
	}
	/* we hit 0, and we hold the lock */
	return 1;
}
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andrew morton
andrew morton
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1
100.00%
Total
59
100.00%
1
100.00%


EXPORT_SYMBOL(atomic_dec_and_mutex_lock);
Overall Contributors
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davidlohr bueso
davidlohr bueso
736
24.99%
14
20.90%
ingo molnar
ingo molnar
681
23.12%
7
10.45%
maarten lankhorst
maarten lankhorst
673
22.85%
4
5.97%
peter zijlstra
peter zijlstra
264
8.96%
11
16.42%
daniel vetter
daniel vetter
149
5.06%
1
1.49%
waiman long
waiman long
95
3.23%
3
4.48%
liam r. howlett
liam r. howlett
94
3.19%
1
1.49%
jason low
jason low
73
2.48%
9
13.43%
andrew morton
andrew morton
65
2.21%
1
1.49%
chris wilson
chris wilson
39
1.32%
1
1.49%
tetsuo handa
tetsuo handa
29
0.98%
1
1.49%
neil brown
neil brown
25
0.85%
1
1.49%
clark williams
clark williams
3
0.10%
1
1.49%
harvey harrison
harvey harrison
3
0.10%
1
1.49%
andi kleen
andi kleen
3
0.10%
1
1.49%
tim chen
tim chen
2
0.07%
1
1.49%
oleg nesterov
oleg nesterov
2
0.07%
1
1.49%
randy dunlap
randy dunlap
2
0.07%
1
1.49%
torok edwin
torok edwin
1
0.03%
1
1.49%
paul gortmaker
paul gortmaker
1
0.03%
1
1.49%
lucas de marchi
lucas de marchi
1
0.03%
1
1.49%
sharon dvir
sharon dvir
1
0.03%
1
1.49%
thomas gleixner
thomas gleixner
1
0.03%
1
1.49%
linus torvalds
linus torvalds
1
0.03%
1
1.49%
roman zippel
roman zippel
1
0.03%
1
1.49%
Total
2945
100.00%
67
100.00%
  
Directory: kernel/locking

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