[net-next-2.6.git] / kernel / mutex.c

/*
 * kernel/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.
 *
 * Also see Documentation/mutex-design.txt.
 */
#include <linux/mutex.h>
#include <linux/sched.h>
#include <linux/module.h>
#include <linux/spinlock.h>
#include <linux/interrupt.h>
#include <linux/debug_locks.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>
#else
# include "mutex.h"
# include <asm/mutex.h>
#endif

/***
 * mutex_init - initialize the mutex
 * @lock: the mutex to be initialized
 * @key: the lock_class_key for the class; used by mutex lock debugging
 *
 * Initialize the mutex to unlocked state.
 *
 * It is not allowed to initialize an already locked mutex.
 */
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);

	debug_mutex_init(lock, name, key);
}

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.
 */
static __used noinline 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 mutex 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 inline __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);
}

EXPORT_SYMBOL(mutex_lock);
#endif

static __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:
	 */
	__mutex_fastpath_unlock(&lock->count, __mutex_unlock_slowpath);
}

EXPORT_SYMBOL(mutex_unlock);

/*
 * Lock a mutex (possibly interruptible), slowpath:
 */
static inline int __sched
__mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
	       	unsigned long ip)
{
	struct task_struct *task = current;
	struct mutex_waiter waiter;
	unsigned int old_val;
	unsigned long flags;

	spin_lock_mutex(&lock->wait_lock, flags);

	debug_mutex_lock_common(lock, &waiter);
	mutex_acquire(&lock->dep_map, subclass, 0, ip);
	debug_mutex_add_waiter(lock, &waiter, task_thread_info(task));

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

	old_val = atomic_xchg(&lock->count, -1);
	if (old_val == 1)
		goto done;

	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:
		 */
		old_val = atomic_xchg(&lock->count, -1);
		if (old_val == 1)
			break;

		/*
		 * got a signal? (This code gets eliminated in the
		 * TASK_UNINTERRUPTIBLE case.)
		 */
		if (unlikely(signal_pending_state(state, task))) {
			mutex_remove_waiter(lock, &waiter,
					    task_thread_info(task));
			mutex_release(&lock->dep_map, 1, ip);
			spin_unlock_mutex(&lock->wait_lock, flags);

			debug_mutex_free_waiter(&waiter);
			return -EINTR;
		}
		__set_task_state(task, state);

		/* didnt get the lock, go to sleep: */
		spin_unlock_mutex(&lock->wait_lock, flags);
		schedule();
		spin_lock_mutex(&lock->wait_lock, flags);
	}

done:
	lock_acquired(&lock->dep_map, ip);
	/* got the lock - rejoice! */
	mutex_remove_waiter(lock, &waiter, task_thread_info(task));
	debug_mutex_set_owner(lock, task_thread_info(task));

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

	spin_unlock_mutex(&lock->wait_lock, flags);

	debug_mutex_free_waiter(&waiter);

	return 0;
}

#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, _RET_IP_);
}

EXPORT_SYMBOL_GPL(mutex_lock_nested);

int __sched
mutex_lock_killable_nested(struct mutex *lock, unsigned int subclass)
{
	might_sleep();
	return __mutex_lock_common(lock, TASK_KILLABLE, subclass, _RET_IP_);
}
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, _RET_IP_);
}

EXPORT_SYMBOL_GPL(mutex_lock_interruptible_nested);
#endif

/*
 * Release the lock, slowpath:
 */
static inline void
__mutex_unlock_common_slowpath(atomic_t *lock_count, int nested)
{
	struct mutex *lock = container_of(lock_count, struct mutex, count);
	unsigned long flags;

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

	/*
	 * 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
	 */
	if (__mutex_slowpath_needs_to_unlock())
		atomic_set(&lock->count, 1);

	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_up_process(waiter->task);
	}

	debug_mutex_clear_owner(lock);

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

/*
 * Release the lock, slowpath:
 */
static __used noinline void
__mutex_unlock_slowpath(atomic_t *lock_count)
{
	__mutex_unlock_common_slowpath(lock_count, 1);
}

#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(atomic_t *lock_count);

static noinline int __sched
__mutex_lock_interruptible_slowpath(atomic_t *lock_count);

/***
 * mutex_lock_interruptible - acquire the mutex, interruptable
 * @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)
{
	might_sleep();
	return __mutex_fastpath_lock_retval
			(&lock->count, __mutex_lock_interruptible_slowpath);
}

EXPORT_SYMBOL(mutex_lock_interruptible);

int __sched mutex_lock_killable(struct mutex *lock)
{
	might_sleep();
	return __mutex_fastpath_lock_retval
			(&lock->count, __mutex_lock_killable_slowpath);
}
EXPORT_SYMBOL(mutex_lock_killable);

static __used noinline 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, _RET_IP_);
}

static noinline int __sched
__mutex_lock_killable_slowpath(atomic_t *lock_count)
{
	struct mutex *lock = container_of(lock_count, struct mutex, count);

	return __mutex_lock_common(lock, TASK_KILLABLE, 0, _RET_IP_);
}

static noinline int __sched
__mutex_lock_interruptible_slowpath(atomic_t *lock_count)
{
	struct mutex *lock = container_of(lock_count, struct mutex, count);

	return __mutex_lock_common(lock, TASK_INTERRUPTIBLE, 0, _RET_IP_);
}
#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;

	spin_lock_mutex(&lock->wait_lock, flags);

	prev = atomic_xchg(&lock->count, -1);
	if (likely(prev == 1)) {
		debug_mutex_set_owner(lock, current_thread_info());
		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;
}

/***
 * mutex_trylock - try 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 to 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)
{
	return __mutex_fastpath_trylock(&lock->count,
					__mutex_trylock_slowpath);
}

EXPORT_SYMBOL(mutex_trylock);
Commit	Line	Data
6053ee3b IM	1	/*
	2	* kernel/mutex.c
	3	*
	4	* Mutexes: blocking mutual exclusion locks
	5	*
	6	* Started by Ingo Molnar:
	7	*
	8	* Copyright (C) 2004, 2005, 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
	9	*
	10	* Many thanks to Arjan van de Ven, Thomas Gleixner, Steven Rostedt and
	11	* David Howells for suggestions and improvements.
	12	*
	13	* Also see Documentation/mutex-design.txt.
	14	*/
	15	#include <linux/mutex.h>
	16	#include <linux/sched.h>
	17	#include <linux/module.h>
	18	#include <linux/spinlock.h>
	19	#include <linux/interrupt.h>
9a11b49a	20	#include <linux/debug_locks.h>
6053ee3b IM	21
	22	/*
	23	* In the DEBUG case we are using the "NULL fastpath" for mutexes,
	24	* which forces all calls into the slowpath:
	25	*/
	26	#ifdef CONFIG_DEBUG_MUTEXES
	27	# include "mutex-debug.h"
	28	# include <asm-generic/mutex-null.h>
	29	#else
	30	# include "mutex.h"
	31	# include <asm/mutex.h>
	32	#endif
	33
	34	/***
	35	* mutex_init - initialize the mutex
	36	* @lock: the mutex to be initialized
0e241ffd	37	* @key: the lock_class_key for the class; used by mutex lock debugging
6053ee3b IM	38	*
	39	* Initialize the mutex to unlocked state.
	40	*
	41	* It is not allowed to initialize an already locked mutex.
	42	*/
ef5d4707 IM	43	void
ef5d4707 IM	44	__mutex_init(struct mutex lock, const char name, struct lock_class_key *key)
6053ee3b IM	45	{
	46	atomic_set(&lock->count, 1);
	47	spin_lock_init(&lock->wait_lock);
	48	INIT_LIST_HEAD(&lock->wait_list);
	49
ef5d4707	50	debug_mutex_init(lock, name, key);
6053ee3b IM	51	}
	52
	53	EXPORT_SYMBOL(__mutex_init);
	54
e4564f79	55	#ifndef CONFIG_DEBUG_LOCK_ALLOC
6053ee3b IM	56	/*
	57	* We split the mutex lock/unlock logic into separate fastpath and
	58	* slowpath functions, to reduce the register pressure on the fastpath.
	59	* We also put the fastpath first in the kernel image, to make sure the
	60	* branch is predicted by the CPU as default-untaken.
	61	*/
7918baa5	62	static __used noinline void __sched
9a11b49a	63	__mutex_lock_slowpath(atomic_t *lock_count);
6053ee3b IM	64
	65	/***
	66	* mutex_lock - acquire the mutex
	67	* @lock: the mutex to be acquired
	68	*
	69	* Lock the mutex exclusively for this task. If the mutex is not
	70	* available right now, it will sleep until it can get it.
	71	*
	72	* The mutex must later on be released by the same task that
	73	* acquired it. Recursive locking is not allowed. The task
	74	* may not exit without first unlocking the mutex. Also, kernel
	75	* memory where the mutex resides mutex must not be freed with
	76	* the mutex still locked. The mutex must first be initialized
	77	* (or statically defined) before it can be locked. memset()-ing
	78	* the mutex to 0 is not allowed.
	79	*
	80	* ( The CONFIG_DEBUG_MUTEXES .config option turns on debugging
	81	* checks that will enforce the restrictions and will also do
	82	* deadlock debugging. )
	83	*
	84	* This function is similar to (but not equivalent to) down().
	85	*/
7ad5b3a5	86	void inline __sched mutex_lock(struct mutex *lock)
6053ee3b	87	{
c544bdb1	88	might_sleep();
6053ee3b IM	89	/*
	90	* The locking fastpath is the 1->0 transition from
	91	* 'unlocked' into 'locked' state.
6053ee3b IM	92	*/
	93	__mutex_fastpath_lock(&lock->count, __mutex_lock_slowpath);
	94	}
	95
	96	EXPORT_SYMBOL(mutex_lock);
e4564f79	97	#endif
6053ee3b	98
7918baa5	99	static __used noinline void __sched __mutex_unlock_slowpath(atomic_t *lock_count);
6053ee3b IM	100
	101	/***
	102	* mutex_unlock - release the mutex
	103	* @lock: the mutex to be released
	104	*
	105	* Unlock a mutex that has been locked by this task previously.
	106	*
	107	* This function must not be used in interrupt context. Unlocking
	108	* of a not locked mutex is not allowed.
	109	*
	110	* This function is similar to (but not equivalent to) up().
	111	*/
7ad5b3a5	112	void __sched mutex_unlock(struct mutex *lock)
6053ee3b IM	113	{
	114	/*
	115	* The unlocking fastpath is the 0->1 transition from 'locked'
	116	* into 'unlocked' state:
6053ee3b IM	117	*/
	118	__mutex_fastpath_unlock(&lock->count, __mutex_unlock_slowpath);
	119	}
	120
	121	EXPORT_SYMBOL(mutex_unlock);
	122
	123	/*
	124	* Lock a mutex (possibly interruptible), slowpath:
	125	*/
	126	static inline int __sched
e4564f79 PZ	127	__mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
e4564f79 PZ	128	unsigned long ip)
6053ee3b IM	129	{
	130	struct task_struct *task = current;
	131	struct mutex_waiter waiter;
	132	unsigned int old_val;
1fb00c6c	133	unsigned long flags;
6053ee3b	134
1fb00c6c	135	spin_lock_mutex(&lock->wait_lock, flags);
6053ee3b	136
9a11b49a	137	debug_mutex_lock_common(lock, &waiter);
e4564f79	138	mutex_acquire(&lock->dep_map, subclass, 0, ip);
c9f4f06d	139	debug_mutex_add_waiter(lock, &waiter, task_thread_info(task));
6053ee3b IM	140
	141	/* add waiting tasks to the end of the waitqueue (FIFO): */
	142	list_add_tail(&waiter.list, &lock->wait_list);
	143	waiter.task = task;
	144
4fe87745 PZ	145	old_val = atomic_xchg(&lock->count, -1);
	146	if (old_val == 1)
	147	goto done;
	148
e4564f79	149	lock_contended(&lock->dep_map, ip);
4fe87745	150
6053ee3b IM	151	for (;;) {
	152	/*
	153	* Lets try to take the lock again - this is needed even if
	154	* we get here for the first time (shortly after failing to
	155	* acquire the lock), to make sure that we get a wakeup once
	156	* it's unlocked. Later on, if we sleep, this is the
	157	* operation that gives us the lock. We xchg it to -1, so
	158	* that when we release the lock, we properly wake up the
	159	* other waiters:
	160	*/
	161	old_val = atomic_xchg(&lock->count, -1);
	162	if (old_val == 1)
	163	break;
	164
	165	/*
	166	* got a signal? (This code gets eliminated in the
	167	* TASK_UNINTERRUPTIBLE case.)
	168	*/
6ad36762	169	if (unlikely(signal_pending_state(state, task))) {
ad776537 LH	170	mutex_remove_waiter(lock, &waiter,
ad776537 LH	171	task_thread_info(task));
e4564f79	172	mutex_release(&lock->dep_map, 1, ip);
1fb00c6c	173	spin_unlock_mutex(&lock->wait_lock, flags);
6053ee3b IM	174
	175	debug_mutex_free_waiter(&waiter);
	176	return -EINTR;
	177	}
	178	__set_task_state(task, state);
	179
	180	/* didnt get the lock, go to sleep: */
1fb00c6c	181	spin_unlock_mutex(&lock->wait_lock, flags);
6053ee3b	182	schedule();
1fb00c6c	183	spin_lock_mutex(&lock->wait_lock, flags);
6053ee3b IM	184	}
6053ee3b IM	185
4fe87745	186	done:
c7e78cff	187	lock_acquired(&lock->dep_map, ip);
6053ee3b	188	/* got the lock - rejoice! */
c9f4f06d RZ	189	mutex_remove_waiter(lock, &waiter, task_thread_info(task));
c9f4f06d RZ	190	debug_mutex_set_owner(lock, task_thread_info(task));
6053ee3b IM	191
	192	/* set it to 0 if there are no waiters left: */
	193	if (likely(list_empty(&lock->wait_list)))
	194	atomic_set(&lock->count, 0);
	195
1fb00c6c	196	spin_unlock_mutex(&lock->wait_lock, flags);
6053ee3b IM	197
	198	debug_mutex_free_waiter(&waiter);
	199
6053ee3b IM	200	return 0;
	201	}
	202
ef5d4707 IM	203	#ifdef CONFIG_DEBUG_LOCK_ALLOC
	204	void __sched
	205	mutex_lock_nested(struct mutex *lock, unsigned int subclass)
	206	{
	207	might_sleep();
e4564f79	208	__mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, subclass, _RET_IP_);
ef5d4707 IM	209	}
	210
	211	EXPORT_SYMBOL_GPL(mutex_lock_nested);
d63a5a74	212
ad776537 LH	213	int __sched
	214	mutex_lock_killable_nested(struct mutex *lock, unsigned int subclass)
	215	{
	216	might_sleep();
	217	return __mutex_lock_common(lock, TASK_KILLABLE, subclass, _RET_IP_);
	218	}
	219	EXPORT_SYMBOL_GPL(mutex_lock_killable_nested);
	220
d63a5a74 N	221	int __sched
	222	mutex_lock_interruptible_nested(struct mutex *lock, unsigned int subclass)
	223	{
	224	might_sleep();
e4564f79	225	return __mutex_lock_common(lock, TASK_INTERRUPTIBLE, subclass, _RET_IP_);
d63a5a74 N	226	}
	227
	228	EXPORT_SYMBOL_GPL(mutex_lock_interruptible_nested);
ef5d4707 IM	229	#endif
ef5d4707 IM	230
6053ee3b IM	231	/*
	232	* Release the lock, slowpath:
	233	*/
7ad5b3a5	234	static inline void
ef5d4707	235	__mutex_unlock_common_slowpath(atomic_t *lock_count, int nested)
6053ee3b	236	{
02706647	237	struct mutex *lock = container_of(lock_count, struct mutex, count);
1fb00c6c	238	unsigned long flags;
6053ee3b	239
1fb00c6c	240	spin_lock_mutex(&lock->wait_lock, flags);
ef5d4707	241	mutex_release(&lock->dep_map, nested, _RET_IP_);
9a11b49a	242	debug_mutex_unlock(lock);
6053ee3b IM	243
	244	/*
	245	* some architectures leave the lock unlocked in the fastpath failure
	246	* case, others need to leave it locked. In the later case we have to
	247	* unlock it here
	248	*/
	249	if (__mutex_slowpath_needs_to_unlock())
	250	atomic_set(&lock->count, 1);
	251
6053ee3b IM	252	if (!list_empty(&lock->wait_list)) {
	253	/* get the first entry from the wait-list: */
	254	struct mutex_waiter *waiter =
	255	list_entry(lock->wait_list.next,
	256	struct mutex_waiter, list);
	257
	258	debug_mutex_wake_waiter(lock, waiter);
	259
	260	wake_up_process(waiter->task);
	261	}
	262
	263	debug_mutex_clear_owner(lock);
	264
1fb00c6c	265	spin_unlock_mutex(&lock->wait_lock, flags);
6053ee3b IM	266	}
6053ee3b IM	267
9a11b49a IM	268	/*
	269	* Release the lock, slowpath:
	270	*/
7918baa5	271	static __used noinline void
9a11b49a IM	272	__mutex_unlock_slowpath(atomic_t *lock_count)
9a11b49a IM	273	{
ef5d4707	274	__mutex_unlock_common_slowpath(lock_count, 1);
9a11b49a IM	275	}
9a11b49a IM	276
e4564f79	277	#ifndef CONFIG_DEBUG_LOCK_ALLOC
6053ee3b IM	278	/*
	279	* Here come the less common (and hence less performance-critical) APIs:
	280	* mutex_lock_interruptible() and mutex_trylock().
	281	*/
7ad5b3a5	282	static noinline int __sched
ad776537 LH	283	__mutex_lock_killable_slowpath(atomic_t *lock_count);
ad776537 LH	284
7ad5b3a5	285	static noinline int __sched
9a11b49a	286	__mutex_lock_interruptible_slowpath(atomic_t *lock_count);
6053ee3b IM	287
	288	/***
	289	* mutex_lock_interruptible - acquire the mutex, interruptable
	290	* @lock: the mutex to be acquired
	291	*
	292	* Lock the mutex like mutex_lock(), and return 0 if the mutex has
	293	* been acquired or sleep until the mutex becomes available. If a
	294	* signal arrives while waiting for the lock then this function
	295	* returns -EINTR.
	296	*
	297	* This function is similar to (but not equivalent to) down_interruptible().
	298	*/
7ad5b3a5	299	int __sched mutex_lock_interruptible(struct mutex *lock)
6053ee3b	300	{
c544bdb1	301	might_sleep();
6053ee3b IM	302	return __mutex_fastpath_lock_retval
	303	(&lock->count, __mutex_lock_interruptible_slowpath);
	304	}
	305
	306	EXPORT_SYMBOL(mutex_lock_interruptible);
	307
7ad5b3a5	308	int __sched mutex_lock_killable(struct mutex *lock)
ad776537 LH	309	{
	310	might_sleep();
	311	return __mutex_fastpath_lock_retval
	312	(&lock->count, __mutex_lock_killable_slowpath);
	313	}
	314	EXPORT_SYMBOL(mutex_lock_killable);
	315
7918baa5	316	static __used noinline void __sched
e4564f79 PZ	317	__mutex_lock_slowpath(atomic_t *lock_count)
	318	{
	319	struct mutex *lock = container_of(lock_count, struct mutex, count);
	320
	321	__mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, 0, _RET_IP_);
	322	}
	323
7ad5b3a5	324	static noinline int __sched
ad776537 LH	325	__mutex_lock_killable_slowpath(atomic_t *lock_count)
	326	{
	327	struct mutex *lock = container_of(lock_count, struct mutex, count);
	328
	329	return __mutex_lock_common(lock, TASK_KILLABLE, 0, _RET_IP_);
	330	}
	331
7ad5b3a5	332	static noinline int __sched
9a11b49a	333	__mutex_lock_interruptible_slowpath(atomic_t *lock_count)
6053ee3b IM	334	{
	335	struct mutex *lock = container_of(lock_count, struct mutex, count);
	336
e4564f79	337	return __mutex_lock_common(lock, TASK_INTERRUPTIBLE, 0, _RET_IP_);
6053ee3b	338	}
e4564f79	339	#endif
6053ee3b IM	340
	341	/*
	342	* Spinlock based trylock, we take the spinlock and check whether we
	343	* can get the lock:
	344	*/
	345	static inline int __mutex_trylock_slowpath(atomic_t *lock_count)
	346	{
	347	struct mutex *lock = container_of(lock_count, struct mutex, count);
1fb00c6c	348	unsigned long flags;
6053ee3b IM	349	int prev;
6053ee3b IM	350
1fb00c6c	351	spin_lock_mutex(&lock->wait_lock, flags);
6053ee3b IM	352
6053ee3b IM	353	prev = atomic_xchg(&lock->count, -1);
ef5d4707	354	if (likely(prev == 1)) {
9a11b49a	355	debug_mutex_set_owner(lock, current_thread_info());
ef5d4707 IM	356	mutex_acquire(&lock->dep_map, 0, 1, _RET_IP_);
ef5d4707 IM	357	}
6053ee3b IM	358	/* Set it back to 0 if there are no waiters: */
	359	if (likely(list_empty(&lock->wait_list)))
	360	atomic_set(&lock->count, 0);
	361
1fb00c6c	362	spin_unlock_mutex(&lock->wait_lock, flags);
6053ee3b IM	363
	364	return prev == 1;
	365	}
	366
	367	/***
	368	* mutex_trylock - try acquire the mutex, without waiting
	369	* @lock: the mutex to be acquired
	370	*
	371	* Try to acquire the mutex atomically. Returns 1 if the mutex
	372	* has been acquired successfully, and 0 on contention.
	373	*
	374	* NOTE: this function follows the spin_trylock() convention, so
	375	* it is negated to the down_trylock() return values! Be careful
	376	* about this when converting semaphore users to mutexes.
	377	*
	378	* This function must not be used in interrupt context. The
	379	* mutex must be released by the same task that acquired it.
	380	*/
7ad5b3a5	381	int __sched mutex_trylock(struct mutex *lock)
6053ee3b IM	382	{
	383	return __mutex_fastpath_trylock(&lock->count,
	384	__mutex_trylock_slowpath);
	385	}
	386
	387	EXPORT_SYMBOL(mutex_trylock);