kernel/include/linux/mutex.h

/* SPDX-License-Identifier: GPL-2.0 */
/*
 * Mutexes: blocking mutual exclusion locks
 *
 * started by Ingo Molnar:
 *
 *  Copyright (C) 2004, 2005, 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
 *
 * This file contains the main data structure and API definitions.
 */
#ifndef __LINUX_MUTEX_H
#define __LINUX_MUTEX_H

#include <asm/current.h>
#include <linux/list.h>
#include <linux/spinlock_types.h>
#include <linux/lockdep.h>
#include <linux/atomic.h>
#include <asm/processor.h>
#include <linux/osq_lock.h>
#include <linux/debug_locks.h>
#include <linux/cleanup.h>
#include <linux/mutex_types.h>

struct device;

#ifdef CONFIG_DEBUG_LOCK_ALLOC
# define __DEP_MAP_MUTEX_INITIALIZER(lockname)			\
		, .dep_map = {					\
			.name = #lockname,			\
			.wait_type_inner = LD_WAIT_SLEEP,	\
		}
#else
# define __DEP_MAP_MUTEX_INITIALIZER(lockname)
#endif

#ifdef CONFIG_DEBUG_MUTEXES

# define __DEBUG_MUTEX_INITIALIZER(lockname)				\
	, .magic = &lockname

extern void mutex_destroy(struct mutex *lock);

#else

# define __DEBUG_MUTEX_INITIALIZER(lockname)

static inline void mutex_destroy(struct mutex *lock) {}

#endif

/**
 * mutex_init - initialize the mutex
 * @mutex: the mutex to be initialized
 *
 * Initialize the mutex to unlocked state.
 *
 * It is not allowed to initialize an already locked mutex.
 */
#define mutex_init(mutex)						\
do {									\
	static struct lock_class_key __key;				\
									\
	__mutex_init((mutex), #mutex, &__key);				\
} while (0)

/**
 * mutex_init_with_key - initialize a mutex with a given lockdep key
 * @mutex: the mutex to be initialized
 * @key: the lockdep key to be associated with the mutex
 *
 * Initialize the mutex to the unlocked state.
 *
 * It is not allowed to initialize an already locked mutex.
 */
#define mutex_init_with_key(mutex, key) __mutex_init((mutex), #mutex, (key))

#ifndef CONFIG_PREEMPT_RT
#define __MUTEX_INITIALIZER(lockname) \
		{ .owner = ATOMIC_LONG_INIT(0) \
		, .wait_lock = __RAW_SPIN_LOCK_UNLOCKED(lockname.wait_lock) \
		, .wait_list = LIST_HEAD_INIT(lockname.wait_list) \
		__DEBUG_MUTEX_INITIALIZER(lockname) \
		__DEP_MAP_MUTEX_INITIALIZER(lockname) }

#define DEFINE_MUTEX(mutexname) \
	struct mutex mutexname = __MUTEX_INITIALIZER(mutexname)

extern void __mutex_init(struct mutex *lock, const char *name,
			 struct lock_class_key *key);

/**
 * mutex_is_locked - is the mutex locked
 * @lock: the mutex to be queried
 *
 * Returns true if the mutex is locked, false if unlocked.
 */
extern bool mutex_is_locked(struct mutex *lock);

#else /* !CONFIG_PREEMPT_RT */
/*
 * Preempt-RT variant based on rtmutexes.
 */

#define __MUTEX_INITIALIZER(mutexname)					\
{									\
	.rtmutex = __RT_MUTEX_BASE_INITIALIZER(mutexname.rtmutex)	\
	__DEP_MAP_MUTEX_INITIALIZER(mutexname)				\
}

#define DEFINE_MUTEX(mutexname)						\
	struct mutex mutexname = __MUTEX_INITIALIZER(mutexname)

extern void __mutex_rt_init(struct mutex *lock, const char *name,
			    struct lock_class_key *key);

#define mutex_is_locked(l)	rt_mutex_base_is_locked(&(l)->rtmutex)

#define __mutex_init(mutex, name, key)			\
do {							\
	rt_mutex_base_init(&(mutex)->rtmutex);		\
	__mutex_rt_init((mutex), name, key);		\
} while (0)

#endif /* CONFIG_PREEMPT_RT */

#ifdef CONFIG_DEBUG_MUTEXES

int __devm_mutex_init(struct device *dev, struct mutex *lock);

#else

static inline int __devm_mutex_init(struct device *dev, struct mutex *lock)
{
	/*
	 * When CONFIG_DEBUG_MUTEXES is off mutex_destroy() is just a nop so
	 * no really need to register it in the devm subsystem.
	 */
	return 0;
}

#endif

#define devm_mutex_init(dev, mutex)			\
({							\
	typeof(mutex) mutex_ = (mutex);			\
							\
	mutex_init(mutex_);				\
	__devm_mutex_init(dev, mutex_);			\
})

/*
 * See kernel/locking/mutex.c for detailed documentation of these APIs.
 * Also see Documentation/locking/mutex-design.rst.
 */
#ifdef CONFIG_DEBUG_LOCK_ALLOC
extern void mutex_lock_nested(struct mutex *lock, unsigned int subclass);
extern void _mutex_lock_nest_lock(struct mutex *lock, struct lockdep_map *nest_lock);

extern int __must_check mutex_lock_interruptible_nested(struct mutex *lock,
					unsigned int subclass);
extern int __must_check mutex_lock_killable_nested(struct mutex *lock,
					unsigned int subclass);
extern void mutex_lock_io_nested(struct mutex *lock, unsigned int subclass);

#define mutex_lock(lock) mutex_lock_nested(lock, 0)
#define mutex_lock_interruptible(lock) mutex_lock_interruptible_nested(lock, 0)
#define mutex_lock_killable(lock) mutex_lock_killable_nested(lock, 0)
#define mutex_lock_io(lock) mutex_lock_io_nested(lock, 0)

#define mutex_lock_nest_lock(lock, nest_lock)				\
do {									\
	typecheck(struct lockdep_map *, &(nest_lock)->dep_map);	\
	_mutex_lock_nest_lock(lock, &(nest_lock)->dep_map);		\
} while (0)

#else
extern void mutex_lock(struct mutex *lock);
extern int __must_check mutex_lock_interruptible(struct mutex *lock);
extern int __must_check mutex_lock_killable(struct mutex *lock);
extern void mutex_lock_io(struct mutex *lock);

# define mutex_lock_nested(lock, subclass) mutex_lock(lock)
# define mutex_lock_interruptible_nested(lock, subclass) mutex_lock_interruptible(lock)
# define mutex_lock_killable_nested(lock, subclass) mutex_lock_killable(lock)
# define mutex_lock_nest_lock(lock, nest_lock) mutex_lock(lock)
# define mutex_lock_io_nested(lock, subclass) mutex_lock_io(lock)
#endif

/*
 * NOTE: mutex_trylock() follows the spin_trylock() convention,
 *       not the down_trylock() convention!
 *
 * Returns 1 if the mutex has been acquired successfully, and 0 on contention.
 */
extern int mutex_trylock(struct mutex *lock);
extern void mutex_unlock(struct mutex *lock);

extern int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock);

DEFINE_GUARD(mutex, struct mutex *, mutex_lock(_T), mutex_unlock(_T))
DEFINE_GUARD_COND(mutex, _try, mutex_trylock(_T))
DEFINE_GUARD_COND(mutex, _intr, mutex_lock_interruptible(_T) == 0)

#endif /* __LINUX_MUTEX_H */