/*
* 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/linkage.h>
#include <linux/lockdep.h>
#include <linux/atomic.h>
#include <asm/processor.h>
#include <linux/osq_lock.h>
#include <linux/debug_locks.h>
/*
* Simple, straightforward mutexes with strict semantics:
*
* - only one task can hold the mutex at a time
* - only the owner can unlock the mutex
* - multiple unlocks are not permitted
* - recursive locking is not permitted
* - a mutex object must be initialized via the API
* - a mutex object must not be initialized via memset or copying
* - task may not exit with mutex held
* - memory areas where held locks reside must not be freed
* - held mutexes must not be reinitialized
* - mutexes may not be used in hardware or software interrupt
* contexts such as tasklets and timers
*
* These semantics are fully enforced when DEBUG_MUTEXES is
* enabled. Furthermore, besides enforcing the above rules, the mutex
* debugging code also implements a number of additional features
* that make lock debugging easier and faster:
*
* - uses symbolic names of mutexes, whenever they are printed in debug output
* - point-of-acquire tracking, symbolic lookup of function names
* - list of all locks held in the system, printout of them
* - owner tracking
* - detects self-recursing locks and prints out all relevant info
* - detects multi-task circular deadlocks and prints out all affected
* locks and tasks (and only those tasks)
*/
struct mutex {
atomic_long_t owner;
spinlock_t wait_lock;
#ifdef CONFIG_MUTEX_SPIN_ON_OWNER
struct optimistic_spin_queue osq; /* Spinner MCS lock */
#endif
struct list_head wait_list;
#ifdef CONFIG_DEBUG_MUTEXES
void *magic;
#endif
#ifdef CONFIG_DEBUG_LOCK_ALLOC
struct lockdep_map dep_map;
#endif
};
static inline struct task_struct *__mutex_owner(struct mutex *lock)
{
return (struct task_struct *)(atomic_long_read(&lock->owner) & ~0x03);
}
/*
* This is the control structure for tasks blocked on mutex,
* which resides on the blocked task's kernel stack:
*/
struct mutex_waiter {
struct list_head list;
struct task_struct *task;
#ifdef CONFIG_DEBUG_MUTEXES
void *magic;
#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)
#ifdef CONFIG_DEBUG_LOCK_ALLOC
# define __DEP_MAP_MUTEX_INITIALIZER(lockname) \
, .dep_map = { .name = #lockname }
#else
# define __DEP_MAP_MUTEX_INITIALIZER(lockname)
#endif
#define __MUTEX_INITIALIZER(lockname) \
{ .owner = ATOMIC_LONG_INIT(0) \
, .wait_lock = __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 1 if the mutex is locked, 0 if unlocked.
*/
static inline int mutex_is_locked(struct mutex *lock)
{
/*
* XXX think about spin_is_locked
*/
return __mutex_owner(lock) != NULL;
}
/*
* See kernel/locking/mutex.c for detailed documentation of these APIs.
* Also see Documentation/locking/mutex-design.txt.
*/
#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);
#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_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);
# 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)
#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);
/*
* These values are chosen such that FAIL and SUCCESS match the
* values of the regular mutex_trylock().
*/
enum mutex_trylock_recursive_enum {
MUTEX_TRYLOCK_FAILED = 0,
MUTEX_TRYLOCK_SUCCESS = 1,
MUTEX_TRYLOCK_RECURSIVE,
};
/**
* mutex_trylock_recursive - trylock variant that allows recursive locking
* @lock: mutex to be locked
*
* This function should not be used, _ever_. It is purely for hysterical GEM
* raisins, and once those are gone this will be removed.
*
* Returns:
* MUTEX_TRYLOCK_FAILED - trylock failed,
* MUTEX_TRYLOCK_SUCCESS - lock acquired,
* MUTEX_TRYLOCK_RECURSIVE - we already owned the lock.
*/
static inline /* __deprecated */ __must_check enum mutex_trylock_recursive_enum
mutex_trylock_recursive(struct mutex *lock)
{
if (unlikely(__mutex_owner(lock) == current))
return MUTEX_TRYLOCK_RECURSIVE;
return mutex_trylock(lock);
}
#endif /* __LINUX_MUTEX_H */
