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/*
* 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 <linux/list.h>
#include <linux/spinlock_types.h>
#include <linux/linkage.h>
#include <asm/atomic.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 irq contexts
*
* 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 {
/* 1: unlocked, 0: locked, negative: locked, possible waiters */
atomic_t count;
spinlock_t wait_lock;
struct list_head wait_list;
#ifdef CONFIG_DEBUG_MUTEXES
struct thread_info *owner;
struct list_head held_list;
unsigned long acquire_ip;
const char *name;
void *magic;
#endif
};
/*
* 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
struct mutex *lock;
void *magic;
#endif
};
#ifdef CONFIG_DEBUG_MUTEXES
# include <linux/mutex-debug.h>
#else
# define __DEBUG_MUTEX_INITIALIZER(lockname)
# define mutex_init(mutex) __mutex_init(mutex, NULL)
# define mutex_destroy(mutex) do { } while (0)
# define mutex_debug_show_all_locks() do { } while (0)
# define mutex_debug_show_held_locks(p) do { } while (0)
# define mutex_debug_check_no_locks_held(task) do { } while (0)
# define mutex_debug_check_no_locks_freed(from, len) do { } while (0)
#endif
#define __MUTEX_INITIALIZER(lockname) \
{ .count = ATOMIC_INIT(1) \
, .wait_lock = SPIN_LOCK_UNLOCKED \
, .wait_list = LIST_HEAD_INIT(lockname.wait_list) \
__DEBUG_MUTEX_INITIALIZER(lockname) }
#define DEFINE_MUTEX(mutexname) \
struct mutex mutexname = __MUTEX_INITIALIZER(mutexname)
extern void fastcall __mutex_init(struct mutex *lock, const char *name);
/***
* 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 fastcall mutex_is_locked(struct mutex *lock)
{
return atomic_read(&lock->count) != 1;
}
/*
* See kernel/mutex.c for detailed documentation of these APIs.
* Also see Documentation/mutex-design.txt.
*/
extern void fastcall mutex_lock(struct mutex *lock);
extern int fastcall mutex_lock_interruptible(struct mutex *lock);
/*
* NOTE: mutex_trylock() follows the spin_trylock() convention,
* not the down_trylock() convention!
*/
extern int fastcall mutex_trylock(struct mutex *lock);
extern void fastcall mutex_unlock(struct mutex *lock);
#endif
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