/* * 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> /* * 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 { /* 1: unlocked, 0: locked, negative: locked, possible waiters */ struct list_head wait_list; atomic_t count; }; /* * 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; int *task; }; #define __MUTEX_INITIALIZER(lockname) \ { .wait_list = LIST_HEAD_INIT(lockname.wait_list), \ .count = ATOMIC_INIT(1) \ } #define DEFINE_MUTEX(mutexname) \ struct mutex mutexname = __MUTEX_INITIALIZER(mutexname) void __attribute__ ((fastcall)) __attribute__ ((dllimport)) mutex_init(struct mutex*)__asm__("MutexInit"); void __attribute__ ((fastcall)) __attribute__ ((dllimport)) mutex_lock(struct mutex*)__asm__("MutexLock"); void __attribute__ ((fastcall)) __attribute__ ((dllimport)) mutex_unlock(struct mutex*)__asm__("MutexUnlock"); static inline int mutex_lock_interruptible(struct mutex *lock) { mutex_lock(lock); return 0; } # define mutex_lock_nest_lock(lock, nest_lock) mutex_lock(lock) /** * 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) { return atomic_read(&lock->count) != 1; } static inline int mutex_trylock(struct mutex *lock) { if (likely(atomic_cmpxchg(&lock->count, 1, 0) == 1)) return 1; return 0; } static inline void mutex_destroy(struct mutex *lock) { }; #endif