1/* 2 * Mutexes: blocking mutual exclusion locks 3 * 4 * started by Ingo Molnar: 5 * 6 * Copyright (C) 2004, 2005, 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com> 7 * 8 * This file contains the main data structure and API definitions. 9 */ 10#ifndef __LINUX_MUTEX_H 11#define __LINUX_MUTEX_H 12 13#include <asm/current.h> 14#include <linux/list.h> 15#include <linux/spinlock_types.h> 16#include <linux/linkage.h> 17#include <linux/lockdep.h> 18#include <linux/atomic.h> 19#include <asm/processor.h> 20#include <linux/osq_lock.h> 21 22/* 23 * Simple, straightforward mutexes with strict semantics: 24 * 25 * - only one task can hold the mutex at a time 26 * - only the owner can unlock the mutex 27 * - multiple unlocks are not permitted 28 * - recursive locking is not permitted 29 * - a mutex object must be initialized via the API 30 * - a mutex object must not be initialized via memset or copying 31 * - task may not exit with mutex held 32 * - memory areas where held locks reside must not be freed 33 * - held mutexes must not be reinitialized 34 * - mutexes may not be used in hardware or software interrupt 35 * contexts such as tasklets and timers 36 * 37 * These semantics are fully enforced when DEBUG_MUTEXES is 38 * enabled. Furthermore, besides enforcing the above rules, the mutex 39 * debugging code also implements a number of additional features 40 * that make lock debugging easier and faster: 41 * 42 * - uses symbolic names of mutexes, whenever they are printed in debug output 43 * - point-of-acquire tracking, symbolic lookup of function names 44 * - list of all locks held in the system, printout of them 45 * - owner tracking 46 * - detects self-recursing locks and prints out all relevant info 47 * - detects multi-task circular deadlocks and prints out all affected 48 * locks and tasks (and only those tasks) 49 */ 50struct mutex { 51 /* 1: unlocked, 0: locked, negative: locked, possible waiters */ 52 atomic_t count; 53 spinlock_t wait_lock; 54 struct list_head wait_list; 55#if defined(CONFIG_DEBUG_MUTEXES) || defined(CONFIG_MUTEX_SPIN_ON_OWNER) 56 struct task_struct *owner; 57#endif 58#ifdef CONFIG_MUTEX_SPIN_ON_OWNER 59 struct optimistic_spin_queue osq; /* Spinner MCS lock */ 60#endif 61#ifdef CONFIG_DEBUG_MUTEXES 62 void *magic; 63#endif 64#ifdef CONFIG_DEBUG_LOCK_ALLOC 65 struct lockdep_map dep_map; 66#endif 67}; 68 69/* 70 * This is the control structure for tasks blocked on mutex, 71 * which resides on the blocked task's kernel stack: 72 */ 73struct mutex_waiter { 74 struct list_head list; 75 struct task_struct *task; 76#ifdef CONFIG_DEBUG_MUTEXES 77 void *magic; 78#endif 79}; 80 81#ifdef CONFIG_DEBUG_MUTEXES 82# include <linux/mutex-debug.h> 83#else 84# define __DEBUG_MUTEX_INITIALIZER(lockname) 85/** 86 * mutex_init - initialize the mutex 87 * @mutex: the mutex to be initialized 88 * 89 * Initialize the mutex to unlocked state. 90 * 91 * It is not allowed to initialize an already locked mutex. 92 */ 93# define mutex_init(mutex) \ 94do { \ 95 static struct lock_class_key __key; \ 96 \ 97 __mutex_init((mutex), #mutex, &__key); \ 98} while (0) 99static inline void mutex_destroy(struct mutex *lock) {} 100#endif 101 102#ifdef CONFIG_DEBUG_LOCK_ALLOC 103# define __DEP_MAP_MUTEX_INITIALIZER(lockname) \ 104 , .dep_map = { .name = #lockname } 105#else 106# define __DEP_MAP_MUTEX_INITIALIZER(lockname) 107#endif 108 109#define __MUTEX_INITIALIZER(lockname) \ 110 { .count = ATOMIC_INIT(1) \ 111 , .wait_lock = __SPIN_LOCK_UNLOCKED(lockname.wait_lock) \ 112 , .wait_list = LIST_HEAD_INIT(lockname.wait_list) \ 113 __DEBUG_MUTEX_INITIALIZER(lockname) \ 114 __DEP_MAP_MUTEX_INITIALIZER(lockname) } 115 116#define DEFINE_MUTEX(mutexname) \ 117 struct mutex mutexname = __MUTEX_INITIALIZER(mutexname) 118 119extern void __mutex_init(struct mutex *lock, const char *name, 120 struct lock_class_key *key); 121 122/** 123 * mutex_is_locked - is the mutex locked 124 * @lock: the mutex to be queried 125 * 126 * Returns 1 if the mutex is locked, 0 if unlocked. 127 */ 128static inline int mutex_is_locked(struct mutex *lock) 129{ 130 return atomic_read(&lock->count) != 1; 131} 132 133/* 134 * See kernel/locking/mutex.c for detailed documentation of these APIs. 135 * Also see Documentation/locking/mutex-design.txt. 136 */ 137#ifdef CONFIG_DEBUG_LOCK_ALLOC 138extern void mutex_lock_nested(struct mutex *lock, unsigned int subclass); 139extern void _mutex_lock_nest_lock(struct mutex *lock, struct lockdep_map *nest_lock); 140 141extern int __must_check mutex_lock_interruptible_nested(struct mutex *lock, 142 unsigned int subclass); 143extern int __must_check mutex_lock_killable_nested(struct mutex *lock, 144 unsigned int subclass); 145 146#define mutex_lock(lock) mutex_lock_nested(lock, 0) 147#define mutex_lock_interruptible(lock) mutex_lock_interruptible_nested(lock, 0) 148#define mutex_lock_killable(lock) mutex_lock_killable_nested(lock, 0) 149 150#define mutex_lock_nest_lock(lock, nest_lock) \ 151do { \ 152 typecheck(struct lockdep_map *, &(nest_lock)->dep_map); \ 153 _mutex_lock_nest_lock(lock, &(nest_lock)->dep_map); \ 154} while (0) 155 156#else 157extern void mutex_lock(struct mutex *lock); 158extern int __must_check mutex_lock_interruptible(struct mutex *lock); 159extern int __must_check mutex_lock_killable(struct mutex *lock); 160 161# define mutex_lock_nested(lock, subclass) mutex_lock(lock) 162# define mutex_lock_interruptible_nested(lock, subclass) mutex_lock_interruptible(lock) 163# define mutex_lock_killable_nested(lock, subclass) mutex_lock_killable(lock) 164# define mutex_lock_nest_lock(lock, nest_lock) mutex_lock(lock) 165#endif 166 167/* 168 * NOTE: mutex_trylock() follows the spin_trylock() convention, 169 * not the down_trylock() convention! 170 * 171 * Returns 1 if the mutex has been acquired successfully, and 0 on contention. 172 */ 173extern int mutex_trylock(struct mutex *lock); 174extern void mutex_unlock(struct mutex *lock); 175 176extern int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock); 177 178#endif /* __LINUX_MUTEX_H */ 179