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Ingo Molnar6053ee32006-01-09 15:59:19 -08001/*
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 <linux/list.h>
14#include <linux/spinlock_types.h>
David S. Millera8b9ee72006-01-11 00:15:16 -080015#include <linux/linkage.h>
Ingo Molnaref5d4702006-07-03 00:24:55 -070016#include <linux/lockdep.h>
Ingo Molnar6053ee32006-01-09 15:59:19 -080017
18#include <asm/atomic.h>
19
20/*
21 * Simple, straightforward mutexes with strict semantics:
22 *
23 * - only one task can hold the mutex at a time
24 * - only the owner can unlock the mutex
25 * - multiple unlocks are not permitted
26 * - recursive locking is not permitted
27 * - a mutex object must be initialized via the API
28 * - a mutex object must not be initialized via memset or copying
29 * - task may not exit with mutex held
30 * - memory areas where held locks reside must not be freed
31 * - held mutexes must not be reinitialized
Matti Linnanvuorif20fda42007-10-16 23:29:41 -070032 * - mutexes may not be used in hardware or software interrupt
33 * contexts such as tasklets and timers
Ingo Molnar6053ee32006-01-09 15:59:19 -080034 *
35 * These semantics are fully enforced when DEBUG_MUTEXES is
36 * enabled. Furthermore, besides enforcing the above rules, the mutex
37 * debugging code also implements a number of additional features
38 * that make lock debugging easier and faster:
39 *
40 * - uses symbolic names of mutexes, whenever they are printed in debug output
41 * - point-of-acquire tracking, symbolic lookup of function names
42 * - list of all locks held in the system, printout of them
43 * - owner tracking
44 * - detects self-recursing locks and prints out all relevant info
45 * - detects multi-task circular deadlocks and prints out all affected
46 * locks and tasks (and only those tasks)
47 */
48struct mutex {
49 /* 1: unlocked, 0: locked, negative: locked, possible waiters */
50 atomic_t count;
51 spinlock_t wait_lock;
52 struct list_head wait_list;
Peter Zijlstra0d66bf62009-01-12 14:01:47 +010053#if defined(CONFIG_DEBUG_MUTEXES) || defined(CONFIG_SMP)
Ingo Molnar6053ee32006-01-09 15:59:19 -080054 struct thread_info *owner;
Peter Zijlstra0d66bf62009-01-12 14:01:47 +010055#endif
56#ifdef CONFIG_DEBUG_MUTEXES
Ingo Molnar6053ee32006-01-09 15:59:19 -080057 const char *name;
58 void *magic;
59#endif
Ingo Molnaref5d4702006-07-03 00:24:55 -070060#ifdef CONFIG_DEBUG_LOCK_ALLOC
61 struct lockdep_map dep_map;
62#endif
Ingo Molnar6053ee32006-01-09 15:59:19 -080063};
64
65/*
66 * This is the control structure for tasks blocked on mutex,
67 * which resides on the blocked task's kernel stack:
68 */
69struct mutex_waiter {
70 struct list_head list;
71 struct task_struct *task;
72#ifdef CONFIG_DEBUG_MUTEXES
Ingo Molnar6053ee32006-01-09 15:59:19 -080073 void *magic;
74#endif
75};
76
77#ifdef CONFIG_DEBUG_MUTEXES
78# include <linux/mutex-debug.h>
79#else
80# define __DEBUG_MUTEX_INITIALIZER(lockname)
Randy Dunlapef5dc122010-09-02 15:48:16 -070081/**
82 * mutex_init - initialize the mutex
83 * @mutex: the mutex to be initialized
84 *
85 * Initialize the mutex to unlocked state.
86 *
87 * It is not allowed to initialize an already locked mutex.
88 */
Ingo Molnaref5d4702006-07-03 00:24:55 -070089# define mutex_init(mutex) \
90do { \
91 static struct lock_class_key __key; \
92 \
93 __mutex_init((mutex), #mutex, &__key); \
94} while (0)
Ingo Molnar6053ee32006-01-09 15:59:19 -080095# define mutex_destroy(mutex) do { } while (0)
Ingo Molnar6053ee32006-01-09 15:59:19 -080096#endif
97
Ingo Molnaref5d4702006-07-03 00:24:55 -070098#ifdef CONFIG_DEBUG_LOCK_ALLOC
99# define __DEP_MAP_MUTEX_INITIALIZER(lockname) \
100 , .dep_map = { .name = #lockname }
101#else
102# define __DEP_MAP_MUTEX_INITIALIZER(lockname)
103#endif
104
Ingo Molnar6053ee32006-01-09 15:59:19 -0800105#define __MUTEX_INITIALIZER(lockname) \
106 { .count = ATOMIC_INIT(1) \
Peter Zijlstra6cfd76a2006-12-06 20:37:22 -0800107 , .wait_lock = __SPIN_LOCK_UNLOCKED(lockname.wait_lock) \
Ingo Molnar6053ee32006-01-09 15:59:19 -0800108 , .wait_list = LIST_HEAD_INIT(lockname.wait_list) \
Ingo Molnaref5d4702006-07-03 00:24:55 -0700109 __DEBUG_MUTEX_INITIALIZER(lockname) \
110 __DEP_MAP_MUTEX_INITIALIZER(lockname) }
Ingo Molnar6053ee32006-01-09 15:59:19 -0800111
112#define DEFINE_MUTEX(mutexname) \
113 struct mutex mutexname = __MUTEX_INITIALIZER(mutexname)
114
Ingo Molnaref5d4702006-07-03 00:24:55 -0700115extern void __mutex_init(struct mutex *lock, const char *name,
116 struct lock_class_key *key);
Ingo Molnar6053ee32006-01-09 15:59:19 -0800117
Robert P. J. Day45f8bde2007-01-26 00:57:09 -0800118/**
Ingo Molnar6053ee32006-01-09 15:59:19 -0800119 * mutex_is_locked - is the mutex locked
120 * @lock: the mutex to be queried
121 *
122 * Returns 1 if the mutex is locked, 0 if unlocked.
123 */
Harvey Harrisonec701582008-02-08 04:19:55 -0800124static inline int mutex_is_locked(struct mutex *lock)
Ingo Molnar6053ee32006-01-09 15:59:19 -0800125{
126 return atomic_read(&lock->count) != 1;
127}
128
129/*
130 * See kernel/mutex.c for detailed documentation of these APIs.
131 * Also see Documentation/mutex-design.txt.
132 */
Ingo Molnaref5d4702006-07-03 00:24:55 -0700133#ifdef CONFIG_DEBUG_LOCK_ALLOC
134extern void mutex_lock_nested(struct mutex *lock, unsigned int subclass);
Andrew Morton18d83622007-05-09 02:33:39 -0700135extern int __must_check mutex_lock_interruptible_nested(struct mutex *lock,
136 unsigned int subclass);
Liam R. Howlettad776532007-12-06 17:37:59 -0500137extern int __must_check mutex_lock_killable_nested(struct mutex *lock,
138 unsigned int subclass);
Peter Zijlstrae4564f72007-10-11 22:11:12 +0200139
140#define mutex_lock(lock) mutex_lock_nested(lock, 0)
141#define mutex_lock_interruptible(lock) mutex_lock_interruptible_nested(lock, 0)
Liam R. Howlettad776532007-12-06 17:37:59 -0500142#define mutex_lock_killable(lock) mutex_lock_killable_nested(lock, 0)
Ingo Molnaref5d4702006-07-03 00:24:55 -0700143#else
Harvey Harrisonec701582008-02-08 04:19:55 -0800144extern void mutex_lock(struct mutex *lock);
145extern int __must_check mutex_lock_interruptible(struct mutex *lock);
146extern int __must_check mutex_lock_killable(struct mutex *lock);
Peter Zijlstrae4564f72007-10-11 22:11:12 +0200147
Ingo Molnaref5d4702006-07-03 00:24:55 -0700148# define mutex_lock_nested(lock, subclass) mutex_lock(lock)
NeilBrownd63a5a72006-12-08 02:36:17 -0800149# define mutex_lock_interruptible_nested(lock, subclass) mutex_lock_interruptible(lock)
Liam R. Howlettad776532007-12-06 17:37:59 -0500150# define mutex_lock_killable_nested(lock, subclass) mutex_lock_killable(lock)
Ingo Molnaref5d4702006-07-03 00:24:55 -0700151#endif
152
Ingo Molnar6053ee32006-01-09 15:59:19 -0800153/*
154 * NOTE: mutex_trylock() follows the spin_trylock() convention,
155 * not the down_trylock() convention!
Arjan van de Vend98d38f2008-10-29 14:24:09 -0700156 *
157 * Returns 1 if the mutex has been acquired successfully, and 0 on contention.
Ingo Molnar6053ee32006-01-09 15:59:19 -0800158 */
Harvey Harrisonec701582008-02-08 04:19:55 -0800159extern int mutex_trylock(struct mutex *lock);
160extern void mutex_unlock(struct mutex *lock);
Andrew Mortona511e3f2009-04-29 15:59:58 -0700161extern int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock);
Eric Parisb1fca262009-03-23 18:22:09 +0100162
Ingo Molnar6053ee32006-01-09 15:59:19 -0800163#endif