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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
Maarten Lankhorst040a0a32013-06-24 10:30:04 +020013#include <asm/current.h>
Ingo Molnar6053ee32006-01-09 15:59:19 -080014#include <linux/list.h>
15#include <linux/spinlock_types.h>
David S. Millera8b9ee72006-01-11 00:15:16 -080016#include <linux/linkage.h>
Ingo Molnaref5d4702006-07-03 00:24:55 -070017#include <linux/lockdep.h>
Arun Sharma600634972011-07-26 16:09:06 -070018#include <linux/atomic.h>
Heiko Carstens083986e2013-09-28 11:23:59 +020019#include <asm/processor.h>
Jason Low90631822014-07-14 10:27:49 -070020#include <linux/osq_lock.h>
Ingo Molnar6053ee32006-01-09 15:59:19 -080021
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
Matti Linnanvuorif20fda42007-10-16 23:29:41 -070034 * - mutexes may not be used in hardware or software interrupt
35 * contexts such as tasklets and timers
Ingo Molnar6053ee32006-01-09 15:59:19 -080036 *
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;
Peter Zijlstra0d66bf62009-01-12 14:01:47 +010055#if defined(CONFIG_DEBUG_MUTEXES) || defined(CONFIG_SMP)
Peter Zijlstrac6eb3dd2011-04-05 17:23:41 +020056 struct task_struct *owner;
Peter Zijlstra0d66bf62009-01-12 14:01:47 +010057#endif
Waiman Long2bd2c922013-04-17 15:23:13 -040058#ifdef CONFIG_MUTEX_SPIN_ON_OWNER
Jason Low90631822014-07-14 10:27:49 -070059 struct optimistic_spin_queue osq; /* Spinner MCS lock */
Waiman Long2bd2c922013-04-17 15:23:13 -040060#endif
Peter Zijlstra0d66bf62009-01-12 14:01:47 +010061#ifdef CONFIG_DEBUG_MUTEXES
Ingo Molnar6053ee32006-01-09 15:59:19 -080062 const char *name;
63 void *magic;
64#endif
Ingo Molnaref5d4702006-07-03 00:24:55 -070065#ifdef CONFIG_DEBUG_LOCK_ALLOC
66 struct lockdep_map dep_map;
67#endif
Ingo Molnar6053ee32006-01-09 15:59:19 -080068};
69
70/*
71 * This is the control structure for tasks blocked on mutex,
72 * which resides on the blocked task's kernel stack:
73 */
74struct mutex_waiter {
75 struct list_head list;
76 struct task_struct *task;
77#ifdef CONFIG_DEBUG_MUTEXES
Ingo Molnar6053ee32006-01-09 15:59:19 -080078 void *magic;
79#endif
80};
81
82#ifdef CONFIG_DEBUG_MUTEXES
83# include <linux/mutex-debug.h>
84#else
85# define __DEBUG_MUTEX_INITIALIZER(lockname)
Randy Dunlapef5dc122010-09-02 15:48:16 -070086/**
87 * mutex_init - initialize the mutex
88 * @mutex: the mutex to be initialized
89 *
90 * Initialize the mutex to unlocked state.
91 *
92 * It is not allowed to initialize an already locked mutex.
93 */
Ingo Molnaref5d4702006-07-03 00:24:55 -070094# define mutex_init(mutex) \
95do { \
96 static struct lock_class_key __key; \
97 \
98 __mutex_init((mutex), #mutex, &__key); \
99} while (0)
Jean Delvare4582c0a2011-07-16 17:42:00 +0200100static inline void mutex_destroy(struct mutex *lock) {}
Ingo Molnar6053ee32006-01-09 15:59:19 -0800101#endif
102
Ingo Molnaref5d4702006-07-03 00:24:55 -0700103#ifdef CONFIG_DEBUG_LOCK_ALLOC
104# define __DEP_MAP_MUTEX_INITIALIZER(lockname) \
105 , .dep_map = { .name = #lockname }
106#else
107# define __DEP_MAP_MUTEX_INITIALIZER(lockname)
108#endif
109
Ingo Molnar6053ee32006-01-09 15:59:19 -0800110#define __MUTEX_INITIALIZER(lockname) \
111 { .count = ATOMIC_INIT(1) \
Peter Zijlstra6cfd76a2006-12-06 20:37:22 -0800112 , .wait_lock = __SPIN_LOCK_UNLOCKED(lockname.wait_lock) \
Ingo Molnar6053ee32006-01-09 15:59:19 -0800113 , .wait_list = LIST_HEAD_INIT(lockname.wait_list) \
Ingo Molnaref5d4702006-07-03 00:24:55 -0700114 __DEBUG_MUTEX_INITIALIZER(lockname) \
115 __DEP_MAP_MUTEX_INITIALIZER(lockname) }
Ingo Molnar6053ee32006-01-09 15:59:19 -0800116
117#define DEFINE_MUTEX(mutexname) \
118 struct mutex mutexname = __MUTEX_INITIALIZER(mutexname)
119
Ingo Molnaref5d4702006-07-03 00:24:55 -0700120extern void __mutex_init(struct mutex *lock, const char *name,
121 struct lock_class_key *key);
Ingo Molnar6053ee32006-01-09 15:59:19 -0800122
Robert P. J. Day45f8bde2007-01-26 00:57:09 -0800123/**
Ingo Molnar6053ee32006-01-09 15:59:19 -0800124 * mutex_is_locked - is the mutex locked
125 * @lock: the mutex to be queried
126 *
127 * Returns 1 if the mutex is locked, 0 if unlocked.
128 */
Harvey Harrisonec701582008-02-08 04:19:55 -0800129static inline int mutex_is_locked(struct mutex *lock)
Ingo Molnar6053ee32006-01-09 15:59:19 -0800130{
131 return atomic_read(&lock->count) != 1;
132}
133
134/*
Peter Zijlstra67a6de42013-11-08 08:26:39 +0100135 * See kernel/locking/mutex.c for detailed documentation of these APIs.
Ingo Molnar6053ee32006-01-09 15:59:19 -0800136 * Also see Documentation/mutex-design.txt.
137 */
Ingo Molnaref5d4702006-07-03 00:24:55 -0700138#ifdef CONFIG_DEBUG_LOCK_ALLOC
139extern void mutex_lock_nested(struct mutex *lock, unsigned int subclass);
Peter Zijlstrae4c70a62011-05-24 17:12:03 -0700140extern void _mutex_lock_nest_lock(struct mutex *lock, struct lockdep_map *nest_lock);
Maarten Lankhorst040a0a32013-06-24 10:30:04 +0200141
Andrew Morton18d83622007-05-09 02:33:39 -0700142extern int __must_check mutex_lock_interruptible_nested(struct mutex *lock,
143 unsigned int subclass);
Liam R. Howlettad776532007-12-06 17:37:59 -0500144extern int __must_check mutex_lock_killable_nested(struct mutex *lock,
145 unsigned int subclass);
Peter Zijlstrae4564f72007-10-11 22:11:12 +0200146
147#define mutex_lock(lock) mutex_lock_nested(lock, 0)
148#define mutex_lock_interruptible(lock) mutex_lock_interruptible_nested(lock, 0)
Liam R. Howlettad776532007-12-06 17:37:59 -0500149#define mutex_lock_killable(lock) mutex_lock_killable_nested(lock, 0)
Peter Zijlstrae4c70a62011-05-24 17:12:03 -0700150
151#define mutex_lock_nest_lock(lock, nest_lock) \
152do { \
Maarten Lankhorst040a0a32013-06-24 10:30:04 +0200153 typecheck(struct lockdep_map *, &(nest_lock)->dep_map); \
Peter Zijlstrae4c70a62011-05-24 17:12:03 -0700154 _mutex_lock_nest_lock(lock, &(nest_lock)->dep_map); \
155} while (0)
156
Ingo Molnaref5d4702006-07-03 00:24:55 -0700157#else
Harvey Harrisonec701582008-02-08 04:19:55 -0800158extern void mutex_lock(struct mutex *lock);
159extern int __must_check mutex_lock_interruptible(struct mutex *lock);
160extern int __must_check mutex_lock_killable(struct mutex *lock);
Peter Zijlstrae4564f72007-10-11 22:11:12 +0200161
Ingo Molnaref5d4702006-07-03 00:24:55 -0700162# define mutex_lock_nested(lock, subclass) mutex_lock(lock)
NeilBrownd63a5a72006-12-08 02:36:17 -0800163# define mutex_lock_interruptible_nested(lock, subclass) mutex_lock_interruptible(lock)
Liam R. Howlettad776532007-12-06 17:37:59 -0500164# define mutex_lock_killable_nested(lock, subclass) mutex_lock_killable(lock)
Peter Zijlstrae4c70a62011-05-24 17:12:03 -0700165# define mutex_lock_nest_lock(lock, nest_lock) mutex_lock(lock)
Ingo Molnaref5d4702006-07-03 00:24:55 -0700166#endif
167
Ingo Molnar6053ee32006-01-09 15:59:19 -0800168/*
169 * NOTE: mutex_trylock() follows the spin_trylock() convention,
170 * not the down_trylock() convention!
Arjan van de Vend98d38f2008-10-29 14:24:09 -0700171 *
172 * Returns 1 if the mutex has been acquired successfully, and 0 on contention.
Ingo Molnar6053ee32006-01-09 15:59:19 -0800173 */
Harvey Harrisonec701582008-02-08 04:19:55 -0800174extern int mutex_trylock(struct mutex *lock);
175extern void mutex_unlock(struct mutex *lock);
Maarten Lankhorst040a0a32013-06-24 10:30:04 +0200176
Andrew Mortona511e3f2009-04-29 15:59:58 -0700177extern int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock);
Eric Parisb1fca262009-03-23 18:22:09 +0100178
Tim Chene7224672014-01-21 15:36:00 -0800179#endif /* __LINUX_MUTEX_H */