Line data Source code
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 <linux/list.h>
14 : #include <linux/spinlock_types.h>
15 : #include <linux/linkage.h>
16 : #include <linux/lockdep.h>
17 :
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
32 : * - mutexes may not be used in hardware or software interrupt
33 : * contexts such as tasklets and timers
34 : *
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 : */
48 : struct 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;
53 : #if defined(CONFIG_DEBUG_MUTEXES) || defined(CONFIG_SMP)
54 : struct thread_info *owner;
55 : #endif
56 : #ifdef CONFIG_DEBUG_MUTEXES
57 : const char *name;
58 : void *magic;
59 : #endif
60 : #ifdef CONFIG_DEBUG_LOCK_ALLOC
61 : struct lockdep_map dep_map;
62 : #endif
63 : };
64 :
65 : /*
66 : * This is the control structure for tasks blocked on mutex,
67 : * which resides on the blocked task's kernel stack:
68 : */
69 : struct mutex_waiter {
70 : struct list_head list;
71 : struct task_struct *task;
72 : #ifdef CONFIG_DEBUG_MUTEXES
73 : 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)
81 : # define mutex_init(mutex) \
82 : do { \
83 : static struct lock_class_key __key; \
84 : \
85 : __mutex_init((mutex), #mutex, &__key); \
86 : } while (0)
87 : # define mutex_destroy(mutex) do { } while (0)
88 : #endif
89 :
90 : #ifdef CONFIG_DEBUG_LOCK_ALLOC
91 : # define __DEP_MAP_MUTEX_INITIALIZER(lockname) \
92 : , .dep_map = { .name = #lockname }
93 : #else
94 : # define __DEP_MAP_MUTEX_INITIALIZER(lockname)
95 : #endif
96 :
97 : #define __MUTEX_INITIALIZER(lockname) \
98 : { .count = ATOMIC_INIT(1) \
99 : , .wait_lock = __SPIN_LOCK_UNLOCKED(lockname.wait_lock) \
100 : , .wait_list = LIST_HEAD_INIT(lockname.wait_list) \
101 : __DEBUG_MUTEX_INITIALIZER(lockname) \
102 : __DEP_MAP_MUTEX_INITIALIZER(lockname) }
103 :
104 : #define DEFINE_MUTEX(mutexname) \
105 : struct mutex mutexname = __MUTEX_INITIALIZER(mutexname)
106 :
107 : extern void __mutex_init(struct mutex *lock, const char *name,
108 : struct lock_class_key *key);
109 :
110 : /**
111 : * mutex_is_locked - is the mutex locked
112 : * @lock: the mutex to be queried
113 : *
114 : * Returns 1 if the mutex is locked, 0 if unlocked.
115 : */
116 : static inline int mutex_is_locked(struct mutex *lock)
117 : {
118 : return atomic_read(&lock->count) != 1;
119 : }
120 :
121 : /*
122 : * See kernel/mutex.c for detailed documentation of these APIs.
123 : * Also see Documentation/mutex-design.txt.
124 : */
125 : #ifdef CONFIG_DEBUG_LOCK_ALLOC
126 : extern void mutex_lock_nested(struct mutex *lock, unsigned int subclass);
127 : extern int __must_check mutex_lock_interruptible_nested(struct mutex *lock,
128 : unsigned int subclass);
129 : extern int __must_check mutex_lock_killable_nested(struct mutex *lock,
130 : unsigned int subclass);
131 :
132 : #define mutex_lock(lock) mutex_lock_nested(lock, 0)
133 : #define mutex_lock_interruptible(lock) mutex_lock_interruptible_nested(lock, 0)
134 : #define mutex_lock_killable(lock) mutex_lock_killable_nested(lock, 0)
135 : #else
136 : extern void mutex_lock(struct mutex *lock);
137 : extern int __must_check mutex_lock_interruptible(struct mutex *lock);
138 : extern int __must_check mutex_lock_killable(struct mutex *lock);
139 :
140 : # define mutex_lock_nested(lock, subclass) mutex_lock(lock)
141 : # define mutex_lock_interruptible_nested(lock, subclass) mutex_lock_interruptible(lock)
142 : # define mutex_lock_killable_nested(lock, subclass) mutex_lock_killable(lock)
143 : #endif
144 :
145 : /*
146 : * NOTE: mutex_trylock() follows the spin_trylock() convention,
147 : * not the down_trylock() convention!
148 : *
149 : * Returns 1 if the mutex has been acquired successfully, and 0 on contention.
150 : */
151 : extern int mutex_trylock(struct mutex *lock);
152 : extern void mutex_unlock(struct mutex *lock);
153 : extern int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock);
154 1 :
155 : #endif
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