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 <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 : */
50 : struct 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_SMP)
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 : const char *name;
63 : void *magic;
64 : #endif
65 : #ifdef CONFIG_DEBUG_LOCK_ALLOC
66 : struct lockdep_map dep_map;
67 : #endif
68 : };
69 :
70 : /*
71 : * This is the control structure for tasks blocked on mutex,
72 : * which resides on the blocked task's kernel stack:
73 : */
74 : struct mutex_waiter {
75 : struct list_head list;
76 : struct task_struct *task;
77 : #ifdef CONFIG_DEBUG_MUTEXES
78 : 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)
86 : /**
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 : */
94 : # define mutex_init(mutex) \
95 : do { \
96 : static struct lock_class_key __key; \
97 : \
98 : __mutex_init((mutex), #mutex, &__key); \
99 : } while (0)
100 : static inline void mutex_destroy(struct mutex *lock) {}
101 : #endif
102 :
103 : #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 :
110 : #define __MUTEX_INITIALIZER(lockname) \
111 : { .count = ATOMIC_INIT(1) \
112 : , .wait_lock = __SPIN_LOCK_UNLOCKED(lockname.wait_lock) \
113 : , .wait_list = LIST_HEAD_INIT(lockname.wait_list) \
114 : __DEBUG_MUTEX_INITIALIZER(lockname) \
115 : __DEP_MAP_MUTEX_INITIALIZER(lockname) }
116 :
117 : #define DEFINE_MUTEX(mutexname) \
118 : struct mutex mutexname = __MUTEX_INITIALIZER(mutexname)
119 :
120 : extern void __mutex_init(struct mutex *lock, const char *name,
121 : struct lock_class_key *key);
122 :
123 : /**
124 : * 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 : */
129 : static inline int mutex_is_locked(struct mutex *lock)
130 : {
131 256445 : return atomic_read(&lock->count) != 1;
132 : }
133 :
134 : /*
135 : * See kernel/locking/mutex.c for detailed documentation of these APIs.
136 : * Also see Documentation/mutex-design.txt.
137 : */
138 : #ifdef CONFIG_DEBUG_LOCK_ALLOC
139 : extern void mutex_lock_nested(struct mutex *lock, unsigned int subclass);
140 : extern void _mutex_lock_nest_lock(struct mutex *lock, struct lockdep_map *nest_lock);
141 :
142 : extern int __must_check mutex_lock_interruptible_nested(struct mutex *lock,
143 : unsigned int subclass);
144 : extern int __must_check mutex_lock_killable_nested(struct mutex *lock,
145 : unsigned int subclass);
146 :
147 : #define mutex_lock(lock) mutex_lock_nested(lock, 0)
148 : #define mutex_lock_interruptible(lock) mutex_lock_interruptible_nested(lock, 0)
149 : #define mutex_lock_killable(lock) mutex_lock_killable_nested(lock, 0)
150 :
151 : #define mutex_lock_nest_lock(lock, nest_lock) \
152 : do { \
153 : typecheck(struct lockdep_map *, &(nest_lock)->dep_map); \
154 : _mutex_lock_nest_lock(lock, &(nest_lock)->dep_map); \
155 : } while (0)
156 :
157 : #else
158 : extern void mutex_lock(struct mutex *lock);
159 : extern int __must_check mutex_lock_interruptible(struct mutex *lock);
160 : extern int __must_check mutex_lock_killable(struct mutex *lock);
161 :
162 : # define mutex_lock_nested(lock, subclass) mutex_lock(lock)
163 : # define mutex_lock_interruptible_nested(lock, subclass) mutex_lock_interruptible(lock)
164 : # define mutex_lock_killable_nested(lock, subclass) mutex_lock_killable(lock)
165 : # define mutex_lock_nest_lock(lock, nest_lock) mutex_lock(lock)
166 : #endif
167 :
168 : /*
169 : * NOTE: mutex_trylock() follows the spin_trylock() convention,
170 : * not the down_trylock() convention!
171 : *
172 : * Returns 1 if the mutex has been acquired successfully, and 0 on contention.
173 : */
174 : extern int mutex_trylock(struct mutex *lock);
175 : extern void mutex_unlock(struct mutex *lock);
176 :
177 : extern int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock);
178 :
179 : #endif /* __LINUX_MUTEX_H */
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