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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> | |
a8b9ee73 | 15 | #include <linux/linkage.h> |
6053ee3b IM |
16 | |
17 | #include <asm/atomic.h> | |
18 | ||
19 | /* | |
20 | * Simple, straightforward mutexes with strict semantics: | |
21 | * | |
22 | * - only one task can hold the mutex at a time | |
23 | * - only the owner can unlock the mutex | |
24 | * - multiple unlocks are not permitted | |
25 | * - recursive locking is not permitted | |
26 | * - a mutex object must be initialized via the API | |
27 | * - a mutex object must not be initialized via memset or copying | |
28 | * - task may not exit with mutex held | |
29 | * - memory areas where held locks reside must not be freed | |
30 | * - held mutexes must not be reinitialized | |
31 | * - mutexes may not be used in irq contexts | |
32 | * | |
33 | * These semantics are fully enforced when DEBUG_MUTEXES is | |
34 | * enabled. Furthermore, besides enforcing the above rules, the mutex | |
35 | * debugging code also implements a number of additional features | |
36 | * that make lock debugging easier and faster: | |
37 | * | |
38 | * - uses symbolic names of mutexes, whenever they are printed in debug output | |
39 | * - point-of-acquire tracking, symbolic lookup of function names | |
40 | * - list of all locks held in the system, printout of them | |
41 | * - owner tracking | |
42 | * - detects self-recursing locks and prints out all relevant info | |
43 | * - detects multi-task circular deadlocks and prints out all affected | |
44 | * locks and tasks (and only those tasks) | |
45 | */ | |
46 | struct mutex { | |
47 | /* 1: unlocked, 0: locked, negative: locked, possible waiters */ | |
48 | atomic_t count; | |
49 | spinlock_t wait_lock; | |
50 | struct list_head wait_list; | |
51 | #ifdef CONFIG_DEBUG_MUTEXES | |
52 | struct thread_info *owner; | |
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53 | const char *name; |
54 | void *magic; | |
55 | #endif | |
56 | }; | |
57 | ||
58 | /* | |
59 | * This is the control structure for tasks blocked on mutex, | |
60 | * which resides on the blocked task's kernel stack: | |
61 | */ | |
62 | struct mutex_waiter { | |
63 | struct list_head list; | |
64 | struct task_struct *task; | |
65 | #ifdef CONFIG_DEBUG_MUTEXES | |
66 | struct mutex *lock; | |
67 | void *magic; | |
68 | #endif | |
69 | }; | |
70 | ||
71 | #ifdef CONFIG_DEBUG_MUTEXES | |
72 | # include <linux/mutex-debug.h> | |
73 | #else | |
74 | # define __DEBUG_MUTEX_INITIALIZER(lockname) | |
75 | # define mutex_init(mutex) __mutex_init(mutex, NULL) | |
76 | # define mutex_destroy(mutex) do { } while (0) | |
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77 | #endif |
78 | ||
79 | #define __MUTEX_INITIALIZER(lockname) \ | |
80 | { .count = ATOMIC_INIT(1) \ | |
81 | , .wait_lock = SPIN_LOCK_UNLOCKED \ | |
82 | , .wait_list = LIST_HEAD_INIT(lockname.wait_list) \ | |
83 | __DEBUG_MUTEX_INITIALIZER(lockname) } | |
84 | ||
85 | #define DEFINE_MUTEX(mutexname) \ | |
86 | struct mutex mutexname = __MUTEX_INITIALIZER(mutexname) | |
87 | ||
88 | extern void fastcall __mutex_init(struct mutex *lock, const char *name); | |
89 | ||
90 | /*** | |
91 | * mutex_is_locked - is the mutex locked | |
92 | * @lock: the mutex to be queried | |
93 | * | |
94 | * Returns 1 if the mutex is locked, 0 if unlocked. | |
95 | */ | |
96 | static inline int fastcall mutex_is_locked(struct mutex *lock) | |
97 | { | |
98 | return atomic_read(&lock->count) != 1; | |
99 | } | |
100 | ||
101 | /* | |
102 | * See kernel/mutex.c for detailed documentation of these APIs. | |
103 | * Also see Documentation/mutex-design.txt. | |
104 | */ | |
105 | extern void fastcall mutex_lock(struct mutex *lock); | |
106 | extern int fastcall mutex_lock_interruptible(struct mutex *lock); | |
107 | /* | |
108 | * NOTE: mutex_trylock() follows the spin_trylock() convention, | |
109 | * not the down_trylock() convention! | |
110 | */ | |
111 | extern int fastcall mutex_trylock(struct mutex *lock); | |
112 | extern void fastcall mutex_unlock(struct mutex *lock); | |
113 | ||
114 | #endif |