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| Rev | Author | Line No. | Line |
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| 1616 | serge | 1 | /* |
| 2 | * Mutexes: blocking mutual exclusion locks |
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| 3 | * |
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| 4 | * started by Ingo Molnar: |
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| 5 | * |
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| 6 | * Copyright (C) 2004, 2005, 2006 Red Hat, Inc., Ingo Molnar |
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| 7 | * |
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| 8 | * This file contains the main data structure and API definitions. |
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| 9 | */ |
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| 10 | #ifndef __LINUX_MUTEX_H |
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| 11 | #define __LINUX_MUTEX_H |
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| 12 | |||
| 13 | #include |
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| 14 | #include |
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| 15 | #include |
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| 16 | |||
| 17 | /* |
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| 18 | * Simple, straightforward mutexes with strict semantics: |
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| 19 | * |
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| 20 | * - only one task can hold the mutex at a time |
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| 21 | * - only the owner can unlock the mutex |
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| 22 | * - multiple unlocks are not permitted |
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| 23 | * - recursive locking is not permitted |
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| 24 | * - a mutex object must be initialized via the API |
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| 25 | * - a mutex object must not be initialized via memset or copying |
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| 26 | * - task may not exit with mutex held |
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| 27 | * - memory areas where held locks reside must not be freed |
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| 28 | * - held mutexes must not be reinitialized |
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| 29 | * - mutexes may not be used in hardware or software interrupt |
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| 30 | * contexts such as tasklets and timers |
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| 31 | * |
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| 32 | * These semantics are fully enforced when DEBUG_MUTEXES is |
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| 33 | * enabled. Furthermore, besides enforcing the above rules, the mutex |
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| 34 | * debugging code also implements a number of additional features |
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| 35 | * that make lock debugging easier and faster: |
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| 36 | * |
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| 37 | * - uses symbolic names of mutexes, whenever they are printed in debug output |
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| 38 | * - point-of-acquire tracking, symbolic lookup of function names |
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| 39 | * - list of all locks held in the system, printout of them |
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| 40 | * - owner tracking |
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| 41 | * - detects self-recursing locks and prints out all relevant info |
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| 42 | * - detects multi-task circular deadlocks and prints out all affected |
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| 43 | * locks and tasks (and only those tasks) |
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| 44 | */ |
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| 45 | struct mutex { |
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| 46 | /* 1: unlocked, 0: locked, negative: locked, possible waiters */ |
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| 47 | atomic_t count; |
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| 48 | struct list_head wait_list; |
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| 49 | }; |
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| 50 | |||
| 51 | /* |
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| 52 | * This is the control structure for tasks blocked on mutex, |
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| 53 | * which resides on the blocked task's kernel stack: |
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| 54 | */ |
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| 55 | struct mutex_waiter { |
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| 56 | struct list_head list; |
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| 57 | int *task; |
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| 58 | }; |
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| 59 | |||
| 60 | |||
| 61 | #define __MUTEX_INITIALIZER(lockname) \ |
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| 62 | { .count = ATOMIC_INIT(1) \ |
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| 63 | , .wait_list = LIST_HEAD_INIT(lockname.wait_list) } |
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| 64 | |||
| 65 | #define DEFINE_MUTEX(mutexname) \ |
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| 66 | struct mutex mutexname = __MUTEX_INITIALIZER(mutexname) |
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| 67 | |||
| 68 | void __attribute__ ((fastcall)) __attribute__ ((dllimport)) |
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| 69 | mutex_init(struct mutex*)__asm__("MutexInit"); |
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| 70 | void __attribute__ ((fastcall)) __attribute__ ((dllimport)) |
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| 71 | mutex_lock(struct mutex*)__asm__("MutexLock"); |
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| 72 | void __attribute__ ((fastcall)) __attribute__ ((dllimport)) |
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| 73 | mutex_unlock(struct mutex*)__asm__("MutexUnlock"); |
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| 74 | |||
| 75 | /** |
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| 76 | * mutex_is_locked - is the mutex locked |
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| 77 | * @lock: the mutex to be queried |
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| 78 | * |
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| 79 | * Returns 1 if the mutex is locked, 0 if unlocked. |
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| 80 | */ |
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| 81 | static inline int mutex_is_locked(struct mutex *lock) |
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| 82 | { |
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| 83 | return atomic_read(&lock->count) != 1; |
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| 84 | } |
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| 85 | |||
| 86 | #endif |