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| 1 /* |
| 2 ** 2007 August 14 |
| 3 ** |
| 4 ** The author disclaims copyright to this source code. In place of |
| 5 ** a legal notice, here is a blessing: |
| 6 ** |
| 7 ** May you do good and not evil. |
| 8 ** May you find forgiveness for yourself and forgive others. |
| 9 ** May you share freely, never taking more than you give. |
| 10 ** |
| 11 ************************************************************************* |
| 12 ** This file contains the C functions that implement mutexes. |
| 13 ** |
| 14 ** This file contains code that is common across all mutex implementations. |
| 15 */ |
| 16 #include "sqliteInt.h" |
| 17 |
| 18 #if defined(SQLITE_DEBUG) && !defined(SQLITE_MUTEX_OMIT) |
| 19 /* |
| 20 ** For debugging purposes, record when the mutex subsystem is initialized |
| 21 ** and uninitialized so that we can assert() if there is an attempt to |
| 22 ** allocate a mutex while the system is uninitialized. |
| 23 */ |
| 24 static SQLITE_WSD int mutexIsInit = 0; |
| 25 #endif /* SQLITE_DEBUG */ |
| 26 |
| 27 |
| 28 #ifndef SQLITE_MUTEX_OMIT |
| 29 /* |
| 30 ** Initialize the mutex system. |
| 31 */ |
| 32 int sqlite3MutexInit(void){ |
| 33 int rc = SQLITE_OK; |
| 34 if( !sqlite3GlobalConfig.mutex.xMutexAlloc ){ |
| 35 /* If the xMutexAlloc method has not been set, then the user did not |
| 36 ** install a mutex implementation via sqlite3_config() prior to |
| 37 ** sqlite3_initialize() being called. This block copies pointers to |
| 38 ** the default implementation into the sqlite3GlobalConfig structure. |
| 39 */ |
| 40 sqlite3_mutex_methods const *pFrom; |
| 41 sqlite3_mutex_methods *pTo = &sqlite3GlobalConfig.mutex; |
| 42 |
| 43 if( sqlite3GlobalConfig.bCoreMutex ){ |
| 44 pFrom = sqlite3DefaultMutex(); |
| 45 }else{ |
| 46 pFrom = sqlite3NoopMutex(); |
| 47 } |
| 48 memcpy(pTo, pFrom, offsetof(sqlite3_mutex_methods, xMutexAlloc)); |
| 49 memcpy(&pTo->xMutexFree, &pFrom->xMutexFree, |
| 50 sizeof(*pTo) - offsetof(sqlite3_mutex_methods, xMutexFree)); |
| 51 pTo->xMutexAlloc = pFrom->xMutexAlloc; |
| 52 } |
| 53 rc = sqlite3GlobalConfig.mutex.xMutexInit(); |
| 54 |
| 55 #ifdef SQLITE_DEBUG |
| 56 GLOBAL(int, mutexIsInit) = 1; |
| 57 #endif |
| 58 |
| 59 return rc; |
| 60 } |
| 61 |
| 62 /* |
| 63 ** Shutdown the mutex system. This call frees resources allocated by |
| 64 ** sqlite3MutexInit(). |
| 65 */ |
| 66 int sqlite3MutexEnd(void){ |
| 67 int rc = SQLITE_OK; |
| 68 if( sqlite3GlobalConfig.mutex.xMutexEnd ){ |
| 69 rc = sqlite3GlobalConfig.mutex.xMutexEnd(); |
| 70 } |
| 71 |
| 72 #ifdef SQLITE_DEBUG |
| 73 GLOBAL(int, mutexIsInit) = 0; |
| 74 #endif |
| 75 |
| 76 return rc; |
| 77 } |
| 78 |
| 79 /* |
| 80 ** Retrieve a pointer to a static mutex or allocate a new dynamic one. |
| 81 */ |
| 82 sqlite3_mutex *sqlite3_mutex_alloc(int id){ |
| 83 #ifndef SQLITE_OMIT_AUTOINIT |
| 84 if( id<=SQLITE_MUTEX_RECURSIVE && sqlite3_initialize() ) return 0; |
| 85 #endif |
| 86 return sqlite3GlobalConfig.mutex.xMutexAlloc(id); |
| 87 } |
| 88 |
| 89 sqlite3_mutex *sqlite3MutexAlloc(int id){ |
| 90 if( !sqlite3GlobalConfig.bCoreMutex ){ |
| 91 return 0; |
| 92 } |
| 93 assert( GLOBAL(int, mutexIsInit) ); |
| 94 return sqlite3GlobalConfig.mutex.xMutexAlloc(id); |
| 95 } |
| 96 |
| 97 /* |
| 98 ** Free a dynamic mutex. |
| 99 */ |
| 100 void sqlite3_mutex_free(sqlite3_mutex *p){ |
| 101 if( p ){ |
| 102 sqlite3GlobalConfig.mutex.xMutexFree(p); |
| 103 } |
| 104 } |
| 105 |
| 106 /* |
| 107 ** Obtain the mutex p. If some other thread already has the mutex, block |
| 108 ** until it can be obtained. |
| 109 */ |
| 110 void sqlite3_mutex_enter(sqlite3_mutex *p){ |
| 111 if( p ){ |
| 112 sqlite3GlobalConfig.mutex.xMutexEnter(p); |
| 113 } |
| 114 } |
| 115 |
| 116 /* |
| 117 ** Obtain the mutex p. If successful, return SQLITE_OK. Otherwise, if another |
| 118 ** thread holds the mutex and it cannot be obtained, return SQLITE_BUSY. |
| 119 */ |
| 120 int sqlite3_mutex_try(sqlite3_mutex *p){ |
| 121 int rc = SQLITE_OK; |
| 122 if( p ){ |
| 123 return sqlite3GlobalConfig.mutex.xMutexTry(p); |
| 124 } |
| 125 return rc; |
| 126 } |
| 127 |
| 128 /* |
| 129 ** The sqlite3_mutex_leave() routine exits a mutex that was previously |
| 130 ** entered by the same thread. The behavior is undefined if the mutex |
| 131 ** is not currently entered. If a NULL pointer is passed as an argument |
| 132 ** this function is a no-op. |
| 133 */ |
| 134 void sqlite3_mutex_leave(sqlite3_mutex *p){ |
| 135 if( p ){ |
| 136 sqlite3GlobalConfig.mutex.xMutexLeave(p); |
| 137 } |
| 138 } |
| 139 |
| 140 #ifndef NDEBUG |
| 141 /* |
| 142 ** The sqlite3_mutex_held() and sqlite3_mutex_notheld() routine are |
| 143 ** intended for use inside assert() statements. |
| 144 */ |
| 145 int sqlite3_mutex_held(sqlite3_mutex *p){ |
| 146 return p==0 || sqlite3GlobalConfig.mutex.xMutexHeld(p); |
| 147 } |
| 148 int sqlite3_mutex_notheld(sqlite3_mutex *p){ |
| 149 return p==0 || sqlite3GlobalConfig.mutex.xMutexNotheld(p); |
| 150 } |
| 151 #endif |
| 152 |
| 153 #endif /* !defined(SQLITE_MUTEX_OMIT) */ |
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