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 pTo->xMutexInit = pFrom->xMutexInit; 49 pTo->xMutexEnd = pFrom->xMutexEnd; 50 pTo->xMutexFree = pFrom->xMutexFree; 51 pTo->xMutexEnter = pFrom->xMutexEnter; 52 pTo->xMutexTry = pFrom->xMutexTry; 53 pTo->xMutexLeave = pFrom->xMutexLeave; 54 pTo->xMutexHeld = pFrom->xMutexHeld; 55 pTo->xMutexNotheld = pFrom->xMutexNotheld; 56 pTo->xMutexAlloc = pFrom->xMutexAlloc; 57 } 58 rc = sqlite3GlobalConfig.mutex.xMutexInit(); 59 60 #ifdef SQLITE_DEBUG 61 GLOBAL(int, mutexIsInit) = 1; 62 #endif 63 64 return rc; 65 } 66 67 /* 68 ** Shutdown the mutex system. This call frees resources allocated by 69 ** sqlite3MutexInit(). 70 */ 71 int sqlite3MutexEnd(void){ 72 int rc = SQLITE_OK; 73 if( sqlite3GlobalConfig.mutex.xMutexEnd ){ 74 rc = sqlite3GlobalConfig.mutex.xMutexEnd(); 75 } 76 77 #ifdef SQLITE_DEBUG 78 GLOBAL(int, mutexIsInit) = 0; 79 #endif 80 81 return rc; 82 } 83 84 /* 85 ** Retrieve a pointer to a static mutex or allocate a new dynamic one. 86 */ 87 sqlite3_mutex *sqlite3_mutex_alloc(int id){ 88 #ifndef SQLITE_OMIT_AUTOINIT 89 if( id<=SQLITE_MUTEX_RECURSIVE && sqlite3_initialize() ) return 0; 90 if( id>SQLITE_MUTEX_RECURSIVE && sqlite3MutexInit() ) return 0; 91 #endif 92 return sqlite3GlobalConfig.mutex.xMutexAlloc(id); 93 } 94 95 sqlite3_mutex *sqlite3MutexAlloc(int id){ 96 if( !sqlite3GlobalConfig.bCoreMutex ){ 97 return 0; 98 } 99 assert( GLOBAL(int, mutexIsInit) ); 100 return sqlite3GlobalConfig.mutex.xMutexAlloc(id); 101 } 102 103 /* 104 ** Free a dynamic mutex. 105 */ 106 void sqlite3_mutex_free(sqlite3_mutex *p){ 107 if( p ){ 108 sqlite3GlobalConfig.mutex.xMutexFree(p); 109 } 110 } 111 112 /* 113 ** Obtain the mutex p. If some other thread already has the mutex, block 114 ** until it can be obtained. 115 */ 116 void sqlite3_mutex_enter(sqlite3_mutex *p){ 117 if( p ){ 118 sqlite3GlobalConfig.mutex.xMutexEnter(p); 119 } 120 } 121 122 /* 123 ** Obtain the mutex p. If successful, return SQLITE_OK. Otherwise, if another 124 ** thread holds the mutex and it cannot be obtained, return SQLITE_BUSY. 125 */ 126 int sqlite3_mutex_try(sqlite3_mutex *p){ 127 int rc = SQLITE_OK; 128 if( p ){ 129 return sqlite3GlobalConfig.mutex.xMutexTry(p); 130 } 131 return rc; 132 } 133 134 /* 135 ** The sqlite3_mutex_leave() routine exits a mutex that was previously 136 ** entered by the same thread. The behavior is undefined if the mutex 137 ** is not currently entered. If a NULL pointer is passed as an argument 138 ** this function is a no-op. 139 */ 140 void sqlite3_mutex_leave(sqlite3_mutex *p){ 141 if( p ){ 142 sqlite3GlobalConfig.mutex.xMutexLeave(p); 143 } 144 } 145 146 #ifndef NDEBUG 147 /* 148 ** The sqlite3_mutex_held() and sqlite3_mutex_notheld() routine are 149 ** intended for use inside assert() statements. 150 */ 151 int sqlite3_mutex_held(sqlite3_mutex *p){ 152 return p==0 || sqlite3GlobalConfig.mutex.xMutexHeld(p); 153 } 154 int sqlite3_mutex_notheld(sqlite3_mutex *p){ 155 return p==0 || sqlite3GlobalConfig.mutex.xMutexNotheld(p); 156 } 157 #endif 158 159 #endif /* !defined(SQLITE_MUTEX_OMIT) */ 160