1 /* 2 ** 2012 July 21 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 ** 13 ** This file presents a simple cross-platform threading interface for 14 ** use internally by SQLite. 15 ** 16 ** A "thread" can be created using sqlite3ThreadCreate(). This thread 17 ** runs independently of its creator until it is joined using 18 ** sqlite3ThreadJoin(), at which point it terminates. 19 ** 20 ** Threads do not have to be real. It could be that the work of the 21 ** "thread" is done by the main thread at either the sqlite3ThreadCreate() 22 ** or sqlite3ThreadJoin() call. This is, in fact, what happens in 23 ** single threaded systems. Nothing in SQLite requires multiple threads. 24 ** This interface exists so that applications that want to take advantage 25 ** of multiple cores can do so, while also allowing applications to stay 26 ** single-threaded if desired. 27 */ 28 #include "sqliteInt.h" 29 30 #if SQLITE_MAX_WORKER_THREADS>0 31 32 /********************************* Unix Pthreads ****************************/ 33 #if SQLITE_OS_UNIX && defined(SQLITE_MUTEX_PTHREADS) && SQLITE_THREADSAFE>0 34 35 #define SQLITE_THREADS_IMPLEMENTED 1 /* Prevent the single-thread code below */ 36 #include <pthread.h> 37 38 /* A running thread */ 39 struct SQLiteThread { 40 pthread_t tid; /* Thread ID */ 41 int done; /* Set to true when thread finishes */ 42 void *pOut; /* Result returned by the thread */ 43 void *(*xTask)(void*); /* The thread routine */ 44 void *pIn; /* Argument to the thread */ 45 }; 46 47 /* Create a new thread */ 48 int sqlite3ThreadCreate( 49 SQLiteThread **ppThread, /* OUT: Write the thread object here */ 50 void *(*xTask)(void*), /* Routine to run in a separate thread */ 51 void *pIn /* Argument passed into xTask() */ 52 ){ 53 SQLiteThread *p; 54 int rc; 55 56 assert( ppThread!=0 ); 57 assert( xTask!=0 ); 58 /* This routine is never used in single-threaded mode */ 59 assert( sqlite3GlobalConfig.bCoreMutex!=0 ); 60 61 *ppThread = 0; 62 p = sqlite3Malloc(sizeof(*p)); 63 if( p==0 ) return SQLITE_NOMEM; 64 memset(p, 0, sizeof(*p)); 65 p->xTask = xTask; 66 p->pIn = pIn; 67 if( sqlite3FaultSim(200) ){ 68 rc = 1; 69 }else{ 70 rc = pthread_create(&p->tid, 0, xTask, pIn); 71 } 72 if( rc ){ 73 p->done = 1; 74 p->pOut = xTask(pIn); 75 } 76 *ppThread = p; 77 return SQLITE_OK; 78 } 79 80 /* Get the results of the thread */ 81 int sqlite3ThreadJoin(SQLiteThread *p, void **ppOut){ 82 int rc; 83 84 assert( ppOut!=0 ); 85 if( NEVER(p==0) ) return SQLITE_NOMEM; 86 if( p->done ){ 87 *ppOut = p->pOut; 88 rc = SQLITE_OK; 89 }else{ 90 rc = pthread_join(p->tid, ppOut) ? SQLITE_ERROR : SQLITE_OK; 91 } 92 sqlite3_free(p); 93 return rc; 94 } 95 96 #endif /* SQLITE_OS_UNIX && defined(SQLITE_MUTEX_PTHREADS) */ 97 /******************************** End Unix Pthreads *************************/ 98 99 100 /********************************* Win32 Threads ****************************/ 101 #if SQLITE_OS_WIN && !SQLITE_OS_WINRT && SQLITE_THREADSAFE>0 102 103 #define SQLITE_THREADS_IMPLEMENTED 1 /* Prevent the single-thread code below */ 104 #include <process.h> 105 106 /* A running thread */ 107 struct SQLiteThread { 108 uintptr_t tid; /* The thread handle */ 109 unsigned id; /* The thread identifier */ 110 void *(*xTask)(void*); /* The routine to run as a thread */ 111 void *pIn; /* Argument to xTask */ 112 void *pResult; /* Result of xTask */ 113 }; 114 115 /* Thread procedure Win32 compatibility shim */ 116 static unsigned __stdcall sqlite3ThreadProc( 117 void *pArg /* IN: Pointer to the SQLiteThread structure */ 118 ){ 119 SQLiteThread *p = (SQLiteThread *)pArg; 120 121 assert( p!=0 ); 122 assert( p->id==GetCurrentThreadId() ); 123 assert( p->xTask!=0 ); 124 p->pResult = p->xTask(p->pIn); 125 126 _endthreadex(0); 127 return 0; /* NOT REACHED */ 128 } 129 130 /* Create a new thread */ 131 int sqlite3ThreadCreate( 132 SQLiteThread **ppThread, /* OUT: Write the thread object here */ 133 void *(*xTask)(void*), /* Routine to run in a separate thread */ 134 void *pIn /* Argument passed into xTask() */ 135 ){ 136 SQLiteThread *p; 137 138 assert( ppThread!=0 ); 139 assert( xTask!=0 ); 140 *ppThread = 0; 141 p = sqlite3Malloc(sizeof(*p)); 142 if( p==0 ) return SQLITE_NOMEM; 143 if( sqlite3GlobalConfig.bCoreMutex==0 ){ 144 memset(p, 0, sizeof(*p)); 145 }else{ 146 p->xTask = xTask; 147 p->pIn = pIn; 148 p->tid = _beginthreadex(0, 0, sqlite3ThreadProc, p, 0, &p->id); 149 if( p->tid==(uintptr_t)-1 ){ 150 memset(p, 0, sizeof(*p)); 151 } 152 } 153 if( p->xTask==0 ){ 154 p->id = GetCurrentThreadId(); 155 p->pResult = xTask(pIn); 156 } 157 *ppThread = p; 158 return SQLITE_OK; 159 } 160 161 DWORD sqlite3Win32Wait(HANDLE hObject); /* os_win.c */ 162 163 /* Get the results of the thread */ 164 int sqlite3ThreadJoin(SQLiteThread *p, void **ppOut){ 165 DWORD rc; 166 BOOL bRc; 167 168 assert( ppOut!=0 ); 169 if( NEVER(p==0) ) return SQLITE_NOMEM; 170 if( p->xTask==0 ){ 171 rc = WAIT_OBJECT_0; 172 }else{ 173 assert( p->id!=0 && p->id!=GetCurrentThreadId() ); 174 rc = sqlite3Win32Wait((HANDLE)p->tid); 175 assert( rc!=WAIT_IO_COMPLETION ); 176 bRc = CloseHandle((HANDLE)p->tid); 177 assert( bRc ); 178 } 179 if( rc==WAIT_OBJECT_0 ) *ppOut = p->pResult; 180 sqlite3_free(p); 181 return (rc==WAIT_OBJECT_0) ? SQLITE_OK : SQLITE_ERROR; 182 } 183 184 #endif /* SQLITE_OS_WIN && !SQLITE_OS_WINRT */ 185 /******************************** End Win32 Threads *************************/ 186 187 188 /********************************* Single-Threaded **************************/ 189 #ifndef SQLITE_THREADS_IMPLEMENTED 190 /* 191 ** This implementation does not actually create a new thread. It does the 192 ** work of the thread in the main thread, when either the thread is created 193 ** or when it is joined 194 */ 195 196 /* A running thread */ 197 struct SQLiteThread { 198 void *(*xTask)(void*); /* The routine to run as a thread */ 199 void *pIn; /* Argument to xTask */ 200 void *pResult; /* Result of xTask */ 201 }; 202 203 /* Create a new thread */ 204 int sqlite3ThreadCreate( 205 SQLiteThread **ppThread, /* OUT: Write the thread object here */ 206 void *(*xTask)(void*), /* Routine to run in a separate thread */ 207 void *pIn /* Argument passed into xTask() */ 208 ){ 209 SQLiteThread *p; 210 211 assert( ppThread!=0 ); 212 assert( xTask!=0 ); 213 *ppThread = 0; 214 p = sqlite3Malloc(sizeof(*p)); 215 if( p==0 ) return SQLITE_NOMEM; 216 if( (SQLITE_PTR_TO_INT(p)/17)&1 ){ 217 p->xTask = xTask; 218 p->pIn = pIn; 219 }else{ 220 p->xTask = 0; 221 p->pResult = xTask(pIn); 222 } 223 *ppThread = p; 224 return SQLITE_OK; 225 } 226 227 /* Get the results of the thread */ 228 int sqlite3ThreadJoin(SQLiteThread *p, void **ppOut){ 229 230 assert( ppOut!=0 ); 231 if( NEVER(p==0) ) return SQLITE_NOMEM; 232 if( p->xTask ){ 233 *ppOut = p->xTask(p->pIn); 234 }else{ 235 *ppOut = p->pResult; 236 } 237 sqlite3_free(p); 238 239 #if defined(SQLITE_TEST) 240 { 241 void *pTstAlloc = sqlite3Malloc(10); 242 if (!pTstAlloc) return SQLITE_NOMEM; 243 sqlite3_free(pTstAlloc); 244 } 245 #endif 246 247 return SQLITE_OK; 248 } 249 250 #endif /* !defined(SQLITE_THREADS_IMPLEMENTED) */ 251 /****************************** End Single-Threaded *************************/ 252 #endif /* SQLITE_MAX_WORKER_THREADS>0 */ 253