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Diffstat (limited to 'lib/libsqlite3/src/mutex_unix.c')
| -rw-r--r-- | lib/libsqlite3/src/mutex_unix.c | 385 |
1 files changed, 0 insertions, 385 deletions
diff --git a/lib/libsqlite3/src/mutex_unix.c b/lib/libsqlite3/src/mutex_unix.c deleted file mode 100644 index dbdaa225b3e..00000000000 --- a/lib/libsqlite3/src/mutex_unix.c +++ /dev/null @@ -1,385 +0,0 @@ -/* -** 2007 August 28 -** -** The author disclaims copyright to this source code. In place of -** a legal notice, here is a blessing: -** -** May you do good and not evil. -** May you find forgiveness for yourself and forgive others. -** May you share freely, never taking more than you give. -** -************************************************************************* -** This file contains the C functions that implement mutexes for pthreads -*/ -#include "sqliteInt.h" - -/* -** The code in this file is only used if we are compiling threadsafe -** under unix with pthreads. -** -** Note that this implementation requires a version of pthreads that -** supports recursive mutexes. -*/ -#ifdef SQLITE_MUTEX_PTHREADS - -#include <pthread.h> - -/* -** The sqlite3_mutex.id, sqlite3_mutex.nRef, and sqlite3_mutex.owner fields -** are necessary under two condidtions: (1) Debug builds and (2) using -** home-grown mutexes. Encapsulate these conditions into a single #define. -*/ -#if defined(SQLITE_DEBUG) || defined(SQLITE_HOMEGROWN_RECURSIVE_MUTEX) -# define SQLITE_MUTEX_NREF 1 -#else -# define SQLITE_MUTEX_NREF 0 -#endif - -/* -** Each recursive mutex is an instance of the following structure. -*/ -struct sqlite3_mutex { - pthread_mutex_t mutex; /* Mutex controlling the lock */ -#if SQLITE_MUTEX_NREF || defined(SQLITE_ENABLE_API_ARMOR) - int id; /* Mutex type */ -#endif -#if SQLITE_MUTEX_NREF - volatile int nRef; /* Number of entrances */ - volatile pthread_t owner; /* Thread that is within this mutex */ - int trace; /* True to trace changes */ -#endif -}; -#if SQLITE_MUTEX_NREF -#define SQLITE3_MUTEX_INITIALIZER { PTHREAD_MUTEX_INITIALIZER, 0, 0, (pthread_t)0, 0 } -#else -#define SQLITE3_MUTEX_INITIALIZER { PTHREAD_MUTEX_INITIALIZER } -#endif - -/* -** The sqlite3_mutex_held() and sqlite3_mutex_notheld() routine are -** intended for use only inside assert() statements. On some platforms, -** there might be race conditions that can cause these routines to -** deliver incorrect results. In particular, if pthread_equal() is -** not an atomic operation, then these routines might delivery -** incorrect results. On most platforms, pthread_equal() is a -** comparison of two integers and is therefore atomic. But we are -** told that HPUX is not such a platform. If so, then these routines -** will not always work correctly on HPUX. -** -** On those platforms where pthread_equal() is not atomic, SQLite -** should be compiled without -DSQLITE_DEBUG and with -DNDEBUG to -** make sure no assert() statements are evaluated and hence these -** routines are never called. -*/ -#if !defined(NDEBUG) || defined(SQLITE_DEBUG) -static int pthreadMutexHeld(sqlite3_mutex *p){ - return (p->nRef!=0 && pthread_equal(p->owner, pthread_self())); -} -static int pthreadMutexNotheld(sqlite3_mutex *p){ - return p->nRef==0 || pthread_equal(p->owner, pthread_self())==0; -} -#endif - -/* -** Try to provide a memory barrier operation, needed for initialization -** and also for the implementation of xShmBarrier in the VFS in cases -** where SQLite is compiled without mutexes. -*/ -void sqlite3MemoryBarrier(void){ -#if defined(SQLITE_MEMORY_BARRIER) - SQLITE_MEMORY_BARRIER; -#elif defined(__GNUC__) && GCC_VERSION>=4001000 - __sync_synchronize(); -#endif -} - -/* -** Initialize and deinitialize the mutex subsystem. -*/ -static int pthreadMutexInit(void){ return SQLITE_OK; } -static int pthreadMutexEnd(void){ return SQLITE_OK; } - -/* -** The sqlite3_mutex_alloc() routine allocates a new -** mutex and returns a pointer to it. If it returns NULL -** that means that a mutex could not be allocated. SQLite -** will unwind its stack and return an error. The argument -** to sqlite3_mutex_alloc() is one of these integer constants: -** -** <ul> -** <li> SQLITE_MUTEX_FAST -** <li> SQLITE_MUTEX_RECURSIVE -** <li> SQLITE_MUTEX_STATIC_MASTER -** <li> SQLITE_MUTEX_STATIC_MEM -** <li> SQLITE_MUTEX_STATIC_OPEN -** <li> SQLITE_MUTEX_STATIC_PRNG -** <li> SQLITE_MUTEX_STATIC_LRU -** <li> SQLITE_MUTEX_STATIC_PMEM -** <li> SQLITE_MUTEX_STATIC_APP1 -** <li> SQLITE_MUTEX_STATIC_APP2 -** <li> SQLITE_MUTEX_STATIC_APP3 -** <li> SQLITE_MUTEX_STATIC_VFS1 -** <li> SQLITE_MUTEX_STATIC_VFS2 -** <li> SQLITE_MUTEX_STATIC_VFS3 -** </ul> -** -** The first two constants cause sqlite3_mutex_alloc() to create -** a new mutex. The new mutex is recursive when SQLITE_MUTEX_RECURSIVE -** is used but not necessarily so when SQLITE_MUTEX_FAST is used. -** The mutex implementation does not need to make a distinction -** between SQLITE_MUTEX_RECURSIVE and SQLITE_MUTEX_FAST if it does -** not want to. But SQLite will only request a recursive mutex in -** cases where it really needs one. If a faster non-recursive mutex -** implementation is available on the host platform, the mutex subsystem -** might return such a mutex in response to SQLITE_MUTEX_FAST. -** -** The other allowed parameters to sqlite3_mutex_alloc() each return -** a pointer to a static preexisting mutex. Six static mutexes are -** used by the current version of SQLite. Future versions of SQLite -** may add additional static mutexes. Static mutexes are for internal -** use by SQLite only. Applications that use SQLite mutexes should -** use only the dynamic mutexes returned by SQLITE_MUTEX_FAST or -** SQLITE_MUTEX_RECURSIVE. -** -** Note that if one of the dynamic mutex parameters (SQLITE_MUTEX_FAST -** or SQLITE_MUTEX_RECURSIVE) is used then sqlite3_mutex_alloc() -** returns a different mutex on every call. But for the static -** mutex types, the same mutex is returned on every call that has -** the same type number. -*/ -static sqlite3_mutex *pthreadMutexAlloc(int iType){ - static sqlite3_mutex staticMutexes[] = { - SQLITE3_MUTEX_INITIALIZER, - SQLITE3_MUTEX_INITIALIZER, - SQLITE3_MUTEX_INITIALIZER, - SQLITE3_MUTEX_INITIALIZER, - SQLITE3_MUTEX_INITIALIZER, - SQLITE3_MUTEX_INITIALIZER, - SQLITE3_MUTEX_INITIALIZER, - SQLITE3_MUTEX_INITIALIZER, - SQLITE3_MUTEX_INITIALIZER, - SQLITE3_MUTEX_INITIALIZER, - SQLITE3_MUTEX_INITIALIZER, - SQLITE3_MUTEX_INITIALIZER - }; - sqlite3_mutex *p; - switch( iType ){ - case SQLITE_MUTEX_RECURSIVE: { - p = sqlite3MallocZero( sizeof(*p) ); - if( p ){ -#ifdef SQLITE_HOMEGROWN_RECURSIVE_MUTEX - /* If recursive mutexes are not available, we will have to - ** build our own. See below. */ - pthread_mutex_init(&p->mutex, 0); -#else - /* Use a recursive mutex if it is available */ - pthread_mutexattr_t recursiveAttr; - pthread_mutexattr_init(&recursiveAttr); - pthread_mutexattr_settype(&recursiveAttr, PTHREAD_MUTEX_RECURSIVE); - pthread_mutex_init(&p->mutex, &recursiveAttr); - pthread_mutexattr_destroy(&recursiveAttr); -#endif - } - break; - } - case SQLITE_MUTEX_FAST: { - p = sqlite3MallocZero( sizeof(*p) ); - if( p ){ - pthread_mutex_init(&p->mutex, 0); - } - break; - } - default: { -#ifdef SQLITE_ENABLE_API_ARMOR - if( iType-2<0 || iType-2>=ArraySize(staticMutexes) ){ - (void)SQLITE_MISUSE_BKPT; - return 0; - } -#endif - p = &staticMutexes[iType-2]; - break; - } - } -#if SQLITE_MUTEX_NREF || defined(SQLITE_ENABLE_API_ARMOR) - if( p ) p->id = iType; -#endif - return p; -} - - -/* -** This routine deallocates a previously -** allocated mutex. SQLite is careful to deallocate every -** mutex that it allocates. -*/ -static void pthreadMutexFree(sqlite3_mutex *p){ - assert( p->nRef==0 ); -#if SQLITE_ENABLE_API_ARMOR - if( p->id==SQLITE_MUTEX_FAST || p->id==SQLITE_MUTEX_RECURSIVE ) -#endif - { - pthread_mutex_destroy(&p->mutex); - sqlite3_free(p); - } -#ifdef SQLITE_ENABLE_API_ARMOR - else{ - (void)SQLITE_MISUSE_BKPT; - } -#endif -} - -/* -** The sqlite3_mutex_enter() and sqlite3_mutex_try() routines attempt -** to enter a mutex. If another thread is already within the mutex, -** sqlite3_mutex_enter() will block and sqlite3_mutex_try() will return -** SQLITE_BUSY. The sqlite3_mutex_try() interface returns SQLITE_OK -** upon successful entry. Mutexes created using SQLITE_MUTEX_RECURSIVE can -** be entered multiple times by the same thread. In such cases the, -** mutex must be exited an equal number of times before another thread -** can enter. If the same thread tries to enter any other kind of mutex -** more than once, the behavior is undefined. -*/ -static void pthreadMutexEnter(sqlite3_mutex *p){ - assert( p->id==SQLITE_MUTEX_RECURSIVE || pthreadMutexNotheld(p) ); - -#ifdef SQLITE_HOMEGROWN_RECURSIVE_MUTEX - /* If recursive mutexes are not available, then we have to grow - ** our own. This implementation assumes that pthread_equal() - ** is atomic - that it cannot be deceived into thinking self - ** and p->owner are equal if p->owner changes between two values - ** that are not equal to self while the comparison is taking place. - ** This implementation also assumes a coherent cache - that - ** separate processes cannot read different values from the same - ** address at the same time. If either of these two conditions - ** are not met, then the mutexes will fail and problems will result. - */ - { - pthread_t self = pthread_self(); - if( p->nRef>0 && pthread_equal(p->owner, self) ){ - p->nRef++; - }else{ - pthread_mutex_lock(&p->mutex); - assert( p->nRef==0 ); - p->owner = self; - p->nRef = 1; - } - } -#else - /* Use the built-in recursive mutexes if they are available. - */ - pthread_mutex_lock(&p->mutex); -#if SQLITE_MUTEX_NREF - assert( p->nRef>0 || p->owner==0 ); - p->owner = pthread_self(); - p->nRef++; -#endif -#endif - -#ifdef SQLITE_DEBUG - if( p->trace ){ - printf("enter mutex %p (%d) with nRef=%d\n", p, p->trace, p->nRef); - } -#endif -} -static int pthreadMutexTry(sqlite3_mutex *p){ - int rc; - assert( p->id==SQLITE_MUTEX_RECURSIVE || pthreadMutexNotheld(p) ); - -#ifdef SQLITE_HOMEGROWN_RECURSIVE_MUTEX - /* If recursive mutexes are not available, then we have to grow - ** our own. This implementation assumes that pthread_equal() - ** is atomic - that it cannot be deceived into thinking self - ** and p->owner are equal if p->owner changes between two values - ** that are not equal to self while the comparison is taking place. - ** This implementation also assumes a coherent cache - that - ** separate processes cannot read different values from the same - ** address at the same time. If either of these two conditions - ** are not met, then the mutexes will fail and problems will result. - */ - { - pthread_t self = pthread_self(); - if( p->nRef>0 && pthread_equal(p->owner, self) ){ - p->nRef++; - rc = SQLITE_OK; - }else if( pthread_mutex_trylock(&p->mutex)==0 ){ - assert( p->nRef==0 ); - p->owner = self; - p->nRef = 1; - rc = SQLITE_OK; - }else{ - rc = SQLITE_BUSY; - } - } -#else - /* Use the built-in recursive mutexes if they are available. - */ - if( pthread_mutex_trylock(&p->mutex)==0 ){ -#if SQLITE_MUTEX_NREF - p->owner = pthread_self(); - p->nRef++; -#endif - rc = SQLITE_OK; - }else{ - rc = SQLITE_BUSY; - } -#endif - -#ifdef SQLITE_DEBUG - if( rc==SQLITE_OK && p->trace ){ - printf("enter mutex %p (%d) with nRef=%d\n", p, p->trace, p->nRef); - } -#endif - return rc; -} - -/* -** The sqlite3_mutex_leave() routine exits a mutex that was -** previously entered by the same thread. The behavior -** is undefined if the mutex is not currently entered or -** is not currently allocated. SQLite will never do either. -*/ -static void pthreadMutexLeave(sqlite3_mutex *p){ - assert( pthreadMutexHeld(p) ); -#if SQLITE_MUTEX_NREF - p->nRef--; - if( p->nRef==0 ) p->owner = 0; -#endif - assert( p->nRef==0 || p->id==SQLITE_MUTEX_RECURSIVE ); - -#ifdef SQLITE_HOMEGROWN_RECURSIVE_MUTEX - if( p->nRef==0 ){ - pthread_mutex_unlock(&p->mutex); - } -#else - pthread_mutex_unlock(&p->mutex); -#endif - -#ifdef SQLITE_DEBUG - if( p->trace ){ - printf("leave mutex %p (%d) with nRef=%d\n", p, p->trace, p->nRef); - } -#endif -} - -sqlite3_mutex_methods const *sqlite3DefaultMutex(void){ - static const sqlite3_mutex_methods sMutex = { - pthreadMutexInit, - pthreadMutexEnd, - pthreadMutexAlloc, - pthreadMutexFree, - pthreadMutexEnter, - pthreadMutexTry, - pthreadMutexLeave, -#ifdef SQLITE_DEBUG - pthreadMutexHeld, - pthreadMutexNotheld -#else - 0, - 0 -#endif - }; - - return &sMutex; -} - -#endif /* SQLITE_MUTEX_PTHREADS */ |