diff options
Diffstat (limited to 'src/mutex.c')
| -rw-r--r-- | src/mutex.c | 471 |
1 files changed, 11 insertions, 460 deletions
diff --git a/src/mutex.c b/src/mutex.c index 9e0de085f..bb33656a2 100644 --- a/src/mutex.c +++ b/src/mutex.c @@ -9,116 +9,22 @@ ** May you share freely, never taking more than you give. ** ************************************************************************* -** This file contains the C functions that implement mutexes for -** use by the SQLite core. +** This file contains the C functions that implement mutexes. ** -** $Id: mutex.c,v 1.14 2007/08/27 17:27:49 danielk1977 Exp $ -*/ -/* -** If SQLITE_MUTEX_APPDEF is defined, then this whole module is -** omitted and equivalent functionality must be provided by the -** application that links against the SQLite library. -*/ -#ifndef SQLITE_MUTEX_APPDEF - - -/* This is the beginning of internal implementation of mutexes -** for SQLite. -*/ -#include "sqliteInt.h" - -/* -** Figure out what version of the code to use. The choices are -** -** SQLITE_MUTEX_NOOP For single-threaded applications that -** do not desire error checking. -** -** SQLITE_MUTEX_NOOP_DEBUG For single-threaded applications with -** error checking to help verify that mutexes -** are being used correctly even though they -** are not needed. Used when SQLITE_DEBUG is -** defined on single-threaded builds. +** The implementation in this file does not provide any mutual +** exclusion and is thus suitable for use only in applications +** that use SQLite in a single thread. But this implementation +** does do a lot of error checking on mutexes to make sure they +** are called correctly and at appropriate times. Hence, this +** implementation is suitable for testing. +** debugging purposes ** -** SQLITE_MUTEX_PTHREADS For multi-threaded applications on Unix. -** -** SQLITE_MUTEX_WIN For multi-threaded applications on Win32. -*/ -#define SQLITE_MUTEX_NOOP 1 /* The default */ -#if defined(SQLITE_DEBUG) && !SQLITE_THREADSAFE -# undef SQLITE_MUTEX_NOOP -# define SQLITE_MUTEX_NOOP_DEBUG -#endif -#if defined(SQLITE_MUTEX_NOOP) && SQLITE_THREADSAFE && OS_UNIX -# undef SQLITE_MUTEX_NOOP -# define SQLITE_MUTEX_PTHREAD -#endif -#if defined(SQLITE_MUTEX_NOOP) && SQLITE_THREADSAFE && OS_WIN -# undef SQLITE_MUTEX_NOOP -# define SQLITE_MUTEX_WIN -#endif - - - -#ifdef SQLITE_MUTEX_NOOP -/************************ No-op Mutex Implementation ********************** -** -** This first implementation of mutexes is really a no-op. In other words, -** no real locking occurs. This implementation is appropriate for use -** in single threaded applications which do not want the extra overhead -** of thread locking primitives. -*/ - -/* -** 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. -*/ -sqlite3_mutex *sqlite3_mutex_alloc(int idNotUsed){ - return (sqlite3_mutex*)8; -} - -/* -** This routine deallocates a previously allocated mutex. -*/ -void sqlite3_mutex_free(sqlite3_mutex *pNotUsed){} - -/* -** 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. +** $Id: mutex.c,v 1.15 2007/08/28 16:34:43 drh Exp $ */ -void sqlite3_mutex_enter(sqlite3_mutex *pNotUsed){} -int sqlite3_mutex_try(sqlite3_mutex *pNotUsed){ return SQLITE_OK; } - -/* -** 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. -*/ -void sqlite3_mutex_leave(sqlite3_mutex *pNotUsed){} - -/* -** The sqlite3_mutex_held() and sqlite3_mutex_notheld() routine are -** intended for use inside assert() statements. -*/ -int sqlite3_mutex_held(sqlite3_mutex *pNotUsed){ - return 1; -} -int sqlite3_mutex_notheld(sqlite3_mutex *pNotUsed){ - return 1; -} -#endif /* SQLITE_MUTEX_NOOP */ +#include "sqliteInt.h" #ifdef SQLITE_MUTEX_NOOP_DEBUG -/*************** Error-checking No-op Mutex Implementation ******************* -** +/* ** In this implementation, mutexes do not provide any mutual exclusion. ** But the error checking is provided. This implementation is useful ** for test purposes. @@ -218,358 +124,3 @@ int sqlite3_mutex_notheld(sqlite3_mutex *p){ return p==0 || p->cnt==0; } #endif /* SQLITE_MUTEX_NOOP_DEBUG */ - - - -#ifdef SQLITE_MUTEX_PTHREAD -/******************** Pthread Mutex Implementation ********************* -** -** This implementation of mutexes is built using a version of pthreads that -** has native support for recursive mutexes. -*/ -#include <pthread.h> - -/* -** Each recursive mutex is an instance of the following structure. -*/ -struct sqlite3_mutex { - pthread_mutex_t mutex; /* Mutex controlling the lock */ - int id; /* Mutex type */ - int nRef; /* Number of entrances */ - pthread_t owner; /* Thread that is within this mutex */ -}; - -/* -** 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_MEM2 -** <li> SQLITE_MUTEX_STATIC_PRNG -** <li> SQLITE_MUTEX_STATIC_LRU -** </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. Three 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. -*/ -sqlite3_mutex *sqlite3_mutex_alloc(int iType){ - static sqlite3_mutex staticMutexes[] = { - { PTHREAD_MUTEX_INITIALIZER, }, - { PTHREAD_MUTEX_INITIALIZER, }, - { PTHREAD_MUTEX_INITIALIZER, }, - { PTHREAD_MUTEX_INITIALIZER, }, - { PTHREAD_MUTEX_INITIALIZER, }, - }; - sqlite3_mutex *p; - switch( iType ){ - case SQLITE_MUTEX_RECURSIVE: { - p = sqlite3MallocZero( sizeof(*p) ); - if( p ){ - 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); - p->id = iType; - } - break; - } - case SQLITE_MUTEX_FAST: { - p = sqlite3MallocZero( sizeof(*p) ); - if( p ){ - p->id = iType; - pthread_mutex_init(&p->mutex, 0); - } - break; - } - default: { - assert( iType-2 >= 0 ); - assert( iType-2 < sizeof(staticMutexes)/sizeof(staticMutexes[0]) ); - p = &staticMutexes[iType-2]; - p->id = iType; - break; - } - } - return p; -} - - -/* -** This routine deallocates a previously -** allocated mutex. SQLite is careful to deallocate every -** mutex that it allocates. -*/ -void sqlite3_mutex_free(sqlite3_mutex *p){ - assert( p ); - assert( p->nRef==0 ); - assert( p->id==SQLITE_MUTEX_FAST || p->id==SQLITE_MUTEX_RECURSIVE ); - pthread_mutex_destroy(&p->mutex); - sqlite3_free(p); -} - -/* -** 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. -*/ -void sqlite3_mutex_enter(sqlite3_mutex *p){ - assert( p ); - assert( p->id==SQLITE_MUTEX_RECURSIVE || sqlite3_mutex_notheld(p) ); - pthread_mutex_lock(&p->mutex); - p->owner = pthread_self(); - p->nRef++; -} -int sqlite3_mutex_try(sqlite3_mutex *p){ - int rc; - assert( p ); - assert( p->id==SQLITE_MUTEX_RECURSIVE || sqlite3_mutex_notheld(p) ); - if( pthread_mutex_trylock(&p->mutex)==0 ){ - p->owner = pthread_self(); - p->nRef++; - rc = SQLITE_OK; - }else{ - rc = SQLITE_BUSY; - } - 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. -*/ -void sqlite3_mutex_leave(sqlite3_mutex *p){ - assert( p ); - assert( sqlite3_mutex_held(p) ); - p->nRef--; - assert( p->nRef==0 || p->id==SQLITE_MUTEX_RECURSIVE ); - pthread_mutex_unlock(&p->mutex); -} - -/* -** 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. -*/ -#ifndef NDEBUG -int sqlite3_mutex_held(sqlite3_mutex *p){ - return p==0 || (p->nRef!=0 && pthread_equal(p->owner, pthread_self())); -} -int sqlite3_mutex_notheld(sqlite3_mutex *p){ - return p==0 || p->nRef==0 || pthread_equal(p->owner, pthread_self())==0; -} -#endif -#endif /* SQLITE_MUTEX_PTHREAD */ - -#ifdef SQLITE_MUTEX_WIN -/********************** Windows Mutex Implementation ********************** -** -** This implementation of mutexes is built using the win32 API. -*/ - -/* -** Each recursive mutex is an instance of the following structure. -*/ -struct sqlite3_mutex { - CRITICAL_SECTION mutex; /* Mutex controlling the lock */ - int id; /* Mutex type */ - int nRef; /* Number of enterances */ - DWORD owner; /* Thread holding this mutex */ -}; - -/* -** 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 0 -** <li> SQLITE_MUTEX_RECURSIVE 1 -** <li> SQLITE_MUTEX_STATIC_MASTER 2 -** <li> SQLITE_MUTEX_STATIC_MEM 3 -** <li> SQLITE_MUTEX_STATIC_PRNG 4 -** </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. Three 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. -*/ -sqlite3_mutex *sqlite3_mutex_alloc(int iType){ - sqlite3_mutex *p; - - switch( iType ){ - case SQLITE_MUTEX_FAST: - case SQLITE_MUTEX_RECURSIVE: { - p = sqlite3MallocZero( sizeof(*p) ); - if( p ){ - p->id = iType; - InitializeCriticalSection(&p->mutex); - } - break; - } - default: { - static sqlite3_mutex staticMutexes[5]; - static int isInit = 0; - while( !isInit ){ - static long lock = 0; - if( InterlockedIncrement(&lock)==1 ){ - int i; - for(i=0; i<sizeof(staticMutexes)/sizeof(staticMutexes[0]); i++){ - InitializeCriticalSection(&staticMutexes[i].mutex); - } - isInit = 1; - }else{ - Sleep(1); - } - } - assert( iType-2 >= 0 ); - assert( iType-2 < sizeof(staticMutexes)/sizeof(staticMutexes[0]) ); - p = &staticMutexes[iType-2]; - p->id = iType; - break; - } - } - return p; -} - - -/* -** This routine deallocates a previously -** allocated mutex. SQLite is careful to deallocate every -** mutex that it allocates. -*/ -void sqlite3_mutex_free(sqlite3_mutex *p){ - assert( p ); - assert( p->nRef==0 ); - assert( p->id==SQLITE_MUTEX_FAST || p->id==SQLITE_MUTEX_RECURSIVE ); - DeleteCriticalSection(&p->mutex); - sqlite3_free(p); -} - -/* -** 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. -*/ -void sqlite3_mutex_enter(sqlite3_mutex *p){ - assert( p ); - assert( p->id==SQLITE_MUTEX_RECURSIVE || sqlite3_mutex_notheld(p) ); - EnterCriticalSection(&p->mutex); - p->owner = GetCurrentThreadId(); - p->nRef++; -} -int sqlite3_mutex_try(sqlite3_mutex *p){ - int rc; - assert( p ); - assert( p->id==SQLITE_MUTEX_RECURSIVE || sqlite3_mutex_notheld(p) ); - if( TryEnterCriticalSection(&p->mutex) ){ - p->owner = GetCurrentThreadId(); - p->nRef++; - rc = SQLITE_OK; - }else{ - rc = SQLITE_BUSY; - } - 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. -*/ -void sqlite3_mutex_leave(sqlite3_mutex *p){ - assert( p->nRef>0 ); - assert( p->owner==GetCurrentThreadId() ); - p->nRef--; - assert( p->nRef==0 || p->id==SQLITE_MUTEX_RECURSIVE ); - LeaveCriticalSection(&p->mutex); -} - -/* -** The sqlite3_mutex_held() and sqlite3_mutex_notheld() routine are -** intended for use only inside assert() statements. -*/ -int sqlite3_mutex_held(sqlite3_mutex *p){ - return p==0 || (p->nRef!=0 && p->owner==GetCurrentThreadId()); -} -int sqlite3_mutex_notheld(sqlite3_mutex *p){ - return p==0 || p->nRef==0 || p->owner!=GetCurrentThreadId(); -} -#endif /* SQLITE_MUTEX_WIN */ - -#endif /* !defined(SQLITE_MUTEX_APPDEF) */ |