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Diffstat (limited to 'src/mutex_os2.c')
-rw-r--r-- | src/mutex_os2.c | 274 |
1 files changed, 274 insertions, 0 deletions
diff --git a/src/mutex_os2.c b/src/mutex_os2.c new file mode 100644 index 0000000..ce650d9 --- /dev/null +++ b/src/mutex_os2.c @@ -0,0 +1,274 @@ +/* +** 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 OS/2 +*/ +#include "sqliteInt.h" + +/* +** The code in this file is only used if SQLITE_MUTEX_OS2 is defined. +** See the mutex.h file for details. +*/ +#ifdef SQLITE_MUTEX_OS2 + +/********************** OS/2 Mutex Implementation ********************** +** +** This implementation of mutexes is built using the OS/2 API. +*/ + +/* +** The mutex object +** Each recursive mutex is an instance of the following structure. +*/ +struct sqlite3_mutex { + HMTX mutex; /* Mutex controlling the lock */ + int id; /* Mutex type */ +#ifdef SQLITE_DEBUG + int trace; /* True to trace changes */ +#endif +}; + +#ifdef SQLITE_DEBUG +#define SQLITE3_MUTEX_INITIALIZER { 0, 0, 0 } +#else +#define SQLITE3_MUTEX_INITIALIZER { 0, 0 } +#endif + +/* +** Initialize and deinitialize the mutex subsystem. +*/ +static int os2MutexInit(void){ return SQLITE_OK; } +static int os2MutexEnd(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_MEM2 +** <li> SQLITE_MUTEX_STATIC_PRNG +** <li> SQLITE_MUTEX_STATIC_LRU +** <li> SQLITE_MUTEX_STATIC_LRU2 +** </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 *os2MutexAlloc(int iType){ + sqlite3_mutex *p = NULL; + switch( iType ){ + case SQLITE_MUTEX_FAST: + case SQLITE_MUTEX_RECURSIVE: { + p = sqlite3MallocZero( sizeof(*p) ); + if( p ){ + p->id = iType; + if( DosCreateMutexSem( 0, &p->mutex, 0, FALSE ) != NO_ERROR ){ + sqlite3_free( p ); + p = NULL; + } + } + break; + } + default: { + static volatile int isInit = 0; + static sqlite3_mutex staticMutexes[6] = { + SQLITE3_MUTEX_INITIALIZER, + SQLITE3_MUTEX_INITIALIZER, + SQLITE3_MUTEX_INITIALIZER, + SQLITE3_MUTEX_INITIALIZER, + SQLITE3_MUTEX_INITIALIZER, + SQLITE3_MUTEX_INITIALIZER, + }; + if ( !isInit ){ + APIRET rc; + PTIB ptib; + PPIB ppib; + HMTX mutex; + char name[32]; + DosGetInfoBlocks( &ptib, &ppib ); + sqlite3_snprintf( sizeof(name), name, "\\SEM32\\SQLITE%04x", + ppib->pib_ulpid ); + while( !isInit ){ + mutex = 0; + rc = DosCreateMutexSem( name, &mutex, 0, FALSE); + if( rc == NO_ERROR ){ + unsigned int i; + if( !isInit ){ + for( i = 0; i < sizeof(staticMutexes)/sizeof(staticMutexes[0]); i++ ){ + DosCreateMutexSem( 0, &staticMutexes[i].mutex, 0, FALSE ); + } + isInit = 1; + } + DosCloseMutexSem( mutex ); + }else if( rc == ERROR_DUPLICATE_NAME ){ + DosSleep( 1 ); + }else{ + return p; + } + } + } + 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. +*/ +static void os2MutexFree(sqlite3_mutex *p){ +#ifdef SQLITE_DEBUG + TID tid; + PID pid; + ULONG ulCount; + DosQueryMutexSem(p->mutex, &pid, &tid, &ulCount); + assert( ulCount==0 ); + assert( p->id==SQLITE_MUTEX_FAST || p->id==SQLITE_MUTEX_RECURSIVE ); +#endif + DosCloseMutexSem( p->mutex ); + sqlite3_free( p ); +} + +#ifdef SQLITE_DEBUG +/* +** The sqlite3_mutex_held() and sqlite3_mutex_notheld() routine are +** intended for use inside assert() statements. +*/ +static int os2MutexHeld(sqlite3_mutex *p){ + TID tid; + PID pid; + ULONG ulCount; + PTIB ptib; + DosQueryMutexSem(p->mutex, &pid, &tid, &ulCount); + if( ulCount==0 || ( ulCount>1 && p->id!=SQLITE_MUTEX_RECURSIVE ) ) + return 0; + DosGetInfoBlocks(&ptib, NULL); + return tid==ptib->tib_ptib2->tib2_ultid; +} +static int os2MutexNotheld(sqlite3_mutex *p){ + TID tid; + PID pid; + ULONG ulCount; + PTIB ptib; + DosQueryMutexSem(p->mutex, &pid, &tid, &ulCount); + if( ulCount==0 ) + return 1; + DosGetInfoBlocks(&ptib, NULL); + return tid!=ptib->tib_ptib2->tib2_ultid; +} +static void os2MutexTrace(sqlite3_mutex *p, char *pAction){ + TID tid; + PID pid; + ULONG ulCount; + DosQueryMutexSem(p->mutex, &pid, &tid, &ulCount); + printf("%s mutex %p (%d) with nRef=%ld\n", pAction, (void*)p, p->trace, ulCount); +} +#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 os2MutexEnter(sqlite3_mutex *p){ + assert( p->id==SQLITE_MUTEX_RECURSIVE || os2MutexNotheld(p) ); + DosRequestMutexSem(p->mutex, SEM_INDEFINITE_WAIT); +#ifdef SQLITE_DEBUG + if( p->trace ) os2MutexTrace(p, "enter"); +#endif +} +static int os2MutexTry(sqlite3_mutex *p){ + int rc = SQLITE_BUSY; + assert( p->id==SQLITE_MUTEX_RECURSIVE || os2MutexNotheld(p) ); + if( DosRequestMutexSem(p->mutex, SEM_IMMEDIATE_RETURN) == NO_ERROR ) { + rc = SQLITE_OK; +#ifdef SQLITE_DEBUG + if( p->trace ) os2MutexTrace(p, "try"); +#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 os2MutexLeave(sqlite3_mutex *p){ + assert( os2MutexHeld(p) ); + DosReleaseMutexSem(p->mutex); +#ifdef SQLITE_DEBUG + if( p->trace ) os2MutexTrace(p, "leave"); +#endif +} + +sqlite3_mutex_methods const *sqlite3DefaultMutex(void){ + static const sqlite3_mutex_methods sMutex = { + os2MutexInit, + os2MutexEnd, + os2MutexAlloc, + os2MutexFree, + os2MutexEnter, + os2MutexTry, + os2MutexLeave, +#ifdef SQLITE_DEBUG + os2MutexHeld, + os2MutexNotheld +#else + 0, + 0 +#endif + }; + + return &sMutex; +} +#endif /* SQLITE_MUTEX_OS2 */ |