/* ** 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: ** ** ** ** 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 */