274 lines
8.2 KiB
C
274 lines
8.2 KiB
C
/*
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** 2007 August 28
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**
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** The author disclaims copyright to this source code. In place of
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** a legal notice, here is a blessing:
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**
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** May you do good and not evil.
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** May you find forgiveness for yourself and forgive others.
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** May you share freely, never taking more than you give.
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**
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*************************************************************************
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** This file contains the C functions that implement mutexes for OS/2
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**
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** $Id: mutex_os2.c,v 1.11 2008/11/22 19:50:54 pweilbacher Exp $
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*/
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#include "sqliteInt.h"
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/*
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** The code in this file is only used if SQLITE_MUTEX_OS2 is defined.
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** See the mutex.h file for details.
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*/
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#ifdef SQLITE_MUTEX_OS2
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/********************** OS/2 Mutex Implementation **********************
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**
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** This implementation of mutexes is built using the OS/2 API.
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*/
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/*
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** The mutex object
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** Each recursive mutex is an instance of the following structure.
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*/
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struct sqlite3_mutex {
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HMTX mutex; /* Mutex controlling the lock */
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int id; /* Mutex type */
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int nRef; /* Number of references */
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TID owner; /* Thread holding this mutex */
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};
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#define OS2_MUTEX_INITIALIZER 0,0,0,0
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/*
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** Initialize and deinitialize the mutex subsystem.
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*/
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static int os2MutexInit(void){ return SQLITE_OK; }
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static int os2MutexEnd(void){ return SQLITE_OK; }
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/*
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** The sqlite3_mutex_alloc() routine allocates a new
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** mutex and returns a pointer to it. If it returns NULL
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** that means that a mutex could not be allocated.
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** SQLite will unwind its stack and return an error. The argument
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** to sqlite3_mutex_alloc() is one of these integer constants:
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**
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** <ul>
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** <li> SQLITE_MUTEX_FAST 0
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** <li> SQLITE_MUTEX_RECURSIVE 1
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** <li> SQLITE_MUTEX_STATIC_MASTER 2
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** <li> SQLITE_MUTEX_STATIC_MEM 3
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** <li> SQLITE_MUTEX_STATIC_PRNG 4
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** </ul>
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**
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** The first two constants cause sqlite3_mutex_alloc() to create
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** a new mutex. The new mutex is recursive when SQLITE_MUTEX_RECURSIVE
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** is used but not necessarily so when SQLITE_MUTEX_FAST is used.
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** The mutex implementation does not need to make a distinction
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** between SQLITE_MUTEX_RECURSIVE and SQLITE_MUTEX_FAST if it does
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** not want to. But SQLite will only request a recursive mutex in
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** cases where it really needs one. If a faster non-recursive mutex
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** implementation is available on the host platform, the mutex subsystem
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** might return such a mutex in response to SQLITE_MUTEX_FAST.
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**
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** The other allowed parameters to sqlite3_mutex_alloc() each return
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** a pointer to a static preexisting mutex. Three static mutexes are
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** used by the current version of SQLite. Future versions of SQLite
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** may add additional static mutexes. Static mutexes are for internal
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** use by SQLite only. Applications that use SQLite mutexes should
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** use only the dynamic mutexes returned by SQLITE_MUTEX_FAST or
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** SQLITE_MUTEX_RECURSIVE.
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**
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** Note that if one of the dynamic mutex parameters (SQLITE_MUTEX_FAST
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** or SQLITE_MUTEX_RECURSIVE) is used then sqlite3_mutex_alloc()
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** returns a different mutex on every call. But for the static
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** mutex types, the same mutex is returned on every call that has
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** the same type number.
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*/
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static sqlite3_mutex *os2MutexAlloc(int iType){
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sqlite3_mutex *p = NULL;
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switch( iType ){
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case SQLITE_MUTEX_FAST:
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case SQLITE_MUTEX_RECURSIVE: {
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p = sqlite3MallocZero( sizeof(*p) );
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if( p ){
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p->id = iType;
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if( DosCreateMutexSem( 0, &p->mutex, 0, FALSE ) != NO_ERROR ){
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sqlite3_free( p );
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p = NULL;
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}
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}
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break;
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}
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default: {
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static volatile int isInit = 0;
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static sqlite3_mutex staticMutexes[] = {
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{ OS2_MUTEX_INITIALIZER, },
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{ OS2_MUTEX_INITIALIZER, },
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{ OS2_MUTEX_INITIALIZER, },
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{ OS2_MUTEX_INITIALIZER, },
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{ OS2_MUTEX_INITIALIZER, },
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{ OS2_MUTEX_INITIALIZER, },
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};
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if ( !isInit ){
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APIRET rc;
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PTIB ptib;
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PPIB ppib;
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HMTX mutex;
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char name[32];
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DosGetInfoBlocks( &ptib, &ppib );
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sqlite3_snprintf( sizeof(name), name, "\\SEM32\\SQLITE%04x",
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ppib->pib_ulpid );
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while( !isInit ){
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mutex = 0;
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rc = DosCreateMutexSem( name, &mutex, 0, FALSE);
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if( rc == NO_ERROR ){
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unsigned int i;
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if( !isInit ){
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for( i = 0; i < sizeof(staticMutexes)/sizeof(staticMutexes[0]); i++ ){
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DosCreateMutexSem( 0, &staticMutexes[i].mutex, 0, FALSE );
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}
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isInit = 1;
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}
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DosCloseMutexSem( mutex );
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}else if( rc == ERROR_DUPLICATE_NAME ){
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DosSleep( 1 );
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}else{
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return p;
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}
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}
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}
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assert( iType-2 >= 0 );
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assert( iType-2 < sizeof(staticMutexes)/sizeof(staticMutexes[0]) );
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p = &staticMutexes[iType-2];
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p->id = iType;
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break;
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}
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}
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return p;
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}
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/*
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** This routine deallocates a previously allocated mutex.
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** SQLite is careful to deallocate every mutex that it allocates.
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*/
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static void os2MutexFree(sqlite3_mutex *p){
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if( p==0 ) return;
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assert( p->nRef==0 );
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assert( p->id==SQLITE_MUTEX_FAST || p->id==SQLITE_MUTEX_RECURSIVE );
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DosCloseMutexSem( p->mutex );
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sqlite3_free( p );
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}
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/*
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** The sqlite3_mutex_enter() and sqlite3_mutex_try() routines attempt
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** to enter a mutex. If another thread is already within the mutex,
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** sqlite3_mutex_enter() will block and sqlite3_mutex_try() will return
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** SQLITE_BUSY. The sqlite3_mutex_try() interface returns SQLITE_OK
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** upon successful entry. Mutexes created using SQLITE_MUTEX_RECURSIVE can
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** be entered multiple times by the same thread. In such cases the,
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** mutex must be exited an equal number of times before another thread
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** can enter. If the same thread tries to enter any other kind of mutex
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** more than once, the behavior is undefined.
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*/
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static void os2MutexEnter(sqlite3_mutex *p){
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TID tid;
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PID holder1;
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ULONG holder2;
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if( p==0 ) return;
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assert( p->id==SQLITE_MUTEX_RECURSIVE || os2MutexNotheld(p) );
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DosRequestMutexSem(p->mutex, SEM_INDEFINITE_WAIT);
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DosQueryMutexSem(p->mutex, &holder1, &tid, &holder2);
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p->owner = tid;
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p->nRef++;
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}
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static int os2MutexTry(sqlite3_mutex *p){
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int rc;
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TID tid;
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PID holder1;
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ULONG holder2;
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if( p==0 ) return SQLITE_OK;
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assert( p->id==SQLITE_MUTEX_RECURSIVE || os2MutexNotheld(p) );
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if( DosRequestMutexSem(p->mutex, SEM_IMMEDIATE_RETURN) == NO_ERROR) {
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DosQueryMutexSem(p->mutex, &holder1, &tid, &holder2);
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p->owner = tid;
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p->nRef++;
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rc = SQLITE_OK;
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} else {
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rc = SQLITE_BUSY;
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}
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return rc;
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}
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/*
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** The sqlite3_mutex_leave() routine exits a mutex that was
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** previously entered by the same thread. The behavior
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** is undefined if the mutex is not currently entered or
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** is not currently allocated. SQLite will never do either.
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*/
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static void os2MutexLeave(sqlite3_mutex *p){
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TID tid;
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PID holder1;
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ULONG holder2;
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if( p==0 ) return;
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assert( p->nRef>0 );
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DosQueryMutexSem(p->mutex, &holder1, &tid, &holder2);
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assert( p->owner==tid );
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p->nRef--;
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assert( p->nRef==0 || p->id==SQLITE_MUTEX_RECURSIVE );
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DosReleaseMutexSem(p->mutex);
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}
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#ifdef SQLITE_DEBUG
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/*
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** The sqlite3_mutex_held() and sqlite3_mutex_notheld() routine are
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** intended for use inside assert() statements.
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*/
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static int os2MutexHeld(sqlite3_mutex *p){
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TID tid;
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PID pid;
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ULONG ulCount;
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PTIB ptib;
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if( p!=0 ) {
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DosQueryMutexSem(p->mutex, &pid, &tid, &ulCount);
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} else {
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DosGetInfoBlocks(&ptib, NULL);
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tid = ptib->tib_ptib2->tib2_ultid;
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}
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return p==0 || (p->nRef!=0 && p->owner==tid);
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}
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static int os2MutexNotheld(sqlite3_mutex *p){
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TID tid;
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PID pid;
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ULONG ulCount;
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PTIB ptib;
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if( p!= 0 ) {
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DosQueryMutexSem(p->mutex, &pid, &tid, &ulCount);
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} else {
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DosGetInfoBlocks(&ptib, NULL);
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tid = ptib->tib_ptib2->tib2_ultid;
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}
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return p==0 || p->nRef==0 || p->owner!=tid;
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}
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#endif
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sqlite3_mutex_methods *sqlite3DefaultMutex(void){
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static sqlite3_mutex_methods sMutex = {
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os2MutexInit,
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os2MutexEnd,
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os2MutexAlloc,
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os2MutexFree,
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os2MutexEnter,
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os2MutexTry,
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os2MutexLeave,
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#ifdef SQLITE_DEBUG
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os2MutexHeld,
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os2MutexNotheld
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#endif
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};
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return &sMutex;
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}
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#endif /* SQLITE_MUTEX_OS2 */
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