*************************************************************************
** This file contains the C functions that implement mutexes for OS/2
**
-** $Id: mutex_os2.c,v 1.1 2007/08/28 16:34:43 drh Exp $
+** $Id: mutex_os2.c,v 1.2 2007/09/20 21:40:23 pweilbacher Exp $
*/
#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
-/**** FIX ME:
-***** This is currently a no-op implementation suitable for use
-***** in single-threaded applications only. Somebody please replace
-***** this with a real mutex implementation for OS/2.
-****/
+/********************** 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 {
- int id; /* The mutex type */
- int cnt; /* Number of entries without a matching leave */
+ PSZ mutexName; /* Mutex name controlling the lock */
+ HMTX mutex; /* Mutex controlling the lock */
+ int id; /* Mutex type */
+ int nRef; /* Number of references */
+ TID 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 id){
- static sqlite3_mutex aStatic[4];
- sqlite3_mutex *pNew = 0;
- switch( id ){
+sqlite3_mutex *sqlite3_mutex_alloc(int iType){
+#define MUTEX_NAME "\\SEM32\\SQLITE\\MUTEX"
+#define MUTEX_NAME_LEN 20 /* name length + null byte */
+ sqlite3_mutex *p;
+
+ switch( iType ){
case SQLITE_MUTEX_FAST:
case SQLITE_MUTEX_RECURSIVE: {
- pNew = sqlite3_malloc(sizeof(*pNew));
- if( pNew ){
- pNew->id = id;
- pNew->cnt = 0;
+ p = sqlite3MallocZero( sizeof(*p) );
+ if( p ){
+ p->mutexName = (PSZ)malloc(MUTEX_NAME_LEN);
+ sqlite3_snprintf(MUTEX_NAME_LEN, p->mutexName, "%s", MUTEX_NAME);
+ p->id = iType;
+ DosCreateMutexSem(p->mutexName, &p->mutex, 0, FALSE);
+ DosOpenMutexSem(p->mutexName, &p->mutex);
}
break;
}
default: {
- assert( id-2 >= 0 );
- assert( id-2 < sizeof(aStatic)/sizeof(aStatic[0]) );
- pNew = &aStatic[id-2];
- pNew->id = id;
+ static sqlite3_mutex staticMutexes[5];
+ static int isInit = 0;
+ while( !isInit ) {
+ static long lock = 0;
+ DosEnterCritSec();
+ lock++;
+ if( lock == 1 ) {
+ DosExitCritSec();
+ int i;
+ for(i = 0; i < sizeof(staticMutexes)/sizeof(staticMutexes[0]); i++) {
+ staticMutexes[i].mutexName = (PSZ)malloc(MUTEX_NAME_LEN + 1);
+ sqlite3_snprintf(MUTEX_NAME_LEN + 1,
+ staticMutexes[i].mutexName, "%s%1d", MUTEX_NAME, i);
+ DosCreateMutexSem(staticMutexes[i].mutexName,
+ &staticMutexes[i].mutex, 0, FALSE);
+ DosOpenMutexSem(staticMutexes[i].mutexName,
+ &staticMutexes[i].mutex);
+ }
+ isInit = 1;
+ } else {
+ DosExitCritSec();
+ DosSleep(1);
+ }
+ }
+ assert( iType-2 >= 0 );
+ assert( iType-2 < sizeof(staticMutexes)/sizeof(staticMutexes[0]) );
+ p = &staticMutexes[iType-2];
+ p->id = iType;
break;
}
}
- return pNew;
+ 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->cnt==0 );
+ assert( p->nRef==0 );
assert( p->id==SQLITE_MUTEX_FAST || p->id==SQLITE_MUTEX_RECURSIVE );
+ DosCloseMutexSem(p->mutex);
+ free(p->mutexName);
sqlite3_free(p);
}
** more than once, the behavior is undefined.
*/
void sqlite3_mutex_enter(sqlite3_mutex *p){
+ TID tid;
+ PID holder1;
+ ULONG holder2;
assert( p );
assert( p->id==SQLITE_MUTEX_RECURSIVE || sqlite3_mutex_notheld(p) );
- p->cnt++;
+ DosRequestMutexSem(p->mutex, SEM_INDEFINITE_WAIT);
+ DosQueryMutexSem(p->mutex, &holder1, &tid, &holder2);
+ p->owner = tid;
+ p->nRef++;
}
int sqlite3_mutex_try(sqlite3_mutex *p){
+ int rc;
+ TID tid;
+ PID holder1;
+ ULONG holder2;
assert( p );
assert( p->id==SQLITE_MUTEX_RECURSIVE || sqlite3_mutex_notheld(p) );
- p->cnt++;
- return SQLITE_OK;
+ if( DosRequestMutexSem(p->mutex, SEM_IMMEDIATE_RETURN) == NO_ERROR) {
+ DosQueryMutexSem(p->mutex, &holder1, &tid, &holder2);
+ p->owner = tid;
+ p->nRef++;
+ rc = SQLITE_OK;
+ } else {
+ rc = SQLITE_BUSY;
+ }
+
+ return rc;
}
/*
** is not currently allocated. SQLite will never do either.
*/
void sqlite3_mutex_leave(sqlite3_mutex *p){
- assert( p );
- assert( sqlite3_mutex_held(p) );
- p->cnt--;
- assert( p->id==SQLITE_MUTEX_RECURSIVE || sqlite3_mutex_notheld(p) );
+ TID tid;
+ PID holder1;
+ ULONG holder2;
+ assert( p->nRef>0 );
+ DosQueryMutexSem(p->mutex, &holder1, &tid, &holder2);
+ assert( p->owner==tid );
+ p->nRef--;
+ assert( p->nRef==0 || p->id==SQLITE_MUTEX_RECURSIVE );
+ DosReleaseMutexSem(p->mutex);
}
/*
** intended for use inside assert() statements.
*/
int sqlite3_mutex_held(sqlite3_mutex *p){
- return p==0 || p->cnt>0;
+ TID tid;
+ PID pid;
+ ULONG ulCount;
+ PTIB ptib;
+ if( p!=0 ) {
+ DosQueryMutexSem(p->mutex, &pid, &tid, &ulCount);
+ } else {
+ DosGetInfoBlocks(&ptib, NULL);
+ tid = ptib->tib_ptib2->tib2_ultid;
+ }
+ return p==0 || (p->nRef!=0 && p->owner==tid);
}
int sqlite3_mutex_notheld(sqlite3_mutex *p){
- return p==0 || p->cnt==0;
+ TID tid;
+ PID pid;
+ ULONG ulCount;
+ PTIB ptib;
+ if( p!= 0 ) {
+ DosQueryMutexSem(p->mutex, &pid, &tid, &ulCount);
+ } else {
+ DosGetInfoBlocks(&ptib, NULL);
+ tid = ptib->tib_ptib2->tib2_ultid;
+ }
+ return p==0 || p->nRef==0 || p->owner!=tid;
}
#endif /* SQLITE_MUTEX_OS2 */
projects / thirdparty / sqlite.git / commitdiff
