/*
** 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 */
int nRef; /* Number of references */
TID owner; /* Thread holding this mutex */
};
#define OS2_MUTEX_INITIALIZER 0,0,0,0
/*
** 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:
**
**
** - SQLITE_MUTEX_FAST 0
**
- SQLITE_MUTEX_RECURSIVE 1
**
- SQLITE_MUTEX_STATIC_MASTER 2
**
- SQLITE_MUTEX_STATIC_MEM 3
**
- SQLITE_MUTEX_STATIC_PRNG 4
**
**
** 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.
*/
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[] = {
{ OS2_MUTEX_INITIALIZER, },
{ OS2_MUTEX_INITIALIZER, },
{ OS2_MUTEX_INITIALIZER, },
{ OS2_MUTEX_INITIALIZER, },
{ OS2_MUTEX_INITIALIZER, },
{ OS2_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){
if( p==0 ) return;
assert( p->nRef==0 );
assert( p->id==SQLITE_MUTEX_FAST || p->id==SQLITE_MUTEX_RECURSIVE );
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;
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);
}
static int os2MutexNotheld(sqlite3_mutex *p){
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
/*
** 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){
TID tid;
PID holder1;
ULONG holder2;
if( p==0 ) return;
assert( p->id==SQLITE_MUTEX_RECURSIVE || os2MutexNotheld(p) );
DosRequestMutexSem(p->mutex, SEM_INDEFINITE_WAIT);
DosQueryMutexSem(p->mutex, &holder1, &tid, &holder2);
p->owner = tid;
p->nRef++;
}
static int os2MutexTry(sqlite3_mutex *p){
int rc;
TID tid;
PID holder1;
ULONG holder2;
if( p==0 ) return SQLITE_OK;
assert( p->id==SQLITE_MUTEX_RECURSIVE || os2MutexNotheld(p) );
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;
}
/*
** 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){
TID tid;
PID holder1;
ULONG holder2;
if( p==0 ) return;
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);
}
sqlite3_mutex_methods const *sqlite3DefaultMutex(void){
static const sqlite3_mutex_methods sMutex = {
os2MutexInit,
os2MutexEnd,
os2MutexAlloc,
os2MutexFree,
os2MutexEnter,
os2MutexTry,
os2MutexLeave,
#ifdef SQLITE_DEBUG
os2MutexHeld,
os2MutexNotheld
#endif
};
return &sMutex;
}
#endif /* SQLITE_MUTEX_OS2 */