/*
** 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 */