/*
** Lower the locking level on file descriptor id to locktype. locktype
** must be either NO_LOCK or SHARED_LOCK.
**
** If the locking level of the file descriptor is already at or below
** the requested locking level, this routine is a no-op.
**
** It is not possible for this routine to fail if the second argument
** is NO_LOCK. If the second argument is SHARED_LOCK then this routine
** might return SQLITE_IOERR;
*/
static int os2Unlock( sqlite3_file *id, int locktype ){
int type;
os2File *pFile = (os2File*)id;
APIRET rc = SQLITE_OK;
APIRET res = NO_ERROR;
FILELOCK LockArea,
UnlockArea;
memset(&LockArea, 0, sizeof(LockArea));
memset(&UnlockArea, 0, sizeof(UnlockArea));
assert( pFile!=0 );
assert( locktype<=SHARED_LOCK );
OSTRACE(( "UNLOCK %d to %d was %d\n", pFile->h, locktype, pFile->locktype ));
type = pFile->locktype;
if( type>=EXCLUSIVE_LOCK ){
LockArea.lOffset = 0L;
LockArea.lRange = 0L;
UnlockArea.lOffset = SHARED_FIRST;
UnlockArea.lRange = SHARED_SIZE;
res = DosSetFileLocks( pFile->h, &UnlockArea, &LockArea, LOCK_TIMEOUT, 0L );
OSTRACE(( "UNLOCK %d exclusive lock res=%d\n", pFile->h, res ));
if( locktype==SHARED_LOCK && getReadLock(pFile) != NO_ERROR ){
/* This should never happen. We should always be able to
** reacquire the read lock */
OSTRACE(( "UNLOCK %d to %d getReadLock() failed\n", pFile->h, locktype ));
rc = SQLITE_IOERR_UNLOCK;
}
}
if( type>=RESERVED_LOCK ){
LockArea.lOffset = 0L;
LockArea.lRange = 0L;
UnlockArea.lOffset = RESERVED_BYTE;
UnlockArea.lRange = 1L;
res = DosSetFileLocks( pFile->h, &UnlockArea, &LockArea, LOCK_TIMEOUT, 0L );
OSTRACE(( "UNLOCK %d reserved res=%d\n", pFile->h, res ));
}
if( locktype==NO_LOCK && type>=SHARED_LOCK ){
res = unlockReadLock(pFile);
OSTRACE(( "UNLOCK %d is %d want %d res=%d\n",
pFile->h, type, locktype, res ));
}
if( type>=PENDING_LOCK ){
LockArea.lOffset = 0L;
LockArea.lRange = 0L;
UnlockArea.lOffset = PENDING_BYTE;
UnlockArea.lRange = 1L;
res = DosSetFileLocks( pFile->h, &UnlockArea, &LockArea, LOCK_TIMEOUT, 0L );
OSTRACE(( "UNLOCK %d pending res=%d\n", pFile->h, res ));
}
pFile->locktype = locktype;
OSTRACE(( "UNLOCK %d now %d\n", pFile->h, pFile->locktype ));
return rc;
}
/*
** Lock the file with the lock specified by parameter locktype - one
** of the following:
**
** (1) SHARED_LOCK
** (2) RESERVED_LOCK
** (3) PENDING_LOCK
** (4) EXCLUSIVE_LOCK
**
** Sometimes when requesting one lock state, additional lock states
** are inserted in between. The locking might fail on one of the later
** transitions leaving the lock state different from what it started but
** still short of its goal. The following chart shows the allowed
** transitions and the inserted intermediate states:
**
** UNLOCKED -> SHARED
** SHARED -> RESERVED
** SHARED -> (PENDING) -> EXCLUSIVE
** RESERVED -> (PENDING) -> EXCLUSIVE
** PENDING -> EXCLUSIVE
**
** This routine will only increase a lock. The os2Unlock() routine
** erases all locks at once and returns us immediately to locking level 0.
** It is not possible to lower the locking level one step at a time. You
** must go straight to locking level 0.
*/
static int os2Lock( sqlite3_file *id, int locktype ){
int rc = SQLITE_OK; /* Return code from subroutines */
APIRET res = NO_ERROR; /* Result of an OS/2 lock call */
int newLocktype; /* Set pFile->locktype to this value before exiting */
int gotPendingLock = 0;/* True if we acquired a PENDING lock this time */
FILELOCK LockArea,
UnlockArea;
os2File *pFile = (os2File*)id;
memset(&LockArea, 0, sizeof(LockArea));
memset(&UnlockArea, 0, sizeof(UnlockArea));
assert( pFile!=0 );
OSTRACE4( "LOCK %d %d was %d\n", pFile->h, locktype, pFile->locktype );
/* If there is already a lock of this type or more restrictive on the
** os2File, do nothing. Don't use the end_lock: exit path, as
** sqlite3_mutex_enter() hasn't been called yet.
*/
if( pFile->locktype>=locktype ){
OSTRACE3( "LOCK %d %d ok (already held)\n", pFile->h, locktype );
return SQLITE_OK;
}
/* Make sure the locking sequence is correct
*/
assert( pFile->locktype!=NO_LOCK || locktype==SHARED_LOCK );
assert( locktype!=PENDING_LOCK );
assert( locktype!=RESERVED_LOCK || pFile->locktype==SHARED_LOCK );
/* Lock the PENDING_LOCK byte if we need to acquire a PENDING lock or
** a SHARED lock. If we are acquiring a SHARED lock, the acquisition of
** the PENDING_LOCK byte is temporary.
*/
newLocktype = pFile->locktype;
if( pFile->locktype==NO_LOCK
|| (locktype==EXCLUSIVE_LOCK && pFile->locktype==RESERVED_LOCK)
){
LockArea.lOffset = PENDING_BYTE;
LockArea.lRange = 1L;
UnlockArea.lOffset = 0L;
UnlockArea.lRange = 0L;
/* wait longer than LOCK_TIMEOUT here not to have to try multiple times */
res = DosSetFileLocks( pFile->h, &UnlockArea, &LockArea, 100L, 0L );
if( res == NO_ERROR ){
gotPendingLock = 1;
OSTRACE3( "LOCK %d pending lock boolean set. res=%d\n", pFile->h, res );
}
}
/* Acquire a shared lock
*/
if( locktype==SHARED_LOCK && res == NO_ERROR ){
assert( pFile->locktype==NO_LOCK );
res = getReadLock(pFile);
if( res == NO_ERROR ){
newLocktype = SHARED_LOCK;
}
OSTRACE3( "LOCK %d acquire shared lock. res=%d\n", pFile->h, res );
}
/* Acquire a RESERVED lock
*/
if( locktype==RESERVED_LOCK && res == NO_ERROR ){
assert( pFile->locktype==SHARED_LOCK );
LockArea.lOffset = RESERVED_BYTE;
LockArea.lRange = 1L;
UnlockArea.lOffset = 0L;
UnlockArea.lRange = 0L;
res = DosSetFileLocks( pFile->h, &UnlockArea, &LockArea, LOCK_TIMEOUT, 0L );
if( res == NO_ERROR ){
newLocktype = RESERVED_LOCK;
}
OSTRACE3( "LOCK %d acquire reserved lock. res=%d\n", pFile->h, res );
}
/* Acquire a PENDING lock
*/
if( locktype==EXCLUSIVE_LOCK && res == NO_ERROR ){
newLocktype = PENDING_LOCK;
gotPendingLock = 0;
OSTRACE2( "LOCK %d acquire pending lock. pending lock boolean unset.\n", pFile->h );
}
/* Acquire an EXCLUSIVE lock
*/
if( locktype==EXCLUSIVE_LOCK && res == NO_ERROR ){
assert( pFile->locktype>=SHARED_LOCK );
res = unlockReadLock(pFile);
OSTRACE2( "unreadlock = %d\n", res );
LockArea.lOffset = SHARED_FIRST;
LockArea.lRange = SHARED_SIZE;
UnlockArea.lOffset = 0L;
UnlockArea.lRange = 0L;
res = DosSetFileLocks( pFile->h, &UnlockArea, &LockArea, LOCK_TIMEOUT, 0L );
if( res == NO_ERROR ){
newLocktype = EXCLUSIVE_LOCK;
}else{
OSTRACE2( "OS/2 error-code = %d\n", res );
getReadLock(pFile);
}
OSTRACE3( "LOCK %d acquire exclusive lock. res=%d\n", pFile->h, res );
}
/* If we are holding a PENDING lock that ought to be released, then
** release it now.
*/
if( gotPendingLock && locktype==SHARED_LOCK ){
int r;
LockArea.lOffset = 0L;
LockArea.lRange = 0L;
UnlockArea.lOffset = PENDING_BYTE;
UnlockArea.lRange = 1L;
r = DosSetFileLocks( pFile->h, &UnlockArea, &LockArea, LOCK_TIMEOUT, 0L );
OSTRACE3( "LOCK %d unlocking pending/is shared. r=%d\n", pFile->h, r );
}
/* Update the state of the lock has held in the file descriptor then
** return the appropriate result code.
*/
if( res == NO_ERROR ){
rc = SQLITE_OK;
}else{
OSTRACE4( "LOCK FAILED %d trying for %d but got %d\n", pFile->h,
locktype, newLocktype );
rc = SQLITE_BUSY;
}
pFile->locktype = newLocktype;
OSTRACE3( "LOCK %d now %d\n", pFile->h, pFile->locktype );
return rc;
}
