Index: src/backend/storage/lmgr/lwlock.c
===================================================================
RCS file: /home/jjanes/pgrepo/pgsql/src/backend/storage/lmgr/lwlock.c,v
retrieving revision 1.53
diff -c -r1.53 lwlock.c
*** src/backend/storage/lmgr/lwlock.c	1 Jan 2009 17:23:48 -0000	1.53
--- src/backend/storage/lmgr/lwlock.c	28 Aug 2009 21:29:41 -0000
***************
*** 308,315 ****
   *
   * Side effect: cancel/die interrupts are held off until lock release.
   */
  void
! LWLockAcquire(LWLockId lockid, LWLockMode mode)
  {
  	volatile LWLock *lock = &(LWLockArray[lockid].lock);
  	PGPROC	   *proc = MyProc;
--- 308,317 ----
   *
   * Side effect: cancel/die interrupts are held off until lock release.
   */
+ 
+ /* put yourself at the head of the queue, instead of the end, to acquire the lock*/
  void
! LWLockAcquire_head(LWLockId lockid, LWLockMode mode)
  {
  	volatile LWLock *lock = &(LWLockArray[lockid].lock);
  	PGPROC	   *proc = MyProc;
***************
*** 420,431 ****
  
  		proc->lwWaiting = true;
  		proc->lwExclusive = (mode == LW_EXCLUSIVE);
! 		proc->lwWaitLink = NULL;
! 		if (lock->head == NULL)
! 			lock->head = proc;
! 		else
! 			lock->tail->lwWaitLink = proc;
! 		lock->tail = proc;
  
  		/* Can release the mutex now */
  		SpinLockRelease(&lock->mutex);
--- 422,430 ----
  
  		proc->lwWaiting = true;
  		proc->lwExclusive = (mode == LW_EXCLUSIVE);
! 		proc->lwWaitLink = lock->head;
!                 if (lock->head == NULL) { lock->tail=proc; };
! 		lock->head=proc;
  
  		/* Can release the mutex now */
  		SpinLockRelease(&lock->mutex);
***************
*** 442,448 ****
  		 * so that the lock manager or signal manager will see the received
  		 * signal when it next waits.
  		 */
! 		LOG_LWDEBUG("LWLockAcquire", lockid, "waiting");
  
  #ifdef LWLOCK_STATS
  		block_counts[lockid]++;
--- 441,447 ----
  		 * so that the lock manager or signal manager will see the received
  		 * signal when it next waits.
  		 */
! 		LOG_LWDEBUG("LWLockAcquire_head", lockid, "waiting");
  
  #ifdef LWLOCK_STATS
  		block_counts[lockid]++;