Applying InnoDB snapshot

Detailed revision comments:

r6560 | sunny | 2010-02-04 16:11:23 +0200 (Thu, 04 Feb 2010) | 7 lines
branches/zip: Remove the additional check introduced in r6534 which tries
to check if the joining transaction has any other transactions waiting on
its locks. This optimization results in excessive deadlocks when running
Sysbench with a large number of threads. The function seems to return
FALSE positives.

rb://250

storage/innodb_plugin/lock/lock0lock.c

@@ -3311,64 +3311,6 @@ lock_deadlock_occurs(
 	return(FALSE);
 }
 
-/********************************************************************//**
-Check that no other transaction is waiting on this transaction's locks.
-@return TRUE if some other transaction is waiting for this lock. */
-static
-ulint
-lock_trx_has_no_waiters(
-/*====================*/
-	const trx_t*	trx)		/*!< in: the transaction to check */
-{
-	const lock_t*	lock;
-
-	ut_ad(mutex_own(&kernel_mutex));
-
-	for (lock = UT_LIST_GET_FIRST(trx->trx_locks);
-	     lock != NULL;
-	     lock = UT_LIST_GET_NEXT(trx_locks, lock)) {
-
-		const lock_t*	wait_lock = lock;
-
-		/* Look for all transactions that could be waiting on this
-		transaction's locks. For that we need to search forward. */
-		if (lock_get_type_low(lock) == LOCK_REC) {
-
-			ulint	heap_no;
-
-			/* It's possible for heap_no to be undefined here.
-			This can happen during lock move from one page to
-			another when we split. */
-
-			heap_no = lock_rec_find_set_bit(lock);
-
-			do {
-				wait_lock = lock_rec_get_next(
-					heap_no, (lock_t*) wait_lock);
-
-				if (wait_lock != NULL
-				    && lock_has_to_wait(wait_lock, lock)) {
-
-					return(FALSE);
-				}
-			} while (wait_lock != NULL);
-		} else {
-			do {
-				wait_lock = UT_LIST_GET_NEXT(
-					un_member.tab_lock.locks, wait_lock);
-
-				if (wait_lock != NULL
-				    && lock_has_to_wait(wait_lock, lock) ) {
-
-					return(FALSE);
-				}
-			} while (wait_lock != NULL);
-		}
-	}
-
-	return(TRUE);
-}
-
 /********************************************************************//**
 Looks recursively for a deadlock.
 @return 0 if no deadlock found, LOCK_VICTIM_IS_START if there was a
@@ -3404,16 +3346,11 @@ lock_deadlock_recursive(
 		/* We have already exhaustively searched the subtree starting
 		from this trx */
 
-		return(0);
-	} else if (lock_trx_has_no_waiters(trx)) {
-		/* If no other transaction is waiting for this transaction
-		to release its locks then no deadlock can occur. */
 		return(0);
 	}
 
 	*cost = *cost + 1;
 
-
 	if (lock_get_type_low(wait_lock) == LOCK_REC) {
 		ulint		space;
 		ulint		page_no;