*** a/src/backend/storage/lmgr/predicate.c
--- b/src/backend/storage/lmgr/predicate.c
***************
*** 3757,3762 **** CheckTargetForConflictsIn(PREDICATELOCKTARGETTAG *targettag)
--- 3757,3773 ----
  					LWLockRelease(partitionLock);
  					LWLockRelease(SerializablePredicateLockListLock);
  					LWLockAcquire(partitionLock, LW_SHARED);
+ 
+ 					/*
+ 					 * The list may have been altered by another process
+ 					 * while we weren't holding the partition lock.  Start
+ 					 * over at the front.
+ 					 */
+ 					nextpredlock = (PREDICATELOCK *)
+ 						SHMQueueNext(&(target->predicateLocks),
+ 									 &(target->predicateLocks),
+ 									 offsetof(PREDICATELOCK, targetLink));
+ 
  					LWLockAcquire(SerializableXactHashLock, LW_SHARED);
  				}
  			}
***************
*** 3770,3776 **** CheckTargetForConflictsIn(PREDICATELOCKTARGETTAG *targettag)
  			LWLockRelease(SerializableXactHashLock);
  			LWLockAcquire(SerializableXactHashLock, LW_EXCLUSIVE);
  
! 			FlagRWConflict(sxact, (SERIALIZABLEXACT *) MySerializableXact);
  
  			LWLockRelease(SerializableXactHashLock);
  			LWLockAcquire(SerializableXactHashLock, LW_SHARED);
--- 3781,3799 ----
  			LWLockRelease(SerializableXactHashLock);
  			LWLockAcquire(SerializableXactHashLock, LW_EXCLUSIVE);
  
! 			/*
! 			 * Re-check after getting exclusive lock because the other
! 			 * transaction may have flagged a conflict.
! 			 */
! 			if (!SxactIsRolledBack(sxact)
! 				&& (!SxactIsCommitted(sxact)
! 					|| TransactionIdPrecedes(GetTransactionSnapshot()->xmin,
! 											 sxact->finishedBefore))
! 				&& !RWConflictExists(sxact,
! 									 (SERIALIZABLEXACT *) MySerializableXact))
! 			{
! 				FlagRWConflict(sxact, (SERIALIZABLEXACT *) MySerializableXact);
! 			}
  
  			LWLockRelease(SerializableXactHashLock);
  			LWLockAcquire(SerializableXactHashLock, LW_SHARED);