*** a/src/backend/access/transam/twophase.c
--- b/src/backend/access/transam/twophase.c
***************
*** 1041,1053 **** EndPrepare(GlobalTransaction gxact)
  
  	/* If we crash now, we have prepared: WAL replay will fix things */
  
- 	/*
- 	 * Wake up all walsenders to send WAL up to the PREPARE record immediately
- 	 * if replication is enabled
- 	 */
- 	if (max_wal_senders > 0)
- 		WalSndWakeup();
- 
  	/* write correct CRC and close file */
  	if ((write(fd, &statefile_crc, sizeof(pg_crc32))) != sizeof(pg_crc32))
  	{
--- 1041,1046 ----
***************
*** 1086,1091 **** EndPrepare(GlobalTransaction gxact)
--- 1079,1091 ----
  	END_CRIT_SECTION();
  
  	/*
+ 	 * Wake up all walsenders to send WAL up to the PREPARE record immediately
+ 	 * outside a critical section if replication is enabled
+ 	 */
+ 	if (max_wal_senders > 0)
+ 		WalSndWakeup();
+ 
+ 	/*
  	 * Wait for synchronous replication, if required.
  	 *
  	 * Note that at this stage we have marked the prepare, but still show as
***************
*** 2048,2060 **** RecordTransactionCommitPrepared(TransactionId xid,
  	/* Flush XLOG to disk */
  	XLogFlush(recptr);
  
- 	/*
- 	 * Wake up all walsenders to send WAL up to the COMMIT PREPARED record
- 	 * immediately if replication is enabled
- 	 */
- 	if (max_wal_senders > 0)
- 		WalSndWakeup();
- 
  	/* Mark the transaction committed in pg_clog */
  	TransactionIdCommitTree(xid, nchildren, children);
  
--- 2048,2053 ----
***************
*** 2064,2069 **** RecordTransactionCommitPrepared(TransactionId xid,
--- 2057,2069 ----
  	END_CRIT_SECTION();
  
  	/*
+ 	 * Wake up all walsenders to send WAL up to the COMMIT PREPARED record
+ 	 * immediately outside a critical section if replication is enabled
+ 	 */
+ 	if (max_wal_senders > 0)
+ 		WalSndWakeup();
+ 
+ 	/*
  	 * Wait for synchronous replication, if required.
  	 *
  	 * Note that at this stage we have marked clog, but still show as running
***************
*** 2136,2148 **** RecordTransactionAbortPrepared(TransactionId xid,
  	XLogFlush(recptr);
  
  	/*
- 	 * Wake up all walsenders to send WAL up to the ABORT PREPARED record
- 	 * immediately if replication is enabled
- 	 */
- 	if (max_wal_senders > 0)
- 		WalSndWakeup();
- 
- 	/*
  	 * Mark the transaction aborted in clog.  This is not absolutely necessary
  	 * but we may as well do it while we are here.
  	 */
--- 2136,2141 ----
***************
*** 2151,2156 **** RecordTransactionAbortPrepared(TransactionId xid,
--- 2144,2156 ----
  	END_CRIT_SECTION();
  
  	/*
+ 	 * Wake up all walsenders to send WAL up to the ABORT PREPARED record
+ 	 * immediately outside a critical section if replication is enabled
+ 	 */
+ 	if (max_wal_senders > 0)
+ 		WalSndWakeup();
+ 
+ 	/*
  	 * Wait for synchronous replication, if required.
  	 *
  	 * Note that at this stage we have marked clog, but still show as running
*** a/src/backend/access/transam/xact.c
--- b/src/backend/access/transam/xact.c
***************
*** 942,947 **** RecordTransactionCommit(void)
--- 942,948 ----
  	SharedInvalidationMessage *invalMessages = NULL;
  	bool		RelcacheInitFileInval = false;
  	bool		wrote_xlog;
+ 	bool		wakeup = false;
  
  	/* Get data needed for commit record */
  	nrels = smgrGetPendingDeletes(true, &rels);
***************
*** 1135,1147 **** RecordTransactionCommit(void)
  			pg_usleep(CommitDelay);
  
  		XLogFlush(XactLastRecEnd);
! 
! 		/*
! 		 * Wake up all walsenders to send WAL up to the COMMIT record
! 		 * immediately if replication is enabled
! 		 */
! 		if (max_wal_senders > 0)
! 			WalSndWakeup();
  
  		/*
  		 * Now we may update the CLOG, if we wrote a COMMIT record above
--- 1136,1142 ----
  			pg_usleep(CommitDelay);
  
  		XLogFlush(XactLastRecEnd);
! 		wakeup = true;
  
  		/*
  		 * Now we may update the CLOG, if we wrote a COMMIT record above
***************
*** 1183,1188 **** RecordTransactionCommit(void)
--- 1178,1190 ----
  		END_CRIT_SECTION();
  	}
  
+ 	/*
+ 	 * Wake up all walsenders to send WAL up to the COMMIT record
+ 	 * immediately outside a critical section if replication is enabled
+ 	 */
+ 	if (max_wal_senders > 0 && wakeup)
+ 		WalSndWakeup();
+ 
  	/* Compute latestXid while we have the child XIDs handy */
  	latestXid = TransactionIdLatest(xid, nchildren, children);
  
*** a/src/backend/access/transam/xlog.c
--- b/src/backend/access/transam/xlog.c
***************
*** 2271,2276 **** XLogBackgroundFlush(void)
--- 2271,2283 ----
  
  	END_CRIT_SECTION();
  
+ 	/*
+ 	 * Wake up all walsenders to send WAL up to the async commit record
+ 	 * immediately outside a critical section is replication is enabled
+ 	 */
+ 	if (max_wal_senders > 0 && !flexible && wrote_something)
+ 		WalSndWakeup();
+ 
  	return wrote_something;
  }