From 48337207244784924fb4408f66fd15207b63dde8 Mon Sep 17 00:00:00 2001
From: Simon Riggs <simon@2ndQuadrant.com>
Date: Mon, 5 Oct 2009 15:13:37 +0100
Subject: [PATCH] Apply
 0014-Make-locking-of-ShmemVariableCache-nextXid-in-multix.patch

---
 src/backend/access/transam/multixact.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/src/backend/access/transam/multixact.c b/src/backend/access/transam/multixact.c
index 6f86961b88..80affa9624 100644
--- a/src/backend/access/transam/multixact.c
+++ b/src/backend/access/transam/multixact.c
@@ -1927,11 +1927,18 @@ multixact_redo(XLogRecPtr lsn, XLogRecord *record)
 			if (TransactionIdPrecedes(max_xid, xids[i]))
 				max_xid = xids[i];
 		}
+
+		/* We don't expect anyone else to modify nextXid, hence we
+		 * don't need to hold a lock while checking this. We still acquire
+		 * the lock to modify it, though.
+		 */
 		if (TransactionIdFollowsOrEquals(max_xid,
 										 ShmemVariableCache->nextXid))
 		{
+			LWLockAcquire(XidGenLock, LW_EXCLUSIVE);
 			ShmemVariableCache->nextXid = max_xid;
 			TransactionIdAdvance(ShmemVariableCache->nextXid);
+			LWLockRelease(XidGenLock);
 		}
 	}
 	else
-- 
2.39.5