From 110147653aebe8eba9a42559e3737ac0d48d107f Mon Sep 17 00:00:00 2001
From: Alvaro Herrera <alvherre@alvh.no-ip.org>
Date: Fri, 11 Jul 2008 02:10:14 +0000
Subject: [PATCH] Make sure we only try to free snapshots that have been passed
through CopySnapshot, per Neil Conway. Also add a comment about the
assumption in GetSnapshotData that the argument is statically allocated.
Also, fix some more typos in comments in snapmgr.c.
---
src/backend/storage/ipc/procarray.c | 5 ++++-
src/backend/utils/time/snapmgr.c | 10 +++++-----
2 files changed, 9 insertions(+), 6 deletions(-)
diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c
index 62a17003c1c..0286809d1c4 100644
--- a/src/backend/storage/ipc/procarray.c
+++ b/src/backend/storage/ipc/procarray.c
@@ -23,7 +23,7 @@
*
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/storage/ipc/procarray.c,v 1.44 2008/05/12 20:02:00 alvherre Exp $
+ * $PostgreSQL: pgsql/src/backend/storage/ipc/procarray.c,v 1.45 2008/07/11 02:10:13 alvherre Exp $
*
*-------------------------------------------------------------------------
*/
@@ -666,6 +666,9 @@ GetOldestXmin(bool allDbs, bool ignoreVacuum)
* RecentGlobalXmin: the global xmin (oldest TransactionXmin across all
* running transactions, except those running LAZY VACUUM). This is
* the same computation done by GetOldestXmin(true, true).
+ *
+ * Note: this function should probably not be called with an argument that's
+ * not statically allocated (see xip allocation below).
*/
Snapshot
GetSnapshotData(Snapshot snapshot)
diff --git a/src/backend/utils/time/snapmgr.c b/src/backend/utils/time/snapmgr.c
index c0f6a97847e..841a92567d1 100644
--- a/src/backend/utils/time/snapmgr.c
+++ b/src/backend/utils/time/snapmgr.c
@@ -3,10 +3,9 @@
* PostgreSQL snapshot manager
*
* We keep track of snapshots in two ways: the "registered snapshots" list,
- * and the "active snapshot" stack. All snapshots in any of them is supposed
- * to be in persistent memory. When a snapshot is no longer in any of these
- * lists (tracked by separate refcounts of each snapshot), its memory can be
- * freed.
+ * and the "active snapshot" stack. All snapshots in either of them live in
+ * persistent memory. When a snapshot is no longer in any of these lists
+ * (tracked by separate refcounts on each snapshot), its memory can be freed.
*
* These arrangements let us reset MyProc->xmin when there are no snapshots
* referenced by this transaction. (One possible improvement would be to be
@@ -23,7 +22,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/utils/time/snapmgr.c,v 1.3 2008/07/11 00:00:29 neilc Exp $
+ * $PostgreSQL: pgsql/src/backend/utils/time/snapmgr.c,v 1.4 2008/07/11 02:10:14 alvherre Exp $
*
*-------------------------------------------------------------------------
*/
@@ -261,6 +260,7 @@ FreeSnapshot(Snapshot snapshot)
{
Assert(snapshot->regd_count == 0);
Assert(snapshot->active_count == 0);
+ Assert(snapshot->copied);
pfree(snapshot);
}