From f59b05c95d60dd0e89a80d6ba601461f488ba669 Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Mon, 12 Sep 2005 22:20:16 +0000
Subject: [PATCH] Ensure that any memory leaked during an error inside the
bgwriter is recovered. I did not see any actual leak while testing this in
CVS tip, but 8.0 definitely has a problem with leaking the space temporarily
palloc'd by BufferSync(). In any case this seems a good idea to forestall
similar problems in future. Per report from Arjen van der Meijden.
---
src/backend/postmaster/bgwriter.c | 21 +++++++++++++++++++--
1 file changed, 19 insertions(+), 2 deletions(-)
diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c
index 830cb897d98..ed1a7b2f271 100644
--- a/src/backend/postmaster/bgwriter.c
+++ b/src/backend/postmaster/bgwriter.c
@@ -37,7 +37,7 @@
*
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/postmaster/bgwriter.c,v 1.19 2005/08/20 23:26:17 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/postmaster/bgwriter.c,v 1.20 2005/09/12 22:20:16 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -160,6 +160,7 @@ void
BackgroundWriterMain(void)
{
sigjmp_buf local_sigjmp_buf;
+ MemoryContext bgwriter_context;
Assert(BgWriterShmem != NULL);
BgWriterShmem->bgwriter_pid = MyProcPid;
@@ -207,6 +208,19 @@ BackgroundWriterMain(void)
*/
last_checkpoint_time = time(NULL);
+ /*
+ * Create a memory context that we will do all our work in. We do this
+ * so that we can reset the context during error recovery and thereby
+ * avoid possible memory leaks. Formerly this code just ran in
+ * TopMemoryContext, but resetting that would be a really bad idea.
+ */
+ bgwriter_context = AllocSetContextCreate(TopMemoryContext,
+ "Background Writer",
+ ALLOCSET_DEFAULT_MINSIZE,
+ ALLOCSET_DEFAULT_INITSIZE,
+ ALLOCSET_DEFAULT_MAXSIZE);
+ MemoryContextSwitchTo(bgwriter_context);
+
/*
* If an exception is encountered, processing resumes here.
*
@@ -247,9 +261,12 @@ BackgroundWriterMain(void)
* Now return to normal top-level context and clear ErrorContext
* for next time.
*/
- MemoryContextSwitchTo(TopMemoryContext);
+ MemoryContextSwitchTo(bgwriter_context);
FlushErrorState();
+ /* Flush any leaked data in the top-level context */
+ MemoryContextResetAndDeleteChildren(bgwriter_context);
+
/* Now we can allow interrupts again */
RESUME_INTERRUPTS();
--
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