From aaa3dfd26c22be1848c1f613171aca4e588e431c Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Thu, 8 Dec 2005 19:19:22 +0000
Subject: [PATCH] Fix bgwriter's failure to release buffer pins and open files
 after an error.  This probably explains bug #2099 and could also account for
 mysterious VACUUM hangups.

---
 src/backend/postmaster/bgwriter.c     | 19 +++++++++++++++++--
 src/backend/utils/resowner/resowner.c |  8 ++++----
 2 files changed, 21 insertions(+), 6 deletions(-)

diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c
index 78fecf4dd6..c9a8baf25a 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 1.21 2005/10/15 02:49:23 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/postmaster/bgwriter.c,v 1.22 2005/12/08 19:19:22 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -51,6 +51,7 @@
 #include "miscadmin.h"
 #include "postmaster/bgwriter.h"
 #include "storage/bufmgr.h"
+#include "storage/fd.h"
 #include "storage/freespace.h"
 #include "storage/ipc.h"
 #include "storage/pmsignal.h"
@@ -58,6 +59,7 @@
 #include "tcop/tcopprot.h"
 #include "utils/guc.h"
 #include "utils/memutils.h"
+#include "utils/resowner.h"
 
 
 /*----------
@@ -208,6 +210,12 @@ BackgroundWriterMain(void)
 	 */
 	last_checkpoint_time = time(NULL);
 
+	/*
+	 * Create a resource owner to keep track of our resources (currently
+	 * only buffer pins).
+	 */
+	CurrentResourceOwner = ResourceOwnerCreate(NULL, "Background Writer");
+
 	/*
 	 * 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
@@ -240,11 +248,18 @@ BackgroundWriterMain(void)
 		/*
 		 * These operations are really just a minimal subset of
 		 * AbortTransaction().	We don't have very many resources to worry
-		 * about in bgwriter, but we do have LWLocks and buffers.
+		 * about in bgwriter, but we do have LWLocks, buffers, and temp files.
 		 */
 		LWLockReleaseAll();
 		AbortBufferIO();
 		UnlockBuffers();
+		/* buffer pins are released here: */
+		ResourceOwnerRelease(CurrentResourceOwner,
+							 RESOURCE_RELEASE_BEFORE_LOCKS,
+							 false, true);
+		/* we needn't bother with the other ResourceOwnerRelease phases */
+		AtEOXact_Buffers(false);
+		AtEOXact_Files();
 
 		/* Warn any waiting backends that the checkpoint failed. */
 		if (ckpt_active)
diff --git a/src/backend/utils/resowner/resowner.c b/src/backend/utils/resowner/resowner.c
index 19c7f8ea8b..d9c830dfc1 100644
--- a/src/backend/utils/resowner/resowner.c
+++ b/src/backend/utils/resowner/resowner.c
@@ -14,7 +14,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/resowner/resowner.c,v 1.16 2005/11/22 18:17:27 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/resowner/resowner.c,v 1.17 2005/12/08 19:19:22 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -437,7 +437,7 @@ UnregisterResourceReleaseCallback(ResourceReleaseCallback callback, void *arg)
  * of memory, it's critical to do so *before* acquiring the resource.
  *
  * We allow the case owner == NULL because the bufmgr is sometimes invoked
- * outside any transaction (for example, in the bgwriter).
+ * outside any transaction (for example, during WAL recovery).
  */
 void
 ResourceOwnerEnlargeBuffers(ResourceOwner owner)
@@ -470,7 +470,7 @@ ResourceOwnerEnlargeBuffers(ResourceOwner owner)
  * Caller must have previously done ResourceOwnerEnlargeBuffers()
  *
  * We allow the case owner == NULL because the bufmgr is sometimes invoked
- * outside any transaction (for example, in the bgwriter).
+ * outside any transaction (for example, during WAL recovery).
  */
 void
 ResourceOwnerRememberBuffer(ResourceOwner owner, Buffer buffer)
@@ -487,7 +487,7 @@ ResourceOwnerRememberBuffer(ResourceOwner owner, Buffer buffer)
  * Forget that a buffer pin is owned by a ResourceOwner
  *
  * We allow the case owner == NULL because the bufmgr is sometimes invoked
- * outside any transaction (for example, in the bgwriter).
+ * outside any transaction (for example, during WAL recovery).
  */
 void
 ResourceOwnerForgetBuffer(ResourceOwner owner, Buffer buffer)