From e6cba71503fa80948a050e7e0126e932855e92cc Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Fri, 11 Jun 2004 16:43:24 +0000
Subject: [PATCH] Add some code to Assert that when we release pin on a buffer,
we are not holding the buffer's cntx_lock or io_in_progress_lock. A recent
report from Litao Wu makes me wonder whether it is ever possible for us to
drop a buffer and forget to release its cntx_lock. The Assert does not fire
in the regression tests, but that proves little ...
---
src/backend/storage/buffer/bufmgr.c | 7 ++++++-
src/backend/storage/lmgr/lwlock.c | 22 +++++++++++++++++++++-
src/include/storage/lwlock.h | 3 ++-
3 files changed, 29 insertions(+), 3 deletions(-)
diff --git a/src/backend/storage/buffer/bufmgr.c b/src/backend/storage/buffer/bufmgr.c
index 400fbcf1ff7..da1998a0d50 100644
--- a/src/backend/storage/buffer/bufmgr.c
+++ b/src/backend/storage/buffer/bufmgr.c
@@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/storage/buffer/bufmgr.c,v 1.169 2004/05/31 20:31:33 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/storage/buffer/bufmgr.c,v 1.170 2004/06/11 16:43:23 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -611,7 +611,12 @@ UnpinBuffer(BufferDesc *buf)
Assert(PrivateRefCount[b] > 0);
PrivateRefCount[b]--;
if (PrivateRefCount[b] == 0)
+ {
buf->refcount--;
+ /* I'd better not still hold any locks on the buffer */
+ Assert(!LWLockHeldByMe(buf->cntx_lock));
+ Assert(!LWLockHeldByMe(buf->io_in_progress_lock));
+ }
if ((buf->flags & BM_PIN_COUNT_WAITER) != 0 &&
buf->refcount == 1)
diff --git a/src/backend/storage/lmgr/lwlock.c b/src/backend/storage/lmgr/lwlock.c
index efb3ac4a90f..d1410d04a05 100644
--- a/src/backend/storage/lmgr/lwlock.c
+++ b/src/backend/storage/lmgr/lwlock.c
@@ -15,7 +15,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/storage/lmgr/lwlock.c,v 1.19 2003/12/20 17:31:21 momjian Exp $
+ * $PostgreSQL: pgsql/src/backend/storage/lmgr/lwlock.c,v 1.20 2004/06/11 16:43:24 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -519,3 +519,23 @@ LWLockReleaseAll(void)
LWLockRelease(held_lwlocks[num_held_lwlocks - 1]);
}
}
+
+
+/*
+ * LWLockHeldByMe - test whether my process currently holds a lock
+ *
+ * This is meant as debug support only. We do not distinguish whether the
+ * lock is held shared or exclusive.
+ */
+bool
+LWLockHeldByMe(LWLockId lockid)
+{
+ int i;
+
+ for (i = 0; i < num_held_lwlocks; i++)
+ {
+ if (held_lwlocks[i] == lockid)
+ return true;
+ }
+ return false;
+}
diff --git a/src/include/storage/lwlock.h b/src/include/storage/lwlock.h
index e06d9a4bf77..b1f6fc95103 100644
--- a/src/include/storage/lwlock.h
+++ b/src/include/storage/lwlock.h
@@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
- * $PostgreSQL: pgsql/src/include/storage/lwlock.h,v 1.11 2004/05/31 03:48:10 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/storage/lwlock.h,v 1.12 2004/06/11 16:43:24 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -62,6 +62,7 @@ extern void LWLockAcquire(LWLockId lockid, LWLockMode mode);
extern bool LWLockConditionalAcquire(LWLockId lockid, LWLockMode mode);
extern void LWLockRelease(LWLockId lockid);
extern void LWLockReleaseAll(void);
+extern bool LWLockHeldByMe(LWLockId lockid);
extern int NumLWLocks(void);
extern int LWLockShmemSize(void);
--
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