v2-0001-Add-Valgrind-buffer-access-instrumentation.patch

From 8e120f9b6079767e656f8ca7eeda447a5c88113b Mon Sep 17 00:00:00 2001
From: Peter Geoghegan <pg@bowt.ie>
Date: Wed, 22 Apr 2020 19:51:43 -0700
Subject: [PATCH v2 1/2] Add Valgrind buffer access instrumentation.
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Based on a patch from Álvaro Herrera posted to:
https://www.postgresql.org/message-id/20150723195349.GW5596@postgresql.org
---
 src/backend/storage/buffer/bufmgr.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/src/backend/storage/buffer/bufmgr.c b/src/backend/storage/buffer/bufmgr.c
index f9980cf80c..5d3211140c 100644
--- a/src/backend/storage/buffer/bufmgr.c
+++ b/src/backend/storage/buffer/bufmgr.c
@@ -49,6 +49,7 @@
 #include "storage/proc.h"
 #include "storage/smgr.h"
 #include "storage/standby.h"
+#include "utils/memdebug.h"
 #include "utils/ps_status.h"
 #include "utils/rel.h"
 #include "utils/resowner_private.h"
@@ -1633,6 +1634,13 @@ PinBuffer(BufferDesc *buf, BufferAccessStrategy strategy)
 											   buf_state))
 			{
 				result = (buf_state & BM_VALID) != 0;
+
+				/*
+				 * If we successfully acquired our first pin on this buffer
+				 * within this backend, mark buffer contents defined
+				 */
+				if (result)
+					VALGRIND_MAKE_MEM_DEFINED(BufHdrGetBlock(buf), BLCKSZ);
 				break;
 			}
 		}
@@ -1683,6 +1691,13 @@ PinBuffer_Locked(BufferDesc *buf)
 	 */
 	Assert(GetPrivateRefCountEntry(BufferDescriptorGetBuffer(buf), false) == NULL);
 
+	/*
+	 * Buffer can't have a preexisting pin, so mark its page as defined to
+	 * Valgrind (this is similar to the PinBuffer() case where the backend
+	 * doesn't already have a buffer pin)
+	 */
+	VALGRIND_MAKE_MEM_DEFINED(BufHdrGetBlock(buf), BLCKSZ);
+
 	/*
 	 * Since we hold the buffer spinlock, we can update the buffer state and
 	 * release the lock in one operation.
@@ -1728,6 +1743,9 @@ UnpinBuffer(BufferDesc *buf, bool fixOwner)
 		uint32		buf_state;
 		uint32		old_buf_state;
 
+		/* Mark undefined, now that no pins remain in backend */
+		VALGRIND_MAKE_MEM_NOACCESS(BufHdrGetBlock(buf), BLCKSZ);
+
 		/* I'd better not still hold any locks on the buffer */
 		Assert(!LWLockHeldByMe(BufferDescriptorGetContentLock(buf)));
 		Assert(!LWLockHeldByMe(BufferDescriptorGetIOLock(buf)));
-- 
2.25.1