Date: Thu, 23 Jul 2015 16:53:49 -0300
From: Alvaro Herrera <alvherre@2ndquadrant.com>
To: Peter Geoghegan <pg@heroku.com>
Cc: Noah Misch <noah@leadboat.com>, Simon Riggs <simon@2ndquadrant.com>,
 Bruce Momjian <bruce@momjian.us>, Andres Freund <andres@anarazel.de>,
 Robert Haas <robertmhaas@gmail.com>, Tom Lane <tgl@sss.pgh.pa.us>,
 Stephen Frost <sfrost@snowman.net>, Magnus Hagander <magnus@hagander.net>,
 "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>,
 pgsql-core <pgsql-core@postgresql.org>
Subject: Re: Restore-reliability mode
Message-ID: <20150723195349.GW5596@postgresql.org>
References: 
 <CA+TgmoYSO0a9YDe2bhpZoPgO4m62CyQL26LRkCQ8=vrQ8ZwdXA@mail.gmail.com>
 <12510.1432958887@sss.pgh.pa.us>
 <CA+TgmoYovkev0xXnxaTD8vnt=M9Cn+RmOkVEouqwj6_9JLkzLw@mail.gmail.com>
 <20150530154559.GA25053@momjian.us>
 <20150530204727.GJ13944@alap3.anarazel.de>
 <20150531024845.GB13697@momjian.us>
 <20150603135049.GA74753@tornado.leadboat.com>
 <CANP8+jJgKpBac77b77xLWTxxBeq9hG3a0uY-JUv6F4k=2=Nsgw@mail.gmail.com>
 <20150606195805.GA118899@tornado.leadboat.com>
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Peter Geoghegan wrote:
> On Sat, Jun 6, 2015 at 12:58 PM, Noah Misch <noah@leadboat.com> wrote:
> >   - Call VALGRIND_MAKE_MEM_NOACCESS() on a shared buffer when its local pin
> >     count falls to zero.  Under CLOBBER_FREED_MEMORY, wipe a shared buffer
> >     when its global pin count falls to zero.
> 
> Did a patch for this ever materialize?

I think the first part would be something like the attached.

-- 
Álvaro Herrera                http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

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diff --git a/src/backend/storage/buffer/bufmgr.c b/src/backend/storage/buffer/bufmgr.c
index e4b25587..83fde10 100644
--- a/src/backend/storage/buffer/bufmgr.c
+++ b/src/backend/storage/buffer/bufmgr.c
@@ -47,6 +47,7 @@
 #include "storage/proc.h"
 #include "storage/smgr.h"
 #include "storage/standby.h"
+#include "utils/memdebug.h"
 #include "utils/rel.h"
 #include "utils/resowner_private.h"
 #include "utils/timestamp.h"
@@ -1438,6 +1439,9 @@ PinBuffer(volatile BufferDesc *buf, BufferAccessStrategy strategy)
 		ref = NewPrivateRefCountEntry(b + 1);
 
 		LockBufHdr(buf);
+
+		VALGRIND_MAKE_MEM_DEFINED(BufHdrGetBlock(buf), BLCKSZ);
+
 		buf->refcount++;
 		if (strategy == NULL)
 		{
@@ -1498,6 +1502,8 @@ PinBuffer_Locked(volatile BufferDesc *buf)
 	 */
 	Assert(GetPrivateRefCountEntry(b + 1, false) == NULL);
 
+	VALGRIND_MAKE_MEM_DEFINED(BufHdrGetBlock(buf), BLCKSZ);
+
 	buf->refcount++;
 	UnlockBufHdr(buf);
 
@@ -1543,6 +1549,8 @@ UnpinBuffer(volatile BufferDesc *buf, bool fixOwner)
 		Assert(buf->refcount > 0);
 		buf->refcount--;
 
+		VALGRIND_MAKE_MEM_NOACCESS(BufHdrGetBlock(buf), BLCKSZ);
+
 		/* Support LockBufferForCleanup() */
 		if ((buf->flags & BM_PIN_COUNT_WAITER) &&
 			buf->refcount == 1)

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