Do all accesses to shared buffer headers through volatile-qualified

pointers, to ensure that compilers won't rearrange accesses to occur
while we're not holding the buffer header spinlock.  It's probably
not necessary to mark volatile in every single place in bufmgr.c,
but better safe than sorry.  Per trouble report from Kevin Grittner.

Author: tglsfdc

contrib/pg_buffercache/pg_buffercache_pages.c

@@ -3,7 +3,7 @@
  * pg_buffercache_pages.c
  *    display some contents of the buffer cache
  *
- *	  $PostgreSQL: pgsql/contrib/pg_buffercache/pg_buffercache_pages.c,v 1.4 2005/05/31 00:07:47 tgl Exp $
+ *	  $PostgreSQL: pgsql/contrib/pg_buffercache/pg_buffercache_pages.c,v 1.5 2005/10/12 16:45:13 tgl Exp $
  *-------------------------------------------------------------------------
  */
 #include "postgres.h"
@@ -72,10 +72,8 @@ pg_buffercache_pages(PG_FUNCTION_ARGS)
 
 	if (SRF_IS_FIRSTCALL())
 	{
-		RelFileNode	rnode;
 		uint32		i;
-		BufferDesc	*bufHdr;
-
+		volatile BufferDesc	*bufHdr;
 
 		funcctx = SRF_FIRSTCALL_INIT();
 
@@ -136,35 +134,24 @@ pg_buffercache_pages(PG_FUNCTION_ARGS)
 			/* Lock each buffer header before inspecting. */
 			LockBufHdr(bufHdr);
 
-			rnode = bufHdr->tag.rnode;
-
 			fctx->record[i].bufferid = BufferDescriptorGetBuffer(bufHdr);
-			fctx->record[i].relfilenode = rnode.relNode;
-			fctx->record[i].reltablespace = rnode.spcNode;
-			fctx->record[i].reldatabase = rnode.dbNode;
+			fctx->record[i].relfilenode = bufHdr->tag.rnode.relNode;
+			fctx->record[i].reltablespace = bufHdr->tag.rnode.spcNode;
+			fctx->record[i].reldatabase = bufHdr->tag.rnode.dbNode;
 			fctx->record[i].blocknum = bufHdr->tag.blockNum;
 
-			if ( bufHdr->flags & BM_DIRTY) 
-			{
+			if (bufHdr->flags & BM_DIRTY) 
 				fctx->record[i].isdirty = true;
-			}
 			else
-			{
 				fctx->record[i].isdirty = false;
-			}
 
 			/* Note if the buffer is valid, and has storage created */
-			if ( (bufHdr->flags & BM_VALID) && (bufHdr->flags & BM_TAG_VALID))
-			{
+			if ((bufHdr->flags & BM_VALID) && (bufHdr->flags & BM_TAG_VALID))
 				fctx->record[i].isvalid = true;
-			}
 			else
-			{
 				fctx->record[i].isvalid = false;
-			}
 
 			UnlockBufHdr(bufHdr);
-
 		}
 
 		/* Release Buffer map. */