From ca7578d45477ee0cb33bdb62c863acfe098347b3 Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Tue, 6 Nov 2001 00:38:26 +0000
Subject: [PATCH] The extra semaphore that proc.c now allocates for checkpoint
 processes should be accounted for in the PROC_SEM_MAP_ENTRIES() macro. 
 Otherwise the ports that rely on this macro to size data structures are
 broken. Mea culpa.

---
 src/backend/storage/lmgr/proc.c | 9 ++++++---
 src/include/storage/proc.h      | 8 +++++---
 2 files changed, 11 insertions(+), 6 deletions(-)

diff --git a/src/backend/storage/lmgr/proc.c b/src/backend/storage/lmgr/proc.c
index 1b0058eaef..84118c78d3 100644
--- a/src/backend/storage/lmgr/proc.c
+++ b/src/backend/storage/lmgr/proc.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/storage/lmgr/proc.c,v 1.114 2001/10/28 06:25:50 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/storage/lmgr/proc.c,v 1.115 2001/11/06 00:38:26 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -124,10 +124,13 @@ InitProcGlobal(int maxBackends)
 
 	/*
 	 * Compute size for ProcGlobal structure.  Note we need one more sema
-	 * besides those used for regular backends.
+	 * besides those used for regular backends; this is accounted for in
+	 * the PROC_SEM_MAP_ENTRIES macro.  (We do it that way so that other
+	 * modules that use PROC_SEM_MAP_ENTRIES(maxBackends) to size data
+	 * structures don't have to know about this explicitly.)
 	 */
 	Assert(maxBackends > 0);
-	semMapEntries = PROC_SEM_MAP_ENTRIES(maxBackends + 1);
+	semMapEntries = PROC_SEM_MAP_ENTRIES(maxBackends);
 	procGlobalSize = sizeof(PROC_HDR) + (semMapEntries - 1) *sizeof(SEM_MAP_ENTRY);
 
 	/* Create or attach to the ProcGlobal shared structure */
diff --git a/src/include/storage/proc.h b/src/include/storage/proc.h
index cba32ecec2..e1700b2372 100644
--- a/src/include/storage/proc.h
+++ b/src/include/storage/proc.h
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $Id: proc.h,v 1.53 2001/11/05 17:46:35 momjian Exp $
+ * $Id: proc.h,v 1.54 2001/11/06 00:38:26 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -93,10 +93,12 @@ extern PROC *MyProc;
  * in each set for identification purposes.)
  *
  * PROC_SEM_MAP_ENTRIES is the number of semaphore sets we need to allocate
- * to keep track of up to maxBackends backends.
+ * to keep track of up to maxBackends backends.  Note that we need one extra
+ * semaphore (see storage/lmgr/proc.c), so the computation may look wrong,
+ * but it's right.
  */
 #define  PROC_NSEMS_PER_SET		16
-#define  PROC_SEM_MAP_ENTRIES(maxBackends)	(((maxBackends)-1)/PROC_NSEMS_PER_SET+1)
+#define  PROC_SEM_MAP_ENTRIES(maxBackends)	((maxBackends)/PROC_NSEMS_PER_SET+1)
 
 typedef struct
 {
-- 
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