From 5dea3158fc41cf1cd398fbcfe685741ce56d4635 Mon Sep 17 00:00:00 2001
From: drh <drh@noemail.net>
Date: Mon, 20 Jul 2009 12:33:32 +0000
Subject: [PATCH] Use an ALWAYS() on a conditional in btmutex.c that is always
 true. (CVS 6910)

FossilOrigin-Name: 609022caff12c010575e704be550da6f52226d33
---
 manifest      | 12 ++++++------
 manifest.uuid |  2 +-
 src/btmutex.c |  6 ++++--
 3 files changed, 11 insertions(+), 9 deletions(-)

diff --git a/manifest b/manifest
index ab2f218158..0e947aaf5b 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Corrections\sto\sthe\scomment\sthat\sis\sinserted\sat\sthe\stop\sof\sthe\samalgamation.\nTicket\s#3981.\s(CVS\s6909)
-D 2009-07-20T12:25:45
+C Use\san\sALWAYS()\son\sa\sconditional\sin\sbtmutex.c\sthat\sis\salways\strue.\s(CVS\s6910)
+D 2009-07-20T12:33:33
 F Makefile.arm-wince-mingw32ce-gcc fcd5e9cd67fe88836360bb4f9ef4cb7f8e2fb5a0
 F Makefile.in df9359da7a726ccb67a45db905c5447d5c00c6ef
 F Makefile.linux-gcc d53183f4aa6a9192d249731c90dbdffbd2c68654
@@ -105,7 +105,7 @@ F src/attach.c 13995348fc5a26cdd136a50806faf292aabc173f
 F src/auth.c 802a9439dfa0b8c208b10055cba400e82ef18025
 F src/backup.c 6f1c2d9862c8a3feb7739dfcca02c1f5352e37f3
 F src/bitvec.c cfbf6af5b0ababb4f06ed3e75c616dadaf47fcbd
-F src/btmutex.c f7b059a9b08e1af2dd222bf3cc5c45054af0bba6
+F src/btmutex.c 0f43a75bb5b8147b386e8e1c3e71ba734e3863b7
 F src/btree.c 4d964398d7291fd536cd6361c70ccad9c8dc3b9a
 F src/btree.h e53a10fd31d16c60a86f03c9467a6f470aa3683b
 F src/btreeInt.h 1c86297e69380f6577e7ae67452597dd8d5c2705
@@ -741,7 +741,7 @@ F tool/speedtest2.tcl ee2149167303ba8e95af97873c575c3e0fab58ff
 F tool/speedtest8.c 2902c46588c40b55661e471d7a86e4dd71a18224
 F tool/speedtest8inst1.c 293327bc76823f473684d589a8160bde1f52c14e
 F tool/vdbe-compress.tcl 672f81d693a03f80f5ae60bfefacd8a349e76746
-P 0ba17c04834c0a44c8690169c0096c1d9cf325e4
-R 05d0df7942efe746c1b7c880d4f23c65
+P 7572991bc2232f57d04c972d516a3e8f85f34f14
+R 9782ac6fe60ba619daf4a6a17cc11b51
 U drh
-Z 5062f6f2c693df8ee94506f10a45abfa
+Z d571a5e8243db19d230ca1d0fe109d34
diff --git a/manifest.uuid b/manifest.uuid
index ccfdca5922..bd354db025 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-7572991bc2232f57d04c972d516a3e8f85f34f14
\ No newline at end of file
+609022caff12c010575e704be550da6f52226d33
\ No newline at end of file
diff --git a/src/btmutex.c b/src/btmutex.c
index ecc2659cb5..9b5e0d7d89 100644
--- a/src/btmutex.c
+++ b/src/btmutex.c
@@ -10,7 +10,7 @@
 **
 *************************************************************************
 **
-** $Id: btmutex.c,v 1.16 2009/07/17 11:44:07 drh Exp $
+** $Id: btmutex.c,v 1.17 2009/07/20 12:33:33 drh Exp $
 **
 ** This file contains code used to implement mutexes on Btree objects.
 ** This code really belongs in btree.c.  But btree.c is getting too
@@ -197,7 +197,9 @@ void sqlite3BtreeEnterAll(sqlite3 *db){
       if( !p->locked ){
         assert( p->wantToLock==1 );
         while( p->pPrev ) p = p->pPrev;
-        while( p->locked && p->pNext ) p = p->pNext;
+        /* Reason for ALWAYS:  There must be at least on unlocked Btree in
+        ** the chain.  Otherwise the !p->locked test above would have failed */
+        while( p->locked && ALWAYS(p->pNext) ) p = p->pNext;
         for(pLater = p->pNext; pLater; pLater=pLater->pNext){
           if( pLater->locked ){
             unlockBtreeMutex(pLater);