Change the way threadsOverrideEachOthersLocks() works to avoid trying to write-lock a (potentially) read-only files. Also, assume that on non-linux systems threads do override each others locks. Ticket #3472. (CVS 5883)

FossilOrigin-Name: 8ecae0943b06102fe22133db0dcaf58ecbd39545

manifest

@@ -1,5 +1,5 @@
-C Cleanup\sin\sflattenSubquery.\s\sAdd\sOOM\stests\sfor\sflattenSubquery.\s\sFix\sissues\nwith\sOOM\serrors\scauses\sproblems\sfor\sflattenSubquery.\s\sTicket\s#3485.\s(CVS\s5882)
-D 2008-11-11T18:28:59
+C Change\sthe\sway\sthreadsOverrideEachOthersLocks()\sworks\sto\savoid\strying\sto\swrite-lock\sa\s(potentially)\sread-only\sfiles.\sAlso,\sassume\sthat\son\snon-linux\ssystems\sthreads\sdo\soverride\seach\sothers\slocks.\sTicket\s#3472.\s(CVS\s5883)
+D 2008-11-11T18:34:35
 F Makefile.arm-wince-mingw32ce-gcc fcd5e9cd67fe88836360bb4f9ef4cb7f8e2fb5a0
 F Makefile.in 48172b58e444a9725ec482e0c022a564749acab4
 F Makefile.linux-gcc d53183f4aa6a9192d249731c90dbdffbd2c68654
@@ -136,7 +136,7 @@ F src/os.c 0b411644b87ad689d7250bbfd1834d99b81a3df4
 F src/os.h ef8abeb9afc694b82dbd169a91c9b7e26db3c892
 F src/os_common.h 24525d8b7bce66c374dfc1810a6c9043f3359b60
 F src/os_os2.c 63be0987dbeb42e9b08c831863d2a315953b86e1
-F src/os_unix.c d17f694eda9d583676bcab87109efad42dd2abe1
+F src/os_unix.c af390f03ebe339e63911aec2d4ccd1e53fde581e
 F src/os_win.c e208cbbceac63c1dd881d0909de5a4679a2c6992
 F src/pager.c 6b6f8eb4938d184d6612ea89631185dbace246b3
 F src/pager.h 4a57b219c0765fe1870238064e3f46e4eb2cf5af
@@ -575,6 +575,7 @@ F test/tkt3424.test 3171193ce340cff6b7ea81c03b8fa1cbc34ec36e
 F test/tkt3442.test 33722a3fa4bdc0614448044eb5e28765aea28eb7
 F test/tkt3457.test e9ca2b90f0eb1fb8be73a30d29aacb2e3abedeb9
 F test/tkt3461.test 5a63e8d8ee5ce00f076b1e2f82aba5480a0f14ed
+F test/tkt3472.test cc1fa004edd040dbc4c5c03327f8f3d3bbcd9ccb
 F test/tokenize.test ce430a7aed48fc98301611429595883fdfcab5d7
 F test/trace.test 951cd0f5f571e7f36bf7bfe04be70f90fb16fb00
 F test/trans.test 2fd24cd7aa0b879d49a224cbd647d698f1e7ac5c
@@ -654,7 +655,7 @@ F tool/speedtest16.c c8a9c793df96db7e4933f0852abb7a03d48f2e81
 F tool/speedtest2.tcl ee2149167303ba8e95af97873c575c3e0fab58ff
 F tool/speedtest8.c 2902c46588c40b55661e471d7a86e4dd71a18224
 F tool/speedtest8inst1.c 293327bc76823f473684d589a8160bde1f52c14e
-P 0659a666ff0a9fc81ee4df3c35e535164c79e588
-R 4feb3b063e6492d2c3095674c86d05b4
-U drh
-Z ccf27dcefe10bea054f7ff323046db0d
+P ea5f4baa041aed934600f0f96b84afb92a14bc47
+R 67f50952a830fd72a8913f41885cf6a5
+U danielk1977
+Z df5f98daf78e83087123ba4df516fc8d

manifest.uuid

@@ -1 +1 @@
-ea5f4baa041aed934600f0f96b84afb92a14bc47
+8ecae0943b06102fe22133db0dcaf58ecbd39545

src/os_unix.c

@@ -12,7 +12,7 @@
 **
 ** This file contains code that is specific to Unix systems.
 **
-** $Id: os_unix.c,v 1.208 2008/11/07 00:06:18 drh Exp $
+** $Id: os_unix.c,v 1.209 2008/11/11 18:34:35 danielk1977 Exp $
 */
 #include "sqliteInt.h"
 #if SQLITE_OS_UNIX              /* This file is used on unix only */
@@ -493,16 +493,19 @@ static int lockTrace(int fd, int op, struct flock *p){
 #define fcntl lockTrace
 #endif /* SQLITE_LOCK_TRACE */
 
+#ifdef __linux__
 /*
-** The testThreadLockingBehavior() routine launches two separate
-** threads on this routine.  This routine attempts to lock a file
-** descriptor then returns.  The success or failure of that attempt
-** allows the testThreadLockingBehavior() procedure to determine
-** whether or not threads can override each others locks.
-*/
+** This function is used as the main routine for a thread launched by
+** testThreadLockingBehavior(). It tests whether the shared-lock obtained
+** by the main thread in testThreadLockingBehavior() conflicts with a
+** hypothetical write-lock obtained by this thread on the same file.
+**
+** The write-lock is not actually acquired, as this is not possible if 
+** the file is open in read-only mode (see ticket #3472).
+*/ 
 static void *threadLockingTest(void *pArg){
   struct threadTestData *pData = (struct threadTestData*)pArg;
-  pData->result = fcntl(pData->fd, F_SETLK, &pData->lock);
+  pData->result = fcntl(pData->fd, F_GETLK, &pData->lock);
   return pArg;
 }
 
@@ -513,26 +516,39 @@ static void *threadLockingTest(void *pArg){
 */
 static void testThreadLockingBehavior(int fd_orig){
   int fd;
-  struct threadTestData d[2];
-  pthread_t t[2];
+  int rc;
+  struct threadTestData d;
+  struct flock l;
+  pthread_t t;
 
   fd = dup(fd_orig);
   if( fd<0 ) return;
-  memset(d, 0, sizeof(d));
-  d[0].fd = fd;
-  d[0].lock.l_type = F_RDLCK;
-  d[0].lock.l_len = 1;
-  d[0].lock.l_start = 0;
-  d[0].lock.l_whence = SEEK_SET;
-  d[1] = d[0];
-  d[1].lock.l_type = F_WRLCK;
-  pthread_create(&t[0], 0, threadLockingTest, &d[0]);
-  pthread_create(&t[1], 0, threadLockingTest, &d[1]);
-  pthread_join(t[0], 0);
-  pthread_join(t[1], 0);
+  memset(&l, 0, sizeof(l));
+  l.l_type = F_RDLCK;
+  l.l_len = 1;
+  l.l_start = 0;
+  l.l_whence = SEEK_SET;
+  rc = fcntl(fd_orig, F_SETLK, &l);
+  if( rc!=0 ) return;
+  memset(&d, 0, sizeof(d));
+  d.fd = fd;
+  d.lock = l;
+  d.lock.l_type = F_WRLCK;
+  pthread_create(&t, 0, threadLockingTest, &d);
+  pthread_join(t, 0);
   close(fd);
-  threadsOverrideEachOthersLocks =  d[0].result==0 && d[1].result==0;
+  if( d.result!=0 ) return;
+  threadsOverrideEachOthersLocks = (d.lock.l_type==F_UNLCK);
 }
+#else
+/*
+** On anything other than linux, assume threads override each others locks.
+*/
+static void testThreadLockingBehavior(int fd_orig){
+  threadsOverrideEachOthersLocks = 1;
+}
+#endif /* __linux__ */
+
 #endif /* SQLITE_THREADSAFE */
 
 /*

test/tkt3472.test

@@ -0,0 +1,35 @@
+# 2008 November 11
+#
+# The author disclaims copyright to this source code.  In place of
+# a legal notice, here is a blessing:
+#
+#    May you do good and not evil.
+#    May you find forgiveness for yourself and forgive others.
+#    May you share freely, never taking more than you give.
+#
+#***********************************************************************
+#     
+# $Id: tkt3472.test,v 1.1 2008/11/11 18:34:35 danielk1977 Exp $
+
+set testdir [file dirname $argv0]
+source $testdir/tester.tcl
+
+set ::correctvalue $threadsOverrideEachOthersLocks
+puts "threadsOverrideEachOthersLocks = $::correctvalue"
+
+do_test tkt3472-1.1 {
+  db close
+  set threadsOverrideEachOthersLocks -1
+  sqlite3 db test.db
+  set threadsOverrideEachOthersLocks
+} $::correctvalue
+
+do_test tkt3472-1.2 {
+  db close
+  set threadsOverrideEachOthersLocks -1
+  sqlite3 db test.db -readonly 1
+  set threadsOverrideEachOthersLocks
+} $::correctvalue
+
+finish_test
+