From: drh <drh@noemail.net>
Date: Wed, 29 Aug 2007 17:43:19 +0000 (+0000)
Subject: Improvements to mutex asserts.  The quick test runs to completion without
X-Git-Tag: version-3.6.10~1853
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=ff0587c63224855534be400c844124d5ce8ab739;p=thirdparty%2Fsqlite.git

Improvements to mutex asserts.  The quick test runs to completion without
assertion faults. (CVS 4324)

FossilOrigin-Name: 2732af0ec77dbc90c0439b6a61d893d9ea3b5697
---

diff --git a/manifest b/manifest
index 1c41fe5ca9..7a130fa31a 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Use\sthe\sDbMalloc()\sand\sDbRealloc()\sfunctions\smore\sconsistently.\s(CVS\s4323)
-D 2007-08-29T14:06:23
+C Improvements\sto\smutex\sasserts.\s\sThe\squick\stest\sruns\sto\scompletion\swithout\nassertion\sfaults.\s(CVS\s4324)
+D 2007-08-29T17:43:20
 F Makefile.in bfcc303429a5d9dcd552d807ee016c77427418c3
 F Makefile.linux-gcc 65241babba6faf1152bf86574477baab19190499
 F README 9c4e2d6706bdcc3efdd773ce752a8cdab4f90028
@@ -77,12 +77,12 @@ F sqlite3.1 6be1ad09113570e1fc8dcaff84c9b0b337db5ffc
 F sqlite3.def a96c1d0d39362b763d2ddba220a32da41a15c4b4
 F sqlite3.pc.in 985b9bf34192a549d7d370e0f0b6b34a4f61369a
 F src/alter.c c9f30b4d6fbf7eff7c5518b002a217d4ecd13bcf
-F src/analyze.c a28b43a5f79bfa7616ab506bb917077242098469
+F src/analyze.c 49b4bd45eb286d833793ed6bf72355a5c1974865
 F src/attach.c a52225c75b107be8c5bc144a2b6d20201be3f8f8
 F src/auth.c 083c1205b45e3f52291ec539d396b4fc557856b3
-F src/btmutex.c c04e67d99d949a12beb17209f307950f21313980
-F src/btree.c 7079a423e0da7eec5147d102202e2b51038002cd
-F src/btree.h 7391b9e78ae441fe0fb3a6d3ae772770d35a4375
+F src/btmutex.c abc2eda085ff7729c4093db8b4e5357e932f082c
+F src/btree.c ff821439edf1fdf85fee7cc7b475b02cacceb2ae
+F src/btree.h a90328ee4d7aa49a1ec4309c94a9fae65f39d969
 F src/btreeInt.h 1fa6510aa8601dc0358a5240d191335236d3cf76
 F src/build.c 830d1a6b2de157fc4d4dd08d4433066ad83f8b72
 F src/callback.c 77b302b0d41468dcda78c70e706e5b84577f0fa0
@@ -138,7 +138,7 @@ F src/table.c 1aeb9eab57b4235db86fe15a35dec76fb445a9c4
 F src/tclsqlite.c d76af53f45c9e9f7f7d39531fa4c7bee7d0adad6
 F src/test1.c 8b20d1f05777ac480d3caf8d5f79ab7a543513fc
 F src/test2.c 4ab230fbdc0decfa7422f6a052b609ba54f4dfac
-F src/test3.c de8f2a245d0adf4215487af8267c11ccca31e750
+F src/test3.c 09098991c3a94a1c7f54d28888fca2951d459585
 F src/test4.c c2c0f5dc907f1346f5d4b65eb5799f11eb9e4071
 F src/test5.c 3a6a5717a149d7ca2e6d14f5be72cf7555d54dc4
 F src/test6.c a6223d9d938aba83f20611a2c01680d8043cd2f7
@@ -166,8 +166,8 @@ F src/vdbe.c 9f2ef520614425016881234965b8146ac771d7dc
 F src/vdbe.h 498e9ddade4baf70f2fc39e585670131dde07caa
 F src/vdbeInt.h 630145b9bfaa19190ab491f52658a7db550f2247
 F src/vdbeapi.c 9c2d681b75e4b90c28b9dd01a3f2e5905267f884
-F src/vdbeaux.c 7cc1e0b33e4d5b8259fd12b7bd28c2180903146c
-F src/vdbeblob.c d12ed95dac0992e1e372d079d76af047cc42f7c7
+F src/vdbeaux.c 77db89679834d55ff026c6311c34d2964bf46431
+F src/vdbeblob.c 4da667be7dff5e197b3b986d6f2095cf97a22917
 F src/vdbefifo.c 334c838c8f42d61a94813d136019ee566b5dc2f6
 F src/vdbemem.c 246d434fa60bde6553490eb686adfd86adcd6712
 F src/vtab.c ace9b41a088f6ad55d2e39084d92180a2bee3276
@@ -182,7 +182,7 @@ F test/altermalloc.test b341e6515fa6cd9f0ac5d19153c556c9add70be9
 F test/analyze.test 2f55535aa335785db1a2f97d3f3831c16c09f8b0
 F test/async.test 464dc7c7ccb144e8c82ecca429e6d7cd1c96bd6e
 F test/async2.test 8f2c70b831dac7292450d0a42580cf2dab497dbb
-F test/attach.test cf289abdb120053136649efd1306ab9d47fa41b2
+F test/attach.test b849e1baae863c3a6132ff8b9b1baf356ab6c178
 F test/attach2.test 78bc1a25ea8785c7571b44f5947ada2bd5d78127
 F test/attach3.test eafcafb107585aecc2ed1569a77914138eef46a9
 F test/attachmalloc.test fdbfd9dc0b600db14f9189690c6c12511cc3a56f
@@ -567,7 +567,7 @@ F www/tclsqlite.tcl 8be95ee6dba05eabcd27a9d91331c803f2ce2130
 F www/vdbe.tcl 87a31ace769f20d3627a64fa1fade7fed47b90d0
 F www/version3.tcl 890248cf7b70e60c383b0e84d77d5132b3ead42b
 F www/whentouse.tcl fc46eae081251c3c181bd79c5faef8195d7991a5
-P d8ef7024172fffee049cfda6707220af2577e9a1
-R 02e243d6b7b8198a44d4e659876a4584
-U danielk1977
-Z e737eb1ddcb93155a8d9637fcf24015b
+P c790c234c369c6b7610e67dcaaa9eee347df729c
+R 673cf3ccb79c2542ccd493ed4a5e1538
+U drh
+Z a367643531757313c52ae724bb0d4a7f
diff --git a/manifest.uuid b/manifest.uuid
index cbab80841e..57297a0329 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-c790c234c369c6b7610e67dcaaa9eee347df729c
\ No newline at end of file
+2732af0ec77dbc90c0439b6a61d893d9ea3b5697
\ No newline at end of file
diff --git a/src/analyze.c b/src/analyze.c
index ae4b5ceb99..119e7f6484 100644
--- a/src/analyze.c
+++ b/src/analyze.c
@@ -11,7 +11,7 @@
 *************************************************************************
 ** This file contains code associated with the ANALYZE command.
 **
-** @(#) $Id: analyze.c,v 1.22 2007/08/29 04:00:58 drh Exp $
+** @(#) $Id: analyze.c,v 1.23 2007/08/29 17:43:20 drh Exp $
 */
 #ifndef SQLITE_OMIT_ANALYZE
 #include "sqliteInt.h"
@@ -386,7 +386,9 @@ int sqlite3AnalysisLoad(sqlite3 *db, int iDb){
   char *zSql;
   int rc;
 
-  assert( sqlite3BtreeHoldsAllMutexes(db) );
+  assert( iDb>=0 && iDb<db->nDb );
+  assert( db->aDb[iDb].pBt!=0 );
+  assert( sqlite3BtreeHoldsMutex(db->aDb[iDb].pBt) );
 
   /* Clear any prior statistics */
   for(i=sqliteHashFirst(&db->aDb[iDb].pSchema->idxHash);i;i=sqliteHashNext(i)){
diff --git a/src/btmutex.c b/src/btmutex.c
index 7df445770b..61644a8af8 100644
--- a/src/btmutex.c
+++ b/src/btmutex.c
@@ -10,7 +10,7 @@
 **
 *************************************************************************
 **
-** $Id: btmutex.c,v 1.5 2007/08/29 04:00:58 drh Exp $
+** $Id: btmutex.c,v 1.6 2007/08/29 17:43:20 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
@@ -111,18 +111,35 @@ void sqlite3BtreeLeave(Btree *p){
 
 #ifndef NDEBUG
 /*
-** Return true if a mutex is held on the btree.
+** Return true if the BtShared mutex is held on the btree.  
+**
+** This routine makes no determination one why or another if the
+** database connection mutex is held.
 **
 ** This routine is used only from within assert() statements.
 */
 int sqlite3BtreeHoldsMutex(Btree *p){
-  return sqlite3_mutex_held(p->pSqlite->mutex) && 
-         (p->sharable==0 ||
+  return (p->sharable==0 ||
              (p->locked && p->wantToLock && sqlite3_mutex_held(p->pBt->mutex)));
 }
 #endif
 
 
+#ifndef SQLITE_OMIT_INCRBLOB
+/*
+** Enter and leave a mutex on a Btree given a cursor owned by that
+** Btree.  These entry points are used by incremental I/O and can be
+** omitted if that module is not used.
+*/
+void sqlite3BtreeEnterCursor(BtCursor *pCur){
+  sqlite3BtreeEnter(pCur->pBtree);
+}
+void sqlite3BtreeLeaveCursor(BtCursor *pCur){
+  sqlite3BtreeLeave(pCur->pBtree);
+}
+#endif /* SQLITE_OMIT_INCRBLOB */
+
+
 /*
 ** Enter the mutex on every Btree associated with a database
 ** connection.  This is needed (for example) prior to parsing
diff --git a/src/btree.c b/src/btree.c
index 46553e5240..187998a3a9 100644
--- a/src/btree.c
+++ b/src/btree.c
@@ -9,7 +9,7 @@
 **    May you share freely, never taking more than you give.
 **
 *************************************************************************
-** $Id: btree.c,v 1.417 2007/08/29 12:31:26 danielk1977 Exp $
+** $Id: btree.c,v 1.418 2007/08/29 17:43:20 drh Exp $
 **
 ** This file implements a external (disk-based) database using BTrees.
 ** See the header comment on "btreeInt.h" for additional information.
@@ -236,7 +236,7 @@ static void releasePage(MemPage *pPage);  /* Forward reference */
 */
 #ifndef NDEBUG
 static int cursorHoldsMutex(BtCursor *p){
-  return sqlite3BtreeHoldsMutex(p->pBtree);
+  return sqlite3_mutex_held(p->pBt->mutex);
 }
 #endif
 
@@ -1150,32 +1150,43 @@ int sqlite3BtreeOpen(
    && isMemdb==0
    && (pSqlite->flags & SQLITE_Vtab)==0
    && zFilename && zFilename[0]
-   && sqlite3SharedCacheEnabled
   ){
-    char *zFullPathname = (char *)sqlite3_malloc(pVfs->mxPathname);
-    sqlite3_mutex *mutexShared;
-    p->sharable = 1;
-    if( pSqlite ){
-      pSqlite->flags |= SQLITE_SharedCache;
-    }
-    if( !zFullPathname ){
-      sqlite3_free(p);
-      return SQLITE_NOMEM;
-    }
-    sqlite3OsFullPathname(pVfs, zFilename, zFullPathname);
-    mutexShared = sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_MASTER);
-    sqlite3_mutex_enter(mutexShared);
-    for(pBt=sqlite3SharedCacheList; pBt; pBt=pBt->pNext){
-      assert( pBt->nRef>0 );
-      if( 0==strcmp(zFullPathname, sqlite3PagerFilename(pBt->pPager))
-               && sqlite3PagerVfs(pBt->pPager)==pVfs ){
-        p->pBt = pBt;
-        pBt->nRef++;
-        break;
+    if( sqlite3SharedCacheEnabled ){
+      char *zFullPathname = (char *)sqlite3_malloc(pVfs->mxPathname);
+      sqlite3_mutex *mutexShared;
+      p->sharable = 1;
+      if( pSqlite ){
+        pSqlite->flags |= SQLITE_SharedCache;
+      }
+      if( !zFullPathname ){
+        sqlite3_free(p);
+        return SQLITE_NOMEM;
       }
+      sqlite3OsFullPathname(pVfs, zFilename, zFullPathname);
+      mutexShared = sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_MASTER);
+      sqlite3_mutex_enter(mutexShared);
+      for(pBt=sqlite3SharedCacheList; pBt; pBt=pBt->pNext){
+        assert( pBt->nRef>0 );
+        if( 0==strcmp(zFullPathname, sqlite3PagerFilename(pBt->pPager))
+                 && sqlite3PagerVfs(pBt->pPager)==pVfs ){
+          p->pBt = pBt;
+          pBt->nRef++;
+          break;
+        }
+      }
+      sqlite3_mutex_leave(mutexShared);
+      sqlite3_free(zFullPathname);
     }
-    sqlite3_mutex_leave(mutexShared);
-    sqlite3_free(zFullPathname);
+#ifdef SQLITE_DEBUG
+    else{
+      /* In debug mode, we mark all persistent databases as sharable
+      ** even when they are not.  This exercises the locking code and
+      ** gives more opportunity for asserts(sqlite3_mutex_held())
+      ** statements to find locking problems.
+      */
+      p->sharable = 1;
+    }
+#endif
   }
 #endif
   if( pBt==0 ){
@@ -1253,6 +1264,11 @@ int sqlite3BtreeOpen(
       pBt->nRef = 1;
       mutexShared = sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_MASTER);
       pBt->mutex = sqlite3_mutex_alloc(SQLITE_MUTEX_FAST);
+      if( pBt->mutex==0 ){
+        rc = SQLITE_NOMEM;
+        pSqlite->mallocFailed = 0;
+        goto btree_open_out;
+      }
       sqlite3_mutex_enter(mutexShared);
       pBt->pNext = sqlite3SharedCacheList;
       sqlite3SharedCacheList = pBt;
@@ -2687,9 +2703,9 @@ int sqlite3BtreeCursor(
 */
 int sqlite3BtreeCloseCursor(BtCursor *pCur){
   BtShared *pBt = pCur->pBt;
+  Btree *pBtree = pCur->pBtree;
 
-  assert( cursorHoldsMutex(pCur) );
-  assert( sqlite3_mutex_held(pCur->pBtree->pSqlite->mutex) );
+  sqlite3BtreeEnter(pBtree);
   clearCursorPosition(pCur);
   if( pCur->pPrev ){
     pCur->pPrev->pNext = pCur->pNext;
@@ -2703,6 +2719,7 @@ int sqlite3BtreeCloseCursor(BtCursor *pCur){
   unlockBtreeIfUnused(pBt);
   invalidateOverflowCache(pCur);
   sqlite3_free(pCur);
+  sqlite3BtreeLeave(pBtree);
   return SQLITE_OK;
 }
 
@@ -6578,7 +6595,6 @@ char *sqlite3BtreeIntegrityCheck(
 */
 const char *sqlite3BtreeGetFilename(Btree *p){
   assert( p->pBt->pPager!=0 );
-  /* assert( sqlite3BtreeHoldsMutex(p) ); */
   return sqlite3PagerFilename(p->pBt->pPager);
 }
 
@@ -6590,7 +6606,6 @@ const char *sqlite3BtreeGetFilename(Btree *p){
 */
 const char *sqlite3BtreeGetDirname(Btree *p){
   assert( p->pBt->pPager!=0 );
-  assert( sqlite3BtreeHoldsMutex(p) );
   return sqlite3PagerDirname(p->pBt->pPager);
 }
 
@@ -6604,7 +6619,6 @@ const char *sqlite3BtreeGetDirname(Btree *p){
 */
 const char *sqlite3BtreeGetJournalname(Btree *p){
   assert( p->pBt->pPager!=0 );
-  assert( sqlite3BtreeHoldsMutex(p) );
   return sqlite3PagerJournalname(p->pBt->pPager);
 }
 
diff --git a/src/btree.h b/src/btree.h
index 6733daa506..032ce9f285 100644
--- a/src/btree.h
+++ b/src/btree.h
@@ -13,7 +13,7 @@
 ** subsystem.  See comments in the source code for a detailed description
 ** of what each interface routine does.
 **
-** @(#) $Id: btree.h,v 1.90 2007/08/29 04:00:58 drh Exp $
+** @(#) $Id: btree.h,v 1.91 2007/08/29 17:43:20 drh Exp $
 */
 #ifndef _BTREE_H_
 #define _BTREE_H_
@@ -176,6 +176,8 @@ int sqlite3BtreePageDump(Btree*, int, int recursive);
   void sqlite3BtreeEnter(Btree*);
   void sqlite3BtreeLeave(Btree*);
   int sqlite3BtreeHoldsMutex(Btree*);
+  void sqlite3BtreeEnterCursor(BtCursor*);
+  void sqlite3BtreeLeaveCursor(BtCursor*);
   void sqlite3BtreeEnterAll(sqlite3*);
   void sqlite3BtreeLeaveAll(sqlite3*);
   int sqlite3BtreeHoldsAllMutexes(sqlite3*);
@@ -186,6 +188,8 @@ int sqlite3BtreePageDump(Btree*, int, int recursive);
 # define sqlite3BtreeEnter(X)
 # define sqlite3BtreeLeave(X)
 # define sqlite3BtreeHoldsMutex(X) 1
+# define sqlite3BtreeEnterCursor(X)
+# define sqlite3BtreeLeaveCursor(X)
 # define sqlite3BtreeEnterAll(X)
 # define sqlite3BtreeLeaveAll(X)
 # define sqlite3BtreeHoldsAllMutexes(X) 1
diff --git a/src/test3.c b/src/test3.c
index d35efaab46..f132db9e8e 100644
--- a/src/test3.c
+++ b/src/test3.c
@@ -13,7 +13,7 @@
 ** is not included in the SQLite library.  It is used for automated
 ** testing of the SQLite library.
 **
-** $Id: test3.c,v 1.83 2007/08/29 12:31:28 danielk1977 Exp $
+** $Id: test3.c,v 1.84 2007/08/29 17:43:20 drh Exp $
 */
 #include "sqliteInt.h"
 #include "btreeInt.h"
@@ -146,7 +146,9 @@ static int btree_begin_transaction(
     return TCL_ERROR;
   }
   pBt = sqlite3TextToPtr(argv[1]);
+  sqlite3BtreeEnter(pBt);
   rc = sqlite3BtreeBeginTrans(pBt, 1);
+  sqlite3BtreeLeave(pBt);
   if( rc!=SQLITE_OK ){
     Tcl_AppendResult(interp, errorName(rc), 0);
     return TCL_ERROR;
@@ -173,7 +175,9 @@ static int btree_rollback(
     return TCL_ERROR;
   }
   pBt = sqlite3TextToPtr(argv[1]);
+  sqlite3BtreeEnter(pBt);
   rc = sqlite3BtreeRollback(pBt);
+  sqlite3BtreeLeave(pBt);
   if( rc!=SQLITE_OK ){
     Tcl_AppendResult(interp, errorName(rc), 0);
     return TCL_ERROR;
@@ -200,7 +204,9 @@ static int btree_commit(
     return TCL_ERROR;
   }
   pBt = sqlite3TextToPtr(argv[1]);
+  sqlite3BtreeEnter(pBt);
   rc = sqlite3BtreeCommit(pBt);
+  sqlite3BtreeLeave(pBt);
   if( rc!=SQLITE_OK ){
     Tcl_AppendResult(interp, errorName(rc), 0);
     return TCL_ERROR;
@@ -227,7 +233,9 @@ static int btree_begin_statement(
     return TCL_ERROR;
   }
   pBt = sqlite3TextToPtr(argv[1]);
+  sqlite3BtreeEnter(pBt);
   rc = sqlite3BtreeBeginStmt(pBt);
+  sqlite3BtreeLeave(pBt);
   if( rc!=SQLITE_OK ){
     Tcl_AppendResult(interp, errorName(rc), 0);
     return TCL_ERROR;
@@ -254,7 +262,9 @@ static int btree_rollback_statement(
     return TCL_ERROR;
   }
   pBt = sqlite3TextToPtr(argv[1]);
+  sqlite3BtreeEnter(pBt);
   rc = sqlite3BtreeRollbackStmt(pBt);
+  sqlite3BtreeLeave(pBt);
   if( rc!=SQLITE_OK ){
     Tcl_AppendResult(interp, errorName(rc), 0);
     return TCL_ERROR;
@@ -281,7 +291,9 @@ static int btree_commit_statement(
     return TCL_ERROR;
   }
   pBt = sqlite3TextToPtr(argv[1]);
+  sqlite3BtreeEnter(pBt);
   rc = sqlite3BtreeCommitStmt(pBt);
+  sqlite3BtreeLeave(pBt);
   if( rc!=SQLITE_OK ){
     Tcl_AppendResult(interp, errorName(rc), 0);
     return TCL_ERROR;
@@ -310,7 +322,9 @@ static int btree_create_table(
   }
   pBt = sqlite3TextToPtr(argv[1]);
   if( Tcl_GetInt(interp, argv[2], &flags) ) return TCL_ERROR;
+  sqlite3BtreeEnter(pBt);
   rc = sqlite3BtreeCreateTable(pBt, &iTable, flags);
+  sqlite3BtreeLeave(pBt);
   if( rc!=SQLITE_OK ){
     Tcl_AppendResult(interp, errorName(rc), 0);
     return TCL_ERROR;
@@ -342,7 +356,9 @@ static int btree_drop_table(
   }
   pBt = sqlite3TextToPtr(argv[1]);
   if( Tcl_GetInt(interp, argv[2], &iTable) ) return TCL_ERROR;
+  sqlite3BtreeEnter(pBt);
   rc = sqlite3BtreeDropTable(pBt, iTable, &notUsed1);
+  sqlite3BtreeLeave(pBt);
   if( rc!=SQLITE_OK ){
     Tcl_AppendResult(interp, errorName(rc), 0);
     return TCL_ERROR;
@@ -371,7 +387,9 @@ static int btree_clear_table(
   }
   pBt = sqlite3TextToPtr(argv[1]);
   if( Tcl_GetInt(interp, argv[2], &iTable) ) return TCL_ERROR;
+  sqlite3BtreeEnter(pBt);
   rc = sqlite3BtreeClearTable(pBt, iTable);
+  sqlite3BtreeLeave(pBt);
   if( rc!=SQLITE_OK ){
     Tcl_AppendResult(interp, errorName(rc), 0);
     return TCL_ERROR;
@@ -402,7 +420,9 @@ static int btree_get_meta(
   for(i=0; i<SQLITE_N_BTREE_META; i++){
     char zBuf[30];
     unsigned int v;
+    sqlite3BtreeEnter(pBt);
     rc = sqlite3BtreeGetMeta(pBt, i, &v);
+    sqlite3BtreeLeave(pBt);
     if( rc!=SQLITE_OK ){
       Tcl_AppendResult(interp, errorName(rc), 0);
       return TCL_ERROR;
@@ -441,7 +461,9 @@ static int btree_update_meta(
     if( Tcl_GetInt(interp, argv[i+2], &aMeta[i]) ) return TCL_ERROR;
   }
   for(i=1; i<SQLITE_N_BTREE_META; i++){
+    sqlite3BtreeEnter(pBt);
     rc = sqlite3BtreeUpdateMeta(pBt, i, aMeta[i]);
+    sqlite3BtreeLeave(pBt);
     if( rc!=SQLITE_OK ){
       Tcl_AppendResult(interp, errorName(rc), 0);
       return TCL_ERROR;
@@ -472,7 +494,9 @@ static int btree_page_dump(
   }
   pBt = sqlite3TextToPtr(argv[1]);
   if( Tcl_GetInt(interp, argv[2], &iPage) ) return TCL_ERROR;
+  sqlite3BtreeEnter(pBt);
   rc = sqlite3BtreePageDump(pBt, iPage, 0);
+  sqlite3BtreeLeave(pBt);
   if( rc!=SQLITE_OK ){
     Tcl_AppendResult(interp, errorName(rc), 0);
     return TCL_ERROR;
@@ -502,7 +526,9 @@ static int btree_tree_dump(
   }
   pBt = sqlite3TextToPtr(argv[1]);
   if( Tcl_GetInt(interp, argv[2], &iPage) ) return TCL_ERROR;
+  sqlite3BtreeEnter(pBt);
   rc = sqlite3BtreePageDump(pBt, iPage, 1);
+  sqlite3BtreeLeave(pBt);
   if( rc!=SQLITE_OK ){
     Tcl_AppendResult(interp, errorName(rc), 0);
     return TCL_ERROR;
@@ -531,7 +557,6 @@ static int btree_pager_stats(
     return TCL_ERROR;
   }
   pBt = sqlite3TextToPtr(argv[1]);
-  sqlite3_mutex_enter(pBt->pSqlite->mutex);
   sqlite3BtreeEnter(pBt);
   a = sqlite3PagerStats(sqlite3BtreePager(pBt));
   for(i=0; i<11; i++){
@@ -545,7 +570,6 @@ static int btree_pager_stats(
     Tcl_AppendElement(interp, zBuf);
   }
   sqlite3BtreeLeave(pBt);
-  sqlite3_mutex_leave(pBt->pSqlite->mutex);
   return TCL_OK;
 }
 
@@ -569,7 +593,9 @@ static int btree_pager_ref_dump(
   }
   pBt = sqlite3TextToPtr(argv[1]);
 #ifdef SQLITE_DEBUG
+  sqlite3BtreeEnter(pBt);
   sqlite3PagerRefdump(sqlite3BtreePager(pBt));
+  sqlite3BtreeLeave(pBt);
 #endif
   return TCL_OK;
 }
@@ -606,7 +632,9 @@ static int btree_integrity_check(
     if( Tcl_GetInt(interp, argv[i+2], &aRoot[i]) ) return TCL_ERROR;
   }
 #ifndef SQLITE_OMIT_INTEGRITY_CHECK
+  sqlite3BtreeEnter(pBt);
   zResult = sqlite3BtreeIntegrityCheck(pBt, aRoot, nRoot, 10000, &nErr);
+  sqlite3BtreeLeave(pBt);
 #else
   zResult = 0;
 #endif
@@ -637,7 +665,9 @@ static int btree_cursor_list(
     return TCL_ERROR;
   }
   pBt = sqlite3TextToPtr(argv[1]);
+  sqlite3BtreeEnter(pBt);
   sqlite3BtreeCursorList(pBt);
+  sqlite3BtreeLeave(pBt);
   return SQLITE_OK;
 }
 
@@ -667,7 +697,9 @@ static int btree_cursor(
   pBt = sqlite3TextToPtr(argv[1]);
   if( Tcl_GetInt(interp, argv[2], &iTable) ) return TCL_ERROR;
   if( Tcl_GetBoolean(interp, argv[3], &wrFlag) ) return TCL_ERROR;
+  sqlite3BtreeEnter(pBt);
   rc = sqlite3BtreeCursor(pBt, iTable, wrFlag, 0, 0, &pCur);
+  sqlite3BtreeLeave(pBt);
   if( rc ){
     Tcl_AppendResult(interp, errorName(rc), 0);
     return TCL_ERROR;
@@ -689,6 +721,7 @@ static int btree_close_cursor(
   const char **argv      /* Text of each argument */
 ){
   BtCursor *pCur;
+  Btree *pBt;
   int rc;
 
   if( argc!=2 ){
@@ -697,7 +730,10 @@ static int btree_close_cursor(
     return TCL_ERROR;
   }
   pCur = sqlite3TextToPtr(argv[1]);
+  pBt = pCur->pBtree;
+  sqlite3BtreeEnter(pBt);
   rc = sqlite3BtreeCloseCursor(pCur);
+  sqlite3BtreeLeave(pBt);
   if( rc ){
     Tcl_AppendResult(interp, errorName(rc), 0);
     return TCL_ERROR;
@@ -727,13 +763,18 @@ static int btree_move_to(
     return TCL_ERROR;
   }
   pCur = sqlite3TextToPtr(argv[1]);
+  sqlite3BtreeEnter(pCur->pBtree);
   if( sqlite3BtreeFlags(pCur) & BTREE_INTKEY ){
     int iKey;
-    if( Tcl_GetInt(interp, argv[2], &iKey) ) return TCL_ERROR;
+    if( Tcl_GetInt(interp, argv[2], &iKey) ){
+      sqlite3BtreeLeave(pCur->pBtree);
+      return TCL_ERROR;
+    }
     rc = sqlite3BtreeMoveto(pCur, 0, iKey, 0, &res);
   }else{
     rc = sqlite3BtreeMoveto(pCur, argv[2], strlen(argv[2]), 0, &res);  
   }
+  sqlite3BtreeLeave(pCur->pBtree);
   if( rc ){
     Tcl_AppendResult(interp, errorName(rc), 0);
     return TCL_ERROR;
@@ -765,7 +806,9 @@ static int btree_delete(
     return TCL_ERROR;
   }
   pCur = sqlite3TextToPtr(argv[1]);
+  sqlite3BtreeEnter(pCur->pBtree);
   rc = sqlite3BtreeDelete(pCur);
+  sqlite3BtreeLeave(pCur->pBtree);
   if( rc ){
     Tcl_AppendResult(interp, errorName(rc), 0);
     return TCL_ERROR;
@@ -799,11 +842,15 @@ static int btree_insert(
   }else{
     nZero = 0;
   }
+  sqlite3BtreeEnter(pCur->pBtree);
   if( sqlite3BtreeFlags(pCur) & BTREE_INTKEY ){
     i64 iKey;
     int len;
     unsigned char *pBuf;
-    if( Tcl_GetWideIntFromObj(interp, objv[2], &iKey) ) return TCL_ERROR;
+    if( Tcl_GetWideIntFromObj(interp, objv[2], &iKey) ){
+      sqlite3BtreeLeave(pCur->pBtree);
+      return TCL_ERROR;
+    }
     pBuf = Tcl_GetByteArrayFromObj(objv[3], &len);
     rc = sqlite3BtreeInsert(pCur, 0, iKey, pBuf, len, nZero, 0);
   }else{
@@ -815,6 +862,7 @@ static int btree_insert(
     pDBuf = Tcl_GetByteArrayFromObj(objv[3], &dlen);
     rc = sqlite3BtreeInsert(pCur, pKBuf, keylen, pDBuf, dlen, nZero, 0);
   }
+  sqlite3BtreeLeave(pCur->pBtree);
   if( rc ){
     Tcl_AppendResult(interp, errorName(rc), 0);
     return TCL_ERROR;
@@ -846,7 +894,9 @@ static int btree_next(
     return TCL_ERROR;
   }
   pCur = sqlite3TextToPtr(argv[1]);
+  sqlite3BtreeEnter(pCur->pBtree);
   rc = sqlite3BtreeNext(pCur, &res);
+  sqlite3BtreeLeave(pCur->pBtree);
   if( rc ){
     Tcl_AppendResult(interp, errorName(rc), 0);
     return TCL_ERROR;
@@ -880,7 +930,9 @@ static int btree_prev(
     return TCL_ERROR;
   }
   pCur = sqlite3TextToPtr(argv[1]);
+  sqlite3BtreeEnter(pCur->pBtree);
   rc = sqlite3BtreePrevious(pCur, &res);
+  sqlite3BtreeLeave(pCur->pBtree);
   if( rc ){
     Tcl_AppendResult(interp, errorName(rc), 0);
     return TCL_ERROR;
@@ -913,7 +965,9 @@ static int btree_first(
     return TCL_ERROR;
   }
   pCur = sqlite3TextToPtr(argv[1]);
+  sqlite3BtreeEnter(pCur->pBtree);
   rc = sqlite3BtreeFirst(pCur, &res);
+  sqlite3BtreeLeave(pCur->pBtree);
   if( rc ){
     Tcl_AppendResult(interp, errorName(rc), 0);
     return TCL_ERROR;
@@ -946,7 +1000,9 @@ static int btree_last(
     return TCL_ERROR;
   }
   pCur = sqlite3TextToPtr(argv[1]);
+  sqlite3BtreeEnter(pCur->pBtree);
   rc = sqlite3BtreeLast(pCur, &res);
+  sqlite3BtreeLeave(pCur->pBtree);
   if( rc ){
     Tcl_AppendResult(interp, errorName(rc), 0);
     return TCL_ERROR;
@@ -969,6 +1025,7 @@ static int btree_eof(
   const char **argv      /* Text of each argument */
 ){
   BtCursor *pCur;
+  int rc;
   char zBuf[50];
 
   if( argc!=2 ){
@@ -977,7 +1034,10 @@ static int btree_eof(
     return TCL_ERROR;
   }
   pCur = sqlite3TextToPtr(argv[1]);
-  sqlite3_snprintf(sizeof(zBuf),zBuf, "%d", sqlite3BtreeEof(pCur));
+  sqlite3BtreeEnter(pCur->pBtree);
+  rc = sqlite3BtreeEof(pCur);
+  sqlite3BtreeLeave(pCur->pBtree);
+  sqlite3_snprintf(sizeof(zBuf),zBuf, "%d", rc);
   Tcl_AppendResult(interp, zBuf, 0);
   return SQLITE_OK;
 }
@@ -1004,7 +1064,9 @@ static int btree_keysize(
     return TCL_ERROR;
   }
   pCur = sqlite3TextToPtr(argv[1]);
+  sqlite3BtreeEnter(pCur->pBtree);
   sqlite3BtreeKeySize(pCur, (i64*)&n);
+  sqlite3BtreeLeave(pCur->pBtree);
   sqlite3_snprintf(sizeof(zBuf),zBuf, "%llu", n);
   Tcl_AppendResult(interp, zBuf, 0);
   return SQLITE_OK;
@@ -1032,6 +1094,7 @@ static int btree_key(
     return TCL_ERROR;
   }
   pCur = sqlite3TextToPtr(argv[1]);
+  sqlite3BtreeEnter(pCur->pBtree);
   sqlite3BtreeKeySize(pCur, (i64*)&n);
   if( sqlite3BtreeFlags(pCur) & BTREE_INTKEY ){
     char zBuf2[60];
@@ -1041,6 +1104,7 @@ static int btree_key(
     zBuf = sqlite3_malloc( n+1 );
     rc = sqlite3BtreeKey(pCur, 0, n, zBuf);
     if( rc ){
+      sqlite3BtreeLeave(pCur->pBtree);
       Tcl_AppendResult(interp, errorName(rc), 0);
       return TCL_ERROR;
     }
@@ -1048,6 +1112,7 @@ static int btree_key(
     Tcl_AppendResult(interp, zBuf, 0);
     sqlite3_free(zBuf);
   }
+  sqlite3BtreeLeave(pCur->pBtree);
   return SQLITE_OK;
 }
 
@@ -1073,6 +1138,7 @@ static int btree_data(
     return TCL_ERROR;
   }
   pCur = sqlite3TextToPtr(argv[1]);
+  sqlite3BtreeEnter(pCur->pBtree);
   if( argc==2 ){
     sqlite3BtreeDataSize(pCur, &n);
   }else{
@@ -1080,6 +1146,7 @@ static int btree_data(
   }
   zBuf = sqlite3_malloc( n+1 );
   rc = sqlite3BtreeData(pCur, 0, n, zBuf);
+  sqlite3BtreeLeave(pCur->pBtree);
   if( rc ){
     Tcl_AppendResult(interp, errorName(rc), 0);
     sqlite3_free(zBuf);
@@ -1117,6 +1184,7 @@ static int btree_fetch_key(
   }
   pCur = sqlite3TextToPtr(argv[1]);
   if( Tcl_GetInt(interp, argv[2], &n) ) return TCL_ERROR;
+  sqlite3BtreeEnter(pCur->pBtree);
   sqlite3BtreeKeySize(pCur, (i64*)&nKey);
   zBuf = sqlite3BtreeKeyFetch(pCur, &amt);
   if( zBuf && amt>=n ){
@@ -1126,6 +1194,7 @@ static int btree_fetch_key(
     zStatic[nKey] = 0;
     Tcl_AppendResult(interp, zStatic, 0);
   }
+  sqlite3BtreeLeave(pCur->pBtree);
   return TCL_OK;
 }
 
@@ -1155,6 +1224,7 @@ static int btree_fetch_data(
   }
   pCur = sqlite3TextToPtr(argv[1]);
   if( Tcl_GetInt(interp, argv[2], &n) ) return TCL_ERROR;
+  sqlite3BtreeEnter(pCur->pBtree);
   sqlite3BtreeDataSize(pCur, &nData);
   zBuf = sqlite3BtreeDataFetch(pCur, &amt);
   if( zBuf && amt>=n ){
@@ -1164,6 +1234,7 @@ static int btree_fetch_data(
     zStatic[nData] = 0;
     Tcl_AppendResult(interp, zStatic, 0);
   }
+  sqlite3BtreeLeave(pCur->pBtree);
   return TCL_OK;
 }
 
@@ -1189,12 +1260,14 @@ static int btree_payload_size(
     return TCL_ERROR;
   }
   pCur = sqlite3TextToPtr(argv[1]);
+  sqlite3BtreeEnter(pCur->pBtree);
   if( sqlite3BtreeFlags(pCur) & BTREE_INTKEY ){
     n1 = 0;
   }else{
     sqlite3BtreeKeySize(pCur, (i64*)&n1);
   }
   sqlite3BtreeDataSize(pCur, (u32*)&n2);
+  sqlite3BtreeLeave(pCur->pBtree);
   sqlite3_snprintf(sizeof(zBuf),zBuf, "%d", (int)(n1+n2));
   Tcl_AppendResult(interp, zBuf, 0);
   return SQLITE_OK;
@@ -1242,9 +1315,11 @@ static int btree_cursor_info(
   }else{
     up = 0;
   }
+  sqlite3BtreeEnter(pCur->pBtree);
   rc = sqlite3BtreeCursorInfo(pCur, aResult, up);
   if( rc ){
     Tcl_AppendResult(interp, errorName(rc), 0);
+    sqlite3BtreeLeave(pCur->pBtree);
     return TCL_ERROR;
   }
   j = 0;
@@ -1252,6 +1327,7 @@ static int btree_cursor_info(
     sqlite3_snprintf(40,&zBuf[j]," %d", aResult[i]);
     j += strlen(&zBuf[j]);
   }
+  sqlite3BtreeLeave(pCur->pBtree);
   Tcl_AppendResult(interp, &zBuf[1], 0);
   return SQLITE_OK;
 }
@@ -1300,10 +1376,12 @@ static int btree_ovfl_info(
        argv[1], 0);
     return TCL_ERROR;
   }
+  sqlite3BtreeEnter(pBt);
   pPager = sqlite3BtreePager(pBt);
   rc = sqlite3BtreeCursorInfo(pCur, aResult, 0);
   if( rc ){
     Tcl_AppendResult(interp, errorName(rc), 0);
+    sqlite3BtreeLeave(pBt);
     return TCL_ERROR;
   }
   dataSize = sqlite3BtreeGetPageSize(pBt) - sqlite3BtreeGetReserve(pBt);
@@ -1318,12 +1396,14 @@ static int btree_ovfl_info(
     if( sqlite3PagerGet(pPager, pgno, &pDbPage)!=SQLITE_OK ){
       Tcl_DStringFree(&str);
       Tcl_AppendResult(interp, "unable to get page ", zElem, 0);
+      sqlite3BtreeLeave(pBt);
       return TCL_ERROR;
     }
     pPage = sqlite3PagerGetData(pDbPage);
     pgno = t4Get4byte((unsigned char*)pPage);
     sqlite3PagerUnref(pDbPage);
   }
+  sqlite3BtreeLeave(pBt);
   Tcl_DStringResult(interp, &str);
   return SQLITE_OK;
 }
@@ -1498,7 +1578,9 @@ static int btree_set_cache_size(
   if( Tcl_GetInt(interp, argv[2], &nCache) ) return TCL_ERROR;
 
   sqlite3_mutex_enter(pBt->pSqlite->mutex);
+  sqlite3BtreeEnter(pBt);
   sqlite3BtreeSetCacheSize(pBt, nCache);
+  sqlite3BtreeLeave(pBt);
   sqlite3_mutex_leave(pBt->pSqlite->mutex);
 
   return TCL_OK;
diff --git a/src/vdbeaux.c b/src/vdbeaux.c
index 55cb88ab36..b0dd09ee9d 100644
--- a/src/vdbeaux.c
+++ b/src/vdbeaux.c
@@ -936,7 +936,7 @@ void sqlite3VdbeMakeReady(
 }
 
 /*
-** Close a cursor and release all the resources that cursor happens
+** Close a VDBE cursor and release all the resources that cursor happens
 ** to hold.
 */
 void sqlite3VdbeFreeCursor(Vdbe *p, Cursor *pCx){
@@ -966,14 +966,16 @@ void sqlite3VdbeFreeCursor(Vdbe *p, Cursor *pCx){
 }
 
 /*
-** Close all cursors
+** Close all cursors except for VTab cursors that are currently
+** in use.
 */
-static void closeAllCursors(Vdbe *p){
+static void closeAllCursorsExceptActiveVtabs(Vdbe *p){
   int i;
   if( p->apCsr==0 ) return;
   for(i=0; i<p->nCursor; i++){
-    if( !p->inVtabMethod || (p->apCsr[i] && !p->apCsr[i]->pVtabCursor) ){
-      sqlite3VdbeFreeCursor(p, p->apCsr[i]);
+    Cursor *pC = p->apCsr[i];
+    if( pC && (!p->inVtabMethod || !pC->pVtabCursor) ){
+      sqlite3VdbeFreeCursor(p, pC);
       p->apCsr[i] = 0;
     }
   }
@@ -992,7 +994,7 @@ static void Cleanup(Vdbe *p){
     releaseMemArray(p->aStack, 1 + (p->pTos - p->aStack));
     p->pTos = &p->aStack[-1];
   }
-  closeAllCursors(p);
+  closeAllCursorsExceptActiveVtabs(p);
   releaseMemArray(p->aMem, p->nMem);
   sqlite3VdbeFifoClear(&p->sFifo);
   if( p->contextStack ){
@@ -1311,7 +1313,7 @@ void sqlite3AbortOtherActiveVdbes(sqlite3 *db, Vdbe *pExcept){
     if( pOther==pExcept ) continue;
     if( pOther->magic!=VDBE_MAGIC_RUN || pOther->pc<0 ) continue;
     checkActiveVdbeCnt(db);
-    closeAllCursors(pOther);
+    closeAllCursorsExceptActiveVtabs(pOther);
     checkActiveVdbeCnt(db);
     pOther->aborted = 1;
   }
@@ -1323,13 +1325,14 @@ void sqlite3AbortOtherActiveVdbes(sqlite3 *db, Vdbe *pExcept){
 ** changes.  If a rollback is needed, then do the rollback.
 **
 ** This routine is the only way to move the state of a VM from
-** SQLITE_MAGIC_RUN to SQLITE_MAGIC_HALT.
+** SQLITE_MAGIC_RUN to SQLITE_MAGIC_HALT.  It is harmless to
+** call this on a VM that is in the SQLITE_MAGIC_HALT state.
 **
 ** Return an error code.  If the commit could not complete because of
 ** lock contention, return SQLITE_BUSY.  If SQLITE_BUSY is returned, it
 ** means the close did not happen and needs to be repeated.
 */
-static int sqlite3VdbeHaltLocked(Vdbe *p){
+int sqlite3VdbeHalt(Vdbe *p){
   sqlite3 *db = p->db;
   int i;
   int (*xFunc)(Btree *pBt) = 0;  /* Function to call on each btree backend */
@@ -1366,20 +1369,19 @@ static int sqlite3VdbeHaltLocked(Vdbe *p){
   if( p->db->mallocFailed ){
     p->rc = SQLITE_NOMEM;
   }
+  closeAllCursorsExceptActiveVtabs(p);
   if( p->magic!=VDBE_MAGIC_RUN ){
-    /* Already halted.  Nothing to do. */
-    assert( p->magic==VDBE_MAGIC_HALT );
-#ifndef SQLITE_OMIT_VIRTUALTABLE
-    closeAllCursors(p);
-#endif
     return SQLITE_OK;
   }
-  closeAllCursors(p);
   checkActiveVdbeCnt(db);
 
   /* No commit or rollback needed if the program never started */
   if( p->pc>=0 ){
     int mrc;   /* Primary error code from p->rc */
+
+    /* Lock all btrees used by the statement */
+    sqlite3BtreeMutexArrayEnter(&p->aMutex);
+
     /* Check for one of the special errors - SQLITE_NOMEM or SQLITE_IOERR */
     mrc = p->rc & 0xff;
     isSpecialError = (
@@ -1423,7 +1425,8 @@ static int sqlite3VdbeHaltLocked(Vdbe *p){
             break;
         }
       }
-  
+
+   
       /* If the query was read-only, we need do no rollback at all. Otherwise,
       ** proceed with the special handling.
       */
@@ -1458,6 +1461,7 @@ static int sqlite3VdbeHaltLocked(Vdbe *p){
         */
         int rc = vdbeCommit(db);
         if( rc==SQLITE_BUSY ){
+          sqlite3BtreeMutexArrayLeave(&p->aMutex);
           return SQLITE_BUSY;
         }else if( rc!=SQLITE_OK ){
           p->rc = rc;
@@ -1520,6 +1524,9 @@ static int sqlite3VdbeHaltLocked(Vdbe *p){
       sqlite3ResetInternalSchema(db, 0);
       db->flags = (db->flags | SQLITE_InternChanges);
     }
+
+    /* Release the locks */
+    sqlite3BtreeMutexArrayLeave(&p->aMutex);
   }
 
   /* We have successfully halted and closed the VM.  Record this fact. */
@@ -1528,16 +1535,13 @@ static int sqlite3VdbeHaltLocked(Vdbe *p){
   }
   p->magic = VDBE_MAGIC_HALT;
   checkActiveVdbeCnt(db);
+  if( p->db->mallocFailed ){
+    p->rc = SQLITE_NOMEM;
+  }
+  checkActiveVdbeCnt(db);
 
   return SQLITE_OK;
 }
-int sqlite3VdbeHalt(Vdbe *p){
-  int rc;
-  sqlite3BtreeMutexArrayEnter(&p->aMutex);
-  rc = sqlite3VdbeHaltLocked(p);
-  sqlite3BtreeMutexArrayLeave(&p->aMutex);
-  return rc;
-}
 
 
 /*
diff --git a/src/vdbeblob.c b/src/vdbeblob.c
index 6acbe40232..161242db5b 100644
--- a/src/vdbeblob.c
+++ b/src/vdbeblob.c
@@ -12,7 +12,7 @@
 **
 ** This file contains code used to implement incremental BLOB I/O.
 **
-** $Id: vdbeblob.c,v 1.14 2007/08/21 19:33:57 drh Exp $
+** $Id: vdbeblob.c,v 1.15 2007/08/29 17:43:20 drh Exp $
 */
 
 #include "sqliteInt.h"
@@ -102,6 +102,7 @@ int sqlite3_blob_open(
       return rc;
     }
 
+    sqlite3BtreeEnterAll(db);
     pTab = sqlite3LocateTable(&sParse, zTable, zDb);
     if( !pTab ){
       if( sParse.zErrMsg ){
@@ -110,6 +111,7 @@ int sqlite3_blob_open(
       sqlite3_free(sParse.zErrMsg);
       rc = SQLITE_ERROR;
       sqlite3SafetyOff(db);
+      sqlite3BtreeLeaveAll(db);
       goto blob_open_out;
     }
 
@@ -123,6 +125,7 @@ int sqlite3_blob_open(
       sqlite3_snprintf(sizeof(zErr), zErr, "no such column: \"%s\"", zColumn);
       rc = SQLITE_ERROR;
       sqlite3SafetyOff(db);
+      sqlite3BtreeLeaveAll(db);
       goto blob_open_out;
     }
 
@@ -140,6 +143,7 @@ int sqlite3_blob_open(
                              "cannot open indexed column for writing");
             rc = SQLITE_ERROR;
             sqlite3SafetyOff(db);
+            sqlite3BtreeLeaveAll(db);
             goto blob_open_out;
           }
         }
@@ -159,6 +163,9 @@ int sqlite3_blob_open(
       sqlite3VdbeChangeP1(v, 1, iDb);
       sqlite3VdbeChangeP2(v, 1, pTab->pSchema->schema_cookie);
 
+      /* Make sure a mutex is held on the table to be accessed */
+      sqlite3VdbeUsesBtree(v, iDb, db->aDb[iDb].pBt); 
+
       /* Configure the db number pushed onto the stack */
       sqlite3VdbeChangeP1(v, 2, iDb);
 
@@ -180,7 +187,8 @@ int sqlite3_blob_open(
         sqlite3VdbeMakeReady(v, 1, 0, 1, 0);
       }
     }
-
+   
+    sqlite3BtreeLeaveAll(db);
     rc = sqlite3SafetyOff(db);
     if( rc!=SQLITE_OK || db->mallocFailed ){
       goto blob_open_out;
@@ -218,7 +226,9 @@ int sqlite3_blob_open(
     }
     pBlob->flags = flags;
     pBlob->pCsr =  v->apCsr[0]->pCursor;
+    sqlite3BtreeEnterCursor(pBlob->pCsr);
     sqlite3BtreeCacheOverflow(pBlob->pCsr);
+    sqlite3BtreeLeaveCursor(pBlob->pCsr);
     pBlob->pStmt = (sqlite3_stmt *)v;
     pBlob->iOffset = v->apCsr[0]->aOffset[iCol];
     pBlob->nByte = sqlite3VdbeSerialTypeLen(type);
@@ -247,12 +257,9 @@ blob_open_out:
 */
 int sqlite3_blob_close(sqlite3_blob *pBlob){
   Incrblob *p = (Incrblob *)pBlob;
-  sqlite3_mutex *mutex = p->db->mutex;
   int rc;
 
-  sqlite3_mutex_enter(mutex);
   rc = sqlite3_finalize(p->pStmt);
-  sqlite3_mutex_leave(mutex);
   sqlite3_free(p);
   return rc;
 }
@@ -289,7 +296,9 @@ static int blobReadWrite(
     ** returned, clean-up the statement handle.
     */
     assert( db == v->db );
+    sqlite3BtreeEnterCursor(p->pCsr);
     rc = xCall(p->pCsr, iOffset+p->iOffset, n, z);
+    sqlite3BtreeLeaveCursor(p->pCsr);
     if( rc==SQLITE_ABORT ){
       sqlite3VdbeFinalize(v);
       p->pStmt = 0;
diff --git a/test/attach.test b/test/attach.test
index b0b7870b3d..af712d04c5 100644
--- a/test/attach.test
+++ b/test/attach.test
@@ -12,7 +12,7 @@
 # focus of this script is testing the ATTACH and DETACH commands
 # and related functionality.
 #
-# $Id: attach.test,v 1.44 2007/05/09 20:31:30 drh Exp $
+# $Id: attach.test,v 1.45 2007/08/29 17:43:20 drh Exp $
 #
 
 set testdir [file dirname $argv0]
@@ -53,6 +53,7 @@ do_test attach-1.4 {
   }
 } {1 x 2 y}
 do_test attach-1.5 {
+btree_breakpoint
   execsql {
     DETACH DATABASE two;
     SELECT * FROM t1;