Bug fix in BTree shared cache locking code. (CVS 4246)

FossilOrigin-Name: 399d3e755253a7b4604a62b9f171e0f1154134e2

manifest

@@ -1,5 +1,5 @@
-C Get\smain.c\sto\scompile\swhen\sHAVE_USLEEP\sis\s0.\s(CVS\s4245)
-D 2007-08-20T11:12:41
+C Bug\sfix\sin\sBTree\sshared\scache\slocking\scode.\s(CVS\s4246)
+D 2007-08-20T13:14:29
 F Makefile.in 0c0e53720f658c7a551046442dd7afba0b72bfbe
 F Makefile.linux-gcc 65241babba6faf1152bf86574477baab19190499
 F README 9c4e2d6706bdcc3efdd773ce752a8cdab4f90028
@@ -68,9 +68,9 @@ F src/alter.c f0aac0060ae8102e58f210b44d35b53438d53173
 F src/analyze.c a14237d869c6bea0846493b59317e4097e81a0b6
 F src/attach.c a52225c75b107be8c5bc144a2b6d20201be3f8f8
 F src/auth.c 5ea90bc93dfea46e9fe4bf531e14c7cd98219ecb
-F src/btree.c f00ed30c442b4934d042af84e065498c542d21aa
+F src/btree.c f8a04f35eb81360773899983f7c2008145e13935
 F src/btree.h 91ee529d581c1473d8e6e15299acc3b8de1d0674
-F src/btreeInt.h 6329e955a7dadd8628d5866e2465721b5fd25ef2
+F src/btreeInt.h 9b4ca8999e52f713420e5f297dd86887a7a9820f
 F src/build.c add67be992307b4b11849a6611bfd3352aacde92
 F src/callback.c 143436453bb93e831c9574fea0b9b9eb90e40ff3
 F src/complete.c ea63834e798a0ab14159bdc6e6cabc3df21aa346
@@ -529,7 +529,7 @@ F www/tclsqlite.tcl 8be95ee6dba05eabcd27a9d91331c803f2ce2130
 F www/vdbe.tcl 87a31ace769f20d3627a64fa1fade7fed47b90d0
 F www/version3.tcl 890248cf7b70e60c383b0e84d77d5132b3ead42b
 F www/whentouse.tcl fc46eae081251c3c181bd79c5faef8195d7991a5
-P 41f2175b1ed7eccf271b687ee5c3ea262a0cd096
-R 3e86c1deeec6de8a6818d829abf2506d
+P b27f022fb924709f1c5e4642d5d59cab942e826d
+R ee810a3824b25c07a2182b7d0dedc3f5
 U drh
-Z e107c976a8aac7848166a53955d0d290
+Z 6c13724b198dff1360ddd718c375cb8a

manifest.uuid

@@ -1 +1 @@
-b27f022fb924709f1c5e4642d5d59cab942e826d
+399d3e755253a7b4604a62b9f171e0f1154134e2

src/btree.c

@@ -9,7 +9,7 @@
 **    May you share freely, never taking more than you give.
 **
 *************************************************************************
-** $Id: btree.c,v 1.401 2007/08/17 16:50:38 danielk1977 Exp $
+** $Id: btree.c,v 1.402 2007/08/20 13:14:29 drh Exp $
 **
 ** This file implements a external (disk-based) database using BTrees.
 ** See the header comment on "btreeInt.h" for additional information.
@@ -1207,7 +1207,7 @@ int sqlite3BtreeOpen(
 #if !defined(SQLITE_OMIT_SHARED_CACHE) && !defined(SQLITE_OMIT_DISKIO)
   /* If the new Btree uses a sharable pBtShared, then link the new
   ** Btree into the list of all sharable Btrees for the same connection.
-  ** The list is kept in ascending order by pBtShared address.
+  ** The list is kept in ascending order by pBt address.
   */
   if( p->sharable ){
     int i;
@@ -1220,7 +1220,7 @@ int sqlite3BtreeOpen(
           p->pPrev = 0;
           pSib->pPrev = p;
         }else{
-          while( pSib->pNext && pSib->pNext->pBt>p->pBt ){
+          while( pSib->pNext && pSib->pNext->pBt<p->pBt ){
             pSib = pSib->pNext;
           }
           p->pNext = pSib->pNext;
@@ -1323,7 +1323,6 @@ int sqlite3BtreeClose(Btree *p){
     ** Clean out and delete the BtShared object.
     */
     assert( !pBt->pCursor );
-    assert( pBt->nRef==0 );
     sqlite3PagerClose(pBt->pPager);
     if( pBt->xFreeSchema && pBt->pSchema ){
       pBt->xFreeSchema(pBt->pSchema);

src/btreeInt.h

@@ -9,7 +9,7 @@
 **    May you share freely, never taking more than you give.
 **
 *************************************************************************
-** $Id: btreeInt.h,v 1.6 2007/08/17 01:14:38 drh Exp $
+** $Id: btreeInt.h,v 1.7 2007/08/20 13:14:29 drh Exp $
 **
 ** This file implements a external (disk-based) database using BTrees.
 ** For a detailed discussion of BTrees, refer to
@@ -314,6 +314,9 @@ struct MemPage {
 ** points to the same BtShared object.  The database cache and the
 ** schema associated with the database file are all contained within
 ** the BtShared object.
+**
+** All fields in this structure are accessed under the sqlite3.pMutex
+** mutex.
 */
 struct Btree {
   sqlite3 *pSqlite;  /* The database connection holding this btree */
@@ -346,6 +349,10 @@ struct Btree {
 ** private Btree object for the file and each of those Btrees points
 ** to this one BtShared object.  BtShared.nRef is the number of
 ** connections currently sharing this database file.
+**
+** Fields in this structure are accessed under the BtShared.mutex
+** mutex, except for nRef and pNext which are accessed under the
+** global SQLITE_MUTEX_STATIC_MASTER mutex.
 */
 struct BtShared {
   Pager *pPager;        /* The page cache */
@@ -370,14 +377,14 @@ struct BtShared {
   int minLeaf;          /* Minimum local payload in a LEAFDATA table */
   BusyHandler *pBusyHandler;   /* Callback for when there is lock contention */
   u8 inTransaction;     /* Transaction state */
-  int nRef;             /* Number of references to this structure */
   int nTransaction;     /* Number of open transactions (read + write) */
   void *pSchema;        /* Pointer to space allocated by sqlite3BtreeSchema() */
   void (*xFreeSchema)(void*);  /* Destructor for BtShared.pSchema */
 #ifndef SQLITE_OMIT_SHARED_CACHE
+  int nRef;             /* Number of references to this structure */
+  BtShared *pNext;      /* Next on a list of sharable BtShared structs */
   sqlite3_mutex *mutex; /* Non-recursive mutex required to access this struct */
   BtLock *pLock;        /* List of locks held on this shared-btree struct */
-  BtShared *pNext;      /* Next in ThreadData.pBtree linked list */
 #endif
 };
 
@@ -408,6 +415,10 @@ struct CellInfo {
 ** When a single database file can shared by two more database connections,
 ** but cursors cannot be shared.  Each cursor is associated with a
 ** particular database connection identified BtCursor.pBtree.pSqlite.
+**
+** The fields in this structure are accessed under the sqlite3.pMutex
+** mutex, specifically the BtCurser.pBtree->pSqlite->pMutex mutex.
+** The pNext and pPrev fields also require the BtShared.mutex mutex.
 */
 struct BtCursor {
   Btree *pBtree;            /* The Btree to which this cursor belongs */