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Rename the unused MEM2 static mutex to OPEN and reuse it to serialize access

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to the sqlite3BtreeOpen() routine to prevent a race condition on detection
of sharable caches.  Ticket #3735. (CVS 6363)

FossilOrigin-Name: 19fa5a29b97f017a9e176e48c848100299ba6920
This commit is contained in:
drh
2009-03-20 13:15:30 +00:00
parent df0f3c06b6
commit 7555d8ec40
6 changed files with 35 additions and 25 deletions
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23
src/btree.c
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@@ -9,7 +9,7 @@
** May you share freely, never taking more than you give.
**
*************************************************************************
** $Id: btree.c,v 1.575 2009/03/18 10:33:01 danielk1977 Exp $
** $Id: btree.c,v 1.576 2009/03/20 13:15:30 drh Exp $
**
** This file implements a external (disk-based) database using BTrees.
** See the header comment on "btreeInt.h" for additional information.
@@ -42,6 +42,8 @@ int sqlite3BtreeTrace=0; /* True to enable tracing */
** in shared cache. This variable has file scope during normal builds,
** but the test harness needs to access it so we make it global for
** test builds.
**
** Access to this variable is protected by SQLITE_MUTEX_STATIC_MASTER.
*/
#ifdef SQLITE_TEST
BtShared *SQLITE_WSD sqlite3SharedCacheList = 0;
@@ -1334,12 +1336,13 @@ int sqlite3BtreeOpen(
int flags, /* Options */
int vfsFlags /* Flags passed through to sqlite3_vfs.xOpen() */
){
sqlite3_vfs *pVfs; /* The VFS to use for this btree */
BtShared *pBt = 0; /* Shared part of btree structure */
Btree *p; /* Handle to return */
int rc = SQLITE_OK;
u8 nReserve;
unsigned char zDbHeader[100];
sqlite3_vfs *pVfs; /* The VFS to use for this btree */
BtShared *pBt = 0; /* Shared part of btree structure */
Btree *p; /* Handle to return */
sqlite3_mutex *mutexOpen = 0; /* Prevents a race condition. Ticket #3537 */
int rc = SQLITE_OK; /* Result code from this function */
u8 nReserve; /* Byte of unused space on each page */
unsigned char zDbHeader[100]; /* Database header content */
/* Set the variable isMemdb to true for an in-memory database, or
** false for a file-based database. This symbol is only required if
@@ -1385,6 +1388,8 @@ int sqlite3BtreeOpen(
return SQLITE_NOMEM;
}
sqlite3OsFullPathname(pVfs, zFilename, nFullPathname, zFullPathname);
mutexOpen = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_OPEN);
sqlite3_mutex_enter(mutexOpen);
mutexShared = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER);
sqlite3_mutex_enter(mutexShared);
for(pBt=GLOBAL(BtShared*,sqlite3SharedCacheList); pBt; pBt=pBt->pNext){
@@ -1538,6 +1543,10 @@ btree_open_out:
sqlite3_free(p);
*ppBtree = 0;
}
if( mutexOpen ){
assert( sqlite3_mutex_held(mutexOpen) );
sqlite3_mutex_leave(mutexOpen);
}
return rc;
}