Relinquish the pcache mutex before calling an xStress callback. This ensures that the pcache mutex is never held while IO is performed. (CVS 5599)

FossilOrigin-Name: 8fe234b2ca1292955162d38922a45c93004fb6ae

manifest

@@ -1,5 +1,5 @@
-C Enhanced\stest\scoverage.\s(CVS\s5598)
+C Relinquish\sthe\spcache\smutex\sbefore\scalling\san\sxStress\scallback.\sThis\sensures\sthat\sthe\spcache\smutex\sis\snever\sheld\swhile\sIO\sis\sperformed.\s(CVS\s5599)
-D 2008-08-22T16:29:51
+D 2008-08-22T17:09:50
 F Makefile.arm-wince-mingw32ce-gcc fcd5e9cd67fe88836360bb4f9ef4cb7f8e2fb5a0
 F Makefile.in 51b727303f84cf055e29514d8248e5eaf9701379
 F Makefile.linux-gcc d53183f4aa6a9192d249731c90dbdffbd2c68654
@@ -138,7 +138,7 @@ F src/os_win.c aefe9ee26430678a19a058a874e4e2bd91398142
 F src/pager.c 3b6625d32cd6f43c54c160f246545f9f26ba7668
 F src/pager.h 3778bea71dfb9658b6c94394e18db4a5b27e6ded
 F src/parse.y d0f76d2cb8d6883d5600dc20beb961a6022b94b8
-F src/pcache.c e12359db2963c379f18b52c657b5ec0ebb7a02cd
+F src/pcache.c 504e6204124c4f90917ab1c0ea0a0ec549ed242f
 F src/pcache.h 1457e4e7ef08f6964399d5c039afdece25071d54
 F src/pragma.c f5b271b090af7fcedd308d7c5807a5503f7a853d
 F src/prepare.c c197041e0c4770672cda75e6bfe10242f885e510
@@ -623,7 +623,7 @@ F tool/speedtest16.c c8a9c793df96db7e4933f0852abb7a03d48f2e81
 F tool/speedtest2.tcl ee2149167303ba8e95af97873c575c3e0fab58ff
 F tool/speedtest8.c 1dbced29de5f59ba2ebf877edcadf171540374d1
 F tool/speedtest8inst1.c 293327bc76823f473684d589a8160bde1f52c14e
-P 93dbc5427bebaa0b3d726731027caad3f70611c7
+P cc36b4e016a1f519ca81d591de3a551ee8aa6813
-R d06c1972a5218a66e3015476bedfa7df
+R 64828ec133db995283a20c7be6e84925
-U drh
+U danielk1977
-Z 9e8818091fbf71d795674002e4d9c171
+Z 7437592fbd9eee9fb3293ff26d588a0d

manifest.uuid

@@ -1 +1 @@
-cc36b4e016a1f519ca81d591de3a551ee8aa6813
+8fe234b2ca1292955162d38922a45c93004fb6ae

src/pcache.c

@@ -11,7 +11,7 @@
 *************************************************************************
 ** This file implements that page cache.
 **
-** @(#) $Id: pcache.c,v 1.8 2008/08/22 16:22:17 danielk1977 Exp $
+** @(#) $Id: pcache.c,v 1.9 2008/08/22 17:09:50 danielk1977 Exp $
 */
 #include "sqliteInt.h"
 
@@ -453,6 +453,14 @@ static int pcachePageSize(PgHdr *p){
   return sqlite3MallocSize(p);
 }
 
+/*
+** Recycle a page from the global LRU list. If no page can be recycled, 
+** return NULL. Otherwise, the pointer returned points to a PgHdr 
+** object that has been removed from all lists and hash tables in
+** which is was referenced. The caller may reuse the allocation directly
+** or may pass it to pcachePageFree() to return the memory to the heap
+** (or pcache.pFree list).
+*/ 
 static PgHdr *pcacheRecycle(PCache *pCache){
   PgHdr *p = 0;
 
@@ -465,31 +473,13 @@ static PgHdr *pcacheRecycle(PCache *pCache){
   }
   if( p && (p->flags&PGHDR_DIRTY) ){
     if( SQLITE_OK==sqlite3_mutex_try(pcache.mutex_mem2) ){
-      int iInUseDB;
       PCache *pC = p->pCache;
-
-      if( pCache==pC ){
-        /* If trying to recycle a page from pCache, then set the iInUseDb
-        ** flag to zero. This is done so that the sqlite3PcacheSetFlags()
-        ** can tell that the LRU mutex is already held.
-        **
-        ** It is quite safe to modify the iInUseDB variable, because we 
-        ** know no other thread will attempt to use pCache (because this
-        ** call is being made from within a call to sqlite3PcacheFetch()
-        ** on pCache). 
-        */
-        assert( pCache->iInUseDB );
-        iInUseDB = pCache->iInUseDB;
-        pCache->iInUseDB = 0;
-      }
-
       assert( pC->iInUseMM==0 );
       pC->iInUseMM = 1;
-      if( pC->xStress && pC->iInUseDB==0 ){
+      if( pC->xStress && (pC->iInUseDB==0 || pC==pCache) ){
+        pcacheExitGlobal();
         pC->xStress(pC->pStress, p);
-      }
+        pcacheEnterGlobal();
-      if( pCache==pC ){
-        pCache->iInUseDB = iInUseDB;
       }
       pC->iInUseMM = 0;
       sqlite3_mutex_leave(pcache.mutex_mem2);
@@ -766,7 +756,6 @@ void sqlite3PcacheMakeClean(PgHdr *p){
   if( (p->flags & PGHDR_DIRTY)==0 ) return;
   assert( p->apSave[0]==0 && p->apSave[1]==0 );
   assert( p->flags & PGHDR_DIRTY );
-  assert( p->nRef>0 || sqlite3_mutex_held(pcache.mutex_lru) );
   pCache = p->pCache;
   pcacheRemoveFromList(&pCache->pDirty, p);
   pcacheAddToList(&pCache->pClean, p);
@@ -1127,15 +1116,10 @@ void sqlite3PcacheSetFlags(PCache *pCache, int andMask, int orMask){
   assert( (orMask&PGHDR_NEED_SYNC)==0 );
   assert( pCache->iInUseDB || pCache->iInUseMM );
 
-  /* If this call is being made from within a call to the xStress callback
+  /* Obtain the global mutex before modifying any PgHdr.flags variables 
-  ** of a pager-cache (i.e. from within pagerRecycle()), then the 
+  ** or traversing the LRU list.
-  ** PCache.iInUseDB will be set to zero. In this case, the LRU mutex is
-  ** already held. Otherwise, obtain it before modifying any PgHdr.flags
-  ** variables or traversing the LRU list.
   */ 
-  if( pCache->iInUseDB ){
+  pcacheEnterGlobal();
-    pcacheEnterGlobal();
-  }
   assert( sqlite3_mutex_held(pcache.mutex_lru) );
 
   for(p=pCache->pDirty; p; p=p->pNext){
@@ -1150,9 +1134,7 @@ void sqlite3PcacheSetFlags(PCache *pCache, int andMask, int orMask){
     pcache.pLruSynced = p;
   }
 
-  if( pCache->iInUseDB ){
+  pcacheExitGlobal();
-    pcacheExitGlobal();
-  }
 }
 
 /*