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

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FossilOrigin-Name: 8fe234b2ca1292955162d38922a45c93004fb6ae
This commit is contained in:
danielk1977
2008-08-22 17:09:49 +00:00
parent 9d8b3072ce
commit ed2781e3c8
3 changed files with 24 additions and 42 deletions
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50
src/pcache.c
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@@ -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);
}
if( pCache==pC ){
pCache->iInUseDB = iInUseDB;
pcacheEnterGlobal();
}
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
** of a pager-cache (i.e. from within pagerRecycle()), then the
** 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.
/* Obtain the global mutex 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();
}
/*