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Make sure the queueMutex is held prior to writing the pQueueLast field

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of the write queue in the async demonstration code.  Ticket #3405. (CVS 5744)

FossilOrigin-Name: 5622a1e285fc4d5720f7180a0eb551952f2df331
This commit is contained in:
drh
2008-09-26 20:02:50 +00:00
parent d326064e0d
commit 9e2d64b8d3
3 changed files with 34 additions and 9 deletions
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27
src/test_async.c
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@@ -10,7 +10,7 @@
**
*************************************************************************
**
** $Id: test_async.c,v 1.47 2008/09/15 15:49:34 danielk1977 Exp $
** $Id: test_async.c,v 1.48 2008/09/26 20:02:50 drh Exp $
**
** This file contains an example implementation of an asynchronous IO
** backend for SQLite.
@@ -571,12 +571,31 @@ static int async_cond_wait(pthread_cond_t *pCond, pthread_mutex_t *pMutex){
return rc;
}
/*
** Assert that the mutex is held by the current thread.
*/
static void assert_mutex_is_held(pthread_mutex_t *pMutex){
int iIdx;
pthread_mutex_t *aMutex = (pthread_mutex_t *)(&async);
pthread_t *aHolder = (pthread_t *)(&asyncdebug);
for(iIdx=0; iIdx<3; iIdx++){
if( pMutex==&aMutex[iIdx] ) break;
}
assert(iIdx<3);
assert( aHolder[iIdx]==pthread_self() );
}
/* Call our async_XX wrappers instead of selected pthread_XX functions */
#define pthread_mutex_lock async_mutex_lock
#define pthread_mutex_unlock async_mutex_unlock
#define pthread_mutex_trylock async_mutex_trylock
#define pthread_cond_wait async_cond_wait
#else /* if defined(NDEBUG) */
#define assert_mutex_is_held(X) /* A no-op when not debugging */
#endif /* !defined(NDEBUG) */
/*
@@ -1482,6 +1501,11 @@ static void *asyncWriterThread(void *pIsStarted){
rc = unlinkAsyncFile(pData);
pthread_mutex_unlock(&async.lockMutex);
if( !holdingMutex ){
pthread_mutex_lock(&async.queueMutex);
holdingMutex = 1;
}
assert_mutex_is_held(&async.queueMutex);
async.pQueueFirst = p->pNext;
sqlite3_free(pData);
doNotFree = 1;
@@ -1534,6 +1558,7 @@ static void *asyncWriterThread(void *pIsStarted){
async.pQueueLast = 0;
}
if( !doNotFree ){
assert_mutex_is_held(&async.queueMutex);
async.pQueueFirst = p->pNext;
sqlite3_free(p);
}