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core/wtp: potential hang during shutdown

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when the wtp worker is cancelled in the final stage of shutting down
while the mutex is locked and there is one worker left, the system
will hang. The reason is that the cancelled thread could not free the
mutex that the other needs in order to shut down orderly.

Deteced with clang thread sanitizer.
This commit is contained in:
Rainer Gerhards 2017-11-09 18:06:32 +01:00
parent b57db5ce3c
commit 3250b21566
1 changed files with 11 additions and 8 deletions
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19
runtime/wtp.c
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@ -322,14 +322,16 @@ wtpWrkrExecCleanup(wti_t *pWti)
wtiSetState(pWti, WRKTHRD_STOPPED);
ATOMIC_DEC(&pThis->iCurNumWrkThrd, &pThis->mutCurNumWrkThrd);
/* note: numWorkersNow is only for message generation, so we do not try
* hard to get it 100% accurate (as curently done, it is not).
*/
const int numWorkersNow = ATOMIC_FETCH_32BIT(&pThis->iCurNumWrkThrd, &pThis->mutCurNumWrkThrd);
DBGPRINTF("%s: Worker thread %lx, terminated, num workers now %d\n",
wtpGetDbgHdr(pThis), (unsigned long) pWti,
ATOMIC_FETCH_32BIT(&pThis->iCurNumWrkThrd, &pThis->mutCurNumWrkThrd));
if(ATOMIC_FETCH_32BIT(&pThis->iCurNumWrkThrd, &pThis->mutCurNumWrkThrd) > 0) {
wtpGetDbgHdr(pThis), (unsigned long) pWti, numWorkersNow);
if(numWorkersNow > 0) {
LogMsg(0, RS_RET_OPERATION_STATUS, LOG_INFO,
"%s: worker thread %lx terminated, now %d active worker threads",
wtpGetDbgHdr(pThis), (unsigned long) pWti,
ATOMIC_FETCH_32BIT(&pThis->iCurNumWrkThrd, &pThis->mutCurNumWrkThrd));
wtpGetDbgHdr(pThis), (unsigned long) pWti, numWorkersNow);
}
ENDfunc
@ -402,17 +404,18 @@ wtpWorker(void *arg) /* the arg is actually a wti object, even though we are in
dbgOutputTID((char*)thrdName);
# endif
pthread_cleanup_push(wtpWrkrExecCancelCleanup, pWti);
/* let the parent know we're done with initialization */
d_pthread_mutex_lock(&pThis->mutWtp);
wtiSetState(pWti, WRKTHRD_RUNNING);
pthread_cond_broadcast(&pThis->condThrdInitDone);
d_pthread_mutex_unlock(&pThis->mutWtp);
pthread_cleanup_push(wtpWrkrExecCancelCleanup, pWti);
wtiWorker(pWti);
pthread_cleanup_pop(0);
d_pthread_mutex_lock(&pThis->mutWtp);
pthread_cleanup_push(mutexCancelCleanup, &pThis->mutWtp);
wtpWrkrExecCleanup(pWti);
ENDfunc
@ -421,7 +424,7 @@ wtpWorker(void *arg) /* the arg is actually a wti object, even though we are in
* segfault. So we need to do the broadcast as actually the last action in our processing
*/
pthread_cond_broadcast(&pThis->condThrdTrm); /* activate anyone waiting on thread shutdown */
d_pthread_mutex_unlock(&pThis->mutWtp);
pthread_cleanup_pop(1); /* unlock mutex */
pthread_exit(0);
}
#if !defined(_AIX)