Daniel P. Berrange wrote:
> On Thu, Jun 21, 2012 at 09:56:54AM -0600, Jim Fehlig wrote:
>
>
>> From 583be33213e922899b23f036494886397b2549dc Mon Sep 17 00:00:00 2001
>> From: Jim Fehlig <jfehlig@xxxxxxxx>
>> Date: Thu, 21 Jun 2012 09:21:44 -0600
>> Subject: [PATCH] Fix deadlock on libvirtd shutdown
>>
>> When shutting down libvirtd, the virNetServer shutdown can deadlock
>> if there are in-flight jobs being handled by virNetServerHandleJob().
>> virNetServerFree() will acquire the virNetServer lock and call
>> virThreadPoolFree() to terminate the workers, waiting for the workers
>> to finish. But in-flight workers will attempt to acquire the
>> virNetServer lock, resulting in deadlock.
>>
>> Fix the deadlock by unlocking the virNetServer lock before calling
>> virThreadPoolFree(). This is safe since the virNetServerPtr object
>> is ref-counted and only decrementing the ref count needs to be
>> protected. Additionally, there is no need to re-acquire the lock
>> after virThreadPoolFree() completes as all the workers have
>> terminated.
>> ---
>> src/rpc/virnetserver.c | 6 ++----
>> 1 file changed, 2 insertions(+), 4 deletions(-)
>>
>> diff --git a/src/rpc/virnetserver.c b/src/rpc/virnetserver.c
>> index ae19e84..9d71e53 100644
>> --- a/src/rpc/virnetserver.c
>> +++ b/src/rpc/virnetserver.c
>> @@ -766,10 +766,9 @@ void virNetServerFree(virNetServerPtr srv)
>> virNetServerLock(srv);
>> VIR_DEBUG("srv=%p refs=%d", srv, srv->refs);
>> srv->refs--;
>> - if (srv->refs > 0) {
>> - virNetServerUnlock(srv);
>> + virNetServerUnlock(srv);
>> + if (srv->refs > 0)
>> return;
>> - }
>>
>> for (i = 0 ; i < srv->nservices ; i++)
>> virNetServerServiceToggle(srv->services[i], false);
>> @@ -805,7 +804,6 @@ void virNetServerFree(virNetServerPtr srv)
>> virNetServerMDNSFree(srv->mdns);
>> #endif
>>
>> - virNetServerUnlock(srv);
>> virMutexDestroy(&srv->lock);
>> VIR_FREE(srv);
>> }
>>
>
> ACK,
>
> We really should resurrect the patches adding virAtomic for refcounting :-)
>
Thanks for the help with this. I've pushed it now.
Regards,
Jim
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