Re: [libvirt] [PATCH] fix bug libvirt daemon deadlock when another force console break down an existed console client when this deadlock hanppened, libvirtd backtrace as follow, a typical ABBA deadlock circumstance:

Thank you! But it looks like libvirtd daemon stream module still has bug lead to process segfault if applied this patch(if not, it will lead libvirtd deadlock).I have got the cause, but it seems difficult to fix it with present codes。 Bug reproduce: 1. add sleep(3) in daemonStreamFilter() so it is easily to get the point, as follows   static int daemonStreamFilter(virNetServerClientPtr client,                    virNetMessagePtr msg,                    void *opaque) {     daemonClientStream *stream = opaque;     int ret = 0;     static int first = 1; //    if (first) { //        notify_force_console(); //        VIR_ERROR("notify force console to break this client down!client: %p", client); //        sleep(30); //        VIR_ERROR("sleep 10 finished"); //    }     VIR_ERROR("stream: %p, filter_id: %d", stream, stream->filterID);     virObjectUnlock(client);     sleep(3);     virMutexLock(&stream->priv->lock);     virObjectLock(client); 2. build the libvirtd with new code, then replace the libvirtd 3. use virsh console to open a vm's console tty, then just input many chars in the console 4. open new terminal, then use virsh console --force to break the previous client, then you'll got libvirtd segfault it looks because when daemonStreamEvent() with para events as VIR_STREAM_EVENT_ERROR  is called, it will remove stream and free stream, but daemonStreamFilter still waiting stream->priv->lock mutex, thus cause invalid memory access

To fix this, I think the most effective and clean way is to drop client->priv->lock elements, just use client object lock。But for current code, it's not easy to do that。 also， a workaroud scheme is  to add a big lock, but is ugly and low efficient。 Any good ideas?