Re: [libvirt] [PATCH] virLXCMonitorClose: Unlock domain while closing monitor

There's a race in lxc driver causing a deadlock. If a domain is destroyed immediately after started, the deadlock can occur. When domain is started, the even loop tries to connect to the monitor. If the connecting succeeds, virLXCProcessMonitorInitNotify() is called with @mon->client locked. The first thing that callee does, is virObjectLock(vm). So the order of locking is: 1) @mon->client, 2) @vm. However, if there's another thread executing virDomainDestroy on the very same domain, the first thing done here is locking the @vm. Then, the corresponding libvirt_lxc process is killed and monitor is closed via calling virLXCMonitorClose(). This callee tries to lock @mon->client too. So the order is reversed to the first case. This situation results in deadlock and unresponsive libvirtd (since the eventloop is involved). The proper solution is to unlock the @vm in virLXCMonitorClose prior entering virNetClientClose(). See the backtrace as follows: