Re: [libvirt] [PATCH] Fix deadlock in QEMU close callback APIs

From: "Daniel P. Berrange" <berrange(a)redhat.com&gt; There is a lock ordering problem in the QEMU close callback APIs. When starting a guest we have a lock on the VM. We then set a autodestroy callback, which acquires a lock on the close callbacks. When running auto-destroy, we obtain a lock on the close callbacks, then run each callbacks - which obtains a lock on the VM. This causes deadlock if anyone tries to start a VM, while autodestroy is taking place. The fix is to do autodestroy in 2 phases. First obtain all the callbacks and remove them from the list under the close callback lock. Then invoke each callback from outside the close callback lock.