Re: [libvirt] [PATCH] qemu: Allow graceful domain destroy

This patch introduces support for domain destroying via 'quit' monitor command which gives qemu time to flush caches and therefore prevent disks corruption. However, qemu can be unresponsive and to prevent waiting indefinitely, execute command in a separate thread and wait reasonable time (QEMU_QUIT_WAIT_SECONDS) on a condition. If we hit timeout, qemu is qemuProcessKill'ed which causes monitor close and therefore also thread being terminable. The synchronization between qemu driver and monitor-quit thread is done through mutex and condition. However, this alone is not enough. If a condition is signalized but without anybody listening signal is lost. To prevent this a boolean variable is used that is set iff nobody is listening but condition would be signalized, or iff driver is waiting on given condition.