On Fri, May 16, 2008 at 05:39:46PM +0100, Daniel P. Berrange wrote:
On Fri, May 16, 2008 at 05:05:08PM +0100, Daniel P. Berrange wrote:
When used with the --daemon arg, libvirtd will write out a pid file to /var/run/libvirtd.pid and exit if this file already exists. Unfortuantely it does this quite late in its startup procedure - in particular *after* the call to qemudInitialize(), which in turns initializes the drivers, which in turn autostarts all the VMs and networks.
So if you start a 2nd libvirtd instance it would do autostart before it got to checking for existing PID file. This is clearly very bad because the same VM would be started twice resulting in data corruption. Fortunately the Red Hat / Fedora initscript also checks the PID file before even starting the daemon, but this can affect people starting the daemon directly.
So this patch makes the goDaemon() / pidfile creation the very first thing the daemon does after parsing command line arguments. This also results in greatly increased startup time for OS, since the initscript doesn't have to wait for it to auto-start all the VMs & networks before it daemonizes. It also initializes the signal handlers before calling qemudInitialize() since these really need to be setup before we start any VMs / child procs.
There were actually some more changes needed. It needs to write the PID file even if not running with --daemon mode to be truely safe, because some init software won't run it in daemon mode at all. So this updated patch will always write a PID file if run as root. It also fixes a few flaws in the cleanup process to ensure it only unlinks the pidfile on failure if it owned the pidfile, and removes a pointless warning when running non-root.
Yes this is a serious problem, patch looks fine, +1 Daniel -- Red Hat Virtualization group http://redhat.com/virtualization/ Daniel Veillard | virtualization library http://libvirt.org/ veillard@redhat.com | libxml GNOME XML XSLT toolkit http://xmlsoft.org/ http://veillard.com/ | Rpmfind RPM search engine http://rpmfind.net/