Re: [libvirt] PATCH: Write pidfile earlier in startup

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.