On Wed, Aug 08, 2012 at 07:07:38PM +0200, Lennart Poettering wrote: > On Mon, 06.08.12 16:52, Daniel P. Berrange ([email protected]) wrote: > > > For libvirt, we (will soon) have a daemon (virtlockd) which maintains > > exclusive fcntl() based locks on disk images/devices, on behalf of both > > libvirtd and any running QEMU or LXC instances. This is a safety critical > > daemon (hence separate from libvirtd), to the extent that if the daemon > > stops / crashes, the entire host should be immediately fenced using a > > kernel watchdog and/or hardware power control device. > > > > We still want to be able to restart this daemon during RPM upgrades to > > newer versions, but we can't use a normal stop+start sequence, because > > that will loose locks for any active VMs. Thus the daemon has the ability > > to re-exec() itself triggered by SIGUSR1, preserving its critical state. > > I've read the manpages for .service, .exec, etc but I've not seen any > > reference to changing config such that > > > > # systemctl restart virtdlockd.service > > > > will simply send SIGUSR1 to the process, instead of stopping it and then > > starting it again. Obviously I could make the RPM %post send SIGUSR1 > > directly and ignore systemctl, but that doesn't help admins who just > > expect to use systemctl. So I want to know if there is a recommended > > way to handle this kind of use case ? > > This is fundamentally difficult to implement, simply because restarting > a service also means that the services binding to it need restarting > too. And the ordering of that gets impossible if the stop/start sequence > is "atomic" because it is done internally in the service, and cannot be > split into two steps that we can order freely against each other. > > So, I fear we cannot really add this for you. As Kay suggested > "systemctl kill" is probably your best choice here, or maybe "systemctl > reload".
Ok, thanks for explaining the issues - I think I'll just use systemctl kill for now. Regards, Daniel -- |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| |: http://libvirt.org -o- http://virt-manager.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :| _______________________________________________ systemd-devel mailing list [email protected] http://lists.freedesktop.org/mailman/listinfo/systemd-devel
