Re: [libvirt] [Xen-devel] [PATCH 00/12] libxl: fork: SIGCHLD flexibility

Daniel P. Berrange wrote: > On Mon, Jan 27, 2014 at 06:39:36PM -0700, Jim Fehlig wrote: > >> [Adding libvirt list...] >> >> Ian Jackson wrote: >> >>> Jim Fehlig writes ("Re: [Xen-devel] [PATCH 00/12] libxl: fork: SIGCHLD flexibility"): >>> > > BTW, I meant to ask before - what is the SIGCHLD reference about in the > subject line ? > This is related to child processes started by libxl. E.g. running a bootloader when creating PV VMs, running a save/restore helper when saving/restoring a VM, etc. > libvirt drivers that live inside libvirtd should never use or rely on > the SIGCHLD signal at all. All VM processes started by libvirtd ought > to be fully daemonized so that their parent is pid 1 / init. This ensures > that the libvirtd daemon can be restarted without all the VMs getting > reaped. Once the VMs are reparented to init, then libvirt or library > code it uses has no way of ever receiving SIGCHLD. > Nod. VMs are "daemonized", in the context of Xen. Once running, libvirtd can be restarted without reaping them.