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.
Regards,
Jim