libvirt users - Oct 2016 - Guest startup process blocks if a hook's child process is still running (i.e : after forking)

I've been having issues with KVM lately where I sometimes put my host 
into sleep while a guest is still running, which prevents it from waking 
up properly. This is somewhat expected due to my setup, but I have 
mistakenly done this more than once and could use a workaround to stop 
this from happening.

So I've been trying to setup a libvirt hook to fork an instance of 
systemd-inhibit when the start hook is called and keep it running until 
the shutdown hook is called. This seems to work well when I run the hook 
script in a normal bash shell, but running it through libvirt simply 
blocks the starting process until systemd-inhibit quits.

Here's the script :

LOCK_FILE="/tmp/vfio-lock-$OBJECT"

if [ "$OPERATION" == "start" ]; then
	(
		touch "$LOCK_FILE";
		systemd-inhibit --what="sleep" \
		--who="libvirt" \
		--mode="block" \
		inotifywait -qq -e delete "$LOCK_FILE"
	) & disown $!
	exit
fi

if [ "$OPERATION" == "shutdown" ]; then
         rm "$LOCK_FILE"
fi

Is there some way to make it so libvirt sees the hook script exiting and 
carries on with the rest of its guest startup process even after a 
process fork or would that require changes in the internal hook handling 
functions?

- Nicolas

I'm still having this issue and I'd really like to know if there's 
something about hooks I'm missing. I've seen a number of people with the
same issue on vfio-users before and it'f something I'd really like to 
find a fix for.

- Nicolas


On 10/23/16 17:24, Nicolas Roy-Renaud wrote:
> I've been having issues with KVM lately where I sometimes put my host 
> into sleep while a guest is still running, which prevents it from 
> waking up properly. This is somewhat expected due to my setup, but I 
> have mistakenly done this more than once and could use a workaround to 
> stop this from happening.
>
> So I've been trying to setup a libvirt hook to fork an instance of 
> systemd-inhibit when the start hook is called and keep it running 
> until the shutdown hook is called. This seems to work well when I run 
> the hook script in a normal bash shell, but running it through libvirt 
> simply blocks the starting process until systemd-inhibit quits.
>
> Here's the script :
>
> LOCK_FILE="/tmp/vfio-lock-$OBJECT"
>
> if [ "$OPERATION" == "start" ]; then
>     (
>         touch "$LOCK_FILE";
>         systemd-inhibit --what="sleep" \
>         --who="libvirt" \
>         --mode="block" \
>         inotifywait -qq -e delete "$LOCK_FILE"
>     ) & disown $!
>     exit
> fi
>
> if [ "$OPERATION" == "shutdown" ]; then
>         rm "$LOCK_FILE"
> fi
>
> Is there some way to make it so libvirt sees the hook script exiting 
> and carries on with the rest of its guest startup process even after a 
> process fork or would that require changes in the internal hook 
> handling functions?
>
> - Nicolas