s6-log: Log rotation during shutdown

Hello Laurent thank you for your software,

I have some devices running unattended somewhere in Swiss Alps,
they run s6 :)

Setup is the following:

1. Logdir is mounted as tmpfs, to avoid trashing flash memory.
2. During log rotation device runs a special script that does
compression and sends them to remote host

I don't want to loose any logs on shutdown/reboot (let's ignore sudden
power loss), so the idea is to force log rotation by sending SIGALRM
and reboot device only if log export was Ok otherwise keep retrying, but
reboot eventually after some timeout.

But, s6-log doesn't seem to wait for script to finish, so sending SIGALRM
and then SIGHUP doesn't work as I expected. Also if I send SIGHUP
immediately after SIGALRM s6-log dies with:

fatal: inconsistent state in logdir_finalize()

I though that SIGHUP might do the trick on its own, but it doesn't trigger
log rotation.

Obviously, I can work around this situation, but I wanted to ask
maybe you have some vision how it should be implemented?

-- 
Thanks,
Alex