Subject: bug#77115: [shepherd] Attempt to suspend fiber within continuation barrier

From: Ludovic Courtès <[email-masked]>
Date: Wed, 19 Mar 2025 19:13:13 +0100

Hi,

Maxim Cournoyer <[email-masked]> skribis:

> $ sudo herd schedule mcron 1000 | grep mumi
> herd: error: exception caught while executing 'schedule' on service 'mcron':
> Attempt to suspend fiber within continuation barrier

(For the record, that’s Shepherd 1.0.1 currently running on berlin.)

Can you reproduce it in a VM?  With 1.0.2 vs. 1.0.3?

On my laptop, which runs 1.0.3ish, I can’t seem to hit this:

--8<---------------cut here---------------start------------->8---
$ sudo herd schedule mcron 20000|wc -l
60000
--8<---------------cut here---------------end--------------->8---

> Another data point; when using virt-manager (which uses libvirt+qemu) to
> run my own operating system definition, it triggers a similar hang/crash
> in Shepherd during the boot; see the screenshot below.  I haven't yet
> isolated which service causes it.

Do you have a reproducer for this one?

This looks a lot like what was fixed by
<https://git.savannah.gnu.org/cgit/shepherd.git/commit/?id=f1a82845eaf8851af9a811e5a1d185b68b1c363f>,
which is in 1.0.3.

Thanks,
Ludo’.