bug#63736: [Shepherd] Loss of SIGCHLD notifications

["Ludovic Courtès" <ludo@gnu.org>]

Ludovic Courtès <ludo@gnu.org> skribis:

> Another possibility is lockup: one of the relevant fibers is either gone
> or stuck in ‘put-message’ or ‘get-message’.
>
> I did two things:
>
>   b9a37f3 shepherd: Make signal handling fiber an essential task.
>   8ae2780 service: Do not attempt to restart transient services.
>
> Commit 8ae2780 fixes a bug whereby ‘herd restart’ could end up
> attempting to restart a transient service, which would lock up the
> calling fiber because the service’s controlling fiber would first
> receive the 'terminate message, so it would return and nobody would be
> reading further messages send on its channel.
>
> Commit b9a37f3 will allows us to ensure that the signal-handling fiber
> never exits (and we’ll get a trace in the log if it tries to).

Apparently these commits, which made it in 0.10.1 months ago, fixed this
particular bug.  Closing!

Ludo’.