Hello Mathieu!

Mathieu Othacehe <othacehe@gnu.org> skribis:

>> +        (begin
>> +          ;; Unblock any signals that might have been blocked by the parent
>> +          ;; process.
>> +          (unblock-signals (list SIGCHLD SIGINT SIGHUP SIGTERM))
>
> This made me realize that we may want to disable/reset SIGINT and
> SIGHUP, in the same way that we do for SIGTERM? This is not related to
> your patch anyway.

I looked into this and came up with the patches below.

What it does is unconditionally block these four signals before forking.
Then the child process installs SIG_DFL handlers for them and unblocks
them.

That way, the child is guaranteed to never execute the original
handlers, and neither the parent nor the child misses any of these
signals (previously, the temporary (sigaction SIGTERM SIG_DFL)
introduced a window during which shepherd could be killed by a SIGTERM
instead of handling it gracefully.)

WDYT?

(I also thought about using ‘call-with-blocked-asyncs’ instead of
‘with-blocked-signals’.  That would have prevented signal handling at
the Scheme level from happening, but the unhandled signals in the child
would be lost.)

If it works for you, I’ll do some more testing, and then hopefully we
can release 0.8.1 in the coming days!

Ludo’.