Re: bash continues after kill(self, TERM) on reboot

Chet Ramey <[email protected]> Thu, 5 Mar 2026 12:40:18 -0500

Newsgroups	gmane.comp.shells.bash.bugs
Organization	ITS, Case Western Reserve University
Message-ID	<[email protected]>

On 3/4/26 2:05 PM, Daniel Villeneuve wrote:

>     Thanks for looking into this.
>     SIGHUP could explain a different behavior for the reboot case, but I
>     still
>     don't see why the following SIGTERM that is sent from the TERM trap and
>     received (seen in the strace output) does not kill the shell right at
>     that
>     moment.
>     I don't see any sign of SIGTERM being blocked or ignored (from the
>     strace
>     output) at the point the shell receives the TERM signal, so how could
>     the
>     shell ignore it and continue with the exit trap?
>     I've just added a line to dump /proc/$$/status just before the re-kill,
>     and
>     here is what I get:
>     SigCgt:    0000000043817efb
>     The 7 here tells me that SIGTERM (15) is still being caught, despite
>     the "trap - EXIT TERM" statement. 

By default, bash catches fatal signals, sets a flag (all you can really
do in a signal handler), and calls a handler when it can if the flag is
set. It uses the handler to clean up resources (removing FIFOs, etc.), runs
the exit trap, then resets the signal disposition to  SIG_DFL and resends
the signal to itself. That is the default handler trap reverts to.

It could be that the shell gets SIGHUP, starts to run the exit trap, gets
SIGTERM, notes that it's already processing a fatal signal, and waits, but
there is code to exit immediately when that happens.

> Could that explain why TERM
>     seems ignored?  But this is also the case (7xxx) in normal
>     "kill process-group" mode, so why the different behavior?

It depends. Do you have a specific reproducer that works outside of reboot?

Chet
-- 
``The lyf so short, the craft so long to lerne.'' - Chaucer
		 ``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, UTech, CWRU    [email protected]    http://tiswww.cwru.edu/~chet/

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