[LTP] [PATCH v3 3/4] lib: ignore SIGINT in _tst_kill_test

Hi all,

...

quoted

To conclude:
- bash does not seem to care about SIGINT delivery to background
processes, but can be blocked using trap
- zsh ignores SIGINT for background processes by default, but can be
allowed using trap
- dash and busybox sh ignore the signal to background processes, and
this cannot be changed with trap

quoted

I tried with the following snippets:
<SHELL> -c 'trap "echo trap;" INT; (sleep 2; echo end sub) & sleep 1;
kill -INT -$$; echo end main'
<SHELL> -c 'trap "echo trap;" INT; (trap - SIGINT sleep 2; echo end sub)
& sleep 1; kill -INT -$$; echo end main'
<SHELL> -c 'trap "echo trap;" INT; (trap "exit" SIGINT sleep 2; echo end
sub) & sleep 1; kill -INT -$$; echo end main'

FYI (you probably know it) SIGINT is a bashism, INT needs to be used.
$ kill -s SIGINT $$
dash: 2: kill: invalid signal number or name: SIGINT

Thanks for the demos above, it shows the difference clearly.

quoted

SIGINT handling for child processes is strange. This might have some
implication for the shell tests,
because it is possible, that SIGINT is not delivered to all processes
and some may reside as orphans.
Since this can happen only in case of timeouts, I guess there is no real
Problem.

Yes.

Looks like the behaviors on signal 'SIGINT' are not unify in background
processes handling for different SHELL. So as you said that using SIGINT
seems NOT a good idea to stop the process in timeout.

Yes, trap looks to be having some portability issues [1] [2]

quoted

A possible fix could be using SIGTERM instead of SIGINT. This signal
does not seem to have some "intelligent" handling for background processes.

I agree. Can you make a patch to replace that INT?

(and this is only a timeout issue, so patch merging may be delayed due
to LTP new release)

quoted

I do not know why LTP used SIGINT in the first place. My first thought
would have been to use SIGTERM.  It is the way to "politely ask
processes to terminate"

Yes, but that not strange to me, the possible reason is just to
stop(ctrl ^c) the LTP test manually for debugging, so we went
too far for using SIGINT but forget the original purpose :).

I'm not the author, but yes, SIGINT was used for stopping with ctrl^c during
debugging.

FYI I tried to use both SIGINT and SIGTERM, but there was some problem.
But I guess it was my error. Please *add* SIGTERM (keep SIGINT).

Kind regards,
Petr

[1] https://unix.stackexchange.com/questions/240723/exit-trap-in-dash-vs-ksh-and-bash/240736#240736
[2] https://stackoverflow.com/questions/27012762/is-trap-exit-required-to-execute-in-case-of-sigint-or-sigterm-received