From mboxrd@z Thu Jan 1 00:00:00 1970 From: Petr Vorel Date: Wed, 12 May 2021 16:20:05 +0200 Subject: [LTP] [PATCH v3 3/4] lib: ignore SIGINT in _tst_kill_test In-Reply-To: References: <20210508055109.16914-4-liwang@redhat.com> Message-ID: List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: ltp@lists.linux.it Hi all, ... > > 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 > > I tried with the following snippets: > > -c 'trap "echo trap;" INT; (sleep 2; echo end sub) & sleep 1; > > kill -INT -$$; echo end main' > > -c 'trap "echo trap;" INT; (trap - SIGINT sleep 2; echo end sub) > > & sleep 1; kill -INT -$$; echo end main' > > -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. > > 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] > > 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) > > 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