Masschelein Bart
7/5/2005 3:54:00 PM
> -----Original Message-----
> From: Guillaume Marcais [mailto:guslist@free.fr]
> Sent: Tuesday, July 05, 2005 16:55
> To: ruby-talk ML
> Subject: Re: Abort a system call
>
>
> > > With parts of other pieces today on the reflector, I
> assembled this
> > >
> > > --------
> > > pid = Process.fork do
> > > exec($decoder, $bitstreamPath, $yuvOutputPath)
> > > end
> > >
> > > trap "SIGINT", proc{ Process.kill("SIGINT", pid); print "^C
> > > was pressed. Process id #{pid}\n" }
> > >
> > > Process.waitpid(pid)
> > > --------
> > For those having similar problems, I just solved it by
> >
> > trap "INT", proc{ Process.kill(9, pid) }
> >
> > so using a hard kill.
> >
> > If people have more elegant ways of solving this, let me know!
>
> Here is what I think is going on. Ruby sets up the signal handler so
> that some system call will resume after the interrupt instead of
> returning with EINTR:
>
> from ruby-signal in signal.c:
>
> #if defined(SA_RESTART)
> /* All other signals but VTALRM shall restart restartable syscall
> VTALRM will cause EINTR to syscall if interrupted.
> */
> if (signum != SIGVTALRM) {
> sigact.sa_flags |= SA_RESTART; /* SVR4, 4.3+BSD */
> }
> #endif
>
> And from man sigaction:
> SA_RESTART
> Provide behaviour compatible with BSD signal
> semantics by
> making certain system calls restartable across
> signals.
>
> That is why Process.waitpid(pid) doesn't return until your decoder
> process dies. Maybe Perl doesn't do that and it would explain the
> difference of behavior.
Wow. A lot of magic going on behind the scenes... I have to catch up big time ;-).
>
> Second, it seems that your decoder process doesn't terminate on a
> SIGINT. Maybe you should send a SIGTERM, to be a little more graceful
> than SIGKILL (9).
Also about these signals I have to learn, but for now I can tell you that SIGTERM works also perfect to do what I want.
>
> Hope it helps,
> Guillaume.
It does! Thanks!
>
> PS: people in the know, please correct me if I got it wrong about the
> way the signals are handled.
I'll get back to you later ;-)