Re: [PATCH v3 06/10] run-command: add clean_on_exit_handler
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> On 02 Aug 2016, at 07:53, Johannes Sixt <j6t@kdbg.org> wrote:
>
> Am 01.08.2016 um 13:14 schrieb Lars Schneider:
> >> On 30 Jul 2016, at 11:50, Johannes Sixt <j6t@kdbg.org> wrote:
> >> Am 30.07.2016 um 01:37 schrieb larsxschneider@gmail.com:
> >>> static struct child_to_clean *children_to_clean;
> >>> @@ -30,6 +31,8 @@ static void cleanup_children(int sig, int in_signal)
> >>> {
> >>> while (children_to_clean) {
> >>> struct child_to_clean *p = children_to_clean;
> >>> + if (p->clean_on_exit_handler)
> >>> + p->clean_on_exit_handler(p->pid);
> >>
> >> This summons demons. cleanup_children() is invoked from a signal
> >> handler. In this case, it can call only async-signal-safe functions.
> >> It does not look like the handler that you are going to install
> >> later will take note of this caveat!
> >>
> >>> children_to_clean = p->next;
> >>> kill(p->pid, sig);
> >>> if (!in_signal)
> >>
> >> The condition that we see here in the context protects free(p)
> >> (which is not async-signal-safe). Perhaps the invocation of the new
> >> callback should be skipped in the same manner when this is called
> >> from a signal handler? 507d7804 (pager: don't use unsafe functions
> >> in signal handlers) may be worth a look.
> >
> > Thanks a lot of pointing this out to me!
> >
> > Do I get it right that after the signal "SIGTERM" I can do a cleanup
> > and don't need to worry about any function calls but if I get any
> > other signal then I can only perform async-signal-safe calls?
>
> No. SIGTERM is not special.
>
> Perhaps you were misled by the SIGTERM mentioned in cleanup_children_on_exit()? This function is invoked on regular exit (not from a signal). SIGTERM is used in this case to terminate children that are still lingering around.Yes, that was my source of confusion. Thanks for the clarification!
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>
> > If this is correct, then the following solution would work great:
> >
> > if (!in_signal && p->clean_on_exit_handler)
> > p->clean_on_exit_handler(p->pid);
>
> This should work nevertheless because in_signal is set when the function is invoked from a signal handler (of any signal that is caught) via cleanup_children_on_signal().
Lars Schneider <larsxschneider@gmail.com>