[systemd-devel] [PATCH] service: don't try to kill the service more than once when the watchdog timeout hits

[Michael Olbrich]

Hi,

On Wed, Jul 17, 2013 at 03:53:09AM +0200, Lennart Poettering wrote:
> On Wed, 12.06.13 01:22, Michael Olbrich (m.olbrich at pengutronix.de) wrote:
> 
> > If ExecStopPost= is defined then it is executed after SIGKILL. Otherwise
> > another round of SIGTERM/SIGSTOP is started which is rather useless when
> > the watchdog timeout hits.
> > So go directly to the final SIGKILL if ExecStopPost= is not defined.
> 
> Hmm, why not go always directly into SERVICE_FINAL_SIGKILL? Why bother
> with SERVICE_STOP_SIGKILL at all? What am I missing?

I think a small summery is necessary here:
The original watchdog code just called service_enter_dead(). This had the
problem that no cleanup happened. The process was not killed.
Then I posted a patch to go irectly into SERVICE_FINAL_SIGKILL to fix that.
It got applied.
Then you changed it to SERVICE_STOP_SIGKILL so that ExecStopPost= is still
called.
However, this has a annoying side effect. Consider a service that enters
service_handle_watchdog() with a process that cannot be killed. What
happens is this:

service_handle_watchdog()
STOP_SIGKILL
wait
ExecStopPost= if available
FINAL_SIGTERM
wait
FINAL_SIGKILL
wait
service_enter_dead()

Without a ExecStopPost= defined anything after the first wait is just more
useless waiting.
I wrote this patch to avoid waiting longer than necessary but still be able
to run ExecStopPost=.
I later realized that this problem is not limited to the watchdog usecase.
So I wrote a second patch (it should be applied instead of this one) that
changes the sequence to:

[...]
STOP_SIGKILL
wait
if (ExecStopPost= is available) {
	ExecStopPost=
	FINAL_SIGTERM
	wait
	FINAL_SIGKILL
	wait
}
service_enter_dead()

I sent it as a reply to the first patch. I've also attached it for
reference.

Michael

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