[systemd-devel] [PATCH] man: document kill behavior after the main process exits

[Lennart Poettering]

On Thu, 23.04.15 09:20, Daniel Drake (drake at endlessm.com) wrote:

> -        timeout, if the normal shutdown procedure left processes of
> -        the service around. Takes a boolean value. Defaults to "yes".
> +        timeout, if the normal shutdown procedure didn't succeed in
> +        shutting down the main process. Takes a boolean value.
> +        Defaults to "yes".

I think this really should clarify that this is about leaving
processes around. 

>          </para></listitem>
>        </varlistentry>
>  
> @@ -163,6 +164,31 @@
>    </refsect1>
>  
>    <refsect1>
> +    <title>Beyond the main process</title>
> +
> +     <para>The <varname>KillMode=</varname> option primarily defines
> +     behavior up until the point where the main process has gone away.
> +     systemd expects that when killed with the signal specified by
> +     <varname>KillSignal=</varname>, the main process will kill and
> +     reap all the other processes in the control group before
> +     exiting itself. 

Well, I don't think this is right. I mean, systemd doesn't really
"expect" this. It's completely OK if daemons leave children around in
this case.

KillMode= is actually very much about the time after the main process
died. If KillMode=process is specified systemd should not send any
signal to anything but the main process, and that applies to both
SIGTERm and the following SIGKILL:


> If that doesn't happen, and the main process
> +     exits with other processes still running in the control group,
> +     systemd gets a bit more heavy-handed:</para>

I'd prefer not using words like "heavy-handed" here.

> +
> +     <para>If <option>KillMode=control-group</option>, systemd will
> +     then send a second <varname>KillSignal=</varname> signal to the
> +     remaining processes, which will then be followed by a
> +     <constant>SIGKILL</constant> if processes are still around, even
> +     if <option>SendSIGKILL=no</option>.</para>

Hmm, no? SendSIGKILL=no should have the effect of not sending any
SIGKILL at all. Anything else would be a bug. 

> +
> +     <para>Or, if <option>KillMode=mixed</option>, systemd will
> +     directly send <constant>SIGKILL</constant> to all remaining members
> +     of the control group, regardless of the
> +     <varname>SendSIGKILL=</varname> preference.</para>

Hmm? No, not at all. If you use "mixed", then SIGTERM is is sent to
the main process of the daemon, and SIGKILL to *al* processes of the
daemon if there are any left after the main process exited.

Lennart

-- 
Lennart Poettering, Red Hat