Re: [PATCH] mdadm/systemd: change KillMode from none to mixed in service files

["NeilBrown" <neilb@suse.de>]

On Thu, 02 Dec 2021, Coly Li wrote:
> On 12/2/21 12:28 AM, Benjamin Brunner wrote:
> > Hi all,
> >
> > On 01.12.21 17:23, Coly Li wrote:
> >> On 12/2/21 12:08 AM, mtkaczyk wrote:
> >>> Hi Coly,
> >>>
> >>>> This patch changes KillMode in above listed service files from "none"
> >>>> to "mixed", to follow systemd recommendation and avoid potential
> >>>> unnecessary issue.
> >>> What about mdmonitor.service? Should we add it there too? Now it is not
> >>> defined.
> >>
> >> It was overlooked when I did grep KillMode. Yes, I agree 
> >> mdmonitor.service should have a KillMode key word as well.
> >>
> >> Let me post a v2 version.
> >>
> > JFYI, when KillMode is not set, it defaults to KillMode=control-group, 
> > see https://www.freedesktop.org/software/systemd/man/systemd.kill.html.
> >
> > Therefore, it shouldn't be necessary to explicitly add it (as long as 
> > control-group is working in case of mdmonitor.service, of course).
> 
> Hi Benjamin,
> 
> Please correct me if I am wrong, I see the difference of the KillMode is,
> -- KillMode=mixed stops the processes more gentally, it kill the main 
> process with SIGTERM and the remaining processes with SIGKILL.
> -- KillMode=control-group kills all in-cgroup processes with SIGKILL, 
> which I feel a bit cruel for the main process.

There is no point sending SIGTERM to a process which doesn't respond to
it.  mdmon is the only mdadm service which handles SIGTERM.  So it might
make sense to uise KillMode=mixed for that.
For anything else, SIGKILL via KillMode=control-group is perfectly
acceptable. 

NeilBrown


> 
> IMHO both method (explicit mixed mode or implicit control-group mode) 
> should works for the fixing issue, but I feel removing the KillMode 
> lines might be better as you indicated since the files can be a bit 
> simpler. Do I understand you correct ?
> 
> Thanks.
> 
> Coly Li
> 
>