Re: [PATCH 1/8] mm,oom_reaper: Remove pointless kthread_run() failure check.

[Oleg Nesterov <oleg@redhat.com>]

On 07/04, Tetsuo Handa wrote:
>
> Oleg Nesterov wrote:
> > On 07/03, Tetsuo Handa wrote:
> > >
> > > If kthread_run() in oom_init() fails due to reasons other than OOM
> > > (e.g. no free pid is available), userspace processes won't be able to
> > > start as well.
> >
> > Why?
> >
> > The kernel will boot with or without your change, but
> >
> > > Therefore, trying to continue with error message is
> > > also pointless.
> >
> > Can't understand...
> >
> > I think this warning makes sense. And since you removed the oom_reaper_the
> > check in wake_oom_reaper(), the kernel will leak every task_struct passed
> > to wake_oom_reaper() ?
>
> We are trying to prove that OOM livelock is impossible for CONFIG_MMU=y
> kernels (as long as OOM killer is invoked) because the OOM reaper always
> gives feedback to the OOM killer, right? Then, preserving code which
> continues without OOM reaper no longer makes sense.
>
> In the past discussion, I suggested Michal to use BUG_ON() or panic()
> ( http://lkml.kernel.org/r/20151127123525.GG2493@dhcp22.suse.cz ). At that
> time, we chose continue with pr_err(). If you think that kthread_run()
> failure in oom_init() will ever happen, I can change my patch to call
> BUG_ON() or panic(). I don't like continuing without OOM reaper.

And probably this makes sense, but

> Anyway, [PATCH 8/8] in this series removes get_task_struct().
> Thus, the kernel won't leak every task_struct after all.

which I can't read yet. I am still trying to clone linux-net, currently
my internet connection is very slow.

Anyway, this means that this 1/1 patch depends on 8/8, but 0/8 says

	[PATCH 1/8] can be sent to current linux.git as a clean up.

IOW, this patch doesn't look correct without other changes?

Oleg.

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