linux-kernel - Re: + freezer-check-oom-kill-while-being-frozen.patch added to -mm tree

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Message-ID: <20141016211136.GA27468@redhat.com>
Date:	Thu, 16 Oct 2014 23:11:36 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Cong Wang <xiyou.wangcong@...il.com>
Cc:	Michal Hocko <mhocko@...e.cz>,
	David Rientjes <rientjes@...gle.com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>, Tejun Heo <tj@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: + freezer-check-oom-kill-while-being-frozen.patch added to -mm
	tree

On 10/16, Cong Wang wrote:
>
> On Thu, Oct 16, 2014 at 1:39 PM, Oleg Nesterov <oleg@...hat.com> wrote:
> >> Fix the issue by checking for TIF_MEMDIE thread flag and get away from the
> >> fridge if it is set.  oom_scan_process_thread doesn't have to check for
> >> the frozen task anymore because do_send_sig_info will wake up the thread
> >> and TIF_MEMDIE is already set by that time.
> >
> > I must have missed something... but __refrigerator() sleeps in
> > TASK_UNINTERRUPTIBLE and do_send_sig_info() won't wake it up?
> >
>
> This is exactly what we are trying to fix. Make sure you read the patch
> as well before reply?

I did read the patch, but I can't understand it. I am sorry about that,
and I am asking for your help.

I agree that oom_scan_process_thread()->__thaw_task() doesn't really
help.

But also I can't understand why this patch helps. The changelog says:

	do_send_sig_info will wake up the thread

why?

Oleg.

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