linux-kernel - Re: [PATCH 3/4] OOM, PM: OOM killed task shouldn't escape PM suspend

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Message-ID: <20141106124953.GD7202@dhcp22.suse.cz>
Date:	Thu, 6 Nov 2014 13:49:53 +0100
From:	Michal Hocko <mhocko@...e.cz>
To:	Tejun Heo <tj@...nel.org>
Cc:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Cong Wang <xiyou.wangcong@...il.com>,
	David Rientjes <rientjes@...gle.com>,
	Oleg Nesterov <oleg@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>, linux-mm@...ck.org,
	Linux PM list <linux-pm@...r.kernel.org>
Subject: Re: [PATCH 3/4] OOM, PM: OOM killed task shouldn't escape PM suspend

On Wed 05-11-14 12:55:27, Tejun Heo wrote:
> On Wed, Nov 05, 2014 at 06:46:09PM +0100, Michal Hocko wrote:
> > Because out_of_memory can be called from mutliple paths. And
> > the only interesting one should be the page allocation path.
> > pagefault_out_of_memory is not interesting because it cannot happen for
> > the frozen task.
> 
> Hmmm.... wouldn't that be broken by definition tho?  So, if the oom
> killer is invoked from somewhere else than page allocation path, it
> would proceed ignoring the disabled setting and would race against PM
> freeze path all the same. 

Not really because try_to_freeze_tasks doesn't finish until _all_ tasks
are frozen and a task in the page fault path cannot be frozen, can it?

I mean there shouldn't be any problem to not invoke OOM killer under
from the page fault path as well but that might lead to looping in the
page fault path without any progress until freezer enables OOM killer on
the failure path because the said task cannot be frozen.

Is this preferable?
-- 
Michal Hocko
SUSE Labs
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