linux-kernel - Re: [PATCH 1/2 v2] memcg: make oom_lock 0 and 1 based rather than coutner

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Date:	Fri, 22 Jul 2011 09:15:57 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Michal Hocko <mhocko@...e.cz>, linux-mm@...ck.org,
	Balbir Singh <bsingharora@...il.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2 v2] memcg: make oom_lock 0 and 1 based rather than
 coutner

On Thu, 21 Jul 2011 13:58:17 -0700
Andrew Morton <akpm@...ux-foundation.org> wrote:

> On Wed, 13 Jul 2011 13:05:49 +0200
> Michal Hocko <mhocko@...e.cz> wrote:
> 
> > @@ -1893,6 +1942,8 @@ bool mem_cgroup_handle_oom(struct mem_cgroup *mem, gfp_t mask)
> 
> does:
> 
> : 	memcg_wakeup_oom(mem);
> : 	mutex_unlock(&memcg_oom_mutex);
> : 
> : 	mem_cgroup_unmark_under_oom(mem);
> : 
> : 	if (test_thread_flag(TIF_MEMDIE) || fatal_signal_pending(current))
> : 		return false;
> : 	/* Give chance to dying process */
> : 	schedule_timeout(1);
> : 	return true;
> : }
> 
> Calling schedule_timeout() in state TASK_RUNNING is equivalent to
> calling schedule() and then pointlessly wasting some CPU cycles.
> 
Ouch (--;

> Someone might want to take a look at that, and wonder why this bug
> wasn't detected in testing ;)
> 
I wonder just removing this is okay....because we didn't noticed this
in our recent oom tests. 

I'll do some.

Thanks,
-Kame

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