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

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Message-Id: <20110721135817.baab2a2c.akpm@linux-foundation.org>
Date:	Thu, 21 Jul 2011 13:58:17 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Michal Hocko <mhocko@...e.cz>
Cc:	linux-mm@...ck.org, Balbir Singh <bsingharora@...il.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2 v2] memcg: make oom_lock 0 and 1 based rather than
 coutner

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.

Someone might want to take a look at that, and wonder why this bug
wasn't detected in testing ;)

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