linux-kernel - Re: [RFC][PATCH 3/4] memcg: fix OOM KILL under hierarchy

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Message-Id: <20090113182542.004556aa.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Tue, 13 Jan 2009 18:25:42 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Li Zefan <lizf@...fujitsu.com>
Cc:	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"balbir@...ux.vnet.ibm.com" <balbir@...ux.vnet.ibm.com>,
	"nishimura@....nes.nec.co.jp" <nishimura@....nes.nec.co.jp>,
	"menage@...gle.com" <menage@...gle.com>
Subject: Re: [RFC][PATCH 3/4] memcg: fix OOM KILL under hierarchy

On Tue, 13 Jan 2009 16:33:12 +0800
Li Zefan <lizf@...fujitsu.com> wrote:

> > -int task_in_mem_cgroup(struct task_struct *task, const struct mem_cgroup *mem)
> > +static int
> > +mm_match_cgroup_hierarchy(struct mm_struct *mm, struct mem_cgroup *mem)
> > +{
> > +	struct mem_cgroup *curr;
> > +	int ret;
> > +
> > +	if (!mm)
> > +		return 0;
> > +	rcu_read_lock();
> > +	curr = mem_cgroup_from_task(mm->owner);
> 
> curr can be NULL ?
> 
Good Catch! You're right.

> > +	if (mem->use_hierarchy)
> > +		ret = css_is_ancestor(&curr->css, &mem->css);
> > +	else
> > +		ret = (curr == mem);
> > +	rcu_read_unlock();
> > +	return ret;
> > +}
> > +
> 
> ...
> 
> > +void mem_cgroup_update_oom_jiffies(struct mem_cgroup *mem)
> > +{
> > +	struct mem_cgroup *cur;
> > +	struct cgroup_subsys_state *css;
> > +	int id, found;
> > +
> > +	if (!mem->use_hierarchy) {
> > +		mem->last_oom_jiffies = jiffies;
> > +		return;
> > +	}
> > +
> > +	id = 0;
> > +	rcu_read_lock();
> > +	while (1) {
> > +		css = css_get_next(&mem_cgroup_subsys, id, &mem->css, &found);
> > +		if (!css)
> > +			break;
> > +		if (css_tryget(css)) {
> > +			cur = container_of(css, struct mem_cgroup, css);
> > +			cur->last_oom_jiffies = jiffies;
> > +			css_put(css);
> > +		}
> > +		id = found + 1;
> > +	}
> > +	rcu_read_unlock();
> > +	return;
> 
> redundant "return"
> 
ok, will remove it.

Thank you.
-Kame

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