From: Oleg Nesterov <oleg@redhat.com>
To: Richard Weinberger <richard@nod.at>
Cc: hannes@cmpxchg.org, mhocko@suse.cz, bsingharora@gmail.com,
kamezawa.hiroyu@jp.fujitsu.com, akpm@linux-foundation.org,
vdavydov@parallels.com, tj@kernel.org, handai.szj@taobao.com,
rientjes@google.com, rusty@rustcorp.com.au,
kirill.shutemov@linux.intel.com, linux-kernel@vger.kernel.org,
cgroups@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [RFC][PATCH] oom: Be less verbose if the oom_control event fd has listeners
Date: Thu, 5 Jun 2014 18:00:29 +0200 [thread overview]
Message-ID: <20140605160029.GA28812@redhat.com> (raw)
In-Reply-To: <539090F1.7090408@nod.at>
On 06/05, Richard Weinberger wrote:
>
> Am 05.06.2014 16:18, schrieb Oleg Nesterov:
> > On 06/05, Richard Weinberger wrote:
> >>
> >> +int mem_cgroup_has_listeners(struct mem_cgroup *memcg)
> >> +{
> >> + int ret = 0;
> >> +
> >> + if (!memcg)
> >> + goto out;
> >> +
> >> + spin_lock(&memcg_oom_lock);
> >> + ret = !list_empty(&memcg->oom_notify);
> >> + spin_unlock(&memcg_oom_lock);
> >> +
> >> +out:
> >> + return ret;
> >> +}
> >
> > Do we really need memcg_oom_lock to check list_empty() ? With or without
> > this lock we can race with list_add/del anyway, and I guess we do not care.
>
> Hmm, in mm/memcontrol.c all list_dev/add are under memcg_oom_lock.
And? How this lock can help to check list_empty() ?
list_add/del can come right after mem_cgroup_has_listeners() and change
the value of list_empty() anyway.
> What do I miss?
Or me...
Oleg.
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next prev parent reply other threads:[~2014-06-05 16:02 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-06-05 14:00 oom: Be less verbose Richard Weinberger
2014-06-05 14:00 ` [RFC][PATCH] oom: Be less verbose if the oom_control event fd has listeners Richard Weinberger
2014-06-05 14:18 ` Oleg Nesterov
2014-06-05 15:46 ` Richard Weinberger
2014-06-05 16:00 ` Oleg Nesterov [this message]
2014-06-05 16:10 ` Richard Weinberger
2014-06-05 15:00 ` Michal Hocko
2014-06-05 15:55 ` Richard Weinberger
2014-06-05 16:18 ` Michal Hocko
2014-06-05 21:58 ` Richard Weinberger
2014-06-05 21:01 ` David Rientjes
2014-06-06 9:10 ` Michal Hocko
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