From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wi0-f180.google.com (mail-wi0-f180.google.com [209.85.212.180]) by kanga.kvack.org (Postfix) with ESMTP id 7A45E6B0037 for ; Thu, 5 Jun 2014 12:10:38 -0400 (EDT) Received: by mail-wi0-f180.google.com with SMTP id hi2so3829015wib.7 for ; Thu, 05 Jun 2014 09:10:37 -0700 (PDT) Received: from radon.swed.at (a.ns.miles-group.at. [95.130.255.143]) by mx.google.com with ESMTPS id pf7si12237207wjb.9.2014.06.05.09.10.26 for (version=TLSv1 cipher=RC4-SHA bits=128/128); Thu, 05 Jun 2014 09:10:26 -0700 (PDT) Message-ID: <53909669.8000007@nod.at> Date: Thu, 05 Jun 2014 18:10:17 +0200 From: Richard Weinberger MIME-Version: 1.0 Subject: Re: [RFC][PATCH] oom: Be less verbose if the oom_control event fd has listeners References: <1401976841-3899-1-git-send-email-richard@nod.at> <1401976841-3899-2-git-send-email-richard@nod.at> <20140605141841.GA23796@redhat.com> <539090F1.7090408@nod.at> <20140605160029.GA28812@redhat.com> In-Reply-To: <20140605160029.GA28812@redhat.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Oleg Nesterov 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 Am 05.06.2014 18:00, schrieb Oleg Nesterov: > 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. Ahh, now I can follow your mind. :) Thanks, //richard -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org