From mboxrd@z Thu Jan 1 00:00:00 1970 From: Richard Weinberger Subject: Re: [RFC][PATCH] oom: Be less verbose if the oom_control event fd has listeners Date: Thu, 05 Jun 2014 17:46:57 +0200 Message-ID: <539090F1.7090408@nod.at> References: <1401976841-3899-1-git-send-email-richard@nod.at> <1401976841-3899-2-git-send-email-richard@nod.at> <20140605141841.GA23796@redhat.com> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20140605141841.GA23796-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> Sender: cgroups-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-ID: Content-Type: text/plain; charset="us-ascii" To: Oleg Nesterov Cc: hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org, mhocko-AlSwsSmVLrQ@public.gmane.org, bsingharora-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, kamezawa.hiroyu-+CUm20s59erQFUHtdCDX3A@public.gmane.org, akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org, vdavydov-bzQdu9zFT3WakBO8gow8eQ@public.gmane.org, tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, handai.szj-3b8fjiQLQpfQT0dZR+AlfA@public.gmane.org, rientjes-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org, rusty-8n+1lVoiYb80n/F98K4Iww@public.gmane.org, kirill.shutemov-VuQAYsv1563Yd54FQh9/CA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org 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. What do I miss? Thanks, //richard