From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f70.google.com (mail-pa0-f70.google.com [209.85.220.70]) by kanga.kvack.org (Postfix) with ESMTP id 91BB26B0005 for ; Mon, 15 Aug 2016 08:46:24 -0400 (EDT) Received: by mail-pa0-f70.google.com with SMTP id ez1so102679977pab.1 for ; Mon, 15 Aug 2016 05:46:24 -0700 (PDT) Received: from mail-pa0-f65.google.com (mail-pa0-f65.google.com. [209.85.220.65]) by mx.google.com with ESMTPS id m10si26590021pab.157.2016.08.15.05.46.23 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 15 Aug 2016 05:46:23 -0700 (PDT) Received: by mail-pa0-f65.google.com with SMTP id hh10so3595364pac.1 for ; Mon, 15 Aug 2016 05:46:23 -0700 (PDT) Date: Mon, 15 Aug 2016 14:46:19 +0200 From: Michal Hocko Subject: Re: [PATCH stable-4.4 1/3] mm: memcontrol: fix cgroup creation failure after many small jobs Message-ID: <20160815124615.GD3360@dhcp22.suse.cz> References: <1470995779-10064-1-git-send-email-mhocko@kernel.org> <1470995779-10064-2-git-send-email-mhocko@kernel.org> <20160815123407.GA1153@cmpxchg.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160815123407.GA1153@cmpxchg.org> Sender: owner-linux-mm@kvack.org List-ID: To: Johannes Weiner Cc: Stable tree , Vladimir Davydov , Andrew Morton , linux-mm@kvack.org, LKML , Nikolay Borisov , Linus Torvalds On Mon 15-08-16 08:34:07, Johannes Weiner wrote: > Hi Michal, thanks for doing this. There is only one issue I can see: > > On Fri, Aug 12, 2016 at 11:56:17AM +0200, Michal Hocko wrote: > > @@ -4171,17 +4211,27 @@ static struct mem_cgroup *mem_cgroup_alloc(void) > > if (!memcg) > > return NULL; > > > > + memcg->id.id = idr_alloc(&mem_cgroup_idr, NULL, > > + 1, MEM_CGROUP_ID_MAX, > > + GFP_KERNEL); > > + if (memcg->id.id < 0) > > + goto out_free; > > + > > memcg->stat = alloc_percpu(struct mem_cgroup_stat_cpu); > > if (!memcg->stat) > > - goto out_free; > > + goto out_idr; > > > > if (memcg_wb_domain_init(memcg, GFP_KERNEL)) > > goto out_free_stat; > > > > + idr_replace(&mem_cgroup_idr, memcg, memcg->id.id); > > This publishes the memcg object too early. Before 4.5, the memcg is > not fully initialized in mem_cgroup_alloc(). You have to move the > idr_replace() down to that function (and idr_remove() on free_out). You are right. I am just wondering whether it matters. Nobody should see the id so nobody will be looking it up, no? > > return memcg; > > > > out_free_stat: > > free_percpu(memcg->stat); > > +out_idr: > > + if (memcg->id.id > 0) > > + idr_remove(&mem_cgroup_idr, memcg->id.id); > > The > 0 check seems unnecessary, no? Yes, I will drop it. Thanks! -- Michal Hocko SUSE Labs -- 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