From mboxrd@z Thu Jan 1 00:00:00 1970 From: Frederic Weisbecker Subject: Re: [PATCH v3 16/28] memcg: kmem controller charge/uncharge infrastructure Date: Wed, 30 May 2012 15:53:21 +0200 Message-ID: <20120530135319.GG25094@somewhere.redhat.com> References: <1337951028-3427-1-git-send-email-glommer@parallels.com> <1337951028-3427-17-git-send-email-glommer@parallels.com> <20120530130416.GD25094@somewhere.redhat.com> <4FC61B4E.2060206@parallels.com> <20120530133736.GF25094@somewhere.redhat.com> <4FC622B5.9080600@parallels.com> Mime-Version: 1.0 Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=date:from:to:cc:subject:message-id:references:mime-version :content-type:content-disposition:in-reply-to:user-agent; bh=uW83YUccwcTDz850xIIaoiDoHGcUzbM4Q3Ld2i/545g=; b=mUgkPz1hXOpdBL9pSqmaNefnEX8M1EUlMAu3lRfuMaj7agvqprjIkF8NRgYfvt/7Rt NVoxmSeTE53GVCwasmPj62JOpAIJcnvlfm60dfAbggT1QTc2BONrCDuvdWL2g4YZI57Q 2mQHIvjXnHtywqZvZ9Ql29lww+VFRF21OnRnFPJ+BT4wkkUf30p+r99e9LLnQGnyUlxx lrNC9X91lbCRF/eSqZWUNA78eWf/3amROmx5iwmukiIqmpH45AntIi2JE5Tjxr/pfxrm XGIpbwc/4ejiXPjjl8TvJekZaZ3LB8VaPvTIQAN4ZNQ9mna2Q/QB9bYnPFNAvulDiaZJ G5FQ== Content-Disposition: inline In-Reply-To: <4FC622B5.9080600@parallels.com> Sender: owner-linux-mm@kvack.org List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Glauber Costa Cc: linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, linux-mm@kvack.org, kamezawa.hiroyu@jp.fujitsu.com, Tejun Heo , Li Zefan , Greg Thelen , Suleiman Souhlal , Michal Hocko , Johannes Weiner , devel@openvz.org, David Rientjes , Christoph Lameter , Pekka Enberg On Wed, May 30, 2012 at 05:37:57PM +0400, Glauber Costa wrote: > On 05/30/2012 05:37 PM, Frederic Weisbecker wrote: > >Right. __mem_cgroup_get_kmem_cache() fetches the memcg of the owner > >and calls memcg_create_cache_enqueue() which does css_tryget(&memcg->css). > >After this tryget I think you're fine. And in-between you're safe against > >css_set removal due to rcu_read_lock(). > > > >I'm less clear with __mem_cgroup_new_kmem_page() though... > > That one does not get memcg->css but it does call mem_cgroup_get(), > that does prevent against the memcg structure being freed, which I > believe to be good enough. What if the owner calls cgroup_exit() between mem_cgroup_from_task() and mem_cgroup_get()? The css_set which contains the memcg gets freed. Also the reference on the memcg doesn't even prevent the css_set to be removed, does it? -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754710Ab2E3Nxd (ORCPT ); Wed, 30 May 2012 09:53:33 -0400 Received: from mail-vb0-f46.google.com ([209.85.212.46]:47971 "EHLO mail-vb0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754633Ab2E3Nxb (ORCPT ); Wed, 30 May 2012 09:53:31 -0400 Date: Wed, 30 May 2012 15:53:21 +0200 From: Frederic Weisbecker To: Glauber Costa Cc: linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, linux-mm@kvack.org, kamezawa.hiroyu@jp.fujitsu.com, Tejun Heo , Li Zefan , Greg Thelen , Suleiman Souhlal , Michal Hocko , Johannes Weiner , devel@openvz.org, David Rientjes , Christoph Lameter , Pekka Enberg Subject: Re: [PATCH v3 16/28] memcg: kmem controller charge/uncharge infrastructure Message-ID: <20120530135319.GG25094@somewhere.redhat.com> References: <1337951028-3427-1-git-send-email-glommer@parallels.com> <1337951028-3427-17-git-send-email-glommer@parallels.com> <20120530130416.GD25094@somewhere.redhat.com> <4FC61B4E.2060206@parallels.com> <20120530133736.GF25094@somewhere.redhat.com> <4FC622B5.9080600@parallels.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4FC622B5.9080600@parallels.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, May 30, 2012 at 05:37:57PM +0400, Glauber Costa wrote: > On 05/30/2012 05:37 PM, Frederic Weisbecker wrote: > >Right. __mem_cgroup_get_kmem_cache() fetches the memcg of the owner > >and calls memcg_create_cache_enqueue() which does css_tryget(&memcg->css). > >After this tryget I think you're fine. And in-between you're safe against > >css_set removal due to rcu_read_lock(). > > > >I'm less clear with __mem_cgroup_new_kmem_page() though... > > That one does not get memcg->css but it does call mem_cgroup_get(), > that does prevent against the memcg structure being freed, which I > believe to be good enough. What if the owner calls cgroup_exit() between mem_cgroup_from_task() and mem_cgroup_get()? The css_set which contains the memcg gets freed. Also the reference on the memcg doesn't even prevent the css_set to be removed, does it?