From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753239AbaBYPGm (ORCPT ); Tue, 25 Feb 2014 10:06:42 -0500 Received: from mail-qa0-f42.google.com ([209.85.216.42]:56924 "EHLO mail-qa0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752683AbaBYPGk (ORCPT ); Tue, 25 Feb 2014 10:06:40 -0500 Date: Tue, 25 Feb 2014 10:06:36 -0500 From: Tejun Heo To: Li Zefan Cc: Fengguang Wu , cgroups@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [cgroup/task_lock] INFO: suspicious RCU usage. Message-ID: <20140225150636.GF26788@htj.dyndns.org> References: <20140221021622.GB13515@localhost> <20140221154025.GB460@htj.dyndns.org> <530C5977.4090402@huawei.com> <530C8615.4020004@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <530C8615.4020004@huawei.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 Hello, Li. On Tue, Feb 25, 2014 at 08:01:25PM +0800, Li Zefan wrote: ... > >> So, this is from removing task_lock from task_css_set_check() and > >> adding rcu_read_lock() in cpuset_cpus_allowed() should fix it. > > > > Yeah, rcu_read_lock() should be sufficient. > > > >> I'm > >> not sure how much of task_lock() locking we currently have in cpuset > >> is actually necessary tho. Shouldn't we be able to do most with just > >> callback_mutex, if not cpuset_mutex? Li, any ideas? > >> > > > > task_lock() is also used to protect task->mems_allowed. I'll see if we > > can get rid of most (if not all) task_lock() lockings in cpuset. > > > > After a quick lock, I think except the one in cpuset_change_task_nodemask(), all > other task_lock() lockings can be replace by rcu_readlock(). I committed the original series as-is. Can you please post follow-up patches to update cpuset locking? Thanks. -- tejun