From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: Re: Is not locking task_lock in cgroup_fork() safe? Date: Mon, 8 Oct 2012 11:01:38 +0900 Message-ID: <20121008020138.GA4188@localhost> References: <20121008020000.GB2575@localhost> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <20121008020000.GB2575@localhost> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: containers-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: containers-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: Frederic Weisbecker , Li Zefan , containers-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: containers.vger.kernel.org On Mon, Oct 08, 2012 at 11:00:00AM +0900, Tejun Heo wrote: > 7e381b0eb1 ("cgroup: Drop task_lock(parent) on cgroup_fork()") removed > task_lock from cgroup_fork citing that current->cgroups can't change > due to threadgroup_change locking; however, threadgroup_change locking > is used only during CLONE_THREAD forking. If @current is forking a > new process, there's nothing preventing someone else to migrate the > parent while forking is in progress and delete the css_set it > currently is using. Am I confused somewhere? Also, please note that task_lock is likely to be hot on local CPU at that point and avoiding it there might not really buy much. Thanks. -- tejun