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: Thu, 18 Oct 2012 17:58:01 -0700 Message-ID: <20121019005801.GF13370@google.com> References: <20121008020000.GB2575@localhost> <20121016193341.GD16166@google.com> <20121018200705.GG13370@google.com> <20121019003835.GE13370@google.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <20121019003835.GE13370-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org> 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 Cc: cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, containers-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, LKML List-Id: containers.vger.kernel.org Hello, again. On Thu, Oct 18, 2012 at 05:38:35PM -0700, Tejun Heo wrote: > Even if there isn't an actual race, the comment is dead wrong. I'm > reverting the following three patches. Let's try again later. > > 7e381b0eb1 ("cgroup: Drop task_lock(parent) on cgroup_fork()") > 7e3aa30ac8 ("cgroup: Remove task_lock() from cgroup_post_fork()") So, after some more looking, I think the following is correct and doesn't need to be reverted. It's depending on threadgroup locking from migration path to synchronize against exit path which is always performed. > c84cdf75cc ("cgroup: Remove unnecessary task_lock before fetching css_set on migration") Frederic, were you trying to say that the above commit is correct? Li, do you agree? Thanks. -- tejun