From mboxrd@z Thu Jan 1 00:00:00 1970 From: Li Zefan Subject: Re: Is not locking task_lock in cgroup_fork() safe? Date: Fri, 19 Oct 2012 16:50:34 +0800 Message-ID: <5081145A.2010307@huawei.com> References: <20121008020000.GB2575@localhost> <20121016193341.GD16166@google.com> <20121018200705.GG13370@google.com> <20121019003835.GE13370@google.com> <20121019005801.GF13370@google.com> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20121019005801.GF13370-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org> Sender: cgroups-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-ID: Content-Type: text/plain; charset="us-ascii" To: Tejun Heo Cc: Frederic Weisbecker , containers-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, LKML On 2012/10/19 8:58, Tejun Heo wrote: > 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? > This one does look innocent.