Is not locking task_lock in cgroup_fork() safe?

Tejun Heo tj at kernel.org
Fri Oct 19 00:38:35 UTC 2012


Hello, Frederic.

On Thu, Oct 18, 2012 at 10:53:47PM +0200, Frederic Weisbecker wrote:
> > For now, I'll revert the patches and cc stable.  Let's think about
> > improving it later.
> 
> Ok for reverting in cgroup_fork(). Is it necessary for the
> cgroup_post_fork() thing? I don't immediately see any race involved
> there.

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()")
  c84cdf75cc ("cgroup: Remove unnecessary task_lock before fetching css_set on migration")

Thanks.

-- 
tejun


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