Re: [PATCH 2/2] cgroup: Walk task list under tasklist_lock incgroup_enable_task_cg_list

[Frederic Weisbecker]

On Wed, Feb 22, 2012 at 07:03:27PM +0100, Oleg Nesterov wrote:
> Hi.
> 
> Sorry, currently I do not have the time to even read this discussion,
> just one note,
> 
> On 02/22, Frederic Weisbecker wrote:
> >
> > On Tue, Feb 21, 2012 at 05:19:34PM -0800, Paul E. McKenney wrote:
> > > On Wed, Feb 22, 2012 at 01:55:28AM +0100, Frederic Weisbecker wrote:
> > > > On Tue, Feb 21, 2012 at 02:23:43PM -0800, Mandeep Singh Baines wrote:
> > > > > Frederic Weisbecker (fweisbec@xxxxxxxxx) wrote:
> > > > > > Walking through the tasklist in cgroup_enable_task_cg_list() inside
> > > > > > an RCU read side critical section is not enough because:
> > > > > >
> > > > > > - RCU is not (yet) safe against while_each_thread()
> 
> Yes. Except I'd say it is while_each_thread() who is not safe ;)

Right.

> 
> Please do not take this into account. This should be fixed, I hope
> to send the fix "soon".

Sure, but anyway we need the read_lock here for ordering/commiting reasons.
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