Re: [PATCH mmotm 1/2] cgroup: fix to stop adding a new task while rmdir going on

[KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>]

On Wed, 10 Dec 2008 14:48:37 -0800
Paul Menage <menage@google.com> wrote:

> On Tue, Dec 9, 2008 at 8:35 PM, KAMEZAWA Hiroyuki
> <kamezawa.hiroyu@jp.fujitsu.com> wrote:
> > still need reviews.
> > ==
> > Recently, pre_destroy() was moved to out of cgroup_lock() for avoiding
> > dead lock. But, by this, serialization between task attach and rmdir()
> > is lost.
> >
> > This adds CGRP_TRY_REMOVE flag to cgroup and check it at attaching.
> > If attach_pid founds CGRP_TRY_REMOVE, it returns -EBUSY.
> 
> As I've mentioned in other threads, I think the fix is to restore the
> locking for pre_destroy(), and solve the other potential deadlocks in
> better ways.
> 
Sure.

> This patch can result in an attach falsely getting an EBUSY when it
> shouldn't really do so (since the cgroup wasn't really going away).
> 
yes, it's also my concern. I'll think again.

-Kame

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