[PATCH 1/8] cgroup: kill cgroup_subsys->__DEPRECATED_clear_css_refs

Tejun Heo tj at kernel.org
Wed Oct 31 16:41:23 UTC 2012

Hey, Michal.

On Wed, Oct 31, 2012 at 03:37:51PM +0100, Michal Hocko wrote:
> > +	for_each_subsys(cgrp->root, ss)
> > +		if (ss->pre_destroy)
> > +			WARN_ON_ONCE(ss->pre_destroy(cgrp));
> Hmm, I am not sure I like this WARN_ON_ONCE. First it can happen for
> more than one controller and second we can just clear CGRP_WAIT_ON_RMDIR
> and return with EBUSY. The only possible failure at the moment is when a
> new task or a child group appear.
> I know it is not a big deal because it will disappear later in the
> series but it would be more readable IMO.

The WARN_ON_ONCE() is just moved from the original
cgroup_call_pre_destroy().  We can add an error out there but that
makes future changes difficult.  It's a chicken and egg problem.  You
gotta break the loop somewhere.



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