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Re: regression 4.4: deadlock in with cgroup percpu_rwsem

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On Wed, Jan 20, 2016 at 11:04:35AM -0500, Tejun Heo wrote:
> On Wed, Jan 20, 2016 at 10:30:07AM -0500, Tejun Heo wrote:
> > > So the current place in free_fair_sched_group() is far too late to be
> > > calling remove_entity_load_avg(). But I'm not sure where I should put
> > > it, it needs to be in a place where we know the group is going to die
> > > but its parent is guaranteed to still exist.
> > > 
> > > Would offline be that place?
> > 
> > Hmmm... css_free would be with the following patch.
> 
> I thought a bit more about this and I think the right thing to do here
> is making both css_offline and css_free follow the ancestry order.
> I'll post a patch to do that soon.  offline is called at the head of
> destruction when the css is made invisble and draining of existing
> refs starts.  free at the end of that process.  Tree ordering
> shouldn't be where the two differ.

OK, that would be good. Meanwhile the above seems to suggest that
css_offline is already hierarchical?

I get the feeling the way sched uses the css_{offline,release,free} is
sub-optimal. cpu_cgrp_subsys::css_free := sched_destroy_group() does a
call_rcu, whereas if I read the comment with css_free_work_fn()
correctly, this is already after a grace-period, so yet another doesn't
make sense.

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Re: regression 4.4: deadlock in with cgroup percpu_rwsem Christian Borntraeger <borntraeger@de.ibm.com> - 2016-01-15 16:20 +0100
  Re: regression 4.4: deadlock in with cgroup percpu_rwsem Peter Zijlstra <peterz@infradead.org> - 2016-01-18 19:40 +0100
    Re: regression 4.4: deadlock in with cgroup percpu_rwsem Christian Borntraeger <borntraeger@de.ibm.com> - 2016-01-18 19:50 +0100
      Re: regression 4.4: deadlock in with cgroup percpu_rwsem Heiko Carstens <heiko.carstens@de.ibm.com> - 2016-01-19 11:00 +0100
        Re: regression 4.4: deadlock in with cgroup percpu_rwsem Christian Borntraeger <borntraeger@de.ibm.com> - 2016-01-19 20:40 +0100
          Re: regression 4.4: deadlock in with cgroup percpu_rwsem Tejun Heo <tj@kernel.org> - 2016-01-19 20:40 +0100
            Re: regression 4.4: deadlock in with cgroup percpu_rwsem Heiko Carstens <heiko.carstens@de.ibm.com> - 2016-01-20 08:10 +0100
              Re: regression 4.4: deadlock in with cgroup percpu_rwsem Christian Borntraeger <borntraeger@de.ibm.com> - 2016-01-20 11:20 +0100
                Re: regression 4.4: deadlock in with cgroup percpu_rwsem Peter Zijlstra <peterz@infradead.org> - 2016-01-20 11:40 +0100
                Re: regression 4.4: deadlock in with cgroup percpu_rwsem Peter Zijlstra <peterz@infradead.org> - 2016-01-20 11:50 +0100
                Re: regression 4.4: deadlock in with cgroup percpu_rwsem Tejun Heo <tj@kernel.org> - 2016-01-20 16:40 +0100
                Re: regression 4.4: deadlock in with cgroup percpu_rwsem Tejun Heo <tj@kernel.org> - 2016-01-20 17:10 +0100
                Re: regression 4.4: deadlock in with cgroup percpu_rwsem Peter Zijlstra <peterz@infradead.org> - 2016-01-20 17:50 +0100
                Re: regression 4.4: deadlock in with cgroup percpu_rwsem Tejun Heo <tj@kernel.org> - 2016-01-20 18:00 +0100
                Re: regression 4.4: deadlock in with cgroup percpu_rwsem "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-01-23 03:10 +0100
                Re: regression 4.4: deadlock in with cgroup percpu_rwsem Christoph Hellwig <hch@lst.de> - 2016-01-25 09:50 +0100
                Re: regression 4.4: deadlock in with cgroup percpu_rwsem Tejun Heo <tj@kernel.org> - 2016-01-25 20:40 +0100
                Re: regression 4.4: deadlock in with cgroup percpu_rwsem Christoph Hellwig <hch@lst.de> - 2016-01-26 16:00 +0100
                Re: regression 4.4: deadlock in with cgroup percpu_rwsem Tejun Heo <tj@kernel.org> - 2016-01-26 16:30 +0100
                Re: regression 4.4: deadlock in with cgroup percpu_rwsem Christoph Hellwig <hch@lst.de> - 2016-01-26 17:50 +0100
                Re: regression 4.4: deadlock in with cgroup percpu_rwsem Peter Zijlstra <peterz@infradead.org> - 2016-01-20 12:00 +0100
                Re: regression 4.4: deadlock in with cgroup percpu_rwsem Christian Borntraeger <borntraeger@de.ibm.com> - 2016-01-21 09:30 +0100
                Re: regression 4.4: deadlock in with cgroup percpu_rwsem Peter Zijlstra <peterz@infradead.org> - 2016-01-21 10:30 +0100

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