Re: 3.10.16 cgroup_mutex deadlock

[Li Zefan]

> Thanks Tejun and Hugh.  Sorry for my late entry in getting around to
> testing this fix. On the surface it sounds correct however I'd like to
> test this on top of 3.10.* since that is what we'll likely be running.
> I've tried to apply Hugh's patch above on top of 3.10.19 but it
> appears there are a number of conflicts.  Looking over the changes and
> my understanding of the problem I believe on 3.10 only the
> cgroup_free_fn needs to be run in a separate workqueue.  Below is the
> patch I've applied on top of 3.10.19, which I'm about to start
> testing.  If it looks like I botched the backport in any way please
> let me know so I can test a propper fix on top of 3.10.19.
> 

You didn't move css free_work to the dedicate wq as Tejun's patch does.
css free_work won't acquire cgroup_mutex, but when destroying a lot of
cgroups, we can have a lot of css free_work in the workqueue, so I'd
suggest you also use cgroup_destroy_wq for it.


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