Re: [4.2] commit d59cfc09c32 (sched, cgroup: replace signal_struct->group_rwsem with a global percpu_rwsem) causes regression for libvirt/kvm

[Tejun Heo]

Hello,

On Tue, Sep 15, 2015 at 11:11:45PM +0200, Christian Borntraeger wrote:
> > In fact, I would say that any userspace-controlled call to *_expedited()
> > is a bug waiting to happen and a bad idea---because userspace can, with
> > little effort, end up calling it in a loop.
> 
> Right. This also implies that we should fix this for 4.2 - I guess.

Are the percpu_rwsem changes enough?  If so, we can try to backport
those.  If those are too risky, we can revert the patches which
switched threadgroup lock to percpu_rwsem.

Thanks.

-- 
tejun
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