On Tue, Mar 5, 2013 at 11:00 PM, Li Zefan [off-list ref] wrote:

quoted

Why should wqh->lock be hard-irq-safe?  Is it actually grabbed from
irq context?

becase cgroup_event_wake() is a callback to a wait queue, and it's wake_up()
that acquires wqh->lock with irq disabled.

So, acquiring a lock with irq disabled doesn't make it a irq lock.
Being grabbed *from* irq handler makes it a irq lock. Would the
wake_up() happen from irq handler?

Thanks.

-- 
tejun