On 2013/3/6 15:02, Tejun Heo wrote:
> On Tue, Mar 5, 2013 at 11:00 PM, Li Zefan <[email protected]> wrote:
>>> 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?
>
wqh->lock is used through out fs/eventfd.c. I don't know if currently there's
any kernel user using eventfd APIs in an irq handler, but at least that should
be allowed.
wake_up() is also allowed to be called from irq handler?
"allowed" should be enough reason we forbid:
spin_lock_irqsave(...)
spin_lock(...)
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