On 2013/3/6 15:02, Tejun Heo wrote: > On Tue, Mar 5, 2013 at 11:00 PM, Li Zefan <lizefan@xxxxxxxxxx> 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(...) -- To unsubscribe from this list: send the line "unsubscribe cgroups" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
