Re: waitqueue lockdep annotation

[Jason Baron]

On 12/01/2017 12:11 PM, Christoph Hellwig wrote:
> On Thu, Nov 30, 2017 at 05:18:07PM -0500, Jason Baron wrote:
>> Yes, but for those cases it uses the ep->poll_wait waitqueue not the
>> ep->wq, which is guarded by the ep->wq->lock.
> 
> True.  So it looks like we have one waitqueue in the system that is
> special in providing its own synchronization for waitqueues while
> entirely ignoring the waitqueue code documentation that states that
> waitqueues are internally synchronized.
> 
> We could drop the lockdep annotation, updated the documentation and
> not add any validation of the assumptions, or just make epoll fit the
> scheme used by everyone else.  So either we can drop these patches, or
> I need to fix up more of the epoll code.
> 

You could leave the annotation and do something like:
s/ep->lock/ep->wq->lock. And then that would remove the ep->lock saving
a bit of space.

Thanks,

-Jason