Re: [PATCH] epoll: Add a flag, EPOLLWAKEUP, to prevent suspend while epoll events are ready

Rafael J. Wysocki
2012-07-16T10:54:39Z

On Monday, July 16, 2012, Michael Kerrisk wrote:
> Arve, Rafael,
>
> On Tue, May 1, 2012 at 7:33 AM, Arve Hjønnevåg <arve@android.com> wrote:
> > When an epoll_event, that has the EPOLLWAKEUP flag set, is ready, a
> > wakeup_source will be active to prevent suspend. This can be used to
> > handle wakeup events from a driver that support poll, e.g. input, if
> > that driver wakes up the waitqueue passed to epoll before allowing
> > suspend.
>
> It's late it the -rc series,

Well, exactly. :-)

> but it strikes me that CAP_EPOLLWAKEUP is
> a poor name for the capability that governs the use of EPOLLWAKEUP.
> While on the one hand some capabilities are overloaded
> (https://lwn.net/Articles/486306/), on the other hand we should avoid
> adding individual capabilities for each new API feature (otherwise
> capabilities become administratively unwieldy).
>
> This capability is not really about "EPOLL". It's about the ability to
> block system suspend. Therefore, IMO, a better name would be something
> like: CAP_BLOCK_SUSPEND. This name is better because there might be
> some other API feature that is later added that also has the effect of
> preventing system suspends, and we could reasonably govern that
> feature with the same capability.
>
> Does that seem sensible to you? I can send a patch for the name change.

I'm not sure what Arve thinks about that, but I'd be fine with that.

Arve, what do you think?

Rafael