Re: [PATCH 0/3] epoll: Add epoll_pwait1 syscall

[Fam Zheng <famz@redhat.com>]

On Thu, 01/08 17:28, Andy Lutomirski wrote:
> On Thu, Jan 8, 2015 at 5:25 PM, Fam Zheng <famz@redhat.com> wrote:
> > On Thu, 01/08 09:57, Andy Lutomirski wrote:
> >> I'd like to see a more ambitious change, since the timer isn't the
> >> only problem like this.  Specifically, I'd like a syscall that does a
> >> list of epoll-related things and then waits.  The list of things could
> >> include, at least:
> >>
> >>  - EPOLL_CTL_MOD actions: level-triggered epoll users are likely to
> >> want to turn on and off their requests for events on a somewhat
> >> regular basis.
> >
> > This sounds good to me.
> >
> >>
> >>  - timerfd_settime actions: this allows a single syscall to wait and
> >> adjust *both* monotonic and real-time wakeups.
> >
> > I'm not sure, doesn't this break orthogonality between epoll and timerfd?
> 
> Yes.  It's not very elegant, and more elegant ideas are welcome.

What is the purpose of embedding timerfd operation here? Modifying timerfd
for each poll doesn't sound a common pattern to me.

> 
> >
> >>
> >> Would this make sense?  It could look like:
> >>
> >> int epoll_mod_and_pwait(int epfd,
> >>   struct epoll_event *events, int maxevents,
> >>   struct epoll_command *commands, int ncommands,
> >>   const sigset_t *sigmask);
> >
> > What about flags?
> >
> 
> No room.  Maybe it should just be a struct for everything instead of
> separate args.

Also no room for timeout. A single struct sounds the only way to go.

Fam