Re: [PATCH v8 net-next 5/7] net: simple poll/select low latency socketpoll

[Eliezer Tamir]

On 03/06/2013 16:59, Eliezer Tamir wrote:
> On 03/06/2013 16:15, Eric Dumazet wrote:
> > On Mon, 2013-06-03 at 11:02 +0300, Eliezer Tamir wrote:
> > >       sock = file->private_data;
> > > -    return sock->ops->poll(file, sock, wait);
> > > +
> > > +    poll_result = sock->ops->poll(file, sock, wait);
> > > +
> > > +    if (!(poll_result & (POLLRDNORM | POLLERR | POLLRDHUP |
> > > POLLHUP)) &&
> > > +        sk_valid_ll(sock->sk) && sk_poll_ll(sock->sk, 1))
> > > +            poll_result = sock->ops->poll(file, sock, NULL);
> > > +
> > > +    return poll_result;
> > >   }
> > >
> > >   static int sock_mmap(struct file *file, struct vm_area_struct *vma)
> >
> >
> > In fact, for TCP, POLLOUT event being ready can also be triggered by
> > incoming messages, as the ACK might allow the user application to push
> > more data in the write queue.
> >
> > And you might check wait->_key to avoid testing flags that user is not
> > interested into.
>
> yes, comparing to _key is more correct.
> In any case this needs to be completely rewritten for support for
> working well with a large number of sockets.

Is it possible for wait to be NULL? (do we need to check for that?)
I see that poll_does_not_wait() checks for that, but I could not find
anywhere this is actually done.

-Eliezer

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