Re: epoll (was Re: [PATCH] async poll for 2.5)

[Dan Kegel]

Mark Mielke wrote:
>>>>>   while (read() == EAGAIN)
>>>>>       wait(POLLIN);
> 
> I find myself still not understanding this thread. Lots of examples of
> code that should or should not be used, but I would always choose:
> 
>    ... ensure file descriptor is blocking ...
>    for (;;) {
>        int nread = read(...);
>        ...
>    }
> 
> Over the above, or any derivative of the above.
> 
> What would be the point of using an event notification mechanism for
> synchronous reads with no other multiplexed options?
> 
> A 'proper' event loop is significantly more complicated. Since everybody
> here knows this... I'm still confused...

I was afraid someone would be confused by the examples.  Davide loves
coroutines (check out http://www.xmailserver.org/linux-patches/nio-improve.html )
and I think his examples are written in that style.  He really means
what you think he should be meaning :-)
which is something like
     while (1) {
         grab next bunch of events from epoll
         for each event
             while (do_io(event->fd) != EAGAIN);
     }
I'm pretty sure.

- Dan