Groups > comp.os.linux.development.apps > #473

Re: Strange EPOLLOUT|EPOLLET behaviour (spurious events)

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From	Christof Meerwald <NOSPAM-seeMySig+upk5+@usenet.cmeerw.org>
Subject	Re: Strange EPOLLOUT\|EPOLLET behaviour (spurious events)
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On Wed, 25 Apr 2012 23:11:51 +0100, Rainer Weikusat wrote:
> Christof Meerwald <NOSPAM-seeMySig+uyk5+@usenet.cmeerw.org> writes:
>> But as I am using EPOLLET, I wouldn't expect to get any EPOLLOUT
>> events on that socket as send never returns EAGAIN (and there isn't
>> any state transition).
> That's expected behaviour: You get EPOLLOUT as soon as 'a send
> operation' completed.

Well, that's what appears to be happening, but is it documented
anywhere?

Looking at http://linux.die.net/man/7/epoll I see:

"The suggested way to use epoll as an edge-triggered (EPOLLET)
interface is as follows: with nonblocking file descriptors; and by
waiting for an event only after read(2) or write(2) return EAGAIN."

and

"Do I need to continuously read/write a file descriptor until EAGAIN
when using the EPOLLET flag (edge-triggered behavior)? Receiving an
event from epoll_wait(2) should suggest to you that such file
descriptor is ready for the requested I/O operation. You must consider
it ready until the next (nonblocking) read/write yields EAGAIN."

Nothing there suggests that I should get an EPOLLOUT as soon as "a
send operation" completed.

Christof

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Strange EPOLLOUT|EPOLLET behaviour (spurious events) Christof Meerwald <NOSPAM-seeMySig+uyk5+@usenet.cmeerw.org> - 2012-04-25 20:38 +0000
  Re: Strange EPOLLOUT|EPOLLET behaviour (spurious events) Rainer Weikusat <rweikusat@mssgmbh.com> - 2012-04-25 23:11 +0100
    Re: Strange EPOLLOUT|EPOLLET behaviour (spurious events) Christof Meerwald <NOSPAM-seeMySig+upk5+@usenet.cmeerw.org> - 2012-04-26 06:01 +0000
      Re: Strange EPOLLOUT|EPOLLET behaviour (spurious events) Rainer Weikusat <rweikusat@mssgmbh.com> - 2012-04-26 15:14 +0100
      Re: Strange EPOLLOUT|EPOLLET behaviour (spurious events) Christof Meerwald <NOSPAM-seeMySig+u0k5+@usenet.cmeerw.org> - 2012-04-26 21:11 +0000

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