Messages in this thread | | | Date | Thu, 17 Jul 2008 21:41:56 +0400 | From | Evgeniy Polyakov <> | Subject | Re: [PATCH] tcp: do not promote SPLICE_F_NONBLOCK to socket O_NONBLOCK |
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On Thu, Jul 17, 2008 at 05:47:27PM +0300, Octavian Purdila (opurdila@ixiacom.com) wrote: > > Existing behaviour was selected to be able to have a progress if socket > > does not have enough data to fill the pipe. With your change if socket > > is not opened with non-blocking mode reading will block not matter if > > SPLICE_F_NONBLOCK is set or not. > > I am probably missing some usecases here, but usually if you want to use > non-blocking I/O you need to use special approach anyway (e.g. code the > poll/epoll/select bits) so then you could open the socket with O_NONBLOCK.
It depends. Splice clearly states that it tries to be nonblocking with given flag being set, and its reading will be non-blocking indeed.
> > This is a quite serious break of the > > overall idea behind SPLICE_F_NONBLOCK. > > > > I don't know... the man page explicitly says that even when you use > SPLICE_F_NONBLOCK splice may block because of the underlying fd blocking.
Yes, but reading from the network will not.
> But more importantly, how can we solve the deadlock issue described in the > patch? Do we need all of the complications of async I/O for such a simple and > common usecase?
I'm not sure I understand how it can deadlock, please explain it in more details.
-- Evgeniy Polyakov
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