Re: UDP recvmsg blocks after select(), 2.6 bug?

[Mark Mielke <mark@mark.mielke.cc>]

On Thu, Oct 07, 2004 at 03:42:04PM -0700, David S. Miller wrote:
> On Thu, 07 Oct 2004 16:39:06 -0600
> Chris Friesen <cfriesen@nortelnetworks.com> wrote:
> > However, you chopped off what I consider the interesting part of my
> > post.  I propose that if we call select() on a blocking file
> > descriptor, we verify the checksum before saying that the socket is
> > readable.  Then, at recvmsg() time, if it hasn't been checked
> > already we would check it (to allow for the case of blocking socket
> > without select()).
> So people who improperly use select() with blocking sockets get punished
> in a different way, with half the performance compared to today?

No. People who use select() and read() in the *other* documented
manner, however ill-advised, would see the expected, and at least from
the perspective of myself and a few other people around here, correct
behaviour. How much it costs to implement the correct behaviour is a
different concern, and perhaps one these people should have considered
when determining whether or not to use O_NONBLOCK...

Your position, I believe has been that the use of select() on a blocking
file descriptor is invalid. Taking this to an extreme, select() should
return EBADF or something to that effect, when passed a file descriptor
that does not have O_NONBLOCK set...

Cheers,
mark

-- 
mark@mielke.cc/markm@ncf.ca/markm@nortelnetworks.com __________________________
.  .  _  ._  . .   .__    .  . ._. .__ .   . . .__  | Neighbourhood Coder
|\/| |_| |_| |/    |_     |\/|  |  |_  |   |/  |_   | 
|  | | | | \ | \   |__ .  |  | .|. |__ |__ | \ |__  | Ottawa, Ontario, Canada

  One ring to rule them all, one ring to find them, one ring to bring them all
                       and in the darkness bind them...

                           http://mark.mielke.cc/