Date: Thu, 25 Oct 2001 19:38:57 -0500 From: Alfred Perlstein <bright@mu.org> To: Robert Watson <rwatson@FreeBSD.org> Cc: arch@FreeBSD.org Subject: Re: Behavior of select() on pipes Message-ID: <20011025193857.U15052@elvis.mu.org> In-Reply-To: <Pine.NEB.3.96L.1011025181348.76017A-100000@fledge.watson.org>; from rwatson@FreeBSD.org on Thu, Oct 25, 2001 at 06:14:45PM -0400 References: <20011025161200.N15052@elvis.mu.org> <Pine.NEB.3.96L.1011025181348.76017A-100000@fledge.watson.org>
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* Robert Watson <rwatson@FreeBSD.org> [011025 17:14] wrote:
>
> On Thu, 25 Oct 2001, Alfred Perlstein wrote:
>
> > * Robert Watson <rwatson@FreeBSD.org> [011025 14:56] wrote:
> > >
> > > Alfred recently pointed me at some FreeBSD pipe behavior that I was
> > > previously unaware of: select() will always return true regarding the
> > > readability of a fifo, regardless of whether data is pending on the fifo.
> > > He referred to this as "brokenness", which is a diagnosis I tend to
> > > accept. However, it turns out to be somewhat more complicated than I
> > > thought, witnessed by the extensive discussion on freebsd-bugs, and logged
> > > in PR/19871. But to the short of it: it sounds to me like we should
> > > modify the behavior of select() to match the more popular (but possibly
> > > standards-incompliant) behavior, which allows select to block on the fifo
> > > until data is ready (found in Solaris, Linux, et al). Rather than just
> > > commit the patch, I thought I'd open myself up for broad flamage.
> > > Comments on what to do are welcome.
> >
> > If the patch safely brings us into compatibility with both Linux and
> > Solaris it's a no-brainer, just put it in, however if it puts FreeBSD
> > into some other 'mode' I think it deserves further discussion.
>
> My understanding, from my reading of the PR, is that it does so. However,
> I'm not familiar with the sections of the standards describing fifos, and
> was hoping for input from those that would.
I'll look at it, I have a couple of non freebsd hosts (blech) to
try it on.
--
-Alfred Perlstein [alfred@freebsd.org]
'Instead of asking why a piece of software is using "1970s technology,"
start asking why software is ignoring 30 years of accumulated wisdom.'
http://www.morons.org/rants/gpl-harmful.php3
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