Date: Thu, 13 Dec 2001 12:08:30 -0600 From: Alfred Perlstein <alfred@FreeBSD.org> To: Bruce Evans <bde@zeta.org.au> Cc: cvs-committers@FreeBSD.org, cvs-all@FreeBSD.org Subject: Re: cvs commit: src/sys/fs/fifofs fifo_vnops.c Message-ID: <20011213120830.E79896@elvis.mu.org> In-Reply-To: <20011213224148.M469-100000@gamplex.bde.org>; from bde@zeta.org.au on Thu, Dec 13, 2001 at 10:57:16PM %2B1100 References: <20011212125324.R92148@elvis.mu.org> <20011213224148.M469-100000@gamplex.bde.org>
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* Bruce Evans <bde@zeta.org.au> [011213 05:56] wrote:
> On Wed, 12 Dec 2001, Alfred Perlstein wrote:
>
> > * Bruce Evans <bde@zeta.org.au> [011212 06:13] wrote:
> > > On Wed, 12 Dec 2001, Alfred Perlstein wrote:
> > >
> > > > alfred 2001/12/12 01:35:33 PST
> > > >
> > > > Modified files:
> > > > sys/fs/fifofs fifo_vnops.c
> > > > Log:
> > > > Fix select on named pipes without a reader.
> ^^^^^^ ITYM "writer"
> > > >
> > > > PR: kern/19871
> > > > MFC after: 1 month
> > >
> > > No, it will be backed out. I believe other systems implement this by
> > > making the semantics of select() incompatible with read(). They don't
> > > just break read().
> >
> > Could you be more clear on how this breaks read(2)?
>
> >From POSIX.1-200x-draft7 (this has not changed since at least the 1990
> version):
>
> ! 36609 When attempting to read from an empty pipe or FIFO:
> !
> ! 36610 * If no process has the pipe open for writing, read( ) shall return 0 to indicate end-of-file.
>
> The changes make read() block instead, at least for the non-O_NONBLOCK case.
> I'm not sure of the effect of the change in the O_NONBLOCK case, but it
> seems likely that -1/EAGAIN is returned instead of 0/no-error.
Ok, I can fix this. (I hope :) )
--
-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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