Date: Tue, 18 Dec 2001 00:09:42 +1100 (EST) From: Bruce Evans <bde@zeta.org.au> To: Alfred Perlstein <alfred@FreeBSD.org> Cc: <wollman@FreeBSD.org>, <net@FreeBSD.org>, <cvs-committers@FreeBSD.org>, <cvs-all@FreeBSD.org> Subject: Re: fifo fix (Re: cvs commit: src/sys/fs/fifofs fifo_vnops.c) Message-ID: <20011217230720.N13599-100000@gamplex.bde.org> In-Reply-To: <20011215151025.A82439@elvis.mu.org>
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On Sat, 15 Dec 2001, Alfred Perlstein wrote:
> Can people take a look at this fix? It seems to dtrt, but I need feedback
> here.
>
> It basically backs out my last two revisions and changes the hacks the
> poll call to seemingly do the right thing.
>
> Index: fifo_vnops.c
> ===================================================================
> RCS file: /home/ncvs/src/sys/fs/fifofs/fifo_vnops.c,v
> retrieving revision 1.57
> diff -u -r1.57 fifo_vnops.c
> --- fifo_vnops.c 12 Dec 2001 09:35:33 -0000 1.57
> +++ fifo_vnops.c 15 Dec 2001 21:25:30 -0000
> ...
> @@ -455,13 +451,23 @@
> } */ *ap;
> {
> struct file filetmp;
> - int revents = 0;
> + int s, revents = 0;
New style bug: disordered declaration. (Old style bug: initialized in
auto declaration.)
>
> if (ap->a_events & (POLLIN | POLLPRI | POLLRDNORM | POLLRDBAND)) {
> + struct socket *so;
> + int oflg;
Style bugs: nested declarations.
> +
> filetmp.f_data = (caddr_t)ap->a_vp->v_fifoinfo->fi_readsock;
> + so = (struct socket *)filetmp.f_data;
> + s = splnet();
> + oflg = so->so_state & SS_CANTRCVMORE;
> + if (ap->a_vp->v_fifoinfo->fi_writers == 0)
> + so->so_state &= ~SS_CANTRCVMORE;
> if (filetmp.f_data)
> revents |= soo_poll(&filetmp, ap->a_events, ap->a_cred,
> ap->a_td);
> + so->so_state |= oflg;
> + splx(s);
I'm not happy with frobbing the socket state. I suggest frobbing the
events mask instead. Either use a flag to tell sopoll() to ignore
SS_CANTRCVMORE, or use new events POLLIN_IGNORE_EOF and
POLLRDNORM_IGNORE_EOF (convert the userland POLLIN/POLLRDNORM to these
and change sopoll() to support them).
> }
> if (ap->a_events & (POLLOUT | POLLWRNORM | POLLWRBAND)) {
> filetmp.f_data = (caddr_t)ap->a_vp->v_fifoinfo->fi_writesock;
>
Similar changes may be needed for kevent(). kevent() has a way to modify
modify the usual watermark handling for reads, but doesn't have anything
similar for EOFs, although it already has more complete EOF handling
(filt_kqread() sets EV_EOF for EOFs, but sopoll() is missing support for
POLLHUP).
Bruce
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