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Date:      Sat, 15 Dec 2001 15:10:25 -0600
From:      Alfred Perlstein <alfred@FreeBSD.org>
To:        Bruce Evans <bde@zeta.org.au>
Cc:        wollman@freebsd.org, net@freebsd.org, cvs-committers@FreeBSD.org, cvs-all@FreeBSD.org
Subject:   fifo fix (Re: cvs commit: src/sys/fs/fifofs fifo_vnops.c)
Message-ID:  <20011215151025.A82439@elvis.mu.org>
In-Reply-To: <20011213120830.E79896@elvis.mu.org>; from alfred@FreeBSD.org on Thu, Dec 13, 2001 at 12:08:30PM -0600
References:  <20011212125324.R92148@elvis.mu.org> <20011213224148.M469-100000@gamplex.bde.org> <20011213120830.E79896@elvis.mu.org>

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* Alfred Perlstein <alfred@FreeBSD.org> [011213 12:08] wrote:
> * Bruce Evans <bde@zeta.org.au> [011213 05:56] wrote:
> > 
> > >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 :) )

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
@@ -199,6 +199,7 @@
 		}
 		fip->fi_readers = fip->fi_writers = 0;
 		wso->so_snd.sb_lowat = PIPE_BUF;
+		rso->so_state |= SS_CANTRCVMORE;
 	}
 	if (ap->a_mode & FREAD) {
 		fip->fi_readers++;
@@ -283,11 +284,6 @@
 	VOP_UNLOCK(ap->a_vp, 0, td);
 	error = soreceive(rso, (struct sockaddr **)0, uio, (struct mbuf **)0,
 	    (struct mbuf **)0, (int *)0);
-	/*
-	 * Clear EOF indication after first such return.
-	 */
-	if (uio->uio_resid == startresid)
-		rso->so_state &= ~SS_CANTRCVMORE;
 	vn_lock(ap->a_vp, LK_EXCLUSIVE | LK_RETRY, td);
 	if (ap->a_ioflag & IO_NDELAY)
 		rso->so_state &= ~SS_NBIO;
@@ -455,13 +451,23 @@
 	} */ *ap;
 {
 	struct file filetmp;
-	int revents = 0;
+	int s, revents = 0;
 
 	if (ap->a_events & (POLLIN | POLLPRI | POLLRDNORM | POLLRDBAND)) {
+		struct socket *so;
+		int oflg;
+
 		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);
 	}
 	if (ap->a_events & (POLLOUT | POLLWRNORM | POLLWRBAND)) {
 		filetmp.f_data = (caddr_t)ap->a_vp->v_fifoinfo->fi_writesock;


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