Instead of trying to emulate select/poll semantics with respect to EOF

by mutating so_state before calling soo_poll(), call soo_poll() normally
but avoid setting SS_CANTRCVMORE in the reader's so_state on first open.
This fixes EOF detection in select/poll on the reader side when the write
side is closed.  Also set SS_ISDISCONNECTED when the writer count reaches
zero so POLLHUP is set in revents.  Unlike Unix domain sockets, we need
to clear the EOF indicator after it has been read so that subsequent
reads will block waiting for a new writer.  This now passes regress.

1 files changed, 10 insertions, 16 deletions

diff --git a/sys/miscfs/fifofs/fifo_vnops.c b/sys/miscfs/fifofs/fifo_vnops.c
index 5b8c10fcb3f..c01becf6e5c 100644
--- a/sys/miscfs/fifofs/fifo_vnops.c
+++ b/sys/miscfs/fifofs/fifo_vnops.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: fifo_vnops.c,v 1.41 2014/09/14 14:17:26 jsg Exp $	*/
+/*	$OpenBSD: fifo_vnops.c,v 1.42 2014/10/09 16:36:36 millert Exp $	*/
 /*	$NetBSD: fifo_vnops.c,v 1.18 1996/03/16 23:52:42 christos Exp $	*/
 
 /*
@@ -147,8 +147,8 @@ fifo_open(void *v)
 			return (error);
 		}
 		fip->fi_readers = fip->fi_writers = 0;
+		wso->so_state |= SS_CANTSENDMORE;
 		wso->so_snd.sb_lowat = PIPE_BUF;
-		rso->so_state |= SS_CANTRCVMORE;
 	}
 	if (ap->a_mode & FREAD) {
 		fip->fi_readers++;
@@ -165,7 +165,7 @@ fifo_open(void *v)
 			goto bad;
 		}
 		if (fip->fi_writers == 1) {
-			fip->fi_readsock->so_state &= ~SS_CANTRCVMORE;
+			fip->fi_readsock->so_state &= ~(SS_CANTRCVMORE|SS_ISDISCONNECTED);
 			if (fip->fi_readers > 0)
 				wakeup(&fip->fi_readers);
 		}
@@ -224,6 +224,9 @@ fifo_read(void *v)
 		    ap->a_vp->v_fifoinfo->fi_writers == 0)
 			error = 0;
 	}
+	/* Clear EOF indicator so we have a clean slate for a new writer. */
+	if (error == 0)
+		rso->so_state &= ~(SS_CANTRCVMORE|SS_ISDISCONNECTED);
 	return (error);
 }
 
@@ -287,24 +290,12 @@ fifo_poll(void *v)
 {
 	struct vop_poll_args *ap = v;
 	struct file filetmp;
-	short ostate;
 	int revents = 0;
 
 	if (ap->a_events & (POLLIN | POLLPRI | POLLRDNORM | POLLRDBAND)) {
-		/*
-		 * Socket and FIFO poll(2) semantics differ wrt EOF on read.
-		 * Unlike a normal socket, FIFOs don't care whether or not
-		 * SS_CANTRCVMORE is set.  To get the correct semantics we
-		 * must clear SS_CANTRCVMORE from so_state temporarily.
-		 */
-		ostate = ap->a_vp->v_fifoinfo->fi_readsock->so_state;
-		if (ap->a_events & (POLLIN | POLLRDNORM))
-			ap->a_vp->v_fifoinfo->fi_readsock->so_state &=
-			    ~SS_CANTRCVMORE;
 		filetmp.f_data = ap->a_vp->v_fifoinfo->fi_readsock;
 		if (filetmp.f_data)
 			revents |= soo_poll(&filetmp, ap->a_events, ap->a_p);
-		ap->a_vp->v_fifoinfo->fi_readsock->so_state = ostate;
 	}
 	if (ap->a_events & (POLLOUT | POLLWRNORM | POLLWRBAND)) {
 		filetmp.f_data = ap->a_vp->v_fifoinfo->fi_writesock;
@@ -344,8 +335,11 @@ fifo_close(void *v)
 			socantsendmore(fip->fi_writesock);
 	}
 	if (ap->a_fflag & FWRITE) {
-		if (--fip->fi_writers == 0)
+		if (--fip->fi_writers == 0) {
+			/* SS_ISDISCONNECTED will result in POLLHUP */
+			fip->fi_readsock->so_state |= SS_ISDISCONNECTED;
 			socantrcvmore(fip->fi_readsock);
+		}
 	}
 	if (fip->fi_readers == 0 && fip->fi_writers == 0) {
 		error1 = soclose(fip->fi_readsock);