Switch behavior of fifos to more closely match what goes on in other OSes.

Basically FIFOs become a real pain to abuse as a rendevous point without
this change because you can't really select(2) on them because they always
return ready even though there is no writer (to signal EOF).

Obtained from: BSD/os

1 files changed, 5 insertions, 0 deletions

diff --git a/sys/fs/fifofs/fifo_vnops.c b/sys/fs/fifofs/fifo_vnops.c
index baddfa4..e69532e 100644
--- a/sys/fs/fifofs/fifo_vnops.c
+++ b/sys/fs/fifofs/fifo_vnops.c
@@ -284,6 +284,11 @@ fifo_read(ap)
 	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;