From ae88b227912c0ec48a0dde46fe47f423ca864059 Mon Sep 17 00:00:00 2001
From: ed <ed@FreeBSD.org>
Date: Thu, 25 Oct 2012 09:05:21 +0000
Subject: [PATCH] Correct SIGTTIN handling.

In the old TTY layer, SIGTTIN was correctly handled like this:

	while (data should be read) {
		send SIGTTIN if not foreground process group
		read data
	}

In the new TTY layer, however, this behaviour was changed, based on a
false interpretation of the standard:

	send SIGTTIN if not foreground process group
	while (data should be read) {
		read data
	}

Correct this by pushing tty_wait_background() into the ttydisc_read_*()
functions.

Reported by:	koitsu
PR:		kern/173010
MFC after:	2 weeks
---
 sys/kern/tty.c         |  9 +--------
 sys/kern/tty_ttydisc.c | 16 ++++++++++++++++
 sys/sys/tty.h          |  1 +
 3 files changed, 18 insertions(+), 8 deletions(-)

diff --git a/sys/kern/tty.c b/sys/kern/tty.c
index e9c0fb6fe554..4da8d384a8e4 100644
--- a/sys/kern/tty.c
+++ b/sys/kern/tty.c
@@ -361,7 +361,7 @@ tty_is_ctty(struct tty *tp, struct proc *p)
 	return (p->p_session == tp->t_session && p->p_flag & P_CONTROLT);
 }
 
-static int
+int
 tty_wait_background(struct tty *tp, struct thread *td, int sig)
 {
 	struct proc *p = td->td_proc;
@@ -433,13 +433,6 @@ ttydev_read(struct cdev *dev, struct uio *uio, int ioflag)
 	error = ttydev_enter(tp);
 	if (error)
 		goto done;
-
-	error = tty_wait_background(tp, curthread, SIGTTIN);
-	if (error) {
-		tty_unlock(tp);
-		goto done;
-	}
-
 	error = ttydisc_read(tp, uio, ioflag);
 	tty_unlock(tp);
 
diff --git a/sys/kern/tty_ttydisc.c b/sys/kern/tty_ttydisc.c
index 52a5df2e580d..63b144ac79d2 100644
--- a/sys/kern/tty_ttydisc.c
+++ b/sys/kern/tty_ttydisc.c
@@ -126,6 +126,10 @@ ttydisc_read_canonical(struct tty *tp, struct uio *uio, int ioflag)
 	breakc[n] = '\0';
 
 	do {
+		error = tty_wait_background(tp, curthread, SIGTTIN);
+		if (error)
+			return (error);
+
 		/*
 		 * Quite a tricky case: unlike the old TTY
 		 * implementation, this implementation copies data back
@@ -192,6 +196,10 @@ ttydisc_read_raw_no_timer(struct tty *tp, struct uio *uio, int ioflag)
 	 */
 
 	for (;;) {
+		error = tty_wait_background(tp, curthread, SIGTTIN);
+		if (error)
+			return (error);
+
 		error = ttyinq_read_uio(&tp->t_inq, tp, uio,
 		    uio->uio_resid, 0);
 		if (error)
@@ -229,6 +237,10 @@ ttydisc_read_raw_read_timer(struct tty *tp, struct uio *uio, int ioflag,
 	timevaladd(&end, &now);
 
 	for (;;) {
+		error = tty_wait_background(tp, curthread, SIGTTIN);
+		if (error)
+			return (error);
+
 		error = ttyinq_read_uio(&tp->t_inq, tp, uio,
 		    uio->uio_resid, 0);
 		if (error)
@@ -278,6 +290,10 @@ ttydisc_read_raw_interbyte_timer(struct tty *tp, struct uio *uio, int ioflag)
 	 */
 
 	for (;;) {
+		error = tty_wait_background(tp, curthread, SIGTTIN);
+		if (error)
+			return (error);
+
 		error = ttyinq_read_uio(&tp->t_inq, tp, uio,
 		    uio->uio_resid, 0);
 		if (error)
diff --git a/sys/sys/tty.h b/sys/sys/tty.h
index 42f264b9545d..96b88212bde9 100644
--- a/sys/sys/tty.h
+++ b/sys/sys/tty.h
@@ -180,6 +180,7 @@ void	tty_signal_sessleader(struct tty *tp, int signal);
 void	tty_signal_pgrp(struct tty *tp, int signal);
 /* Waking up readers/writers. */
 int	tty_wait(struct tty *tp, struct cv *cv);
+int	tty_wait_background(struct tty *tp, struct thread *td, int sig);
 int	tty_timedwait(struct tty *tp, struct cv *cv, int timo);
 void	tty_wakeup(struct tty *tp, int flags);