From df528eacaf4f626fb9ea05ff7ed250f79e58ae57 Mon Sep 17 00:00:00 2001
From: Jiri Slaby <jslaby@suse.cz>
Date: Sun, 31 Oct 2010 23:17:51 +0100
Subject: [PATCH] --- yaml --- r: 221903 b: refs/heads/master c:
 100eeae2c5ce23b4db93ff320ee330ef1d740151 h: refs/heads/master i:   221901:
 1628de906865b68e208f40a887b2048cf7ac8c1c   221899:
 8dea15e89b53374f65594f75e9e26d7e2b44d313   221895:
 c4ade9cae937739e6092f0b1fd48609244837795   221887:
 be681279e7bfbc0baa0ed300711c7070adee6f05 v: v3

---
 [refs]                        |  2 +-
 trunk/drivers/tty/tty_ldisc.c | 29 +++++++++++++++++++++++++++++
 2 files changed, 30 insertions(+), 1 deletion(-)

diff --git a/[refs] b/[refs]
index d795d45ed6e9..1876fbae37d0 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: ebf7c06635fbcf21a59e60187e166c5c23c57b06
+refs/heads/master: 100eeae2c5ce23b4db93ff320ee330ef1d740151
diff --git a/trunk/drivers/tty/tty_ldisc.c b/trunk/drivers/tty/tty_ldisc.c
index 412f9775d19c..5bbf33ad49f1 100644
--- a/trunk/drivers/tty/tty_ldisc.c
+++ b/trunk/drivers/tty/tty_ldisc.c
@@ -47,6 +47,7 @@
 
 static DEFINE_SPINLOCK(tty_ldisc_lock);
 static DECLARE_WAIT_QUEUE_HEAD(tty_ldisc_wait);
+static DECLARE_WAIT_QUEUE_HEAD(tty_ldisc_idle);
 /* Line disc dispatch table */
 static struct tty_ldisc_ops *tty_ldiscs[NR_LDISCS];
 
@@ -83,6 +84,7 @@ static void put_ldisc(struct tty_ldisc *ld)
 		return;
 	}
 	local_irq_restore(flags);
+	wake_up(&tty_ldisc_idle);
 }
 
 /**
@@ -530,6 +532,23 @@ static int tty_ldisc_halt(struct tty_struct *tty)
 	return cancel_delayed_work_sync(&tty->buf.work);
 }
 
+/**
+ *	tty_ldisc_wait_idle	-	wait for the ldisc to become idle
+ *	@tty: tty to wait for
+ *
+ *	Wait for the line discipline to become idle. The discipline must
+ *	have been halted for this to guarantee it remains idle.
+ */
+static int tty_ldisc_wait_idle(struct tty_struct *tty)
+{
+	int ret;
+	ret = wait_event_interruptible_timeout(tty_ldisc_idle,
+			atomic_read(&tty->ldisc->users) == 1, 5 * HZ);
+	if (ret < 0)
+		return ret;
+	return ret > 0 ? 0 : -EBUSY;
+}
+
 /**
  *	tty_set_ldisc		-	set line discipline
  *	@tty: the terminal to set
@@ -634,8 +653,17 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc)
 
 	flush_scheduled_work();
 
+	retval = tty_ldisc_wait_idle(tty);
+
 	tty_lock();
 	mutex_lock(&tty->ldisc_mutex);
+
+	/* handle wait idle failure locked */
+	if (retval) {
+		tty_ldisc_put(new_ldisc);
+		goto enable;
+	}
+
 	if (test_bit(TTY_HUPPED, &tty->flags)) {
 		/* We were raced by the hangup method. It will have stomped
 		   the ldisc data and closed the ldisc down */
@@ -669,6 +697,7 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc)
 
 	tty_ldisc_put(o_ldisc);
 
+enable:
 	/*
 	 *	Allow ldisc referencing to occur again
 	 */