From 0e42d26f9cf75079dae4c99c734dc6e99b7258eb Mon Sep 17 00:00:00 2001
From: Ingo Molnar <mingo@elte.hu>
Date: Fri, 3 Jul 2009 08:30:01 -0500
Subject: [PATCH] drivers/serial: call flush_to_ldisc when the irq is threaded

commit 7f36d9deaafb246caadc3a94d785e9d856209e01 in tip.

Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/drivers/char/tty_buffer.c b/drivers/char/tty_buffer.c
index 66fa4e1..17dfa02 100644
--- a/drivers/char/tty_buffer.c
+++ b/drivers/char/tty_buffer.c
@@ -492,10 +492,14 @@ void tty_flip_buffer_push(struct tty_struct *tty)
 		tty->buf.tail->commit = tty->buf.tail->used;
 	spin_unlock_irqrestore(&tty->buf.lock, flags);
 
+#ifndef CONFIG_PREEMPT_RT
 	if (tty->low_latency)
 		flush_to_ldisc(&tty->buf.work.work);
 	else
 		schedule_delayed_work(&tty->buf.work, 1);
+#else
+	flush_to_ldisc(&tty->buf.work.work);
+#endif
 }
 EXPORT_SYMBOL(tty_flip_buffer_push);
 
diff --git a/drivers/serial/8250.c b/drivers/serial/8250.c
index e348e3c..708b6d9 100644
--- a/drivers/serial/8250.c
+++ b/drivers/serial/8250.c
@@ -1598,7 +1598,12 @@ static irqreturn_t serial8250_interrupt(int irq, void *dev_id)
 
 		l = l->next;
 
-		if (l == i->head && pass_counter++ > PASS_LIMIT) {
+		/*
+		 * On preempt-rt we can be preempted and run in our
+		 * own thread.
+		 */
+		if (!preempt_rt() && l == i->head &&
+		    pass_counter++ > PASS_LIMIT) {
 			/* If we hit this, we're dead. */
 			printk(KERN_ERR "serial8250: too much work for "
 				"irq%d\n", irq);
-- 
1.7.1.1