From 079317a65d05ce52b69b7d47fe1fb419d40a4395 Mon Sep 17 00:00:00 2001
From: Vijay Kumar <vijay.ac.kumar@oracle.com>
Date: Wed, 23 Dec 2015 10:55:33 -0800
Subject: tty/serial: Skip 'NULL' char after console break when sysrq enabled

When sysrq is triggered from console, serial driver for SUN hypervisor
console receives a console break and enables the sysrq. It expects a valid
sysrq char following with break. Meanwhile if driver receives 'NULL'
ASCII char then it disables sysrq and sysrq handler will never be invoked.

This fix skips calling uart sysrq handler when 'NULL' is received while
sysrq is enabled.

Signed-off-by: Vijay Kumar <vijay.ac.kumar@oracle.com>
Acked-by: Karl Volz <karl.volz@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/tty/serial/sunhv.c b/drivers/tty/serial/sunhv.c
index f224e8a..ca0d380 100644
--- a/drivers/tty/serial/sunhv.c
+++ b/drivers/tty/serial/sunhv.c
@@ -148,8 +148,10 @@ static int receive_chars_read(struct uart_port *port)
 			uart_handle_dcd_change(port, 1);
 		}
 
-		for (i = 0; i < bytes_read; i++)
-			uart_handle_sysrq_char(port, con_read_page[i]);
+		if (port->sysrq != 0 &&  *con_read_page) {
+			for (i = 0; i < bytes_read; i++)
+				uart_handle_sysrq_char(port, con_read_page[i]);
+		}
 
 		if (port->state == NULL)
 			continue;
-- 
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