[PATCH 4.4 137/210] xtensa: ISS: dont hang if stdin EOF is reached

From: Greg Kroah-Hartman
Date: Sun Apr 10 2016 - 15:50:58 EST


4.4-stable review patch. If anyone has any objections, please let me know.

------------------

From: Max Filippov <jcmvbkbc@xxxxxxxxx>

commit 362014c8d9d51d504c167c44ac280169457732be upstream.

Simulator stdin may be connected to a file, when its end is reached
kernel hangs in infinite loop inside rs_poll, because simc_poll always
signals that descriptor 0 is readable and simc_read always returns 0.
Check simc_read return value and exit loop if it's not positive. Also
don't rewind polling timer if it's zero.

Signed-off-by: Max Filippov <jcmvbkbc@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
arch/xtensa/platforms/iss/console.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)

--- a/arch/xtensa/platforms/iss/console.c
+++ b/arch/xtensa/platforms/iss/console.c
@@ -100,21 +100,23 @@ static void rs_poll(unsigned long priv)
{
struct tty_port *port = (struct tty_port *)priv;
int i = 0;
+ int rd = 1;
unsigned char c;

spin_lock(&timer_lock);

while (simc_poll(0)) {
- simc_read(0, &c, 1);
+ rd = simc_read(0, &c, 1);
+ if (rd <= 0)
+ break;
tty_insert_flip_char(port, c, TTY_NORMAL);
i++;
}

if (i)
tty_flip_buffer_push(port);
-
-
- mod_timer(&serial_timer, jiffies + SERIAL_TIMER_VALUE);
+ if (rd)
+ mod_timer(&serial_timer, jiffies + SERIAL_TIMER_VALUE);
spin_unlock(&timer_lock);
}