[PATCH 3.19.y-ckt 086/170] xtensa: ISS: don't hang if stdin EOF is reached

[Kamal Mostafa]

3.19.8-ckt18 -stable review patch.  If anyone has any objections, please let me 
know.

---8<------------------------------------------------------------

From: Max Filippov <jcmvb...@gmail.com>

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 <jcmvb...@gmail.com>
Signed-off-by: Kamal Mostafa <ka...@canonical.com>
---
 arch/xtensa/platforms/iss/console.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/arch/xtensa/platforms/iss/console.c 
b/arch/xtensa/platforms/iss/console.c
index 70cb408..92d785f 100644
--- 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);
 }
 
-- 
2.7.4