xtensa: ISS: don't hang if stdin EOF is reached

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.

Cc: stable@vger.kernel.org
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

1 files changed, 6 insertions, 4 deletions

diff --git a/arch/xtensa/platforms/iss/console.c b/arch/xtensa/platforms/iss/console.c
index 70cb408bc20d..92d785fefb6d 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);
 }