tty: amiserial: fix broken TIOCMIWAIT

A change replacing interruptible_sleep_on() inadvertently broke the TIOCMIWAIT implementation which now immediately returns -EIO (unless there is a racing modem status update).

Replace the old hangup (and signal) detection with a check for the TTY_IO_ERROR flag which is set on hangup.

Fixes 591cee0a3563 ("tty/amiserial: avoid interruptible_sleep_on")

Reported-by [email protected]

Link https://lore.kernel.org/[email protected] open here

Cc [email protected] # 3.14

Cc Arnd Bergmann <[email protected]>

Signed-off-by Johan Hovold <[email protected]>

---
  drivers/tty/amiserial.c | 9 ++++-----
  1 file changed, 4 insertions(+), 5 deletions(-)

drivers/tty/amiserial.c +4 -5

index 28af0fd98181..60f6060b893d 100644
@@ -1138,11 +1138,6 @@ static int rs_ioctl(struct tty_struct *tty,
  				local_irq_save(flags);
  				cnow = info->icount; /* atomic copy */
  				local_irq_restore(flags);
-				if (cnow.rng == cprev.rng && cnow.dsr == cprev.dsr &&
-				    cnow.dcd == cprev.dcd && cnow.cts == cprev.cts) {
-					ret = -EIO; /* no change => error */
-					break;
-				}
  				if ( ((arg & TIOCM_RNG) && (cnow.rng != cprev.rng)) ||
  				     ((arg & TIOCM_DSR) && (cnow.dsr != cprev.dsr)) ||
  				     ((arg & TIOCM_CD)  && (cnow.dcd != cprev.dcd)) ||

@@ -1150,6 +1145,10 @@ static int rs_ioctl(struct tty_struct *tty,
  					ret = 0;
  					break;
  				}
+				if (tty_io_error(tty)) {
+					ret = -EIO;
+					break;
+				}
  				schedule();
  				/* see if a signal did it */
  				if (signal_pending(current)) {