tty: Only guarantee termios read safety for throttle/unthrottle
No tty driver modifies termios during throttle() or unthrottle().
Therefore, only read safety is required.
However, tty_throttle_safe and tty_unthrottle_safe must still be
mutually exclusive; introduce throttle_mutex for that purpose.
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/tty/tty_ioctl.c b/drivers/tty/tty_ioctl.c
index 9ce20df..03ba081 100644
--- a/drivers/tty/tty_ioctl.c
+++ b/drivers/tty/tty_ioctl.c
@@ -151,7 +151,7 @@
{
int ret = 0;
- down_write(&tty->termios_rwsem);
+ mutex_lock(&tty->throttle_mutex);
if (!test_bit(TTY_THROTTLED, &tty->flags)) {
if (tty->flow_change != TTY_THROTTLE_SAFE)
ret = 1;
@@ -161,7 +161,7 @@
tty->ops->throttle(tty);
}
}
- up_write(&tty->termios_rwsem);
+ mutex_unlock(&tty->throttle_mutex);
return ret;
}
@@ -182,7 +182,7 @@
{
int ret = 0;
- down_write(&tty->termios_rwsem);
+ mutex_lock(&tty->throttle_mutex);
if (test_bit(TTY_THROTTLED, &tty->flags)) {
if (tty->flow_change != TTY_UNTHROTTLE_SAFE)
ret = 1;
@@ -192,7 +192,7 @@
tty->ops->unthrottle(tty);
}
}
- up_write(&tty->termios_rwsem);
+ mutex_unlock(&tty->throttle_mutex);
return ret;
}