diff options
| -rw-r--r-- | drivers/char/tty_ioctl.c | 13 | ||||
| -rw-r--r-- | include/linux/tty_driver.h | 6 |
2 files changed, 17 insertions, 2 deletions
diff --git a/drivers/char/tty_ioctl.c b/drivers/char/tty_ioctl.c index 6f4c7d0a53b..2401dbcbee9 100644 --- a/drivers/char/tty_ioctl.c +++ b/drivers/char/tty_ioctl.c @@ -97,14 +97,19 @@ EXPORT_SYMBOL(tty_driver_flush_buffer); * @tty: terminal * * Indicate that a tty should stop transmitting data down the stack. + * Takes the termios mutex to protect against parallel throttle/unthrottle + * and also to ensure the driver can consistently reference its own + * termios data at this point when implementing software flow control. */ void tty_throttle(struct tty_struct *tty) { + mutex_lock(&tty->termios_mutex); /* check TTY_THROTTLED first so it indicates our state */ if (!test_and_set_bit(TTY_THROTTLED, &tty->flags) && tty->ops->throttle) tty->ops->throttle(tty); + mutex_unlock(&tty->termios_mutex); } EXPORT_SYMBOL(tty_throttle); @@ -113,13 +118,21 @@ EXPORT_SYMBOL(tty_throttle); * @tty: terminal * * Indicate that a tty may continue transmitting data down the stack. + * Takes the termios mutex to protect against parallel throttle/unthrottle + * and also to ensure the driver can consistently reference its own + * termios data at this point when implementing software flow control. + * + * Drivers should however remember that the stack can issue a throttle, + * then change flow control method, then unthrottle. */ void tty_unthrottle(struct tty_struct *tty) { + mutex_lock(&tty->termios_mutex); if (test_and_clear_bit(TTY_THROTTLED, &tty->flags) && tty->ops->unthrottle) tty->ops->unthrottle(tty); + mutex_unlock(&tty->termios_mutex); } EXPORT_SYMBOL(tty_unthrottle); diff --git a/include/linux/tty_driver.h b/include/linux/tty_driver.h index bcba84ea2d8..3566129384a 100644 --- a/include/linux/tty_driver.h +++ b/include/linux/tty_driver.h @@ -127,7 +127,8 @@ * the line discipline are close to full, and it should somehow * signal that no more characters should be sent to the tty. * - * Optional: Always invoke via tty_throttle(); + * Optional: Always invoke via tty_throttle(), called under the + * termios lock. * * void (*unthrottle)(struct tty_struct * tty); * @@ -135,7 +136,8 @@ * that characters can now be sent to the tty without fear of * overrunning the input buffers of the line disciplines. * - * Optional: Always invoke via tty_unthrottle(); + * Optional: Always invoke via tty_unthrottle(), called under the + * termios lock. * * void (*stop)(struct tty_struct *tty); * |