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-rw-r--r--drivers/char/tty_ioctl.c13
1 files changed, 13 insertions, 0 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);