Commit a1bf9584 authored Jan 16, 2013 by Ilya Zykov Committed by Greg Kroah-Hartman Jan 18, 2013

tty: Add driver unthrottle in ioctl(...,TCFLSH,..).



Regression 'tty: fix "IRQ45: nobody cared"'
Regression commit 7b292b4b

  Function reset_buffer_flags() also invoked during the ioctl(...,TCFLSH,..).
At the time of request we can have full buffers and throttled driver too.
If we don't unthrottle driver, we can get forever throttled driver, because,
after request, we will have empty buffers and throttled driver and
there is no place to unthrottle driver.
It simple reproduce with "pty" pair then one side sleep on tty->write_wait,
and other side do ioctl(...,TCFLSH,..). Then there is no place to do writers wake up.

Signed-off-by: Ilya Zykov <ilya@ilyx.ru>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent 33aeb9da

drivers/tty/tty_ioctl.c

+6 −2

Original line number	Diff line number	Diff line
		@@ -1096,12 +1096,16 @@ int tty_perform_flush(struct tty_struct *tty, unsigned long arg)
		ld = tty_ldisc_ref_wait(tty);
		switch (arg) {
		case TCIFLUSH:
		if (ld && ld->ops->flush_buffer)
		if (ld && ld->ops->flush_buffer) {
		ld->ops->flush_buffer(tty);
		tty_unthrottle(tty);
		}
		break;
		case TCIOFLUSH:
		if (ld && ld->ops->flush_buffer)
		if (ld && ld->ops->flush_buffer) {
		ld->ops->flush_buffer(tty);
		tty_unthrottle(tty);
		}
		/* fall through */
		case TCOFLUSH:
		tty_driver_flush_buffer(tty);

Admin message