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

Regression 'tty: fix "IRQ45: nobody cared"'
Regression commit 7b292b4bf9

  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>
hifive-unleashed-5.1
Ilya Zykov 2013-01-16 13:07:50 +04:00 committed by Greg Kroah-Hartman
parent 33aeb9da1b
commit a1bf958442
1 changed files with 6 additions and 2 deletions
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8
drivers/tty/tty_ioctl.c
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@ -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);