[PATCH v2 5/7] n_tty: Fix stuck write wakeup

Peter Hurley
2016-01-10T05:46:12Z

If signal-driven i/o is disabled while write wakeup is pending (ie.,
n_tty_write() has set TTY_DO_WRITE_WAKEUP but then signal-driven i/o
is disabled), the TTY_DO_WRITE_WAKEUP bit will never be cleared and
will cause tty_wakeup() to always call n_tty_write_wakeup.

Unconditionally clear the write wakeup, and since kill_fasync()
already checks if the fasync ptr is null, call kill_fasync()
unconditionally as well.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
---
drivers/tty/n_tty.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c
index a93e4c7..086fd99 100644
--- a/drivers/tty/n_tty.c
+++ b/drivers/tty/n_tty.c
@@ -228,8 +228,8 @@ static ssize_t chars_in_buffer(struct tty_struct *tty)

static void n_tty_write_wakeup(struct tty_struct *tty)
{
- if (tty->fasync && test_and_clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags))
- kill_fasync(&tty->fasync, SIGIO, POLL_OUT);
+ clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
+ kill_fasync(&tty->fasync, SIGIO, POLL_OUT);
}

static void n_tty_check_throttle(struct tty_struct *tty)
--
2.7.0