Re: [PATCH] tty: fix timeout equals to 0 problem in tty_ioctl

From: Greg KH
Date: Thu Jan 07 2021 - 10:28:26 EST


On Sat, Dec 19, 2020 at 11:27:31AM +0800, zhangqiumiao1@xxxxxxxxx wrote:
> From: zhangqiumiao <zhangqiumiao1@xxxxxxxxxx>
>
> Fix the problem that tty buffer data was not flushed when timeout=0.

How can that happen? We need a lot better changelog text here please.

>
> Signed-off-by: zhangqiumiao <zhangqiumiao1@xxxxxxxxxx>

I need a "full" name here, please.

> ---
> drivers/tty/tty_ioctl.c | 12 ++++++++++--
> 1 file changed, 10 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/tty/tty_ioctl.c b/drivers/tty/tty_ioctl.c
> index 4de1c6ddb8ff..f9d4b6e22308 100644
> --- a/drivers/tty/tty_ioctl.c
> +++ b/drivers/tty/tty_ioctl.c
> @@ -220,13 +220,21 @@ void tty_wait_until_sent(struct tty_struct *tty, long timeout)
> tty_debug_wait_until_sent(tty, "wait until sent, timeout=%ld\n", timeout);
>
> if (!timeout)
> - timeout = MAX_SCHEDULE_TIMEOUT;
> + timeout = 60 * HZ;

Why pick this random number?

>
> timeout = wait_event_interruptible_timeout(tty->write_wait,
> !tty_chars_in_buffer(tty), timeout);
> - if (timeout <= 0)
> + if (timeout < 0)
> return;
>
> + if (timeout == 0) {
> + if (tty->ops->flush_buffer) {
> + pr_info("%s: flush buffer\n", __func__);

Debugging code needs to be removed.

thanks,

greg k-h