Re: [PATCH 01/26] tty: mxser: drop low-latency workaround

Jiri Slaby
2021-04-22T05:59:35Z

On 21. 04. 21, 11:54, Johan Hovold wrote:
> Commit 67d2bc58afdd ("Char: mxser_new, fix recursive locking") worked
> around the infamous low_latency behaviour of tty_flip_buffer_push() by
> simply dropping and reacquiring the port lock in the interrupt handler.
>
> Since commit a9c3f68f3cd8 ("tty: Fix low_latency BUG"),
> tty_flip_buffer_push() always schedules a work item to push data to the
> line discipline and there's no need to keep any low_latency hacks around.
>
> Link: https://lore.kernel.org/lkml/3018694794025219@wsc.cz/T/#m06b04c640a7b6f41afb3d34a4cf29b1df4935d3a
> Signed-off-by: Johan Hovold <johan@kernel.org>

Reviewed-by: Jiri Slaby <jirislaby@kernel.org>

> ---
> drivers/tty/mxser.c | 7 -------
> 1 file changed, 7 deletions(-)
>
> diff --git a/drivers/tty/mxser.c b/drivers/tty/mxser.c
> index 2d8e76263a25..16a852ecbe8a 100644
> --- a/drivers/tty/mxser.c
> +++ b/drivers/tty/mxser.c
> @@ -2155,14 +2155,7 @@ static void mxser_receive_chars(struct tty_struct *tty,
> port->mon_data.rxcnt += cnt;
> port->mon_data.up_rxcnt += cnt;
>
> - /*
> - * We are called from an interrupt context with &port->slock
> - * being held. Drop it temporarily in order to prevent
> - * recursive locking.
> - */
> - spin_unlock(&port->slock);
> tty_flip_buffer_push(&port->port);
> - spin_lock(&port->slock);
> }
>
> static void mxser_transmit_chars(struct tty_struct *tty, struct mxser_port *port)
>

thanks,
--
js