Re: [PATCH v2 4/9] tty: n_gsm: fix missing timer to handle stalled links

Jiri Slaby
2022-05-23T11:50:07Z

On 19. 05. 22, 9:07, D. Starke wrote:
> From: Daniel Starke <daniel.starke@siemens.com>
>
> The current implementation does not handle the situation that no data is in
> the internal queue and needs to be sent out while the user tty fifo is
> full.
> Add a timer that moves more data from user tty down to the internal queue
> which is then serialized on the ldisc. This timer is triggered if no data
> was moved from a user tty to the internal queue within 10 * T1.
>
> Fixes: e1eaea46bb40 ("tty: n_gsm line discipline")
> Cc: stable@vger.kernel.org
> Signed-off-by: Daniel Starke <daniel.starke@siemens.com>
> ---
> drivers/tty/n_gsm.c | 43 +++++++++++++++++++++++++++++++++++--------
> 1 file changed, 35 insertions(+), 8 deletions(-)
>
> See patch 6 regarding changes since to v1.
>
> diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
> index 0a9924445968..3a4a2394d970 100644
> --- a/drivers/tty/n_gsm.c
> +++ b/drivers/tty/n_gsm.c
...
> @@ -833,6 +834,7 @@ static void __gsm_data_queue(struct gsm_dlci *dlci, struct gsm_msg *msg)
> list_add_tail(&msg->list, &gsm->tx_list);
> gsm->tx_bytes += msg->len;
> gsm_data_kick(gsm, dlci);
> + mod_timer(&gsm->kick_timer, jiffies + 10 * gsm->t1 * HZ / 100);

The formula deserves an explanation. And why 10 * X / 100, and not X / 10?

> @@ -1062,9 +1058,9 @@ static int gsm_dlci_modem_output(struct gsm_mux *gsm, struct gsm_dlci *dlci,
> * renegotiate DLCI priorities with optional stuff. Needs optimising.
> */
>
> -static void gsm_dlci_data_sweep(struct gsm_mux *gsm)
> +static int gsm_dlci_data_sweep(struct gsm_mux *gsm)
> {
> - int len;
> + int len, ret = 0;

Why is ret signed?

> /* Priority ordering: We should do priority with RR of the groups */
> int i = 1;
>
> @@ -1087,7 +1083,11 @@ static void gsm_dlci_data_sweep(struct gsm_mux *gsm)
> /* DLCI empty - try the next */
> if (len == 0)
> i++;
> + else
> + ret++;
> }
> +
> + return ret;
> }
>
> /**

thanks,
--
js
suse labs