linux-kernel - Re: [PATCH v2 3/3] tty: n_gsm: Fix waking up upper tty layer when room available

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Date:   Mon, 18 May 2020 08:44:17 +0200
From:   Jiri Slaby <jslaby@...e.cz>
To:     Gregory CLEMENT <gregory.clement@...tlin.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org
Cc:     Thomas Petazzoni <thomas.petazzoni@...tlin.com>
Subject: Re: [PATCH v2 3/3] tty: n_gsm: Fix waking up upper tty layer when
 room available

On 12. 05. 20, 13:53, Gregory CLEMENT wrote:
> Warn the upper layer when n_gms is ready to receive data
> again. Without this the associated virtual tty remains blocked
> indefinitely.
> 
> Fixes: e1eaea46bb40 ("tty: n_gsm line discipline")
> Signed-off-by: Gregory CLEMENT <gregory.clement@...tlin.com>
> ---
>  drivers/tty/n_gsm.c | 26 ++++++++++++++++++++++----
>  1 file changed, 22 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
> index d8d196645500..69200bd411f7 100644
> --- a/drivers/tty/n_gsm.c
> +++ b/drivers/tty/n_gsm.c
> @@ -663,7 +663,7 @@ static struct gsm_msg *gsm_data_alloc(struct gsm_mux *gsm, u8 addr, int len,
>   *	FIXME: lock against link layer control transmissions
>   */
>  
> -static void gsm_data_kick(struct gsm_mux *gsm)
> +static void gsm_data_kick(struct gsm_mux *gsm, struct gsm_dlci *dlci)
>  {
>  	struct gsm_msg *msg, *nmsg;
>  	int len;
> @@ -695,6 +695,24 @@ static void gsm_data_kick(struct gsm_mux *gsm)
>  
>  		list_del(&msg->list);
>  		kfree(msg);
> +
> +		if (dlci) {
> +			tty_port_tty_wakeup(&dlci->port);
> +		} else {
> +			int i = 0;
> +
> +			for (i = 0; i < NUM_DLCI; i++) {
> +				struct gsm_dlci *dlci;
> +
> +				dlci = gsm->dlci[i];
> +				if (dlci == NULL) {
> +					i++;

This "i++" looks bogus here.

> +					continue;
> +				}
> +
> +				tty_port_tty_wakeup(&dlci->port);


So simply:
for (i = 0; i < NUM_DLCI; i++) {
  struct gsm_dlci *dlci = gsm->dlci[i];
  if (dlci)
    tty_port_tty_wakeup(&dlci->port);
}

? Or even maybe directly:
for (i = 0; i < NUM_DLCI; i++)
  if (gsm->dlci[i])
    tty_port_tty_wakeup(&gsm->dlci[i]->port);

thanks,
-- 
js
suse labs