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

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Message-ID: <dee67599-a3bf-3904-e26b-4a02f36cf67f@suse.cz>
Date:   Mon, 4 May 2020 08:30:56 +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 3/3] tty: n_gsm: Fix waking up upper tty layer when room
 available

On 30. 04. 20, 13:34, Gregory CLEMENT wrote:
> Warn the upper layer when n_gms is ready to receive data
> again. Without this the associated virtual tty remain blocked

s/remain/&s/

> indefinitely.
> 
> Fixes: 96fd7ce58ffb ("TTY: create drivers/tty and move the tty core files there")

This looks invalid. Did you use git blame? Or git log, with --follow -M?

> Signed-off-by: Gregory CLEMENT <gregory.clement@...tlin.com>
> ---
>  drivers/tty/n_gsm.c | 33 +++++++++++++++++++++++++++++----
>  1 file changed, 29 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
> index 58950b33e5ac..4ff2b981aa7e 100644
> --- a/drivers/tty/n_gsm.c
> +++ b/drivers/tty/n_gsm.c
> @@ -665,10 +665,12 @@ 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;
> +	struct tty_struct *tty_dlci = NULL;
> +
>  
>  	list_for_each_entry_safe(msg, nmsg, &gsm->tx_list, list) {
>  		if (gsm->constipated && msg->addr)
> @@ -697,6 +699,29 @@ static void gsm_data_kick(struct gsm_mux *gsm)
>  
>  		list_del(&msg->list);
>  		kfree(msg);
> +
> +		if (dlci) {
> +			tty_dlci = tty_port_tty_get(&dlci->port);
> +			if (tty_dlci)
> +				tty_wakeup(tty_dlci);

No tty_port_put looks wrong to me?

Why not to use tty_port_tty_wakeup?

> +		} else {
> +			int i = 0;
> +
> +			while (i < NUM_DLCI) {

Hmm, feels like 'for' loop fits better here.

> +				struct gsm_dlci *dlci;
> +
> +				dlci = gsm->dlci[i];
> +				if (dlci == NULL) {
> +					i++;
> +					continue;
> +				}
> +
> +				tty_dlci = tty_port_tty_get(&dlci->port);
> +				if (tty_dlci)
> +					tty_wakeup(tty_dlci);

Dtto

> +				i++;
> +			}
> +		}
>  	}
>  }
>  
> @@ -748,7 +773,7 @@ static void __gsm_data_queue(struct gsm_dlci *dlci, struct gsm_msg *msg)
>  	/* Add to the actual output queue */
>  	list_add_tail(&msg->list, &gsm->tx_list);
>  	gsm->tx_bytes += msg->len;
> -	gsm_data_kick(gsm);
> +	gsm_data_kick(gsm, dlci);

thanks,
-- 
js
suse labs