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Date:   Tue, 30 Aug 2022 09:30:27 +0200
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Subject: Re: [PATCH v4 1/2] tty: n_gsm: replace kicktimer with delayed_work
Content-Language: en-US
To:     Fedor Pchelkin <pchelkin@ispras.ru>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc:     linux-kernel@vger.kernel.org,
        Alexey Khoroshilov <khoroshilov@ispras.ru>,
        ldv-project@linuxtesting.org, Hillf Danton <hdanton@sina.com>
References: <20220829131640.69254-1-pchelkin@ispras.ru>
 <20220829131640.69254-2-pchelkin@ispras.ru>
From:   Jiri Slaby <jirislaby@kernel.org>
In-Reply-To: <20220829131640.69254-2-pchelkin@ispras.ru>
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On 29. 08. 22, 15:16, Fedor Pchelkin wrote:
> A kick_timer timer_list is replaced with kick_timeout delayed_work to be
> able to synchronize with mutexes as a prerequisite for the introduction
> of tx_mutex.
> 
> Found by Linux Verification Center (linuxtesting.org) with Syzkaller.

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

But I think this conflicts with Tetsuo's cleanup [1]. So one of you will 
likely have to rebase and resubmit.

[1] 
https://lore.kernel.org/all/2110618e-57f0-c1ce-b2ad-b6cacef3f60e@I-love.SAKURA.ne.jp/

> Fixes: c568f7086c6e ("tty: n_gsm: fix missing timer to handle stalled links")
> Suggested-by: Hillf Danton <hdanton@sina.com>
> Signed-off-by: Fedor Pchelkin <pchelkin@ispras.ru>
> Signed-off-by: Alexey Khoroshilov <khoroshilov@ispras.ru>
> ---
> v1->v2: sorry, now adapted patch from 5.10 to upstream
> v2->v3: replaced a kick_timer with a delayed_work
> v3->v4: separated kick_timer and tx_mutex into different patches
> 
>   drivers/tty/n_gsm.c | 18 +++++++++---------
>   1 file changed, 9 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
> index caa5c14ed57f..c4164c85ffd4 100644
> --- a/drivers/tty/n_gsm.c
> +++ b/drivers/tty/n_gsm.c
> @@ -256,7 +256,7 @@ struct gsm_mux {
>   	struct list_head tx_data_list;	/* Pending data packets */
>   
>   	/* Control messages */
> -	struct timer_list kick_timer;	/* Kick TX queuing on timeout */
> +	struct delayed_work kick_timeout;	/* Kick TX queuing on timeout */
>   	struct timer_list t2_timer;	/* Retransmit timer for commands */
>   	int cretries;			/* Command retry counter */
>   	struct gsm_control *pending_cmd;/* Our current pending command */
> @@ -1009,7 +1009,7 @@ static void __gsm_data_queue(struct gsm_dlci *dlci, struct gsm_msg *msg)
>   	gsm->tx_bytes += msg->len;
>   
>   	gsmld_write_trigger(gsm);
> -	mod_timer(&gsm->kick_timer, jiffies + 10 * gsm->t1 * HZ / 100);
> +	schedule_delayed_work(&gsm->kick_timeout, 10 * gsm->t1 * HZ / 100);
>   }
>   
>   /**
> @@ -1984,16 +1984,16 @@ static void gsm_dlci_command(struct gsm_dlci *dlci, const u8 *data, int len)
>   }
>   
>   /**
> - *	gsm_kick_timer	-	transmit if possible
> - *	@t: timer contained in our gsm object
> + *	gsm_kick_timeout	-	transmit if possible
> + *	@work: work contained in our gsm object
>    *
>    *	Transmit data from DLCIs if the queue is empty. We can't rely on
>    *	a tty wakeup except when we filled the pipe so we need to fire off
>    *	new data ourselves in other cases.
>    */
> -static void gsm_kick_timer(struct timer_list *t)
> +static void gsm_kick_timeout(struct work_struct *work)
>   {
> -	struct gsm_mux *gsm = from_timer(gsm, t, kick_timer);
> +	struct gsm_mux *gsm = container_of(work, struct gsm_mux, kick_timeout.work);
>   	unsigned long flags;
>   	int sent = 0;
>   
> @@ -2458,7 +2458,7 @@ static void gsm_cleanup_mux(struct gsm_mux *gsm, bool disc)
>   	}
>   
>   	/* Finish outstanding timers, making sure they are done */
> -	del_timer_sync(&gsm->kick_timer);
> +	cancel_delayed_work_sync(&gsm->kick_timeout);
>   	del_timer_sync(&gsm->t2_timer);
>   
>   	/* Finish writing to ldisc */
> @@ -2501,7 +2501,7 @@ static int gsm_activate_mux(struct gsm_mux *gsm)
>   	if (dlci == NULL)
>   		return -ENOMEM;
>   
> -	timer_setup(&gsm->kick_timer, gsm_kick_timer, 0);
> +	INIT_DELAYED_WORK(&gsm->kick_timeout, gsm_kick_timeout);
>   	timer_setup(&gsm->t2_timer, gsm_control_retransmit, 0);
>   	INIT_WORK(&gsm->tx_work, gsmld_write_task);
>   	init_waitqueue_head(&gsm->event);
> @@ -2946,7 +2946,7 @@ static int gsmld_open(struct tty_struct *tty)
>   
>   	gsmld_attach_gsm(tty, gsm);
>   
> -	timer_setup(&gsm->kick_timer, gsm_kick_timer, 0);
> +	INIT_DELAYED_WORK(&gsm->kick_timeout, gsm_kick_timeout);
>   	timer_setup(&gsm->t2_timer, gsm_control_retransmit, 0);
>   	INIT_WORK(&gsm->tx_work, gsmld_write_task);
>   

-- 
js
suse labs