linux-kernel - Re: [PATCH] tty:n_gsm.c: destroy port by tty_port

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Message-ID: <1fd7d2eb-7497-254b-b40f-84bc4114f8a3@suse.com>
Date:   Thu, 31 Oct 2019 11:11:24 +0100
From:   Jiri Slaby <jslaby@...e.com>
To:     Xiaoming Ni <nixiaoming@...wei.com>, gregkh@...uxfoundation.org
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH] tty:n_gsm.c: destroy port by tty_port_destroy()

On 24. 09. 19, 11:25, Xiaoming Ni wrote:
> According to the comment of tty_port_destroy():
>     When a port was initialized using tty_port_init, one has to destroy
>     the port by tty_port_destroy();

It continues with a part saying:
   Either indirectly by using tty_port refcounting
   (tty_port_put) or directly if refcounting is not used.

> tty_port_init() is called in gsm_dlci_alloc()
> so tty_port_destroy() needs to be called in gsm_dlci_free()
> 
> Signed-off-by: Xiaoming Ni <nixiaoming@...wei.com>
> ---
>  drivers/tty/n_gsm.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
> index 36a3eb4..3f5bcc9 100644
> --- a/drivers/tty/n_gsm.c
> +++ b/drivers/tty/n_gsm.c
> @@ -1681,6 +1681,7 @@ static void gsm_dlci_free(struct tty_port *port)
>  
>  	del_timer_sync(&dlci->t1);
>  	dlci->gsm->dlci[dlci->addr] = NULL;
> +	tty_port_destroy(&dlci->port);

This is wrong. gsm_dlci_free is tty_port_operations->destruct, i.e.
n_gsm uses tty_port refcounting and tty_port_destroy was called on this
port in tty_port_destructor already.

Greg, please revert.

thanks,
-- 
js
suse labs