linux-kernel - Re: [PATCH] can: slcan: do not sleep with a spin lock held

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Message-ID: <Ys7mWmIfuJy+1ax7@kroah.com>
Date:   Wed, 13 Jul 2022 17:35:54 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Dario Binacchi <dario.binacchi@...rulasolutions.com>
Cc:     linux-kernel@...r.kernel.org,
        Richard Palethorpe <rpalethorpe@...e.de>,
        Jeroen Hofstee <jhofstee@...tronenergy.com>,
        Linux Memory Management List <linux-mm@...ck.org>,
        kernel test robot <oliver.sang@...el.com>, lkp@...el.com,
        lkp@...ts.01.org, ltp@...ts.linux.it,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Jiri Slaby <jirislaby@...nel.org>,
        Marc Kleine-Budde <mkl@...gutronix.de>,
        Paolo Abeni <pabeni@...hat.com>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Vincent Mailhol <mailhol.vincent@...adoo.fr>,
        Wolfgang Grandegger <wg@...ndegger.com>,
        linux-can@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH] can: slcan: do not sleep with a spin lock held

On Wed, Jul 13, 2022 at 05:19:47PM +0200, Dario Binacchi wrote:
> We can't call close_candev() with a spin lock held, so release the lock
> before calling it.
> 
> Fixes: c4e54b063f42f ("can: slcan: use CAN network device driver API")
> Reported-by: kernel test robot <oliver.sang@...el.com>
> Link: https://lore.kernel.org/linux-kernel/Ysrf1Yc5DaRGN1WE@xsang-OptiPlex-9020/
> Signed-off-by: Dario Binacchi <dario.binacchi@...rulasolutions.com>
> 
> ---
> 
>  drivers/net/can/slcan/slcan-core.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/can/slcan/slcan-core.c b/drivers/net/can/slcan/slcan-core.c
> index 54d29a410ad5..6aaf2986effc 100644
> --- a/drivers/net/can/slcan/slcan-core.c
> +++ b/drivers/net/can/slcan/slcan-core.c
> @@ -688,6 +688,7 @@ static int slc_close(struct net_device *dev)
>  		/* TTY discipline is running. */
>  		clear_bit(TTY_DO_WRITE_WAKEUP, &sl->tty->flags);
>  	}
> +	spin_unlock_bh(&sl->lock);
>  	netif_stop_queue(dev);

Can you have a lock held when calling netif_stop_queue()?  You don't
mention this in your changelog text :(

thanks,

greg k-h