linux-kernel - Re: [PATCH v2] can: slcan: do not sleep with a spin lock held

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Message-ID: <78cd3375-e95e-51b2-bf89-bad645e16ea4@kernel.org>
Date:   Thu, 14 Jul 2022 12:38:03 +0200
From:   Jiri Slaby <jirislaby@...nel.org>
To:     Dario Binacchi <dario.binacchi@...rulasolutions.com>,
        linux-kernel@...r.kernel.org
Cc:     lkp@...ts.01.org, Jeroen Hofstee <jhofstee@...tronenergy.com>,
        lkp@...el.com, kernel test robot <oliver.sang@...el.com>,
        Richard Palethorpe <rpalethorpe@...e.de>,
        Linux Memory Management List <linux-mm@...ck.org>,
        ltp@...ts.linux.it, "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jakub Kicinski <kuba@...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 v2] can: slcan: do not sleep with a spin lock held

On 13. 07. 22, 17:44, 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>
> 
> ---
> 
> Changes in v2:
> - Release the lock just before calling the close_candev().
> 
>   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..5214421dedf3 100644
> --- a/drivers/net/can/slcan/slcan-core.c
> +++ b/drivers/net/can/slcan/slcan-core.c
> @@ -689,6 +689,7 @@ static int slc_close(struct net_device *dev)
>   		clear_bit(TTY_DO_WRITE_WAKEUP, &sl->tty->flags);
>   	}
>   	netif_stop_queue(dev);
> +	spin_unlock_bh(&sl->lock);
>   	close_candev(dev);
>   	sl->can.state = CAN_STATE_STOPPED;
>   	if (sl->can.bittiming.bitrate == CAN_BITRATE_UNKNOWN)
> @@ -696,7 +697,6 @@ static int slc_close(struct net_device *dev)
>   
>   	sl->rcount   = 0;
>   	sl->xleft    = 0;

So all these sets need not be under the spinlock?

If so, you should explain why in the commit message.

> -	spin_unlock_bh(&sl->lock);
>   
>   	return 0;
>   }

thanks,
-- 
js
suse labs