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

From: Jiri Slaby <[email-masked]>
Date: Thu, 14 Jul 2022 12:38:03 +0200

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 <[email-masked]>
> Link: https://lore.kernel.org/linux-kernel/Ysrf1Yc5DaRGN1WE@xsang-OptiPlex-9020/
> Signed-off-by: Dario Binacchi <[email-masked]>
> 
> ---
> 
> 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