linux-kernel - Re: [PATCH] Revert "char: pcmcia: cm4000_cs: Replace mdelay with usleep_range in set

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Date:   Sun, 18 Dec 2022 12:43:27 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Duoming Zhou <duoming@....edu.cn>
Cc:     linux-kernel@...r.kernel.org, laforge@...monks.org, arnd@...db.de,
        linux@...inikbrodowski.net, baijiaju1990@...il.com
Subject: Re: [PATCH] Revert "char: pcmcia: cm4000_cs: Replace mdelay with
 usleep_range in set_protocol"

On Mon, Nov 28, 2022 at 01:39:15PM +0800, Duoming Zhou wrote:
> This reverts commit be826ada52f1fcabed5b5217c94609ebf5967211.
> 
> The function monitor_card() is a timer handler that runs in an
> atomic context, but it calls usleep_range() that can sleep.
> As a result, the sleep-in-atomic-context bugs will happen.
> The process is shown below:
> 
>     (atomic context)
> monitor_card()
>   set_protocol()
>     usleep_range() //sleep
> 
> The origin commit c1986ee9bea3 ("[PATCH] New Omnikey Cardman
> 4000 driver") works fine.
> 
> Fixes: be826ada52f1 ("char: pcmcia: cm4000_cs: Replace mdelay with usleep_range in set_protocol")
> Signed-off-by: Duoming Zhou <duoming@....edu.cn>
> ---
>  drivers/char/pcmcia/cm4000_cs.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/char/pcmcia/cm4000_cs.c b/drivers/char/pcmcia/cm4000_cs.c
> index adaec8fd4b1..7125f89531f 100644
> --- a/drivers/char/pcmcia/cm4000_cs.c
> +++ b/drivers/char/pcmcia/cm4000_cs.c
> @@ -529,7 +529,7 @@ static int set_protocol(struct cm4000_dev *dev, struct ptsreq *ptsreq)
>  			DEBUGP(5, dev, "NumRecBytes is valid\n");
>  			break;
>  		}
> -		usleep_range(10000, 11000);
> +		mdelay(10);
>  	}
>  	if (i == 100) {
>  		DEBUGP(5, dev, "Timeout waiting for NumRecBytes getting "
> @@ -549,7 +549,7 @@ static int set_protocol(struct cm4000_dev *dev, struct ptsreq *ptsreq)
>  			}
>  			break;
>  		}
> -		usleep_range(10000, 11000);
> +		mdelay(10);

Can you add a comment that says "can not sleep as this is atomic
context" for these calls so that this doesn't get changed again in the
future?

thanks,

greg k-h