linux-kernel - Re: [PATCH 2/2] driver core: Print device in really

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Date:   Thu, 21 Nov 2019 14:57:43 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Geert Uytterhoeven <geert+renesas@...der.be>
Cc:     "Rafael J . Wysocki" <rafael@...nel.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] driver core: Print device in really_probe() warning
 backtrace

On Wed, Nov 20, 2019 at 03:36:19PM +0100, Geert Uytterhoeven wrote:
> If a device already has devres items attached before probing, a warning
> backtrace is printed.  However, this backtrace does not reveal the
> offending device, leaving the user uninformed.
> 
> Use dev_WARN_ON() instead of WARN_ON() to fix this.
> 
> Signed-off-by: Geert Uytterhoeven <geert+renesas@...der.be>
> ---
>  drivers/base/dd.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/base/dd.c b/drivers/base/dd.c
> index d811e60610d33ae9..a7e8040ef0003f44 100644
> --- a/drivers/base/dd.c
> +++ b/drivers/base/dd.c
> @@ -516,7 +516,7 @@ static int really_probe(struct device *dev, struct device_driver *drv)
>  	atomic_inc(&probe_count);
>  	pr_debug("bus: '%s': %s: probing driver %s with device %s\n",
>  		 drv->bus->name, __func__, drv->name, dev_name(dev));
> -	WARN_ON(!list_empty(&dev->devres_head));
> +	dev_WARN_ON(dev, !list_empty(&dev->devres_head));

We really do not want WARN_ON() anywhere, as that causes systems with
panic-on-warn to reboot.

If this can happen, we should switch it to a real error message, with
dev_err() and the like, and recover properly.

I don't want to make it easier to add WARN_ON() lines, like
dev_WARN_ON() would allow, instead we should be removing them, as they
encourage slopping programming habits.

thanks,

greg k-h