linux-kernel - Re: [PATCH 2/9] staging: fsl-mc: fix device ref counting

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Date:   Fri, 3 Feb 2017 10:56:45 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     laurentiu.tudor@....com
Cc:     devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org,
        agraf@...e.de, arnd@...db.de, ioana.ciornei@....com,
        ruxandra.radulescu@....com, bharat.bhushan@....com,
        stuart.yoder@....com, catalin.horghidan@....com,
        leoyang.li@....com, roy.pledge@....com
Subject: Re: [PATCH 2/9] staging: fsl-mc: fix device ref counting

On Wed, Feb 01, 2017 at 05:43:22AM -0600, laurentiu.tudor@....com wrote:
> From: Laurentiu Tudor <laurentiu.tudor@....com>
> 
> Drop unneeded get_device() call at device creation
> and, as per documentation, drop reference count
> after using device_find_child() return.
> 
> Signed-off-by: Laurentiu Tudor <laurentiu.tudor@....com>
> ---
>  drivers/staging/fsl-mc/bus/dprc-driver.c | 1 +
>  drivers/staging/fsl-mc/bus/fsl-mc-bus.c  | 1 -
>  2 files changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/staging/fsl-mc/bus/dprc-driver.c b/drivers/staging/fsl-mc/bus/dprc-driver.c
> index 4e416d8..e4b0341 100644
> --- a/drivers/staging/fsl-mc/bus/dprc-driver.c
> +++ b/drivers/staging/fsl-mc/bus/dprc-driver.c
> @@ -188,6 +188,7 @@ static void dprc_add_new_devices(struct fsl_mc_device *mc_bus_dev,
>  		child_dev = fsl_mc_device_lookup(obj_desc, mc_bus_dev);
>  		if (child_dev) {
>  			check_plugged_state_change(child_dev, obj_desc);
> +			put_device(&child_dev->dev);
>  			continue;
>  		}
>  
> diff --git a/drivers/staging/fsl-mc/bus/fsl-mc-bus.c b/drivers/staging/fsl-mc/bus/fsl-mc-bus.c
> index cc20dc4..7c6a43b 100644
> --- a/drivers/staging/fsl-mc/bus/fsl-mc-bus.c
> +++ b/drivers/staging/fsl-mc/bus/fsl-mc-bus.c
> @@ -537,7 +537,6 @@ int fsl_mc_device_add(struct dprc_obj_desc *obj_desc,
>  		goto error_cleanup_dev;
>  	}
>  
> -	(void)get_device(&mc_dev->dev);

This implies that your device reference counting is totally wrong and
messed up.  Does this fix anything?  Break anything?  It should do
something different now...

thanks,

greg k-h