[PATCH] drm: Don't race connector registration

[Daniel Vetter]

On Thu, Jan 12, 2017 at 05:15:56PM +0100, Daniel Vetter wrote:
> I was under the misconception that the sysfs dev stuff can be fully
> set up, and then registered all in one step with device_add. That's
> true for properties and property groups, but not for parents and child
> devices. Those must be fully registered before you can register a
> child.
> 
> Add a bit of tracking to make sure that asynchronous mst connector
> hotplugging gets this right. For consistency we rely upon the implicit
> barriers of the connector->mutex, which is taken anyway, to ensure
> that at least either the connector or device registration call will
> work out.
> 
> Mildly tested since I can't reliably reproduce this on my mst box
> here.
> 
> Reported-by: Dave Hansen <dave.hansen at intel.com>
> Cc: Dave Hansen <dave.hansen at intel.com>
> Cc: Chris Wilson <chris at chris-wilson.co.uk>
> Signed-off-by: Daniel Vetter <daniel.vetter at intel.com>

Cc: stable at vger.kernel.org

> ---
>  drivers/gpu/drm/drm_connector.c | 3 +++
>  drivers/gpu/drm/drm_drv.c       | 4 ++++
>  include/drm/drmP.h              | 1 +
>  3 files changed, 8 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
> index c75ab242f907..5999cb83d05b 100644
> --- a/drivers/gpu/drm/drm_connector.c
> +++ b/drivers/gpu/drm/drm_connector.c
> @@ -378,6 +378,9 @@ int drm_connector_register(struct drm_connector *connector)
>  {
>  	int ret = 0;
>  
> +	if (!connector->dev->registered)
> +		return 0;
> +
>  	mutex_lock(&connector->mutex);
>  	if (connector->registered)
>  		goto unlock;
> diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
> index 7e24103c47f1..cad6df626678 100644
> --- a/drivers/gpu/drm/drm_drv.c
> +++ b/drivers/gpu/drm/drm_drv.c
> @@ -749,6 +749,8 @@ int drm_dev_register(struct drm_device *dev, unsigned long flags)
>  	if (ret)
>  		goto err_minors;
>  
> +	dev->registered = true;
> +
>  	if (dev->driver->load) {
>  		ret = dev->driver->load(dev, flags);
>  		if (ret)
> @@ -796,6 +798,8 @@ void drm_dev_unregister(struct drm_device *dev)
>  
>  	drm_lastclose(dev);
>  
> +	dev->registered = false;
> +
>  	if (drm_core_check_feature(dev, DRIVER_MODESET))
>  		drm_modeset_unregister_all(dev);
>  
> diff --git a/include/drm/drmP.h b/include/drm/drmP.h
> index c537c278a4be..ec105c339347 100644
> --- a/include/drm/drmP.h
> +++ b/include/drm/drmP.h
> @@ -518,6 +518,7 @@ struct drm_device {
>  	struct drm_minor *control;		/**< Control node */
>  	struct drm_minor *primary;		/**< Primary node */
>  	struct drm_minor *render;		/**< Render node */
> +	bool registered;
>  
>  	/* currently active master for this device. Protected by master_mutex */
>  	struct drm_master *master;
> -- 
> 2.5.5
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch