[PATCH] drm: Don't race connector registration

[Daniel Vetter]

Hi Dave,

Still waiting for your testing results on this one here ...
-Daniel

On Thu, Jan 12, 2017 at 05:17:21PM +0100, Daniel Vetter wrote:
> 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

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