[PATCH] drm: Don't race connector registration

[Daniel Vetter]

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>
---
 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