[PATCH 4.9 050/108] drm: Dont race connector registration

Greg Kroah-Hartman
2017-06-15T17:58:33Z

From: Daniel Vetter <daniel.vetter@ffwll.ch>

[ Upstream commit e6e7b48b295afa5a5ab440de0a94d9ad8b3ce2d0 ]

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@intel.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Acked-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1484237756-2720-1-git-send-email-daniel.vetter@ffwll.ch
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.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(+)

--- a/drivers/gpu/drm/drm_connector.c
+++ b/drivers/gpu/drm/drm_connector.c
@@ -379,6 +379,9 @@ int drm_connector_register(struct drm_co
{
int ret = 0;

+ if (!connector->dev->registered)
+ return 0;
+
mutex_lock(&connector->mutex);
if (connector->registered)
goto unlock;
--- a/drivers/gpu/drm/drm_drv.c
+++ b/drivers/gpu/drm/drm_drv.c
@@ -710,6 +710,8 @@ int drm_dev_register(struct drm_device *
if (ret)
goto err_minors;

+ dev->registered = true;
+
if (dev->driver->load) {
ret = dev->driver->load(dev, flags);
if (ret)
@@ -749,6 +751,8 @@ void drm_dev_unregister(struct drm_devic

drm_lastclose(dev);

+ dev->registered = false;
+
if (drm_core_check_feature(dev, DRIVER_MODESET))
drm_modeset_unregister_all(dev);

--- a/include/drm/drmP.h
+++ b/include/drm/drmP.h
@@ -776,6 +776,7 @@ 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;