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

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Message-Id: <20170615175339.539339720@linuxfoundation.org>
Date:   Thu, 15 Jun 2017 19:52:56 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Dave Hansen <dave.hansen@...el.com>,
        Chris Wilson <chris@...is-wilson.co.uk>,
        Daniel Vetter <daniel.vetter@...el.com>,
        Sasha Levin <alexander.levin@...izon.com>
Subject: [PATCH 4.9 050/108] drm: Dont race connector registration

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Daniel Vetter <daniel.vetter@...ll.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@...el.com>
Cc: Dave Hansen <dave.hansen@...el.com>
Acked-by: Chris Wilson <chris@...is-wilson.co.uk>
Cc: Chris Wilson <chris@...is-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@...el.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@...izon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.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;