[PATCH v10] drm: Unplug drm device when unregistering it (v7)

[Jeffy Chen]

After unbinding drm, the user space may still owns the drm dev fd, and
may still be able to call drm ioctl.

We're using an unplugged state to prevent something like that, so let's
reuse it here.

Also drop drm_unplug_dev, because it would be unused after other changes.

Verified on rk3399 chromebook kevin(with cros 4.4 kernel), no more crashes
when unbinding drm with ui service still running.

v2: Fix some commit messages.
v3: Reuse unplug status.
v4: Add drm_device_set_plug_state helper.
v5: Fix hang when unregistering drm dev with open_count 0.
v6: Move drm_device_set_plug_state into drm_drv.
v7: Add missing drm_dev_unref in udl_drv.

Signed-off-by: Jeffy Chen <jeffy.chen@xxxxxxxxxxxxxx>

---

 drivers/gpu/drm/drm_drv.c     | 26 ++++++++++----------------
 drivers/gpu/drm/udl/udl_drv.c |  3 ++-
 include/drm/drmP.h            |  6 ------
 include/drm/drm_drv.h         |  1 -
 4 files changed, 12 insertions(+), 24 deletions(-)

diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
index b5c6bb4..e1da4d1 100644
--- a/drivers/gpu/drm/drm_drv.c
+++ b/drivers/gpu/drm/drm_drv.c
@@ -355,22 +355,6 @@ void drm_put_dev(struct drm_device *dev)
 }
 EXPORT_SYMBOL(drm_put_dev);
 
-void drm_unplug_dev(struct drm_device *dev)
-{
-	/* for a USB device */
-	drm_dev_unregister(dev);
-
-	mutex_lock(&drm_global_mutex);
-
-	drm_device_set_unplugged(dev);
-
-	if (dev->open_count == 0) {
-		drm_put_dev(dev);
-	}
-	mutex_unlock(&drm_global_mutex);
-}
-EXPORT_SYMBOL(drm_unplug_dev);
-
 /*
  * DRM internal mount
  * We want to be able to allocate our own "struct address_space" to control
@@ -733,6 +717,13 @@ static void remove_compat_control_link(struct drm_device *dev)
 	kfree(name);
 }
 
+static inline void drm_device_set_plug_state(struct drm_device *dev,
+					     bool plugged)
+{
+	smp_wmb();
+	atomic_set(&dev->unplugged, !plugged);
+}
+
 /**
  * drm_dev_register - Register DRM device
  * @dev: Device to register
@@ -787,6 +778,8 @@ int drm_dev_register(struct drm_device *dev, unsigned long flags)
 	if (drm_core_check_feature(dev, DRIVER_MODESET))
 		drm_modeset_register_all(dev);
 
+	drm_device_set_plug_state(dev, true);
+
 	ret = 0;
 
 	DRM_INFO("Initialized %s %d.%d.%d %s for %s on minor %d\n",
@@ -826,6 +819,7 @@ void drm_dev_unregister(struct drm_device *dev)
 	drm_lastclose(dev);
 
 	dev->registered = false;
+	drm_device_set_plug_state(dev, false);
 
 	if (drm_core_check_feature(dev, DRIVER_MODESET))
 		drm_modeset_unregister_all(dev);
diff --git a/drivers/gpu/drm/udl/udl_drv.c b/drivers/gpu/drm/udl/udl_drv.c
index cd8b017..98ebf0f 100644
--- a/drivers/gpu/drm/udl/udl_drv.c
+++ b/drivers/gpu/drm/udl/udl_drv.c
@@ -108,7 +108,8 @@ static void udl_usb_disconnect(struct usb_interface *interface)
 	drm_kms_helper_poll_disable(dev);
 	udl_fbdev_unplug(dev);
 	udl_drop_usb(dev);
-	drm_unplug_dev(dev);
+	drm_dev_unregister(dev);
+	drm_dev_unref(drm_dev);
 }
 
 /*
diff --git a/include/drm/drmP.h b/include/drm/drmP.h
index 3bfafcd..980a204 100644
--- a/include/drm/drmP.h
+++ b/include/drm/drmP.h
@@ -488,12 +488,6 @@ static __inline__ int drm_core_check_feature(struct drm_device *dev,
 	return ((dev->driver->driver_features & feature) ? 1 : 0);
 }
 
-static inline void drm_device_set_unplugged(struct drm_device *dev)
-{
-	smp_wmb();
-	atomic_set(&dev->unplugged, 1);
-}
-
 static inline int drm_device_is_unplugged(struct drm_device *dev)
 {
 	int ret = atomic_read(&dev->unplugged);
diff --git a/include/drm/drm_drv.h b/include/drm/drm_drv.h
index 0fefc3f..eb63078 100644
--- a/include/drm/drm_drv.h
+++ b/include/drm/drm_drv.h
@@ -544,7 +544,6 @@ void drm_dev_unregister(struct drm_device *dev);
 void drm_dev_ref(struct drm_device *dev);
 void drm_dev_unref(struct drm_device *dev);
 void drm_put_dev(struct drm_device *dev);
-void drm_unplug_dev(struct drm_device *dev);
 
 int drm_dev_set_unique(struct drm_device *dev, const char *name);
 
-- 
2.1.4