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Commit 3f04e0a6 authored by Noralf Trønnes's avatar Noralf Trønnes Committed by Dave Airlie
Browse files

drm: Fix drm_release() and device unplug 



If userspace has open fd(s) when drm_dev_unplug() is run, it will result
in drm_dev_unregister() being called twice. First in drm_dev_unplug() and
then later in drm_release() through the call to drm_put_dev().

Since userspace already holds a ref on drm_device through the drm_minor,
it's not necessary to add extra ref counting based on no open file
handles. Instead just drm_dev_put() unconditionally in drm_dev_unplug().

We now have this:
- Userpace holds a ref on drm_device as long as there's open fd(s)
- The driver holds a ref on drm_device as long as it's bound to the
  struct device

When both sides are done with drm_device, it is released.

Signed-off-by: default avatarNoralf Trønnes <noralf@tronnes.org>
Reviewed-by: default avatarOleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Reviewed-by: default avatarDaniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: default avatarSean Paul <sean@poorly.run>
Signed-off-by: default avatarDave Airlie <airlied@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190208140103.28919-2-noralf@tronnes.org
parent b23b52b6

drivers/gpu/drm/drm_drv.c

+1 −5
Original line number Diff line number Diff line
@@ -376,11 +376,7 @@ void drm_dev_unplug(struct drm_device *dev) 
	synchronize_srcu(&drm_unplug_srcu);



	drm_dev_unregister(dev);



	mutex_lock(&drm_global_mutex);

	if (dev->open_count == 0)

	drm_dev_put(dev);

	mutex_unlock(&drm_global_mutex);

}

EXPORT_SYMBOL(drm_dev_unplug);

drivers/gpu/drm/drm_file.c

+2 −4
Original line number Diff line number Diff line
@@ -489,11 +489,9 @@ int drm_release(struct inode *inode, struct file *filp) 


	drm_close_helper(filp);



	if (!--dev->open_count) {

	if (!--dev->open_count)

		drm_lastclose(dev);

		if (drm_dev_is_unplugged(dev))

			drm_put_dev(dev);

	}



	mutex_unlock(&drm_global_mutex);



	drm_minor_release(minor);