drm: Fix drm_release() and device unplug
authorNoralf Trønnes <noralf@tronnes.org>
Fri, 8 Feb 2019 14:01:02 +0000 (15:01 +0100)
committerDave Airlie <airlied@redhat.com>
Mon, 25 Mar 2019 05:58:05 +0000 (15:58 +1000)
commit3f04e0a6cfebf48152ac64502346cdc258811f79
tree4ccc47708c31d7198068575adf781b581eb00d91
parentb23b52b6720e4be1652a4c92819f34d91e735559
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: Noralf Trønnes <noralf@tronnes.org>
Reviewed-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Sean Paul <sean@poorly.run>
Signed-off-by: Dave Airlie <airlied@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190208140103.28919-2-noralf@tronnes.org
drivers/gpu/drm/drm_drv.c
drivers/gpu/drm/drm_file.c