From: Noralf Trønnes noralf@tronnes.org
[ Upstream commit 3f04e0a6cfebf48152ac64502346cdc258811f79 ]
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@... Signed-off-by: Sasha Levin (Microsoft) sashal@kernel.org --- drivers/gpu/drm/drm_drv.c | 6 +----- drivers/gpu/drm/drm_file.c | 6 ++---- 2 files changed, 3 insertions(+), 9 deletions(-)
diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c index ea4941da9b27..0201ccb22f4c 100644 --- a/drivers/gpu/drm/drm_drv.c +++ b/drivers/gpu/drm/drm_drv.c @@ -381,11 +381,7 @@ 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); + drm_dev_put(dev); } EXPORT_SYMBOL(drm_dev_unplug);
diff --git a/drivers/gpu/drm/drm_file.c b/drivers/gpu/drm/drm_file.c index ffa8dc35515f..e4ccb52c67ea 100644 --- a/drivers/gpu/drm/drm_file.c +++ b/drivers/gpu/drm/drm_file.c @@ -479,11 +479,9 @@ int drm_release(struct inode *inode, struct file *filp)
drm_file_free(file_priv);
- 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);