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Subject[PATCH v7 2/5] drm: separate locks in __drm_mode_object_find
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In a future patch, _drm_lease_held will dereference drm_file->master
only after making a call to drm_file_get_master. This will increment
the reference count of drm_file->master while holding onto a new
drm_file.master_lock.

In preparation for this, the call to _drm_lease_held should be moved
out from the section locked by &dev->mode_config.idr_mutex. This
avoids creating new lock hierarchies between
&dev->mode_config.idr_mutex and &drm_file->master_lock.

Reported-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Desmond Cheong Zhi Xi <desmondcheongzx@gmail.com>
---
drivers/gpu/drm/drm_mode_object.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/drm_mode_object.c b/drivers/gpu/drm/drm_mode_object.c
index b26588b52795..83e35ff3b13a 100644
--- a/drivers/gpu/drm/drm_mode_object.c
+++ b/drivers/gpu/drm/drm_mode_object.c
@@ -146,16 +146,18 @@ struct drm_mode_object *__drm_mode_object_find(struct drm_device *dev,
if (obj && obj->id != id)
obj = NULL;

- if (obj && drm_mode_object_lease_required(obj->type) &&
- !_drm_lease_held(file_priv, obj->id))
- obj = NULL;
-
if (obj && obj->free_cb) {
if (!kref_get_unless_zero(&obj->refcount))
obj = NULL;
}
mutex_unlock(&dev->mode_config.idr_mutex);

+ if (obj && drm_mode_object_lease_required(obj->type) &&
+ !_drm_lease_held(file_priv, obj->id)) {
+ drm_mode_object_put(obj);
+ obj = NULL;
+ }
+
return obj;
}

--
2.25.1
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