drm/ttm, drm/vmwgfx: Use RCU locking for object lookups v3

The mostly used lookup+get put+potential_destroy path of TTM objects
is converted to use RCU locks. This will substantially decrease the amount
of locked bus cycles during normal operation.
Since we use kfree_rcu to free the objects, no rcu synchronization is needed
at module unload time.

v2: Don't touch include/linux/kref.h
v3: Adapt to kref_get_unless_zero return value change

Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/include/drm/ttm/ttm_object.h b/include/drm/ttm/ttm_object.h
index b01c563b2751..fc0cf0649901 100644
--- a/include/drm/ttm/ttm_object.h
+++ b/include/drm/ttm/ttm_object.h
@@ -40,6 +40,7 @@
 #include <linux/list.h>
 #include <drm/drm_hashtab.h>
 #include <linux/kref.h>
+#include <linux/rcupdate.h>
 #include <ttm/ttm_memory.h>
 
 /**
@@ -120,6 +121,7 @@ struct ttm_object_device;
  */
 
 struct ttm_base_object {
+        struct rcu_head rhead;
         struct drm_hash_item hash;
         enum ttm_object_type object_type;
         bool shareable;
@@ -268,4 +270,6 @@ extern struct ttm_object_device *ttm_object_device_init
 
 extern void ttm_object_device_release(struct ttm_object_device **p_tdev);
 
+#define ttm_base_object_kfree(__object, __base)\
+        kfree_rcu(__object, __base.rhead)
 #endif