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>
diff --git a/drivers/gpu/drm/ttm/ttm_object.c b/drivers/gpu/drm/ttm/ttm_object.c
index c785787..f18eeb4 100644
--- a/drivers/gpu/drm/ttm/ttm_object.c
+++ b/drivers/gpu/drm/ttm/ttm_object.c
@@ -80,7 +80,7 @@
*/
struct ttm_object_device {
- rwlock_t object_lock;
+ spinlock_t object_lock;
struct drm_open_hash object_hash;
atomic_t object_count;
struct ttm_mem_global *mem_glob;
@@ -157,12 +157,12 @@
base->refcount_release = refcount_release;
base->ref_obj_release = ref_obj_release;
base->object_type = object_type;
- write_lock(&tdev->object_lock);
+ spin_lock(&tdev->object_lock);
kref_init(&base->refcount);
ret = drm_ht_just_insert_please(&tdev->object_hash,
&base->hash,
(unsigned long)base, 31, 0, 0);
- write_unlock(&tdev->object_lock);
+ spin_unlock(&tdev->object_lock);
if (unlikely(ret != 0))
goto out_err0;
@@ -186,30 +186,22 @@
container_of(kref, struct ttm_base_object, refcount);
struct ttm_object_device *tdev = base->tfile->tdev;
+ spin_lock(&tdev->object_lock);
(void)drm_ht_remove_item(&tdev->object_hash, &base->hash);
- write_unlock(&tdev->object_lock);
+ spin_unlock(&tdev->object_lock);
if (base->refcount_release) {
ttm_object_file_unref(&base->tfile);
base->refcount_release(&base);
}
- write_lock(&tdev->object_lock);
}
void ttm_base_object_unref(struct ttm_base_object **p_base)
{
struct ttm_base_object *base = *p_base;
- struct ttm_object_device *tdev = base->tfile->tdev;
*p_base = NULL;
- /*
- * Need to take the lock here to avoid racing with
- * users trying to look up the object.
- */
-
- write_lock(&tdev->object_lock);
kref_put(&base->refcount, ttm_release_base);
- write_unlock(&tdev->object_lock);
}
EXPORT_SYMBOL(ttm_base_object_unref);
@@ -221,14 +213,14 @@
struct drm_hash_item *hash;
int ret;
- read_lock(&tdev->object_lock);
+ rcu_read_lock();
ret = drm_ht_find_item(&tdev->object_hash, key, &hash);
if (likely(ret == 0)) {
base = drm_hash_entry(hash, struct ttm_base_object, hash);
- kref_get(&base->refcount);
+ ret = kref_get_unless_zero(&base->refcount) ? 0 : -EINVAL;
}
- read_unlock(&tdev->object_lock);
+ rcu_read_unlock();
if (unlikely(ret != 0))
return NULL;
@@ -426,7 +418,7 @@
return NULL;
tdev->mem_glob = mem_glob;
- rwlock_init(&tdev->object_lock);
+ spin_lock_init(&tdev->object_lock);
atomic_set(&tdev->object_count, 0);
ret = drm_ht_create(&tdev->object_hash, hash_order);
@@ -444,9 +436,9 @@
*p_tdev = NULL;
- write_lock(&tdev->object_lock);
+ spin_lock(&tdev->object_lock);
drm_ht_remove(&tdev->object_hash);
- write_unlock(&tdev->object_lock);
+ spin_unlock(&tdev->object_lock);
kfree(tdev);
}