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 (file)
--- a/drivers/gpu/drm/ttm/ttm_object.c
+++ b/drivers/gpu/drm/ttm/ttm_object.c
@@ -80,7 +80,7 @@ struct ttm_object_file {
  */
 
 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 @@ int ttm_base_object_init(struct ttm_object_file *tfile,
        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 @@ static void ttm_release_base(struct kref *kref)
            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 ttm_base_object *ttm_base_object_lookup(struct ttm_object_file *tfile,
        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 @@ struct ttm_object_device *ttm_object_device_init(struct ttm_mem_global
                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 @@ void ttm_object_device_release(struct ttm_object_device **p_tdev)
 
        *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);
 }

diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_resource.c b/drivers/gpu/drm/vmwgfx/vmwgfx_resource.c
index 596cef3..292c988 100644 (file)
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_resource.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_resource.c
@@ -351,7 +351,7 @@ static void vmw_user_context_free(struct vmw_resource *res)
            container_of(res, struct vmw_user_context, res);
        struct vmw_private *dev_priv = res->dev_priv;
 
-       kfree(ctx);
+       ttm_base_object_kfree(ctx, base);
        ttm_mem_global_free(vmw_mem_glob(dev_priv),
                            vmw_user_context_size);
 }
@@ -1143,7 +1143,7 @@ static void vmw_user_surface_free(struct vmw_resource *res)
        kfree(srf->offsets);
        kfree(srf->sizes);
        kfree(srf->snooper.image);
-       kfree(user_srf);
+       ttm_base_object_kfree(user_srf, base);
        ttm_mem_global_free(vmw_mem_glob(dev_priv), size);
 }
 
@@ -1571,7 +1571,7 @@ static void vmw_user_dmabuf_destroy(struct ttm_buffer_object *bo)
 {
        struct vmw_user_dma_buffer *vmw_user_bo = vmw_user_dma_buffer(bo);
 
-       kfree(vmw_user_bo);
+       ttm_base_object_kfree(vmw_user_bo, base);
 }
 
 static void vmw_user_dmabuf_release(struct ttm_base_object **p_base)
@@ -1759,7 +1759,7 @@ static void vmw_user_stream_free(struct vmw_resource *res)
            container_of(res, struct vmw_user_stream, stream.res);
        struct vmw_private *dev_priv = res->dev_priv;
 
-       kfree(stream);
+       ttm_base_object_kfree(stream, base);
        ttm_mem_global_free(vmw_mem_glob(dev_priv),
                            vmw_user_stream_size);
 }

diff --git a/include/drm/ttm/ttm_object.h b/include/drm/ttm/ttm_object.h
index b01c563..fc0cf06 100644 (file)
--- 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