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Commit cdad0521 authored by Thomas Hellstrom's avatar Thomas Hellstrom Committed by Dave Airlie
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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: default avatarThomas Hellstrom <thellstrom@vmware.com>
Signed-off-by: default avatarDave Airlie <airlied@redhat.com>
parent 4b20db3d

drivers/gpu/drm/ttm/ttm_object.c

+11 −19
Original line number Diff line number Diff line
@@ -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);

}

drivers/gpu/drm/vmwgfx/vmwgfx_resource.c

+4 −4
Original line number Diff line number Diff line
@@ -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);

}

include/drm/ttm/ttm_object.h

+4 −0
Original line number Diff line number Diff line
@@ -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