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Message-Id: <1352122278-12896-4-git-send-email-thellstrom@vmware.com>
Date: Mon, 5 Nov 2012 14:31:17 +0100
From: Thomas Hellstrom <thellstrom@...are.com>
To: airlied@...il.com, airlied@...hat.com
Cc: dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
Thomas Hellstrom <thellstrom@...are.com>
Subject: [PATCH 3/4] drm/ttm, drm/vmwgfx: Use RCU locking for object lookups
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.
Signed-off-by: Thomas Hellstrom <thellstrom@...are.com>
---
drivers/gpu/drm/ttm/ttm_object.c | 30 +++++++++++-------------------
drivers/gpu/drm/vmwgfx/vmwgfx_resource.c | 8 ++++----
include/drm/ttm/ttm_object.h | 4 ++++
include/linux/kref.h | 2 +-
4 files changed, 20 insertions(+), 24 deletions(-)
diff --git a/drivers/gpu/drm/ttm/ttm_object.c b/drivers/gpu/drm/ttm/ttm_object.c
index c785787..9d7f674 100644
--- 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);
}
- 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 da3c6b5..ae675c6 100644
--- 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);
}
@@ -1147,7 +1147,7 @@ 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);
}
@@ -1575,7 +1575,7 @@ 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)
@@ -1763,7 +1763,7 @@ 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
--- 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
diff --git a/include/linux/kref.h b/include/linux/kref.h
index fd16042..bae91d0 100644
--- a/include/linux/kref.h
+++ b/include/linux/kref.h
@@ -117,7 +117,7 @@ static inline int kref_put_mutex(struct kref *kref,
* @kref: object.
*
* Return 0 if the increment succeeded. Otherwise return non-zero.
-
+ *
* This function is intended to simplify locking around refcounting for
* objects that can be looked up from a lookup structure, and which are
* removed from that lookup structure in the object destructor.
--
1.7.4.4
--
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