[PATCH 4/7] drm/syncobj: use only a single stub fence

["Christian König" <ckoenig.leichtzumerken@xxxxxxxxx>]

Extract of useful code from the timeline work. Let's use just a single
stub fence instance instead of allocating a new one all the time.

Signed-off-by: Chunming Zhou <david1.zhou@xxxxxxx>
Signed-off-by: Christian König <christian.koenig@xxxxxxx>
---
 drivers/gpu/drm/drm_syncobj.c | 67 ++++++++++++++++++++++---------------------
 1 file changed, 35 insertions(+), 32 deletions(-)

diff --git a/drivers/gpu/drm/drm_syncobj.c b/drivers/gpu/drm/drm_syncobj.c
index f190414511ae..4c45acb326b9 100644
--- a/drivers/gpu/drm/drm_syncobj.c
+++ b/drivers/gpu/drm/drm_syncobj.c
@@ -56,10 +56,8 @@
 #include "drm_internal.h"
 #include <drm/drm_syncobj.h>
 
-struct drm_syncobj_stub_fence {
-	struct dma_fence base;
-	spinlock_t lock;
-};
+static DEFINE_SPINLOCK(stub_fence_lock);
+static struct dma_fence stub_fence;
 
 static const char *drm_syncobj_stub_fence_get_name(struct dma_fence *fence)
 {
@@ -71,6 +69,25 @@ static const struct dma_fence_ops drm_syncobj_stub_fence_ops = {
 	.get_timeline_name = drm_syncobj_stub_fence_get_name,
 };
 
+/**
+ * drm_syncobj_get_stub_fence - return a signaled fence
+ *
+ * Return a stub fence which is already signaled.
+ */
+static struct dma_fence *drm_syncobj_get_stub_fence(void)
+{
+	spin_lock(&stub_fence_lock);
+	if (!stub_fence.ops) {
+		dma_fence_init(&stub_fence,
+			       &drm_syncobj_stub_fence_ops,
+			       &stub_fence_lock,
+			       0, 0);
+		dma_fence_signal_locked(&stub_fence);
+	}
+	spin_unlock(&stub_fence_lock);
+
+	return dma_fence_get(&stub_fence);
+}
 
 /**
  * drm_syncobj_find - lookup and reference a sync object.
@@ -190,23 +207,18 @@ void drm_syncobj_replace_fence(struct drm_syncobj *syncobj,
 }
 EXPORT_SYMBOL(drm_syncobj_replace_fence);
 
-static int drm_syncobj_assign_null_handle(struct drm_syncobj *syncobj)
+/**
+ * drm_syncobj_assign_null_handle - assign a stub fence to the sync object
+ * @syncobj: sync object to assign the fence on
+ *
+ * Assign a already signaled stub fence to the sync object.
+ */
+static void drm_syncobj_assign_null_handle(struct drm_syncobj *syncobj)
 {
-	struct drm_syncobj_stub_fence *fence;
-	fence = kzalloc(sizeof(*fence), GFP_KERNEL);
-	if (fence == NULL)
-		return -ENOMEM;
+	struct dma_fence *fence = drm_syncobj_get_stub_fence();
 
-	spin_lock_init(&fence->lock);
-	dma_fence_init(&fence->base, &drm_syncobj_stub_fence_ops,
-		       &fence->lock, 0, 0);
-	dma_fence_signal(&fence->base);
-
-	drm_syncobj_replace_fence(syncobj, &fence->base);
-
-	dma_fence_put(&fence->base);
-
-	return 0;
+	drm_syncobj_replace_fence(syncobj, fence);
+	dma_fence_put(fence);
 }
 
 /**
@@ -273,7 +285,6 @@ EXPORT_SYMBOL(drm_syncobj_free);
 int drm_syncobj_create(struct drm_syncobj **out_syncobj, uint32_t flags,
 		       struct dma_fence *fence)
 {
-	int ret;
 	struct drm_syncobj *syncobj;
 
 	syncobj = kzalloc(sizeof(struct drm_syncobj), GFP_KERNEL);
@@ -284,13 +295,8 @@ int drm_syncobj_create(struct drm_syncobj **out_syncobj, uint32_t flags,
 	INIT_LIST_HEAD(&syncobj->cb_list);
 	spin_lock_init(&syncobj->lock);
 
-	if (flags & DRM_SYNCOBJ_CREATE_SIGNALED) {
-		ret = drm_syncobj_assign_null_handle(syncobj);
-		if (ret < 0) {
-			drm_syncobj_put(syncobj);
-			return ret;
-		}
-	}
+	if (flags & DRM_SYNCOBJ_CREATE_SIGNALED)
+		drm_syncobj_assign_null_handle(syncobj);
 
 	if (fence)
 		drm_syncobj_replace_fence(syncobj, fence);
@@ -984,11 +990,8 @@ drm_syncobj_signal_ioctl(struct drm_device *dev, void *data,
 	if (ret < 0)
 		return ret;
 
-	for (i = 0; i < args->count_handles; i++) {
-		ret = drm_syncobj_assign_null_handle(syncobjs[i]);
-		if (ret < 0)
-			break;
-	}
+	for (i = 0; i < args->count_handles; i++)
+		drm_syncobj_assign_null_handle(syncobjs[i]);
 
 	drm_syncobj_array_free(syncobjs, args->count_handles);
 
-- 
2.14.1

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