[PATCH 05/10] drm/ttm: add sense to ttm_bo_cleanup_refs, v4

[Maarten Lankhorst]

Require lru_lock and reservation to be held, kill off the loop, no
new sync objects should be attached at this point any more.

v2:
 - moved upwards in patch list and fixed conflicts.
v3:
 - rebase for fence lock, and rename to ttm_bo_cleanup_refs_and_unlock
   for clarity that it unlocks lru.
v4:
 - add WARN_ON(!atomic_read(&bo->kref.refcount)) in reserve to ensure
   that nobody accidentally reserves a dead buffer.

Signed-off-by: Maarten Lankhorst <maarten.lankhorst at canonical.com>
---
 drivers/gpu/drm/ttm/ttm_bo.c           | 123 ++++++++++++++++-----------------
 drivers/gpu/drm/ttm/ttm_execbuf_util.c |   1 +
 2 files changed, 62 insertions(+), 62 deletions(-)

diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
index 70285ff..e6df086 100644
--- a/drivers/gpu/drm/ttm/ttm_bo.c
+++ b/drivers/gpu/drm/ttm/ttm_bo.c
@@ -296,6 +296,8 @@ int ttm_bo_reserve(struct ttm_buffer_object *bo,
 	int put_count = 0;
 	int ret;
 
+	WARN_ON(!atomic_read(&bo->kref.refcount));
+
 	spin_lock(&glob->lru_lock);
 	ret = ttm_bo_reserve_locked(bo, interruptible, no_wait, use_sequence,
 				    sequence);
@@ -522,82 +524,78 @@ queue:
 }
 
 /**
- * function ttm_bo_cleanup_refs
+ * function ttm_bo_cleanup_refs_and_unlock
  * If bo idle, remove from delayed- and lru lists, and unref.
  * If not idle, do nothing.
  *
+ * Must be called with lru_lock and reservation held, this function
+ * will drop both before returning.
+ *
  * @interruptible         Any sleeps should occur interruptibly.
- * @no_wait_reserve       Never wait for reserve. Return -EBUSY instead.
  * @no_wait_gpu           Never wait for gpu. Return -EBUSY instead.
  */
 
-static int ttm_bo_cleanup_refs(struct ttm_buffer_object *bo,
-			       bool interruptible,
-			       bool no_wait_reserve,
-			       bool no_wait_gpu)
+static int ttm_bo_cleanup_refs_and_unlock(struct ttm_buffer_object *bo,
+					  bool interruptible,
+					  bool no_wait_gpu)
 {
 	struct ttm_bo_device *bdev = bo->bdev;
 	struct ttm_bo_driver *driver = bdev->driver;
 	struct ttm_bo_global *glob = bo->glob;
 	int put_count;
 	int ret = 0;
-	void *sync_obj;
-
-retry:
-	spin_lock(&glob->lru_lock);
-
-	ret = ttm_bo_reserve_locked(bo, interruptible,
-				    no_wait_reserve, false, 0);
 
-	if (unlikely(ret)) {
-		spin_unlock(&glob->lru_lock);
-		return ret;
-	}
+	spin_lock(&bdev->fence_lock);
+	ret = ttm_bo_wait(bo, false, false, true);
 
-	if (unlikely(list_empty(&bo->ddestroy))) {
+	if (ret && no_wait_gpu) {
+		spin_unlock(&bdev->fence_lock);
 		atomic_set(&bo->reserved, 0);
 		wake_up_all(&bo->event_queue);
 		spin_unlock(&glob->lru_lock);
-		return 0;
-	}
-
-	spin_lock(&bdev->fence_lock);
-	ret = ttm_bo_wait(bo, false, false, true);
-	if (ret) {
-		if (no_wait_gpu) {
-			spin_unlock(&bdev->fence_lock);
-			atomic_set(&bo->reserved, 0);
-			wake_up_all(&bo->event_queue);
-			spin_unlock(&glob->lru_lock);
-			return ret;
-		}
+		return ret;
+	} else if (ret) {
+		void *sync_obj;
 
 		/**
-		 * Take a reference to the fence and unreserve, if the wait
-		 * was succesful and no new sync_obj was attached,
-		 * ttm_bo_wait in retry will return ret = 0, and end the loop.
+		 * Take a reference to the fence and unreserve,
+		 * at this point the buffer should be dead, so
+		 * no new sync objects can be attached.
 		 */
-
 		sync_obj = driver->sync_obj_ref(&bo->sync_obj);
 		spin_unlock(&bdev->fence_lock);
 		atomic_set(&bo->reserved, 0);
 		wake_up_all(&bo->event_queue);
 		spin_unlock(&glob->lru_lock);
 
-		ret = driver->sync_obj_wait(bo->sync_obj, false, interruptible);
+		ret = driver->sync_obj_wait(sync_obj, false, interruptible);
 		driver->sync_obj_unref(&sync_obj);
 		if (ret)
 			return ret;
-		goto retry;
+		spin_lock(&glob->lru_lock);
+
+		/* remove sync_obj with ttm_bo_wait */
+		spin_lock(&bdev->fence_lock);
+		ret = ttm_bo_wait(bo, false, false, true);
+		spin_unlock(&bdev->fence_lock);
+
+		WARN_ON(ret);
+
+	} else {
+		spin_unlock(&bdev->fence_lock);
+		atomic_set(&bo->reserved, 0);
+		wake_up_all(&bo->event_queue);
+	}
+
+	if (unlikely(list_empty(&bo->ddestroy))) {
+		spin_unlock(&glob->lru_lock);
+		return 0;
 	}
-	spin_unlock(&bdev->fence_lock);
 
 	put_count = ttm_bo_del_from_lru(bo);
 	list_del_init(&bo->ddestroy);
 	++put_count;
 
-	atomic_set(&bo->reserved, 0);
-	wake_up_all(&bo->event_queue);
 	spin_unlock(&glob->lru_lock);
 
 	ttm_bo_list_ref_sub(bo, put_count, true);
@@ -606,8 +604,8 @@ retry:
 }
 
 /**
- * Traverse the delayed list, and call ttm_bo_cleanup_refs on all
- * encountered buffers.
+ * Traverse the delayed list, and call ttm_bo_cleanup_refs_and_unlock
+ * on all encountered buffers.
  */
 
 static int ttm_bo_delayed_delete(struct ttm_bo_device *bdev, bool remove_all)
@@ -633,9 +631,14 @@ static int ttm_bo_delayed_delete(struct ttm_bo_device *bdev, bool remove_all)
 			kref_get(&nentry->list_kref);
 		}
 
-		spin_unlock(&glob->lru_lock);
-		ret = ttm_bo_cleanup_refs(entry, false, !remove_all,
-					  !remove_all);
+		ret = ttm_bo_reserve_locked(entry, false, !remove_all,
+					    false, 0);
+		if (ret)
+			spin_unlock(&glob->lru_lock);
+		else
+			ret = ttm_bo_cleanup_refs_and_unlock(entry, false,
+							     !remove_all);
+
 		kref_put(&entry->list_kref, ttm_bo_release_list);
 		entry = nentry;
 
@@ -788,15 +791,6 @@ retry:
 	bo = list_first_entry(&man->lru, struct ttm_buffer_object, lru);
 	kref_get(&bo->list_kref);
 
-	if (!list_empty(&bo->ddestroy)) {
-		spin_unlock(&glob->lru_lock);
-		ret = ttm_bo_cleanup_refs(bo, interruptible,
-					  no_wait_reserve, no_wait_gpu);
-		kref_put(&bo->list_kref, ttm_bo_release_list);
-
-		return ret;
-	}
-
 	ret = ttm_bo_reserve_locked(bo, false, true, false, 0);
 
 	if (unlikely(ret == -EBUSY)) {
@@ -815,6 +809,13 @@ retry:
 		goto retry;
 	}
 
+	if (!list_empty(&bo->ddestroy)) {
+		ret = ttm_bo_cleanup_refs_and_unlock(bo, interruptible,
+						     no_wait_gpu);
+		kref_put(&bo->list_kref, ttm_bo_release_list);
+		return ret;
+	}
+
 	put_count = ttm_bo_del_from_lru(bo);
 	spin_unlock(&glob->lru_lock);
 
@@ -1778,14 +1779,6 @@ static int ttm_bo_swapout(struct ttm_mem_shrink *shrink)
 				      struct ttm_buffer_object, swap);
 		kref_get(&bo->list_kref);
 
-		if (!list_empty(&bo->ddestroy)) {
-			spin_unlock(&glob->lru_lock);
-			(void) ttm_bo_cleanup_refs(bo, false, false, false);
-			kref_put(&bo->list_kref, ttm_bo_release_list);
-			spin_lock(&glob->lru_lock);
-			continue;
-		}
-
 		/**
 		 * Reserve buffer. Since we unlock while sleeping, we need
 		 * to re-check that nobody removed us from the swap-list while
@@ -1801,6 +1794,12 @@ static int ttm_bo_swapout(struct ttm_mem_shrink *shrink)
 		}
 	}
 
+	if (!list_empty(&bo->ddestroy)) {
+		ret = ttm_bo_cleanup_refs_and_unlock(bo, false, false);
+		kref_put(&bo->list_kref, ttm_bo_release_list);
+		return ret;
+	}
+
 	BUG_ON(ret != 0);
 	put_count = ttm_bo_del_from_lru(bo);
 	spin_unlock(&glob->lru_lock);
diff --git a/drivers/gpu/drm/ttm/ttm_execbuf_util.c b/drivers/gpu/drm/ttm/ttm_execbuf_util.c
index cd9e452..5490492 100644
--- a/drivers/gpu/drm/ttm/ttm_execbuf_util.c
+++ b/drivers/gpu/drm/ttm/ttm_execbuf_util.c
@@ -152,6 +152,7 @@ retry:
 	list_for_each_entry(entry, list, head) {
 		struct ttm_buffer_object *bo = entry->bo;
 
+		WARN_ON(!atomic_read(&bo->kref.refcount));
 retry_this_bo:
 		ret = ttm_bo_reserve_locked(bo, true, true, true, val_seq);
 		switch (ret) {
-- 
1.8.0