[PATCH 3/4] drm/ttm: make unlocking in ttm_bo_cleanup_refs optional

[He, Roger]

Please see comments inline

-----Original Message-----
From: Christian König [mailto:ckoenig.leichtzumerken at gmail.com] 
Sent: Wednesday, November 08, 2017 11:00 PM
To: He, Roger <Hongbo.He at amd.com>; amd-gfx at lists.freedesktop.org; dri-devel at lists.freedesktop.org
Subject: [PATCH 3/4] drm/ttm: make unlocking in ttm_bo_cleanup_refs optional

Needed for the next patch.

Signed-off-by: Christian König <christian.koenig at amd.com>
---
 drivers/gpu/drm/ttm/ttm_bo.c | 52 ++++++++++++++++++++++++--------------------
 1 file changed, 28 insertions(+), 24 deletions(-)

diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c index 6f55310a9d09..d23592cfe42e 100644
--- a/drivers/gpu/drm/ttm/ttm_bo.c
+++ b/drivers/gpu/drm/ttm/ttm_bo.c
@@ -486,20 +486,21 @@ static void ttm_bo_cleanup_refs_or_queue(struct ttm_buffer_object *bo)  }
 
 /**
- * function ttm_bo_cleanup_refs_and_unlock
+ * function ttm_bo_cleanup_refs
  * 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.
+ * will drop the lru lock and optionally the reservation lock before returning.
  *
  * @interruptible         Any sleeps should occur interruptibly.
  * @no_wait_gpu           Never wait for gpu. Return -EBUSY instead.
+ * @unlock_resv           Unlock the reservation lock as well.
  */
 
-static int ttm_bo_cleanup_refs_and_unlock(struct ttm_buffer_object *bo,
-					  bool interruptible,
-					  bool no_wait_gpu)
+static int ttm_bo_cleanup_refs(struct ttm_buffer_object *bo,
+			       bool interruptible, bool no_wait_gpu,
+			       bool unlock_resv)
 {
 	struct ttm_bo_global *glob = bo->glob;
 	struct reservation_object *resv;
@@ -518,7 +519,8 @@ static int ttm_bo_cleanup_refs_and_unlock(struct ttm_buffer_object *bo,
 	if (ret && !no_wait_gpu) {
 		long lret;
 
-		reservation_object_unlock(bo->resv);
+		if (unlock_resv)
+			reservation_object_unlock(bo->resv);
 		spin_unlock(&glob->lru_lock);
 
 		lret = reservation_object_wait_timeout_rcu(resv, true, @@ -531,19 +533,22 @@ static int ttm_bo_cleanup_refs_and_unlock(struct ttm_buffer_object *bo,
 			return -EBUSY;
 
 		spin_lock(&glob->lru_lock);
-		ret = __ttm_bo_reserve(bo, false, true, NULL);
-
-		/*
-		 * We raced, and lost, someone else holds the reservation now,
-		 * and is probably busy in ttm_bo_cleanup_memtype_use.
-		 *
-		 * Even if it's not the case, because we finished waiting any
-		 * delayed destruction would succeed, so just return success
-		 * here.
-		 */
-		if (ret) {
-			spin_unlock(&glob->lru_lock);
-			return 0;
+		if (unlock_resv) {
+			ret = __ttm_bo_reserve(bo, false, true, NULL);
+			/*
+			 * We raced, and lost, someone else holds the reservation now,
+			 * and is probably busy in ttm_bo_cleanup_memtype_use.
+			 *
+			 * Even if it's not the case, because we finished waiting any
+			 * delayed destruction would succeed, so just return success
+			 * here.
+			 */
+			if (ret) {
+				spin_unlock(&glob->lru_lock);
+				return 0;
+			}
+		} else {
+			ret = 0;
 		}
 	}

[Roger]: 
	//Looks like we also need the condition adjudge here.  Otherwise, it will unlock the vm root bo reservation that is not what we want here I think.
	if (unlock_resv)     //need this condition here
		reservation_object_unlock(bo->resv);

	return 0;
}

 
@@ -600,8 +605,8 @@ static int ttm_bo_delayed_delete(struct ttm_bo_device *bdev, bool remove_all)
 		}
 
 		if (!ret)
-			ret = ttm_bo_cleanup_refs_and_unlock(entry, false,
-							     !remove_all);
+			ret = ttm_bo_cleanup_refs(entry, false, !remove_all,
+						  true);
 		else
 			spin_unlock(&glob->lru_lock);
 
@@ -770,8 +775,7 @@ static int ttm_mem_evict_first(struct ttm_bo_device *bdev,
 	kref_get(&bo->list_kref);
 
 	if (!list_empty(&bo->ddestroy)) {
-		ret = ttm_bo_cleanup_refs_and_unlock(bo, interruptible,
-						     no_wait_gpu);
+		ret = ttm_bo_cleanup_refs(bo, interruptible, no_wait_gpu, true);
 		kref_put(&bo->list_kref, ttm_bo_release_list);
 		return ret;
 	}
@@ -1735,7 +1739,7 @@ static int ttm_bo_swapout(struct ttm_mem_shrink *shrink)
 	kref_get(&bo->list_kref);
 
 	if (!list_empty(&bo->ddestroy)) {
-		ret = ttm_bo_cleanup_refs_and_unlock(bo, false, false);
+		ret = ttm_bo_cleanup_refs(bo, false, false, true);
 		kref_put(&bo->list_kref, ttm_bo_release_list);
 		return ret;
 	}
--
2.11.0