[PATCH 2/6] drm/ttm: cleanup ttm_eu_reserve_buffers handling

[Maarten Lankhorst]

With the lru lock no longer required for protecting reservations we
can just do a ttm_bo_reserve_nolru on -EBUSY, and handle all errors
in a single path.

Signed-off-by: Maarten Lankhorst <maarten.lankhorst at canonical.com>
---
 drivers/gpu/drm/ttm/ttm_execbuf_util.c | 53 ++++++++++++++--------------------
 1 file changed, 21 insertions(+), 32 deletions(-)

diff --git a/drivers/gpu/drm/ttm/ttm_execbuf_util.c 
b/drivers/gpu/drm/ttm/ttm_execbuf_util.c
index bd37b5c..c7d3236 100644
--- a/drivers/gpu/drm/ttm/ttm_execbuf_util.c
+++ b/drivers/gpu/drm/ttm/ttm_execbuf_util.c
@@ -82,22 +82,6 @@ static void ttm_eu_list_ref_sub(struct list_head *list)
        }
 }

-static int ttm_eu_wait_unreserved_locked(struct list_head *list,
-                                        struct ttm_buffer_object *bo)
-{
-       struct ttm_bo_global *glob = bo->glob;
-       int ret;
-
-       ttm_eu_del_from_lru_locked(list);
-       spin_unlock(&glob->lru_lock);
-       ret = ttm_bo_wait_unreserved(bo, true);
-       spin_lock(&glob->lru_lock);
-       if (unlikely(ret != 0))
-               ttm_eu_backoff_reservation_locked(list);
-       return ret;
-}
-
-
 void ttm_eu_backoff_reservation(struct list_head *list)
 {
        struct ttm_validate_buffer *entry;
@@ -152,19 +136,23 @@ retry:
        list_for_each_entry(entry, list, head) {
                struct ttm_buffer_object *bo = entry->bo;

-retry_this_bo:
                ret = ttm_bo_reserve_nolru(bo, true, true, true, val_seq);
                switch (ret) {
                case 0:
                        break;
                case -EBUSY:
-                       ret = ttm_eu_wait_unreserved_locked(list, bo);
-                       if (unlikely(ret != 0)) {
-                               spin_unlock(&glob->lru_lock);
-                               ttm_eu_list_ref_sub(list);
-                               return ret;
-                       }
-                       goto retry_this_bo;
+                       ttm_eu_del_from_lru_locked(list);
+                       spin_unlock(&glob->lru_lock);
+                       ret = ttm_bo_reserve_nolru(bo, true, false,
+                                                  true, val_seq);
+                       spin_lock(&glob->lru_lock);
+                       if (!ret)
+                               break;
+
+                       if (unlikely(ret != -EAGAIN))
+                               goto err;
+
+                       /* fallthrough */
                case -EAGAIN:
                        ttm_eu_backoff_reservation_locked(list);
                        spin_unlock(&glob->lru_lock);
@@ -174,18 +162,13 @@ retry_this_bo:
                                return ret;
                        goto retry;
                default:
-                       ttm_eu_backoff_reservation_locked(list);
-                       spin_unlock(&glob->lru_lock);
-                       ttm_eu_list_ref_sub(list);
-                       return ret;
+                       goto err;
                }

                entry->reserved = true;
                if (unlikely(atomic_read(&bo->cpu_writers) > 0)) {
-                       ttm_eu_backoff_reservation_locked(list);
-                       spin_unlock(&glob->lru_lock);
-                       ttm_eu_list_ref_sub(list);
-                       return -EBUSY;
+                       ret = -EBUSY;
+                       goto err;
                }
        }

@@ -194,6 +177,12 @@ retry_this_bo:
        ttm_eu_list_ref_sub(list);

        return 0;
+
+err:
+       ttm_eu_backoff_reservation_locked(list);
+       spin_unlock(&glob->lru_lock);
+       ttm_eu_list_ref_sub(list);
+       return ret;
 }
 EXPORT_SYMBOL(ttm_eu_reserve_buffers);

-- 
1.8.0