[PATCH 4/6] dma-fence: Avoid list_del during fence->cb_list iteration

[Chris Wilson]

Before we notify the fence signal callback, we remove the cb from the
list. However, since we are processing the entire list from underneath
the spinlock, we do not need to individual delete each element, but can
simply reset the link and the entire list.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
Cc: Christian König <christian.koenig at amd.com>
Reviewed-by: Christian König <christian.koenig at amd.com>
---
 drivers/dma-buf/dma-fence.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/drivers/dma-buf/dma-fence.c b/drivers/dma-buf/dma-fence.c
index 8025a891d3e9..ff0cd6eae766 100644
--- a/drivers/dma-buf/dma-fence.c
+++ b/drivers/dma-buf/dma-fence.c
@@ -149,9 +149,12 @@ int dma_fence_signal_locked(struct dma_fence *fence)
 		trace_dma_fence_signaled(fence);
 	}
 
-	list_for_each_entry_safe(cur, tmp, &fence->cb_list, node) {
-		list_del_init(&cur->node);
-		cur->func(fence, cur);
+	if (!list_empty(&fence->cb_list)) {
+		list_for_each_entry_safe(cur, tmp, &fence->cb_list, node) {
+			INIT_LIST_HEAD(&cur->node);
+			cur->func(fence, cur);
+		}
+		INIT_LIST_HEAD(&fence->cb_list);
 	}
 	return ret;
 }
-- 
2.23.0.rc1