dma-fence: Avoid list_del during fence->cb_list iteration

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@chris-wilson.co.uk>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Christian König <christian.koenig@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190817144736.7826-4-chris@chris-wilson.co.uk

1 files 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;
 }