From 4518cd28d81fa4d2872268e4f8f7b35f387642cc Mon Sep 17 00:00:00 2001
From: Oded Gabbay <oded.gabbay@gmail.com>
Date: Mon, 29 Jan 2018 17:31:40 +0200
Subject: [PATCH] dma-fence: add comment for WARN_ON in dma_fence_release()
Git-commit: 4518cd28d81fa4d2872268e4f8f7b35f387642cc
Patch-mainline: v4.17-rc1
References: bsc#794563

In dma_fence_release() there is a WARN_ON which could be triggered by
several cases of wrong dma-fence usage. This patch adds a comment to
explain two use-cases to help driver developers that use dma-fence
and trigger that WARN_ON to better understand the reasons for it.

V2: change to a more generic, one-liner comment

Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Oded Gabbay <oded.gabbay@gmail.com>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/dma-buf/dma-fence.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/dma-buf/dma-fence.c b/drivers/dma-buf/dma-fence.c
index 5d101c4053e0..4edb9fd3cf47 100644
--- a/drivers/dma-buf/dma-fence.c
+++ b/drivers/dma-buf/dma-fence.c
@@ -171,6 +171,7 @@ void dma_fence_release(struct kref *kref)
 
 	trace_dma_fence_destroy(fence);
 
+	/* Failed to signal before release, could be a refcounting issue */
 	WARN_ON(!list_empty(&fence->cb_list));
 
 	if (fence->ops->release)
-- 
2.20.1