Re: [PATCH] dma-buf: make dma_fence structure a bit smaller v2

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Daniel any more comments on this one?

If not I'm going to push it.

Christian.

Am 08.08.19 um 15:22 schrieb Christian König:
We clear the callback list on kref_put so that by the time we
release the fence it is unused. No one should be adding to the cb_list
that they don't themselves hold a reference for.

This small change is actually making the structure 16% smaller.

v2: add the comment to the code as well.

Signed-off-by: Christian König <christian.koenig@xxxxxxx>
Reviewed-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
---
  include/linux/dma-fence.h | 10 ++++++++--
  1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/include/linux/dma-fence.h b/include/linux/dma-fence.h
index 05d29dbc7e62..bea1d05cf51e 100644
--- a/include/linux/dma-fence.h
+++ b/include/linux/dma-fence.h
@@ -65,8 +65,14 @@ struct dma_fence_cb;
  struct dma_fence {
  	struct kref refcount;
  	const struct dma_fence_ops *ops;
-	struct rcu_head rcu;
-	struct list_head cb_list;
+	/* We clear the callback list on kref_put so that by the time we
+	 * release the fence it is unused. No one should be adding to the cb_list
+	 * that they don't themselves hold a reference for.
+	 */
+	union {
+		struct rcu_head rcu;
+		struct list_head cb_list;
+	};
  	spinlock_t *lock;
  	u64 context;
  	u64 seqno;

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