[RFC 08/12] dma-fence-chain: Propagate wait status to contained fences

[Tvrtko Ursulin]

From: Tvrtko Ursulin <tvrtko.ursulin at intel.com>

As signaling is enabled on the container fence we need to propagate any
external waiting status to individual fences in order to enable owning
drivers see it.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
---
 drivers/dma-buf/dma-fence-chain.c | 22 ++++++++++++++++------
 include/linux/dma-fence-chain.h   |  1 +
 2 files changed, 17 insertions(+), 6 deletions(-)

diff --git a/drivers/dma-buf/dma-fence-chain.c b/drivers/dma-buf/dma-fence-chain.c
index a0d920576ba6..ef6a5988c8aa 100644
--- a/drivers/dma-buf/dma-fence-chain.c
+++ b/drivers/dma-buf/dma-fence-chain.c
@@ -145,20 +145,30 @@ static void dma_fence_chain_cb(struct dma_fence *f, struct dma_fence_cb *cb)
 static bool dma_fence_chain_enable_signaling(struct dma_fence *fence)
 {
 	struct dma_fence_chain *head = to_dma_fence_chain(fence);
+	struct dma_fence *callback = NULL;
 
 	dma_fence_get(&head->base);
 	dma_fence_chain_for_each(fence, &head->base) {
 		struct dma_fence *f = dma_fence_chain_contained(fence);
 
-		dma_fence_get(f);
-		if (!dma_fence_add_callback(f, &head->cb, dma_fence_chain_cb)) {
+		if (!callback) {
+			dma_fence_get(f);
+			if (!dma_fence_add_callback(f, &head->cb,
+						    dma_fence_chain_cb))
+				callback = f;
+			else
+				dma_fence_put(f);
+		} else if (head->base.waitcount && !head->waitcount) {
+			dma_fence_enable_sw_signaling(f);
+		} else {
 			dma_fence_put(fence);
-			return true;
+			break;
 		}
-		dma_fence_put(f);
 	}
-	dma_fence_put(&head->base);
-	return false;
+	head->waitcount = head->base.waitcount;
+	if (!callback)
+		dma_fence_put(&head->base);
+	return callback;
 }
 
 static bool dma_fence_chain_signaled(struct dma_fence *fence)
diff --git a/include/linux/dma-fence-chain.h b/include/linux/dma-fence-chain.h
index 4bdf0b96da28..349b882d31ea 100644
--- a/include/linux/dma-fence-chain.h
+++ b/include/linux/dma-fence-chain.h
@@ -25,6 +25,7 @@
 struct dma_fence_chain {
 	struct dma_fence base;
 	struct dma_fence __rcu *prev;
+	bool waitcount;
 	u64 prev_seqno;
 	struct dma_fence *fence;
 	union {
-- 
2.37.2