[PATCH 1/4] dma-fence: Propagate errors to dma-fence-array container

[Chris Wilson]

When one of the array of fences is signaled, propagate its errors to the
parent fence-array (keeping the first error to be raised).

v2: Opencode cmpxchg_local to avoid compiler freakout.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Sumit Semwal <sumit.semwal at linaro.org>
Cc: Gustavo Padovan <gustavo at padovan.org>
---
 drivers/dma-buf/dma-fence-array.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/drivers/dma-buf/dma-fence-array.c b/drivers/dma-buf/dma-fence-array.c
index 12c6f64c0bc2..d90675bb4fcc 100644
--- a/drivers/dma-buf/dma-fence-array.c
+++ b/drivers/dma-buf/dma-fence-array.c
@@ -13,6 +13,12 @@
 #include <linux/slab.h>
 #include <linux/dma-fence-array.h>
 
+static void fence_set_error_once(struct dma_fence *fence, int error)
+{
+	if (!fence->error && error)
+		dma_fence_set_error(fence, error);
+}
+
 static const char *dma_fence_array_get_driver_name(struct dma_fence *fence)
 {
 	return "dma_fence_array";
@@ -38,6 +44,13 @@ static void dma_fence_array_cb_func(struct dma_fence *f,
 		container_of(cb, struct dma_fence_array_cb, cb);
 	struct dma_fence_array *array = array_cb->array;
 
+	/*
+	 * Propagate the first error reported by any of our fences, but only
+	 * before we ourselves are signaled.
+	 */
+	if (atomic_read(&array->num_pending) > 0)
+		fence_set_error_once(&array->base, f->error);
+
 	if (atomic_dec_and_test(&array->num_pending))
 		irq_work_queue(&array->work);
 	else
@@ -63,6 +76,8 @@ static bool dma_fence_array_enable_signaling(struct dma_fence *fence)
 		dma_fence_get(&array->base);
 		if (dma_fence_add_callback(array->fences[i], &cb[i].cb,
 					   dma_fence_array_cb_func)) {
+			fence_set_error_once(&array->base,
+					     array->fences[i]->error);
 			dma_fence_put(&array->base);
 			if (atomic_dec_and_test(&array->num_pending))
 				return false;
-- 
2.23.0.rc1