drm/amdgpu/fence: add helper to extract the guilty fence

Add a helper to extract the first amdgpu_fence which has
not yet signalled and is thus guilty or at least collateral
damage.

Reviewed-by: Jesse Zhang <jesse.zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

1 files changed, 31 insertions, 0 deletions

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c
index a7a6db0bc694..733e9b668ed8 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c
@@ -831,6 +831,37 @@ void amdgpu_ring_backup_unprocessed_commands(struct amdgpu_ring *ring,
 	} while (last_seq != seq);
 }
 
+struct amdgpu_fence *
+amdgpu_ring_find_guilty_fence(struct amdgpu_ring *ring)
+{
+	struct dma_fence *unprocessed;
+	struct dma_fence __rcu **ptr;
+	struct amdgpu_fence *fence;
+	u32 seq, last_seq;
+
+	last_seq = amdgpu_fence_read(ring) & ring->fence_drv.num_fences_mask;
+	seq = ring->fence_drv.sync_seq & ring->fence_drv.num_fences_mask;
+	ring->ring_backup_entries_to_copy = 0;
+
+	do {
+		last_seq++;
+		last_seq &= ring->fence_drv.num_fences_mask;
+
+		ptr = &ring->fence_drv.fences[last_seq];
+		rcu_read_lock();
+		unprocessed = rcu_dereference(*ptr);
+
+		if (unprocessed && !dma_fence_is_signaled(unprocessed)) {
+			fence = container_of(unprocessed, struct amdgpu_fence, base);
+			rcu_read_unlock();
+			return fence;
+		}
+		rcu_read_unlock();
+	} while (last_seq != seq);
+
+	return NULL;
+}
+
 /*
  * Common fence implementation
  */