Movie render sequence: Race conditions between game thread and render thread happen for UGFurComponent

[GreenCloudZhang]

When rendering a high-load sequence scene with gFur using UE's Movie Render Pipeline plugin, an issue occurs where the gFur becomes detached from the parent skeleton mesh. After extensive investigation, it was confirmed that the problem is caused by the ReferenceToLocal variable being corrupted during multithreaded execution.It seems that race condition will happen,
However, I saw that when someone previously raised an issue titled “Does race conditions between game thread and render thread happen for UGFurComponent #10,” the response was “Seems like this is intended.” Why would that be the case?

[chena1982]

I've also encountered this problem. UpdateFur_RenderThread can't use the data from UGFurComponent, must use data from FFurSceneProxy or temp data. I add a temp data TempReferenceToLocal , and send it to UpdateFur_RenderThread, fixed the problem.

if (MasterPoseComponent.IsValid())
	{
		// queue a call to update this data
		FMorphTargetWeightMap ActiveMorphTargets = MasterPoseComponent->ActiveMorphTargets;
		TArray<float> MorphTargetWeights = MasterPoseComponent->MorphTargetWeights;
        TArray<FMatrix> TempReferenceToLocal = ReferenceToLocal;
		ENQUEUE_RENDER_COMMAND(SkelMeshObjectUpdateDataCommand)(
			[this, Discontinuous, ActiveMorphTargets, MorphTargetWeights, TempReferenceToLocal](FRHICommandListImmediate& RHICmdList)
			{
				UpdateFur_RenderThread(RHICmdList, Discontinuous, ActiveMorphTargets, MorphTargetWeights, TempReferenceToLocal);
			}
			);

	}

void UGFurComponent::UpdateFur_RenderThread(FRHICommandListImmediate& RHICmdList, bool Discontinuous, const FMorphTargetWeightMap& ActiveMorphTargets, const TArray<float>& MorphTargetWeights, const TArray<FMatrix> & TempReferenceToLocal)
{
	FFurSceneProxy* FurProxy = (FFurSceneProxy*)SceneProxy;

	if (FurProxy)
	{
		ERHIFeatureLevel::Type SceneFeatureLevel = GetWorld()->GetFeatureLevel();

		int32 CurrentLOD = FurProxy->GetCurrentFurLodLevel();
		if (SkeletalGrowMesh)
		{
			const auto& LOD = SkeletalGrowMesh->GetResourceForRendering()->LODRenderData[FurProxy->GetCurrentMeshLodLevel()];
			const auto& Sections = LOD.RenderSections;
			for (int32 SectionIdx = 0; SectionIdx < Sections.Num(); SectionIdx++)
			{
				FurProxy->GetVertexFactory(SectionIdx, true)->UpdateSkeletonShaderData(ForceDistribution, MaxPhysicsOffsetLength, TempReferenceToLocal, LinearOffsets, AngularOffsets, Transformations,
					Sections[SectionIdx].BoneMap, Discontinuous || CurrentLOD != LastLOD, SceneFeatureLevel);
			}
}

I'm not sure if this is the correct way to fix this problem, because I don't check all the code, give these code for reference, hope help to fix this problem, Thanks.