From a1a91dd76663ecd5fddd6e3388857a839ec097dc Mon Sep 17 00:00:00 2001
From: Robin Kertels <robin.kertels@gmail.com>
Date: Sun, 11 Jun 2023 13:42:01 +0200
Subject: [PATCH] [d3d9] Fix potential race when discarding systemmem textures

---
 src/d3d9/d3d9_device.cpp | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/d3d9/d3d9_device.cpp b/src/d3d9/d3d9_device.cpp
index d6788c3a..8764aab3 100644
--- a/src/d3d9/d3d9_device.cpp
+++ b/src/d3d9/d3d9_device.cpp
@@ -4384,7 +4384,11 @@ namespace dxvk {
     // then we need to copy -> buffer
     // We are also always dirty if we are a render target,
     // a depth stencil, or auto generate mipmaps.
-    bool needsReadback = (pResource->NeedsReadback(Subresource) || renderable) && !(Flags & D3DLOCK_DISCARD);
+    bool needsReadback = pResource->NeedsReadback(Subresource) || renderable;
+
+    // Skip readback if we discard is specified. We can only do this for textures that have an associated Vulkan image.
+    // Any other texture might write to the Vulkan staging buffer directly. (GetBackbufferData for example)
+    needsReadback &= pResource->GetImage() != nullptr || !(Flags & D3DLOCK_DISCARD);
     pResource->SetNeedsReadback(Subresource, false);