From 603f5ce0204f854c7d090c302fe2c86c75f23767 Mon Sep 17 00:00:00 2001
From: Liangsheng Yin <hnyls2002@gmail.com>
Date: Sun, 3 Aug 2025 06:23:11 +0800
Subject: [PATCH] [Bug] fix green context's incompatibility with `cuda < 12.4`
 (#8701)

---
 sgl-kernel/csrc/spatial/greenctx_stream.cu | 17 +++++++++++++++++
 sgl-kernel/python/sgl_kernel/spatial.py    |  5 +++++
 2 files changed, 22 insertions(+)

diff --git a/sgl-kernel/csrc/spatial/greenctx_stream.cu b/sgl-kernel/csrc/spatial/greenctx_stream.cu
index 9d7a44a1a..cf3e7da65 100644
--- a/sgl-kernel/csrc/spatial/greenctx_stream.cu
+++ b/sgl-kernel/csrc/spatial/greenctx_stream.cu
@@ -7,6 +7,8 @@
 #include "cuda_utils.h"
 #include "greenctx_stream.h"
 
+#if CUDA_VERSION >= 12040
+
 static std::vector<int64_t> create_greenctx_stream_fallback(CUgreenCtx gctx[2]) {
   CUstream streamA, streamB;
   CUcontext ctx;
@@ -94,3 +96,18 @@ std::vector<int64_t> create_greenctx_stream_by_value(int64_t smA, int64_t smB, i
 
   return vec;
 }
+
+#else
+
+std::vector<int64_t> create_greenctx_stream_by_value(int64_t smA, int64_t smB, int64_t device) {
+  TORCH_CHECK(
+      false,
+      "Green Contexts feature requires CUDA Toolkit 12.4 or newer. Current CUDA version: " +
+          std::to_string(CUDA_VERSION));
+
+  // This is a stub function that should never be reached
+  // Return empty vector to satisfy return type requirement
+  return {};
+}
+
+#endif
diff --git a/sgl-kernel/python/sgl_kernel/spatial.py b/sgl-kernel/python/sgl_kernel/spatial.py
index 8fe2a3dd7..25490d253 100644
--- a/sgl-kernel/python/sgl_kernel/spatial.py
+++ b/sgl-kernel/python/sgl_kernel/spatial.py
@@ -14,6 +14,11 @@ def create_greenctx_stream_by_value(
     Returns:
         tuple[ExternalStream, ExternalStream]: The two streams.
     """
+    if torch.version.cuda < "12.4":
+        raise RuntimeError(
+            "Green Contexts feature requires CUDA Toolkit 12.4 or newer."
+        )
+
     if device_id is None:
         device_id = torch.cuda.current_device()