[sgl-kernel] fix runtime error while preloading CUDA runtime (#13089)

sgl-kernel/python/sgl_kernel/load_utils.py

@@ -205,20 +205,28 @@ def _find_cuda_home():
 
 
 def _preload_cuda_library():
+    """Preload the CUDA runtime library to help avoid 'libcudart.so.12 not found' issues."""
     cuda_home = Path(_find_cuda_home())
 
-    if (cuda_home / "lib").is_dir():
+    candidate_dirs = [
-        cuda_path = cuda_home / "lib"
+        cuda_home / "lib",
-    elif (cuda_home / "lib64").is_dir():
+        cuda_home / "lib64",
-        cuda_path = cuda_home / "lib64"
+        Path("/usr/lib/x86_64-linux-gnu"),
-    else:
+        Path("/usr/lib/aarch64-linux-gnu"),
-        # Search for 'libcudart.so.12' in subdirectories
+        Path("/usr/lib64"),
-        for path in cuda_home.rglob("libcudart.so.12"):
+        Path("/usr/lib"),
-            cuda_path = path.parent
+    ]
-            break
-        else:
-            raise RuntimeError("Could not find CUDA lib directory.")
 
-    cuda_include = (cuda_path / "libcudart.so.12").resolve()
+    for base in candidate_dirs:
-    if cuda_include.exists():
+        candidate = base / "libcudart.so.12"
-        ctypes.CDLL(str(cuda_include), mode=ctypes.RTLD_GLOBAL)
+        if candidate.exists():
+            try:
+                cuda_runtime_lib = candidate.resolve()
+                ctypes.CDLL(str(cuda_runtime_lib), mode=ctypes.RTLD_GLOBAL)
+                logger.debug(f"Preloaded CUDA runtime under {cuda_runtime_lib}")
+                return
+            except Exception as e:
+                logger.debug(f"Failed to load {candidate}: {e}")
+                continue
+
+    logger.debug("[sgl_kernel] Could not preload CUDA runtime library")