[hardware][rocm] allow rocm to override default env var (#7926)

vllm/platforms/rocm.py

@@ -1,10 +1,21 @@
+import os
 from functools import lru_cache
 from typing import Tuple
 
 import torch
 
+from vllm.logger import init_logger
+
 from .interface import Platform, PlatformEnum
 
+logger = init_logger(__name__)
+
+if os.environ.get("VLLM_WORKER_MULTIPROC_METHOD", None) in ["fork", None]:
+    logger.warning("`fork` method is not supported by ROCm. "
+                   "VLLM_WORKER_MULTIPROC_METHOD is overridden to"
+                   " `spawn` instead.")
+    os.environ["VLLM_WORKER_MULTIPROC_METHOD"] = "spawn"
+
 
 class RocmPlatform(Platform):
     _enum = PlatformEnum.ROCM