[Bugfix] Fix unclean shutdown crash with AllReduce Fusion workspace (#36955)

Signed-off-by: Jarvis <brayden.stanley.0127@gmail.com>

vllm/distributed/device_communicators/flashinfer_all_reduce.py

@@ -2,6 +2,9 @@
 # SPDX-FileCopyrightText: Copyright contributors to the vLLM project
 
 
+import atexit
+import threading
+
 import torch
 import torch.distributed as dist
 from torch.distributed import ProcessGroup
@@ -132,9 +135,13 @@ def initialize_fi_ar_quant_workspace(
     )
 
 
+_fi_ar_workspace_lock = threading.Lock()
+
+
 def destroy_fi_ar_workspace():
     global _fi_ar_workspace
     global _fi_ar_quant_workspace
+    with _fi_ar_workspace_lock:
         if (
             _fi_ar_quant_workspace is not None
             and _fi_ar_quant_workspace is not _fi_ar_workspace
@@ -146,6 +153,9 @@ def destroy_fi_ar_workspace():
             _fi_ar_workspace = None
 
 
+atexit.register(destroy_fi_ar_workspace)
+
+
 class FlashInferAllReduce:
     def __init__(
         self,