[misc][distributed] fix benign error in is_in_the_same_node (vllm-project#5512)

Author: youkaichao

vllm/distributed/parallel_state.py

@@ -23,8 +23,9 @@
 from collections import namedtuple
 from contextlib import contextmanager, nullcontext
 from dataclasses import dataclass
-from multiprocessing import resource_tracker, shared_memory
+from multiprocessing import shared_memory
 from typing import Any, Dict, List, Optional, Tuple, Union
+from unittest.mock import patch
 
 import torch
 from torch.distributed import Backend, ProcessGroup
@@ -744,7 +745,12 @@ def is_in_the_same_node(pg: ProcessGroup):
                                                         src=ranks[0],
                                                         group=pg)
                 name = recv[0]
-                shm = shared_memory.SharedMemory(name=name)
+                # fix to https://stackoverflow.com/q/62748654/9191338
+                # Python incorrectly tracks shared memory even if it is not
+                # created by the process. The following patch is a workaround.
+                with patch("multiprocessing.resource_tracker.register",
+                           lambda *args, **kwargs: None):
+                    shm = shared_memory.SharedMemory(name=name)
                 if shm.buf[:len(magic_message)] == magic_message:
                     is_in_the_same_node[rank] = 1
     except Exception as e:
@@ -757,14 +763,8 @@ def is_in_the_same_node(pg: ProcessGroup):
 
     # clean up the shared memory segment
     with contextlib.suppress(OSError):
-        if rank == 0:
-            if shm:
-                shm.unlink()
-        else:
-            if shm:
-                # fix to https://stackoverflow.com/q/62748654/9191338
-                resource_tracker.unregister(
-                    shm._name, "shared_memory")  # type: ignore[attr-defined]
+        if rank == 0 and shm:
+            shm.unlink()
     torch.distributed.all_reduce(is_in_the_same_node, group=pg)
 
     return is_in_the_same_node.sum().item() == world_size