[Bugfix] Quickfix followups to busy loop removal in #28053 (#36068)

Signed-off-by: Travis Johnson <tsjohnso@us.ibm.com>
Signed-off-by: Nick Hill <nickhill123@gmail.com>
Co-authored-by: Nick Hill <nickhill123@gmail.com>

vllm/v1/executor/multiproc_executor.py

@@ -157,10 +157,13 @@ class MultiprocExecutor(Executor):
             global_start_rank = (
                 self.local_world_size * self.parallel_config.node_rank_within_dp
             )
-            # Keep track of socket file descriptors that are inherited by the
-            # worker when using fork, so that we can close them in subsequent
+            # When using fork, keep track of socket file descriptors that are
+            # inherited by the worker, so that we can close them in subsequent
             # workers
-            inherited_fds: list[int] = []
+            inherited_fds: list[int] | None = (
+                [] if context.get_start_method() == "fork" else None
+            )
+
             for local_rank in range(self.local_world_size):
                 global_rank = global_start_rank + local_rank
                 is_driver_worker = self._is_driver_worker(global_rank)
@@ -175,13 +178,9 @@ class MultiprocExecutor(Executor):
                     inherited_fds=inherited_fds,
                 )
                 unready_workers.append(unready_worker_handle)
-                if context.get_start_method() == "fork":
-                    inherited_fds.extend(
-                        [
-                            unready_worker_handle.death_writer.fileno(),
-                            unready_worker_handle.ready_pipe.fileno(),
-                        ]
-                    )
+                if inherited_fds is not None:
+                    inherited_fds.append(unready_worker_handle.death_writer.fileno())
+                    inherited_fds.append(unready_worker_handle.ready_pipe.fileno())
 
             # Workers must be created before wait_for_ready to avoid
             # deadlock, since worker.init_device() does a device sync.
@@ -453,10 +452,11 @@ class MultiprocExecutor(Executor):
                         w.worker_response_mq.shutdown()
                         w.worker_response_mq = None
 
-        if self.rpc_broadcast_mq is not None:
-            self.rpc_broadcast_mq.shutdown()
+        if rpc_broadcast_mq := getattr(self, "rpc_broadcast_mq", None):
+            rpc_broadcast_mq.shutdown()
             self.rpc_broadcast_mq = None
-        for mq in self.response_mqs:
+        if response_mqs := getattr(self, "response_mqs", None):
+            for mq in response_mqs:
                 mq.shutdown()
             self.response_mqs = []
 
@@ -634,13 +634,16 @@ class WorkerProc:
         input_shm_handle,  # Receive SchedulerOutput
         shared_worker_lock: LockType,
         is_driver_worker: bool,
-        inherited_fds: list[int],
+        inherited_fds: list[int] | None = None,
     ) -> UnreadyWorkerProcHandle:
         context = get_mp_context()
         # Ready pipe to communicate readiness from child to parent
         ready_reader, ready_writer = context.Pipe(duplex=False)
         # Death pipe to let child detect parent process exit
         death_reader, death_writer = context.Pipe(duplex=False)
+        if inherited_fds is not None:
+            inherited_fds = inherited_fds.copy()
+            inherited_fds.extend((ready_reader.fileno(), death_writer.fileno()))
         process_kwargs = {
             "vllm_config": vllm_config,
             "local_rank": local_rank,
@@ -652,8 +655,7 @@ class WorkerProc:
             "shared_worker_lock": shared_worker_lock,
             "is_driver_worker": is_driver_worker,
             # Have the worker close parent end of this worker's pipes too
-            "inherited_fds": inherited_fds
-            + [ready_reader.fileno(), death_writer.fileno()],
+            "inherited_fds": inherited_fds if inherited_fds is not None else [],
         }
         # Run EngineCore busy loop in background process.
         proc = context.Process(
@@ -697,9 +699,8 @@ class WorkerProc:
         unready_proc_handles: list[UnreadyWorkerProcHandle],
     ) -> list[WorkerProcHandle]:
         e = Exception(
-            "WorkerProc initialization failed due to "
-            "an exception in a background process. "
-            "See stack trace for root cause."
+            "WorkerProc initialization failed due to an exception in a "
+            "background process. See stack trace for root cause."
         )
 
         pipes = {handle.ready_pipe: handle for handle in unready_proc_handles}
@@ -802,7 +803,7 @@ class WorkerProc:
             try:
                 os.close(fd)
             except Exception as e:
-                logger.warning("Exception closing inherited connection: %s", e)
+                logger.warning("Error closing inherited connection: %s: %s", type(e), e)
 
         try:
             # Initialize tracer