executor: dump worker stacks on SIGUSR2

Author: fergusfinn

vllm/v1/executor/multiproc_executor.py

@@ -1,10 +1,12 @@
 # SPDX-License-Identifier: Apache-2.0
 # SPDX-FileCopyrightText: Copyright contributors to the vLLM project
+import faulthandler
 import multiprocessing
 import os
 import pickle
 import queue
 import signal
+import sys
 import threading
 import time
 import traceback
@@ -810,6 +812,14 @@ def signal_handler(signum, frame):
         # Either SIGTERM or SIGINT will terminate the worker
         signal.signal(signal.SIGTERM, signal_handler)
         signal.signal(signal.SIGINT, signal_handler)
+        if hasattr(signal, "SIGUSR2"):
+
+            def dump_stack_handler(signum, frame):
+                del frame
+                logger.warning("WorkerProc dumping stacks for signal %d", signum)
+                faulthandler.dump_traceback(file=sys.stderr, all_threads=True)
+
+            signal.signal(signal.SIGUSR2, dump_stack_handler)
 
         worker = None
         ready_writer = kwargs.pop("ready_pipe")