Terminate fuzzer workers in atexit() handler

CHANGELOG.md

@@ -12,6 +12,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Crash result simplification (#30)
 - Configurable simplification steps (#54)
 - Parallel simplification (#53)
+- Terminate fuzzer workers in atexit() handler
 
 ### Changed
 

cobrafuzz/fuzzer.py

@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+import atexit
 import hashlib
 import io
 import logging
@@ -391,16 +392,23 @@ def _initialize_process(self, wid: int) -> tuple[MPProcess, mp.Queue[Update]]:
         return result, queue
 
     def _terminate_workers(self) -> None:
+        if not self._workers:
+            return
+
         self._result_queue.cancel_join_thread()
+
         for p, q in self._workers:
             q.cancel_join_thread()
             p.terminate()
             p.join(timeout=1)
 
+        del self._workers[:]
+
     def start(self) -> None:  # noqa: PLR0912
         start_time = time.time()
 
         self._workers = [self._initialize_process(wid=wid) for wid in range(self._num_workers)]
+        atexit.register(self._terminate_workers)
 
         logging.info(
             "START units: %d, workers: %d, seeds: %d",

tests/unit/test_fuzzer.py

@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+import copy
 import hashlib
 import logging
 import multiprocessing
@@ -651,6 +652,10 @@ def target(_: bytes) -> None:
             w[0].terminated and w[0].joined and w[0].timeout == 1 and w[1].canceled for w in workers
         )
 
+        previous_workers = copy.copy(workers)
+        f._terminate_workers()  # noqa: SLF001
+        assert workers == previous_workers
+
 
 def test_worker_run_ignored_exception() -> None:
     class Error: