Use pytest_sessionfinish instead of atexit

With 3.12, it is no longer possible to create a new thread in an
`atexit` handler. Stopping the monitor process requires writing a
message in the queue, which itself may require the creation of a thread.

This commit will remove the need to have an `atexit` handler, by using
the `pytest_sessionfinish` hook instead, which should work in our case.

Signed-off-by: Gus Monod <gmonod1@bloomberg.net>

Author: sarahmonod

src/pytest_pystack/_monitor_process.py

@@ -1,4 +1,3 @@
-import atexit
 import multiprocessing
 import os
 import shlex
@@ -9,22 +8,31 @@
 from ._config import PystackConfig
 from ._debug_detect import debug_detected
 
+_queue = multiprocessing.Queue()
+_process = None
 
-def start(config):
-    queue = multiprocessing.Queue()
 
-    process = multiprocessing.Process(
+def start(config):
+    global _process
+    _process = multiprocessing.Process(
         target=_run_monitor,
         args=(
             config,
             os.getpid(),
-            queue,
+            _queue,
         ),
         name="pystack_monitor",
     )
-    process.start()
-    atexit.register(_stop, process, queue)
-    return queue
+    _process.start()
+    return _queue
+
+
+def stop():
+    if _process:
+        _queue.put_nowait(None)
+        _process.join(timeout=5)
+        if _process.is_alive():
+            _process.kill()
 
 
 def _run_monitor(config: PystackConfig, pid, queue):
@@ -67,8 +75,3 @@ def _run_monitor(config: PystackConfig, pid, queue):
             if config.output_file:
                 with open(config.output_file, "a") as f:
                     print(output, file=f)
-
-
-def _stop(process, queue):
-    queue.put(None)
-    process.join(timeout=5)

src/pytest_pystack/plugin.py

@@ -93,3 +93,8 @@ def pytest_configure(config) -> None:
         print_stderr=True,
     )
     config._pystack_queue = _monitor_process.start(pystack_config)
+
+
+@pytest.hookimpl
+def pytest_sessionfinish(session, exitstatus):
+    _monitor_process.stop()