name : threading_helper.py import _thread import contextlib import functools import sys import threading import time import unittest from test import support #======================================================================= # Threading support to prevent reporting refleaks when running regrtest.py -R # NOTE: we use thread._count() rather than threading.enumerate() (or the # moral equivalent thereof) because a threading.Thread object is still alive # until its __bootstrap() method has returned, even after it has been # unregistered from the threading module. # thread._count(), on the other hand, only gets decremented *after* the # __bootstrap() method has returned, which gives us reliable reference counts # at the end of a test run. def threading_setup(): return _thread._count(), len(threading._dangling) def threading_cleanup(*original_values): orig_count, orig_ndangling = original_values timeout = 1.0 for _ in support.sleeping_retry(timeout, error=False): # Copy the thread list to get a consistent output. threading._dangling # is a WeakSet, its value changes when it's read. dangling_threads = list(threading._dangling) count = _thread._count() if count <= orig_count: return # Timeout! support.environment_altered = True support.print_warning( f"threading_cleanup() failed to clean up threads " f"in {timeout:.1f} seconds\n" f" before: thread count={orig_count}, dangling={orig_ndangling}\n" f" after: thread count={count}, dangling={len(dangling_threads)}") for thread in dangling_threads: support.print_warning(f"Dangling thread: {thread!r}") # The warning happens when a test spawns threads and some of these threads # are still running after the test completes. To fix this warning, join # threads explicitly to wait until they complete. # # To make the warning more likely, reduce the timeout. def reap_threads(func): """Use this function when threads are being used. This will ensure that the threads are cleaned up even when the test fails. """ @functools.wraps(func) def decorator(*args): key = threading_setup() try: return func(*args) finally: threading_cleanup(*key) return decorator @contextlib.contextmanager def wait_threads_exit(timeout=None): """ bpo-31234: Context manager to wait until all threads created in the with statement exit. Use _thread.count() to check if threads exited. Indirectly, wait until threads exit the internal t_bootstrap() C function of the _thread module. threading_setup() and threading_cleanup() are designed to emit a warning if a test leaves running threads in the background. This context manager is designed to cleanup threads started by the _thread.start_new_thread() which doesn't allow to wait for thread exit, whereas thread.Thread has a join() method. """ if timeout is None: timeout = support.SHORT_TIMEOUT old_count = _thread._count() try: yield finally: start_time = time.monotonic() for _ in support.sleeping_retry(timeout, error=False): support.gc_collect() count = _thread._count() if count <= old_count: break else: dt = time.monotonic() - start_time msg = (f"wait_threads() failed to cleanup {count - old_count} " f"threads after {dt:.1f} seconds " f"(count: {count}, old count: {old_count})") raise AssertionError(msg) def join_thread(thread, timeout=None): """Join a thread. Raise an AssertionError if the thread is still alive after timeout seconds. """ if timeout is None: timeout = support.SHORT_TIMEOUT thread.join(timeout) if thread.is_alive(): msg = f"failed to join the thread in {timeout:.1f} seconds" raise AssertionError(msg) @contextlib.contextmanager def start_threads(threads, unlock=None): try: import faulthandler except ImportError: # It isn't supported on subinterpreters yet. faulthandler = None threads = list(threads) started = [] try: try: for t in threads: t.start() started.append(t) except: if support.verbose: print("Can't start %d threads, only %d threads started" % (len(threads), len(started))) raise yield finally: try: if unlock: unlock() endtime = time.monotonic() for timeout in range(1, 16): endtime += 60 for t in started: t.join(max(endtime - time.monotonic(), 0.01)) started = [t for t in started if t.is_alive()] if not started: break if support.verbose: print('Unable to join %d threads during a period of ' '%d minutes' % (len(started), timeout)) finally: started = [t for t in started if t.is_alive()] if started: if faulthandler is not None: faulthandler.dump_traceback(sys.stdout) raise AssertionError('Unable to join %d threads' % len(started)) class catch_threading_exception: """ Context manager catching threading.Thread exception using threading.excepthook. Attributes set when an exception is caught: * exc_type * exc_value * exc_traceback * thread See threading.excepthook() documentation for these attributes. These attributes are deleted at the context manager exit. Usage: with threading_helper.catch_threading_exception() as cm: # code spawning a thread which raises an exception ... # check the thread exception, use cm attributes: # exc_type, exc_value, exc_traceback, thread ... # exc_type, exc_value, exc_traceback, thread attributes of cm no longer # exists at this point # (to avoid reference cycles) """ def __init__(self): self.exc_type = None self.exc_value = None self.exc_traceback = None self.thread = None self._old_hook = None def _hook(self, args): self.exc_type = args.exc_type self.exc_value = args.exc_value self.exc_traceback = args.exc_traceback self.thread = args.thread def __enter__(self): self._old_hook = threading.excepthook threading.excepthook = self._hook return self def __exit__(self, *exc_info): threading.excepthook = self._old_hook del self.exc_type del self.exc_value del self.exc_traceback del self.thread def _can_start_thread() -> bool: """Detect whether Python can start new threads. Some WebAssembly platforms do not provide a working pthread implementation. Thread support is stubbed and any attempt to create a new thread fails. - wasm32-wasi does not have threading. - wasm32-emscripten can be compiled with or without pthread support (-s USE_PTHREADS / __EMSCRIPTEN_PTHREADS__). """ if sys.platform == "emscripten": return sys._emscripten_info.pthreads elif sys.platform == "wasi": return False else: # assume all other platforms have working thread support. return True can_start_thread = _can_start_thread() def requires_working_threading(*, module=False): """Skip tests or modules that require working threading. Can be used as a function/class decorator or to skip an entire module. """ msg = "requires threading support" if module: if not can_start_thread: raise unittest.SkipTest(msg) else: return unittest.skipUnless(can_start_thread, msg)