Tim Peters | aa22223 | 2001-05-22 09:34:27 +0000 | [diff] [blame] | 1 | # This is a variant of the very old (early 90's) file |
| 2 | # Demo/threads/bug.py. It simply provokes a number of threads into |
| 3 | # trying to import the same module "at the same time". |
| 4 | # There are no pleasant failure modes -- most likely is that Python |
| 5 | # complains several times about module random having no attribute |
| 6 | # randrange, and then Python hangs. |
| 7 | |
Antoine Pitrou | 1f9dea0 | 2010-07-14 11:52:38 +0000 | [diff] [blame] | 8 | import imp |
| 9 | import sys |
Antoine Pitrou | 7224d07 | 2010-08-22 10:18:36 +0000 | [diff] [blame^] | 10 | import time |
Georg Brandl | 89fad14 | 2010-03-14 10:23:39 +0000 | [diff] [blame] | 11 | import unittest |
Antoine Pitrou | 1f9dea0 | 2010-07-14 11:52:38 +0000 | [diff] [blame] | 12 | from test.support import verbose, TestFailed, import_module, run_unittest |
Victor Stinner | 45df820 | 2010-04-28 22:31:17 +0000 | [diff] [blame] | 13 | thread = import_module('_thread') |
Tim Peters | aa22223 | 2001-05-22 09:34:27 +0000 | [diff] [blame] | 14 | |
Antoine Pitrou | 1f9dea0 | 2010-07-14 11:52:38 +0000 | [diff] [blame] | 15 | def task(N, done, done_tasks, errors): |
| 16 | try: |
Antoine Pitrou | 7224d07 | 2010-08-22 10:18:36 +0000 | [diff] [blame^] | 17 | # We don't use modulefinder but still import it in order to stress |
| 18 | # importing of different modules from several threads. |
| 19 | if len(done_tasks) % 2: |
| 20 | import modulefinder |
| 21 | import random |
| 22 | else: |
| 23 | import random |
| 24 | import modulefinder |
Antoine Pitrou | 1f9dea0 | 2010-07-14 11:52:38 +0000 | [diff] [blame] | 25 | # This will fail if random is not completely initialized |
| 26 | x = random.randrange(1, 3) |
| 27 | except Exception as e: |
| 28 | errors.append(e.with_traceback(None)) |
| 29 | finally: |
| 30 | done_tasks.append(thread.get_ident()) |
| 31 | finished = len(done_tasks) == N |
| 32 | if finished: |
| 33 | done.release() |
Tim Peters | aa22223 | 2001-05-22 09:34:27 +0000 | [diff] [blame] | 34 | |
Antoine Pitrou | 1f9dea0 | 2010-07-14 11:52:38 +0000 | [diff] [blame] | 35 | |
Antoine Pitrou | 7224d07 | 2010-08-22 10:18:36 +0000 | [diff] [blame^] | 36 | class Finder: |
| 37 | """A dummy finder to detect concurrent access to its find_module() |
| 38 | method.""" |
| 39 | |
| 40 | def __init__(self): |
| 41 | self.numcalls = 0 |
| 42 | self.x = 0 |
| 43 | self.lock = thread.allocate_lock() |
| 44 | |
| 45 | def find_module(self, name, path=None): |
| 46 | # Simulate some thread-unsafe behaviour. If calls to find_module() |
| 47 | # are properly serialized, `x` will end up the same as `numcalls`. |
| 48 | # Otherwise not. |
| 49 | with self.lock: |
| 50 | self.numcalls += 1 |
| 51 | x = self.x |
| 52 | time.sleep(0.1) |
| 53 | self.x = x + 1 |
| 54 | |
| 55 | class FlushingFinder: |
| 56 | """A dummy finder which flushes sys.path_importer_cache when it gets |
| 57 | called.""" |
| 58 | |
| 59 | def find_module(self, name, path=None): |
| 60 | sys.path_importer_cache.clear() |
| 61 | |
| 62 | |
Antoine Pitrou | 1f9dea0 | 2010-07-14 11:52:38 +0000 | [diff] [blame] | 63 | class ThreadedImportTests(unittest.TestCase): |
| 64 | |
Antoine Pitrou | 448acd0 | 2010-07-16 19:10:38 +0000 | [diff] [blame] | 65 | def setUp(self): |
| 66 | self.old_random = sys.modules.pop('random', None) |
| 67 | |
| 68 | def tearDown(self): |
| 69 | # If the `random` module was already initialized, we restore the |
| 70 | # old module at the end so that pickling tests don't fail. |
| 71 | # See http://bugs.python.org/issue3657#msg110461 |
| 72 | if self.old_random is not None: |
| 73 | sys.modules['random'] = self.old_random |
| 74 | |
Antoine Pitrou | 7224d07 | 2010-08-22 10:18:36 +0000 | [diff] [blame^] | 75 | def check_parallel_module_init(self): |
Antoine Pitrou | 1f9dea0 | 2010-07-14 11:52:38 +0000 | [diff] [blame] | 76 | if imp.lock_held(): |
| 77 | # This triggers on, e.g., from test import autotest. |
| 78 | raise unittest.SkipTest("can't run when import lock is held") |
| 79 | |
| 80 | done = thread.allocate_lock() |
| 81 | done.acquire() |
| 82 | for N in (20, 50) * 3: |
| 83 | if verbose: |
| 84 | print("Trying", N, "threads ...", end=' ') |
Antoine Pitrou | 7224d07 | 2010-08-22 10:18:36 +0000 | [diff] [blame^] | 85 | # Make sure that random and modulefinder get reimported freshly |
| 86 | for modname in ['random', 'modulefinder']: |
| 87 | try: |
| 88 | del sys.modules[modname] |
| 89 | except KeyError: |
| 90 | pass |
Antoine Pitrou | 1f9dea0 | 2010-07-14 11:52:38 +0000 | [diff] [blame] | 91 | errors = [] |
| 92 | done_tasks = [] |
| 93 | for i in range(N): |
| 94 | thread.start_new_thread(task, (N, done, done_tasks, errors,)) |
| 95 | done.acquire() |
| 96 | self.assertFalse(errors) |
| 97 | if verbose: |
| 98 | print("OK.") |
Tim Peters | 20882dd | 2002-02-16 07:26:27 +0000 | [diff] [blame] | 99 | done.release() |
Tim Peters | aa22223 | 2001-05-22 09:34:27 +0000 | [diff] [blame] | 100 | |
Antoine Pitrou | 7224d07 | 2010-08-22 10:18:36 +0000 | [diff] [blame^] | 101 | def test_parallel_module_init(self): |
| 102 | self.check_parallel_module_init() |
| 103 | |
| 104 | def test_parallel_meta_path(self): |
| 105 | finder = Finder() |
| 106 | sys.meta_path.append(finder) |
| 107 | try: |
| 108 | self.check_parallel_module_init() |
| 109 | self.assertGreater(finder.numcalls, 0) |
| 110 | self.assertEqual(finder.x, finder.numcalls) |
| 111 | finally: |
| 112 | sys.meta_path.remove(finder) |
| 113 | |
| 114 | def test_parallel_path_hooks(self): |
| 115 | # Here the Finder instance is only used to check concurrent calls |
| 116 | # to path_hook(). |
| 117 | finder = Finder() |
| 118 | # In order for our path hook to be called at each import, we need |
| 119 | # to flush the path_importer_cache, which we do by registering a |
| 120 | # dedicated meta_path entry. |
| 121 | flushing_finder = FlushingFinder() |
| 122 | def path_hook(path): |
| 123 | finder.find_module('') |
| 124 | raise ImportError |
| 125 | sys.path_hooks.append(path_hook) |
| 126 | sys.meta_path.append(flushing_finder) |
| 127 | try: |
| 128 | # Flush the cache a first time |
| 129 | flushing_finder.find_module('') |
| 130 | numtests = self.check_parallel_module_init() |
| 131 | self.assertGreater(finder.numcalls, 0) |
| 132 | self.assertEqual(finder.x, finder.numcalls) |
| 133 | finally: |
| 134 | sys.meta_path.remove(flushing_finder) |
| 135 | sys.path_hooks.remove(path_hook) |
| 136 | |
Antoine Pitrou | 1f9dea0 | 2010-07-14 11:52:38 +0000 | [diff] [blame] | 137 | def test_import_hangers(self): |
Thomas Wouters | 477c8d5 | 2006-05-27 19:21:47 +0000 | [diff] [blame] | 138 | # In case this test is run again, make sure the helper module |
| 139 | # gets loaded from scratch again. |
Antoine Pitrou | 1f9dea0 | 2010-07-14 11:52:38 +0000 | [diff] [blame] | 140 | try: |
| 141 | del sys.modules['test.threaded_import_hangers'] |
| 142 | except KeyError: |
| 143 | pass |
| 144 | import test.threaded_import_hangers |
| 145 | self.assertFalse(test.threaded_import_hangers.errors) |
Thomas Wouters | 477c8d5 | 2006-05-27 19:21:47 +0000 | [diff] [blame] | 146 | |
Tim Peters | aa22223 | 2001-05-22 09:34:27 +0000 | [diff] [blame] | 147 | |
Antoine Pitrou | 1f9dea0 | 2010-07-14 11:52:38 +0000 | [diff] [blame] | 148 | def test_main(): |
| 149 | run_unittest(ThreadedImportTests) |
Tim Peters | 6923234 | 2001-08-30 05:16:13 +0000 | [diff] [blame] | 150 | |
Thomas Wouters | 477c8d5 | 2006-05-27 19:21:47 +0000 | [diff] [blame] | 151 | |
Tim Peters | d974221 | 2001-05-22 18:28:25 +0000 | [diff] [blame] | 152 | if __name__ == "__main__": |
| 153 | test_main() |