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2bb9173caf
* Suspend Python threads before fork()
Add stop-the-world thread suspension around fork() to prevent
deadlocks from locks held by dead parent threads in the child.
- Thread states: DETACHED / ATTACHED / SUSPENDED with atomic CAS
transitions matching _PyThreadState_{Attach,Detach,Suspend}
- stop_the_world / start_the_world: park all non-requester threads
before fork, resume after (parent) or reset (child)
- allow_threads (Py_BEGIN/END_ALLOW_THREADS): detach around blocking
syscalls (os.read/write, waitpid, Lock.acquire, time.sleep) so
stop_the_world can force-park via CAS
- Acquire/release import lock around fork lifecycle
- zero_reinit_after_fork: generic lock reset for parking_lot types
- gc_clear_raw: detach dict instead of clearing entries
- Lock-free double-check for descriptor cache reads (no read-side
seqlock); write-side seqlock retained for writer serialization
- fork() returns PyResult, checks PythonFinalizationError, calls
sys.audit
103 lines
3.3 KiB
Python
Vendored
103 lines
3.3 KiB
Python
Vendored
"""This test checks for correct fork() behavior.
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"""
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import _imp as imp
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import os
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import signal
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import sys
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import threading
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import time
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import unittest
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from test.fork_wait import ForkWait
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from test import support
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# Skip test if fork does not exist.
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if not support.has_fork_support:
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raise unittest.SkipTest("test module requires working os.fork")
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class ForkTest(ForkWait):
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def test_threaded_import_lock_fork(self):
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"""Check fork() in main thread works while a subthread is doing an import"""
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import_started = threading.Event()
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fake_module_name = "fake test module"
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partial_module = "partial"
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complete_module = "complete"
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def importer():
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imp.acquire_lock()
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sys.modules[fake_module_name] = partial_module
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import_started.set()
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time.sleep(0.01) # Give the other thread time to try and acquire.
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sys.modules[fake_module_name] = complete_module
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imp.release_lock()
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t = threading.Thread(target=importer)
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t.start()
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import_started.wait()
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exitcode = 42
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pid = os.fork()
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try:
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# PyOS_BeforeFork should have waited for the import to complete
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# before forking, so the child can recreate the import lock
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# correctly, but also won't see a partially initialised module
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if not pid:
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m = __import__(fake_module_name)
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if m == complete_module:
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os._exit(exitcode)
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else:
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if support.verbose > 1:
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print("Child encountered partial module")
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os._exit(1)
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else:
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t.join()
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# Exitcode 1 means the child got a partial module (bad.) No
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# exitcode (but a hang, which manifests as 'got pid 0')
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# means the child deadlocked (also bad.)
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self.wait_impl(pid, exitcode=exitcode)
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finally:
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try:
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os.kill(pid, signal.SIGKILL)
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except OSError:
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pass
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def test_nested_import_lock_fork(self):
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"""Check fork() in main thread works while the main thread is doing an import"""
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exitcode = 42
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# Issue 9573: this used to trigger RuntimeError in the child process
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def fork_with_import_lock(level):
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release = 0
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in_child = False
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try:
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try:
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for i in range(level):
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imp.acquire_lock()
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release += 1
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pid = os.fork()
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in_child = not pid
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finally:
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for i in range(release):
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imp.release_lock()
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except RuntimeError:
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if in_child:
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if support.verbose > 1:
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print("RuntimeError in child")
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os._exit(1)
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raise
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if in_child:
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os._exit(exitcode)
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self.wait_impl(pid, exitcode=exitcode)
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# Check this works with various levels of nested
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# import in the main thread
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for level in range(5):
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fork_with_import_lock(level)
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def tearDownModule():
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support.reap_children()
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if __name__ == "__main__":
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unittest.main()
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