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@@ -0,0 +1,168 @@
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+ From 583bb07116505dcc73c0fc4aa3c1cf5074f3522d Mon Sep 17 00:00:00 2001
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+ From: =?UTF-8?q?Miro=20Hron=C4=8Dok?= <miro@hroncok.cz>
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+ Date: Fri, 2 Nov 2018 14:01:28 +0100
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+ Subject: [PATCH] Revert "bpo-6721: Hold logging locks across fork() (GH-4071)
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+ (#9291)"
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+
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+ This reverts commit 3b699932e5ac3e76031bbb6d700fbea07492641d.
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+ ---
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+ Lib/logging/__init__.py | 50 ------------------------------
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+ Lib/test/test_logging.py | 67 ----------------------------------------
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+ 2 files changed, 117 deletions(-)
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+
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+ diff --git a/Lib/logging/__init__.py b/Lib/logging/__init__.py
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+ index 3ad2cc38f6..53780cd600 100644
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+ --- a/Lib/logging/__init__.py
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+ +++ b/Lib/logging/__init__.py
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+ @@ -225,55 +225,6 @@ def _releaseLock():
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+ if _lock:
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+ _lock.release()
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+
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+ -
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+ -# Prevent a held logging lock from blocking a child from logging.
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+ -
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+ -if not hasattr(os, 'register_at_fork'): # Windows and friends.
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+ - def _register_at_fork_acquire_release(instance):
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+ - pass # no-op when os.register_at_fork does not exist.
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+ -else: # The os.register_at_fork API exists
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+ - os.register_at_fork(before=_acquireLock,
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+ - after_in_child=_releaseLock,
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+ - after_in_parent=_releaseLock)
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+ -
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+ - # A collection of instances with acquire and release methods (logging.Handler)
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+ - # to be called before and after fork. The weakref avoids us keeping discarded
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+ - # Handler instances alive forever in case an odd program creates and destroys
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+ - # many over its lifetime.
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+ - _at_fork_acquire_release_weakset = weakref.WeakSet()
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+ -
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+ -
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+ - def _register_at_fork_acquire_release(instance):
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+ - # We put the instance itself in a single WeakSet as we MUST have only
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+ - # one atomic weak ref. used by both before and after atfork calls to
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+ - # guarantee matched pairs of acquire and release calls.
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+ - _at_fork_acquire_release_weakset.add(instance)
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+ -
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+ -
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+ - def _at_fork_weak_calls(method_name):
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+ - for instance in _at_fork_acquire_release_weakset:
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+ - method = getattr(instance, method_name)
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+ - try:
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+ - method()
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+ - except Exception as err:
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+ - # Similar to what PyErr_WriteUnraisable does.
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+ - print("Ignoring exception from logging atfork", instance,
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+ - method_name, "method:", err, file=sys.stderr)
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+ -
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+ -
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+ - def _before_at_fork_weak_calls():
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+ - _at_fork_weak_calls('acquire')
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+ -
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+ -
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+ - def _after_at_fork_weak_calls():
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+ - _at_fork_weak_calls('release')
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+ -
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+ -
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+ - os.register_at_fork(before=_before_at_fork_weak_calls,
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+ - after_in_child=_after_at_fork_weak_calls,
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+ - after_in_parent=_after_at_fork_weak_calls)
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+ -
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+ -
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+ #---------------------------------------------------------------------------
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+ # The logging record
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+ #---------------------------------------------------------------------------
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+ @@ -844,7 +795,6 @@ class Handler(Filterer):
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+ Acquire a thread lock for serializing access to the underlying I/O.
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+ """
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+ self.lock = threading.RLock()
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+ - _register_at_fork_acquire_release(self)
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+
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+ def acquire(self):
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+ """
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+ diff --git a/Lib/test/test_logging.py b/Lib/test/test_logging.py
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+ index 1ea2967f5b..5d5eba7357 100644
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+ --- a/Lib/test/test_logging.py
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+ +++ b/Lib/test/test_logging.py
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+ @@ -35,7 +35,6 @@ import os
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+ import queue
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+ import random
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+ import re
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+ -import signal
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+ import socket
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+ import struct
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+ import sys
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+ @@ -667,72 +666,6 @@ class HandlerTest(BaseTest):
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+ if os.path.exists(fn):
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+ os.unlink(fn)
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+
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+ - # The implementation relies on os.register_at_fork existing, but we test
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+ - # based on os.fork existing because that is what users and this test use.
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+ - # This helps ensure that when fork exists (the important concept) that the
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+ - # register_at_fork mechanism is also present and used.
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+ - @unittest.skipIf(not hasattr(os, 'fork'), 'Test requires os.fork().')
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+ - def test_post_fork_child_no_deadlock(self):
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+ - """Ensure forked child logging locks are not held; bpo-6721."""
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+ - refed_h = logging.Handler()
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+ - refed_h.name = 'because we need at least one for this test'
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+ - self.assertGreater(len(logging._handlers), 0)
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+ -
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+ - locks_held__ready_to_fork = threading.Event()
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+ - fork_happened__release_locks_and_end_thread = threading.Event()
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+ -
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+ - def lock_holder_thread_fn():
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+ - logging._acquireLock()
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+ - try:
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+ - refed_h.acquire()
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+ - try:
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+ - # Tell the main thread to do the fork.
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+ - locks_held__ready_to_fork.set()
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+ -
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+ - # If the deadlock bug exists, the fork will happen
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+ - # without dealing with the locks we hold, deadlocking
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+ - # the child.
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+ -
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+ - # Wait for a successful fork or an unreasonable amount of
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+ - # time before releasing our locks. To avoid a timing based
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+ - # test we'd need communication from os.fork() as to when it
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+ - # has actually happened. Given this is a regression test
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+ - # for a fixed issue, potentially less reliably detecting
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+ - # regression via timing is acceptable for simplicity.
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+ - # The test will always take at least this long. :(
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+ - fork_happened__release_locks_and_end_thread.wait(0.5)
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+ - finally:
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+ - refed_h.release()
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+ - finally:
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+ - logging._releaseLock()
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+ -
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+ - lock_holder_thread = threading.Thread(
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+ - target=lock_holder_thread_fn,
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+ - name='test_post_fork_child_no_deadlock lock holder')
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+ - lock_holder_thread.start()
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+ -
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+ - locks_held__ready_to_fork.wait()
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+ - pid = os.fork()
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+ - if pid == 0: # Child.
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+ - logging.error(r'Child process did not deadlock. \o/')
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+ - os._exit(0)
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+ - else: # Parent.
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+ - fork_happened__release_locks_and_end_thread.set()
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+ - lock_holder_thread.join()
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+ - start_time = time.monotonic()
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+ - while True:
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+ - waited_pid, status = os.waitpid(pid, os.WNOHANG)
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+ - if waited_pid == pid:
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+ - break # child process exited.
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+ - if time.monotonic() - start_time > 7:
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+ - break # so long? implies child deadlock.
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+ - time.sleep(0.05)
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+ - if waited_pid != pid:
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+ - os.kill(pid, signal.SIGKILL)
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+ - waited_pid, status = os.waitpid(pid, 0)
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+ - self.fail("child process deadlocked.")
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+ - self.assertEqual(status, 0, msg="child process error")
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+ -
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+
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+ class BadStream(object):
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+ def write(self, data):
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+ --
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+ 2.19.1
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+
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churchyard
commented 5 years ago
This is dirty workaround for https://bugzilla.redhat.com/show_bug.cgi?id=1644936