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