diff options
Diffstat (limited to 'Lib/logging')
-rw-r--r-- | Lib/logging/__init__.py | 50 |
1 files changed, 50 insertions, 0 deletions
diff --git a/Lib/logging/__init__.py b/Lib/logging/__init__.py index a4a950d..7aeff45 100644 --- a/Lib/logging/__init__.py +++ b/Lib/logging/__init__.py @@ -225,6 +225,55 @@ 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 #--------------------------------------------------------------------------- @@ -795,6 +844,7 @@ 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): """ |