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from eventlet import hubs
from eventlet.semaphore import Semaphore
class Lock(Semaphore):
"""A lock.
This is API-compatible with :class:`threading.Lock`.
It is a context manager, and thus can be used in a with block::
lock = Lock()
with lock:
do_some_stuff()
"""
def release(self, blocking=True):
"""Modify behaviour vs :class:`Semaphore` to raise a RuntimeError
exception if the value is greater than zero. This corrects behaviour
to realign with :class:`threading.Lock`.
"""
if self.counter > 0:
raise RuntimeError("release unlocked lock")
# Consciously *do not* call super().release(), but instead inline
# Semaphore.release() here. We've seen issues with logging._lock
# deadlocking because garbage collection happened to run mid-release
# and eliminating the extra stack frame should help prevent that.
# See https://github.com/eventlet/eventlet/issues/742
self.counter += 1
if self._waiters:
hubs.get_hub().schedule_call_global(0, self._do_acquire)
return True
def _at_fork_reinit(self):
self.counter = 1
self._waiters.clear()
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