Clean up the the locmem cache backend and utils.synch by using context managers. Puch prettier.
git-svn-id: http://code.djangoproject.com/svn/django/trunk@17152 bcc190cf-cafb-0310-a4f2-bffc1f526a37
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1086a9a845
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@ -1,5 +1,7 @@
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"Thread-safe in-memory cache backend."
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from __future__ import with_statement
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import time
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try:
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import cPickle as pickle
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@ -26,8 +28,7 @@ class LocMemCache(BaseCache):
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def add(self, key, value, timeout=None, version=None):
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key = self.make_key(key, version=version)
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self.validate_key(key)
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self._lock.writer_enters()
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try:
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with self._lock.writer():
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exp = self._expire_info.get(key)
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if exp is None or exp <= time.time():
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try:
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@ -37,14 +38,11 @@ class LocMemCache(BaseCache):
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except pickle.PickleError:
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pass
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return False
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finally:
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self._lock.writer_leaves()
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def get(self, key, default=None, version=None):
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key = self.make_key(key, version=version)
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self.validate_key(key)
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self._lock.reader_enters()
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try:
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with self._lock.reader():
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exp = self._expire_info.get(key)
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if exp is None:
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return default
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@ -54,18 +52,13 @@ class LocMemCache(BaseCache):
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return pickle.loads(pickled)
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except pickle.PickleError:
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return default
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finally:
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self._lock.reader_leaves()
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self._lock.writer_enters()
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try:
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with self._lock.writer():
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try:
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del self._cache[key]
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del self._expire_info[key]
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except KeyError:
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pass
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return default
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finally:
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self._lock.writer_leaves()
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def _set(self, key, value, timeout=None):
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if len(self._cache) >= self._max_entries:
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@ -78,14 +71,12 @@ class LocMemCache(BaseCache):
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def set(self, key, value, timeout=None, version=None):
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key = self.make_key(key, version=version)
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self.validate_key(key)
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self._lock.writer_enters()
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try:
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pickled = pickle.dumps(value, pickle.HIGHEST_PROTOCOL)
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self._set(key, pickled, timeout)
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except pickle.PickleError:
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pass
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finally:
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self._lock.writer_leaves()
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with self._lock.writer():
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try:
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pickled = pickle.dumps(value, pickle.HIGHEST_PROTOCOL)
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self._set(key, pickled, timeout)
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except pickle.PickleError:
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pass
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def incr(self, key, delta=1, version=None):
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value = self.get(key, version=version)
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@ -93,39 +84,31 @@ class LocMemCache(BaseCache):
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raise ValueError("Key '%s' not found" % key)
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new_value = value + delta
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key = self.make_key(key, version=version)
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self._lock.writer_enters()
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try:
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pickled = pickle.dumps(new_value, pickle.HIGHEST_PROTOCOL)
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self._cache[key] = pickled
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except pickle.PickleError:
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pass
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finally:
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self._lock.writer_leaves()
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with self._lock.writer():
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try:
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pickled = pickle.dumps(new_value, pickle.HIGHEST_PROTOCOL)
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self._cache[key] = pickled
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except pickle.PickleError:
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pass
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return new_value
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def has_key(self, key, version=None):
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key = self.make_key(key, version=version)
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self.validate_key(key)
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self._lock.reader_enters()
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try:
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with self._lock.reader():
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exp = self._expire_info.get(key)
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if exp is None:
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return False
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elif exp > time.time():
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return True
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finally:
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self._lock.reader_leaves()
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self._lock.writer_enters()
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try:
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with self._lock.writer():
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try:
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del self._cache[key]
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del self._expire_info[key]
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except KeyError:
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pass
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return False
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finally:
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self._lock.writer_leaves()
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def _cull(self):
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if self._cull_frequency == 0:
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@ -148,11 +131,8 @@ class LocMemCache(BaseCache):
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def delete(self, key, version=None):
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key = self.make_key(key, version=version)
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self.validate_key(key)
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self._lock.writer_enters()
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try:
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with self._lock.writer():
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self._delete(key)
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finally:
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self._lock.writer_leaves()
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def clear(self):
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self._cache.clear()
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@ -6,12 +6,16 @@ Synchronization primitives:
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(Contributed to Django by eugene@lazutkin.com)
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"""
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from __future__ import with_statement
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import contextlib
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try:
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import threading
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except ImportError:
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import dummy_threading as threading
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class RWLock:
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class RWLock(object):
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"""
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Classic implementation of reader-writer lock with preference to writers.
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@ -34,43 +38,41 @@ class RWLock:
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self.waiting_writers = 0
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def reader_enters(self):
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self.mutex.acquire()
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try:
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with self.mutex:
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if self.active_writers == 0 and self.waiting_writers == 0:
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self.active_readers += 1
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self.can_read.release()
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else:
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self.waiting_readers += 1
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finally:
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self.mutex.release()
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self.can_read.acquire()
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def reader_leaves(self):
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self.mutex.acquire()
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try:
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with self.mutex:
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self.active_readers -= 1
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if self.active_readers == 0 and self.waiting_writers != 0:
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self.active_writers += 1
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self.waiting_writers -= 1
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self.can_write.release()
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@contextlib.contextmanager
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def reader(self):
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self.reader_enters()
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try:
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yield
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finally:
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self.mutex.release()
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self.reader_leaves()
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def writer_enters(self):
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self.mutex.acquire()
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try:
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with self.mutex:
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if self.active_writers == 0 and self.waiting_writers == 0 and self.active_readers == 0:
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self.active_writers += 1
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self.can_write.release()
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else:
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self.waiting_writers += 1
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finally:
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self.mutex.release()
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self.can_write.acquire()
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def writer_leaves(self):
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self.mutex.acquire()
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try:
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with self.mutex:
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self.active_writers -= 1
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if self.waiting_writers != 0:
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self.active_writers += 1
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@ -83,5 +85,11 @@ class RWLock:
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while t > 0:
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self.can_read.release()
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t -= 1
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@contextlib.contextmanager
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def writer(self):
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self.writer_enters()
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try:
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yield
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finally:
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self.mutex.release()
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self.writer_leaves()
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