from cpython cimport pythread
from cpython.exc cimport PyErr_NoMemory
cdef class FastRLock:
"""Fast, re-entrant locking.
Under uncongested conditions, the lock is never acquired but only
counted. Only when a second thread comes in and notices that the
lock is needed, it acquires the lock and notifies the first thread
to release it when it's done. This is all made possible by the
wonderful GIL.
"""
cdef pythread.PyThread_type_lock _real_lock
cdef long _owner # ID of thread owning the lock
cdef int _count # re-entry count
cdef int _pending_requests # number of pending requests for real lock
cdef bint _is_locked # whether the real lock is acquired
def __cinit__(self):
self._owner = -1
self._count = 0
self._is_locked = False
self._pending_requests = 0
self._real_lock = pythread.PyThread_allocate_lock()
if self._real_lock is NULL:
PyErr_NoMemory()
def __dealloc__(self):
if self._real_lock is not NULL:
pythread.PyThread_free_lock(self._real_lock)
self._real_lock = NULL
def acquire(self, bint blocking=True):
return lock_lock(self, pythread.PyThread_get_thread_ident(), blocking)
def release(self):
if self._owner != pythread.PyThread_get_thread_ident():
raise RuntimeError("cannot release un-acquired lock")
unlock_lock(self)
cdef inline bint lock_lock(FastRLock lock, long current_thread, bint blocking) nogil:
# Note that this function *must* hold the GIL when being called.
# We just use 'nogil' in the signature to make sure that no Python
# code execution slips in that might free the GIL
if lock._count:
# locked! - by myself?
if current_thread == lock._owner:
lock._count += 1
return 1
elif not lock._pending_requests:
# not locked, not requested - go!
lock._owner = current_thread
lock._count = 1
return 1
# need to get the real lock
return _acquire_lock(
lock, current_thread,
pythread.WAIT_LOCK if blocking else pythread.NOWAIT_LOCK)
cdef bint _acquire_lock(FastRLock lock, long current_thread, int wait) nogil:
# Note that this function *must* hold the GIL when being called.
# We just use 'nogil' in the signature to make sure that no Python
# code execution slips in that might free the GIL
if not lock._is_locked and not lock._pending_requests:
# someone owns it but didn't acquire the real lock - do that
# now and tell the owner to release it when done. Note that we
# do not release the GIL here as we must absolutely be the one
# who acquires the lock now.
if not pythread.PyThread_acquire_lock(lock._real_lock, wait):
return 0
#assert not lock._is_locked
lock._is_locked = True
lock._pending_requests += 1
with nogil:
# wait for the lock owning thread to release it
locked = pythread.PyThread_acquire_lock(lock._real_lock, wait)
lock._pending_requests -= 1
#assert not lock._is_locked
#assert lock._count == 0
if not locked:
return 0
lock._is_locked = True
lock._owner = current_thread
lock._count = 1
return 1
cdef inline void unlock_lock(FastRLock lock) nogil:
# Note that this function *must* hold the GIL when being called.
# We just use 'nogil' in the signature to make sure that no Python
# code execution slips in that might free the GIL
#assert lock._owner == pythread.PyThread_get_thread_ident()
#assert lock._count > 0
lock._count -= 1
if lock._count == 0:
lock._owner = -1
if lock._is_locked:
pythread.PyThread_release_lock(lock._real_lock)
lock._is_locked = False
Diff to Previous Revision
--- revision 1 2010-07-27 19:06:12
+++ revision 2 2010-07-27 19:40:43
@@ -1,7 +1,7 @@
from cpython cimport pythread
from cpython.exc cimport PyErr_NoMemory
-cdef class FastLock:
+cdef class FastRLock:
"""Fast, re-entrant locking.
Under uncongested conditions, the lock is never acquired but only
@@ -39,7 +39,7 @@
unlock_lock(self)
-cdef inline bint lock_lock(FastLock lock, long current_thread, bint blocking) nogil:
+cdef inline bint lock_lock(FastRLock lock, long current_thread, bint blocking) nogil:
# Note that this function *must* hold the GIL when being called.
# We just use 'nogil' in the signature to make sure that no Python
# code execution slips in that might free the GIL
@@ -59,7 +59,7 @@
lock, current_thread,
pythread.WAIT_LOCK if blocking else pythread.NOWAIT_LOCK)
-cdef bint _acquire_lock(FastLock lock, long current_thread, int wait) nogil:
+cdef bint _acquire_lock(FastRLock lock, long current_thread, int wait) nogil:
# Note that this function *must* hold the GIL when being called.
# We just use 'nogil' in the signature to make sure that no Python
# code execution slips in that might free the GIL
@@ -87,7 +87,7 @@
lock._count = 1
return 1
-cdef inline void unlock_lock(FastLock lock) nogil:
+cdef inline void unlock_lock(FastRLock lock) nogil:
# Note that this function *must* hold the GIL when being called.
# We just use 'nogil' in the signature to make sure that no Python
# code execution slips in that might free the GIL
