U VÚd§'ã@s8dZddlmZmZmZddlmZGdd„deƒZdS)zî ReadWriteLock Taken from http://code.activestate.com/recipes/502283/ locks.py - Read-Write lock thread lock implementation See the class documentation for more info. Copyright (C) 2007, Heiko Wundram. Released under the BSD-license. é)Ú ConditionÚ currentThreadÚLock)Útimec@s4eZdZdZdd„Zd dd„Zd dd„Zd d „ZdS) Ú ReadWriteLocka[Read-Write lock class. A read-write lock differs from a standard threading.RLock() by allowing multiple threads to simultaneously hold a read lock, while allowing only a single thread to hold a write lock at the same point of time. When a read lock is requested while a write lock is held, the reader is blocked; when a write lock is requested while another write lock is held or there are read locks, the writer is blocked. Writers are always preferred by this implementation: if there are blocked threads waiting for a write lock, current readers may request more read locks (which they eventually should free, as they starve the waiting writers otherwise), but a new thread requesting a read lock will not be granted one, and block. This might mean starvation for readers if two writer threads interweave their calls to acquire_write() without leaving a window only for readers. In case a current reader requests a write lock, this can and will be satisfied without giving up the read locks first, but, only one thread may perform this kind of lock upgrade, as a deadlock would otherwise occur. After the write lock has been granted, the thread will hold a full write lock, and not be downgraded after the upgrading call to acquire_write() has been match by a corresponding release(). cCs(ttƒƒ|_d|_d|_g|_i|_dS)z Initialize this read-write lock.Nr)rrÚ_ReadWriteLock__conditionÚ_ReadWriteLock__writerÚ"_ReadWriteLock__upgradewritercountÚ_ReadWriteLock__pendingwritersÚ_ReadWriteLock__readers)Úself©r ú/opt/wsgidav/wsgidav/rw_lock.pyÚ__init__4s  zReadWriteLock.__init__NcCsð|dk rtƒ|}tƒ}|j ¡z¼|j|krD|jd7_W¢ dS|jdkr |jsZ|jr€||j kr |j |d7<W¢fdSn |j   |d¡d|j |<W¢DdS|dk rÐ|tƒ}|dkrÂt dƒ‚|j  |¡qD|j  ¡qDW5|j ¡XdS)afAcquire a read lock for the current thread, waiting at most timeout seconds or doing a non-blocking check in case timeout is <= 0. In case timeout is None, the call to acquire_read blocks until the lock request can be serviced. In case the timeout expires before the lock could be serviced, a RuntimeError is thrown.NérzAcquiring read lock timed out) rrrÚacquireÚreleaserÚ_ReadWriteLock__writercountr r r ÚgetÚ RuntimeErrorÚwait)r ÚtimeoutÚendtimeÚmeÚ remainingr r rÚ acquire_readCs,         zReadWriteLock.acquire_readcCsn|dk rtƒ|}tƒd}}|j ¡z2|j|krN|jd7_W¢dS||jkrz|jrft dƒ‚d}|j  |¡|_n |j   |¡|jsô|jdkrô|jrÂ|rô||_|jd|_d|_W¢¢dSn2|j d|krô||_d|_|j dd…|_ W¢ndS|dk rN|tƒ}|dkr@|r,|j|j|<d|_n |j   |¡tdƒ‚|j |¡q†|j ¡q†W5|j ¡XdS)aêAcquire a write lock for the current thread, waiting at most timeout seconds or doing a non-blocking check in case timeout is <= 0. In case the write lock cannot be serviced due to the deadlock condition mentioned above, a ValueError is raised. In case timeout is None, the call to acquire_write blocks until the lock request can be serviced. In case the timeout expires before the lock could be serviced, a RuntimeError is thrown.NFrz(Inevitable dead lock, denying write lockTrzAcquiring write lock timed out)rrrrrrrr r Ú ValueErrorÚpopr ÚappendÚremoverr)r rrrZ upgradewriterrr r rÚ acquire_writersJ               zReadWriteLock.acquire_writecCsžtƒ}|j ¡z||j|krB|jd8_|jsŠd|_|j ¡nH||jkr‚|j|d8<|j|sŠ|j|=|jsŠ|j ¡ntdƒ‚W5|j ¡XdS)zkRelease the currently held lock. In case the current thread holds no lock, a ValueError is thrown.rNzTrying to release unheld lock) rrrrrrÚ notifyAllr r)r rr r rrÇs        zReadWriteLock.release)N)N)Ú__name__Ú __module__Ú __qualname__Ú__doc__rrr rr r r rrs  / UrN)r%Ú threadingrrrrÚobjectrr r r rÚs