A python implementation of the three Reader-Writer problems.
Reader Writer Lock
A python implementation of a solution for the three Reader-Writer problems.
Not only does it implement the reader-writer problems, it is also compliant with the python lock interface which among others include support for timeout.
For reading about the theory behind the reader-writer problems refer to Wikipedia.
Install the python package readerwriterlock
python3 -m pip install -U readerwriterlock
- Choose a rwlock class base on your access priority need and feature need which is going to be use by the threads:
|Reader priority (aka First readers-writers problem)||RWLockRead||RWLockReadD|
|Writer priority (aka Second readers-writers problem)||RWLockWrite||RWLockWriteD|
|Fair priority (aka Third readers-writers problem)||RWLockFair||RWLockFairD|
* Downgradable feature allows the locks to be atomically downgraded from being locked in write-mode to locked in read-mode
ⓘ Downgradable classes come with a theoretical ~20% negative effect on performance for acquiring and releasing locks.
- Instantiate an instance of the chosen RWLock class:
from readerwriterlock import rwlock a = rwlock.RWLockFairD()
- Generate read locks and write locks using the following methods:
a_reader_lock = a.gen_rlock() a_writer_lock = a.gen_wlock()
- Use the generated read/write locks to protect section in your code:
Pythonic usage example
with a.gen_rlock(): #Read stuff with a.gen_wlock(): #Write stuff
Use case (Timeout) example
b = a.gen_wlock() if b.acquire(blocking=True, timeout=5): try: #Do stuff finally: b.release()
Use case (Downgrade) example
b = a.gen_wlock() if b.acquire(): try: #Read/Write stuff b = b.downgrade() #Read stuff finally: b.release()
The tests can be initiated by doing
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