线程Python语言扩展

python-safethread is a large modification of CPython intended to provide safe, easy, and scalable concurrency mechanisms. It focuses on local concurrency, not distributed or parallel programs. Note: As an implementation, python-safethread is dead. It is not worth the effort to continue rewriting CPython to have a true tracing GC. However, the semantics presented are still viable and I intend to reuse them in future projects. Some major features: * Exceptions from threads propagate naturally and cause the program to shut down gracefully. * No memory model is necessary. All mutable objects are safely contained with monitors (similar to Concurrent Pascal"s monitors, but different from Java"s monitors), or otherwise provide explicit semantics. * Deadlocks are detected and broken automatically. * Finalization is thread-safe (and uses a much simpler mechanism at a low-level.) * Most existing single-threaded code will continu