# ch12/example1.py

import threading
import time

def thread_a():
    print('Thread A is starting...')

    print('Thread A waiting to acquire lock A.')
    lock_a.acquire()
    print('Thread A has acquired lock A, performing some calculation...')
    time.sleep(2)

    print('Thread A waiting to acquire lock B.')
    lock_b.acquire()
    print('Thread A has acquired lock B, performing some calculation...')
    time.sleep(2)

    print('Thread A releasing both locks.')
    lock_a.release()
    lock_b.release()

def thread_b():
    print('Thread B is starting...')

    print('Thread B waiting to acquire lock B.')
    lock_b.acquire()
    print('Thread B has acquired lock B, performing some calculation...')
    time.sleep(5)

    print('Thread B waiting to acquire lock A.')
    lock_a.acquire()
    print('Thread B has acquired lock A, performing some calculation...')
    time.sleep(5)

    print('Thread B releasing both locks.')
    lock_b.release()
    lock_a.release()

lock_a = threading.Lock()
lock_b = threading.Lock()

thread1 = threading.Thread(target=thread_a)
thread2 = threading.Thread(target=thread_b)

thread1.start()
thread2.start()

thread1.join()
thread2.join()

print('Finished.')