Concurrent Programming recursive lock

Recursive lock

The first case: a lock with a thread lock many times, does not affect the execution

from threading import RLock,currentThread,Thread
r = RLock()

r.acquire()
r.acquire()
print("over")

over

The second case: Multithreaded must ensure that the number of locking and unlocking of the same number, other threads to be able to grab the lock

from threading import RLock,currentThread,Thread
import time
r = RLock()

def task():
    #r.acquire()    # 如果增加这行代码，程序将无法结束
    r.acquire()
    time.sleep(2)
    print(currentThread().name)
    r.release()     # 只释放了一次，但加锁了两次

def task2():
    r.acquire()     # 出现了死锁的情况
    time.sleep(2)
    print(currentThread().name)
    r.release()


Thread(target=task).start()
Thread(target=task2).start()

Thread-1
Thread-2

to sum up:

1. The same thread of the same lock locked many times, does not affect the execution
2. We must ensure that the same thread, the number of locked and unlocked same number of times, other threads to be able to grab the lock