死锁

死锁状态

from multiprocessing import Process
from multiprocessing import Lock,RLock

def func(lock):
    lock.acquire()  # 持有锁
    print('子进程成功拿锁')
    lock.acquire()  # 持有锁
    print('子进程再次成功拿锁')

    lock.release()    # 使用release() 释放资源
    lock.release()
    return
def main():
    l = RLock()         # 使用Lock()会发生死锁，使用RLock()避免死锁
    p = Process(target=func,args=(l,))
    p.start()
    p.join()

if __name__ == '__main__':
    main()

比较两个进程认识死锁

from multiprocessing import Process
from multiprocessing import Lock,RLock
import time

def a(l1,l2):
    l1.acquire()   # 持有l1锁
    print('a进程拿到了l1锁')
    time.sleep(3)          # 加时间体现死锁状态
    l2.acquire()   # 持有l2锁
    print('a进程拿到了l2锁')

    print('a进程运行中')
    l1.release()
    l2.release()

def b(l1,l2):
    l2.acquire()   # 持有l2锁
    print('b进程拿到了l2锁')

    l1.acquire()   # 持有l1锁
    print('b进程拿到了l1锁')

    print('b进程运行中')
    l2.release()
    l1.release()
def main():
    l1 = RLock()         # 使用Lock()会发生死锁，使用RLock()避免死锁
    l2 = RLock()         # 使用Lock()会发生死锁，使用RLock()避免死锁

    p1 = Process(target=a,args=(l1,l2))
    p2 = Process(target=b,args=(l1,l2))
    p1.start()
    p2.start()
    p1.join()
    p2.join()

if __name__ == '__main__':
    main()