python 多线程 锁lock/rlock(并行编程 4)

threading.Lock() lock.acquire() lock.release()

import threading

withlock=0 nolock=0 count=10000 lock=threading.Lock()

def inwithlock(): global withlock for i in range(count): lock.acquire() withlock+=1 lock.release() def dewithlock(): global withlock for i in range(count): lock.acquire() withlock-=1 lock.release() def innolock(): global nolock for i in range(count): nolock+=1 def denolock(): global nolock for i in range(count): nolock-=1

t1=threading.Thread(target=inwithlock) t2=threading.Thread(target=dewithlock) t3=threading.Thread(target=innolock) t4=threading.Thread(target=denolock) t1.start() t2.start() t3.start() t4.start() t1.join() t2.join() t3.join() t4.join() print("%s" % withlock) print("%s" % nolock)

线程安全的操作

import threading

global var

count = 0 lock = threading.Lock()

Define a function for the thread

def print_time(threadName): global count

c=0
with lock:
    while(c<100):
        c+=1
        count+=1
        print("{0}: set count to {1}".format( threadName, count) )

Create and run threads as follows

try: threading.Thread( target=print_time, args=("Thread-1", ) ).start() threading.Thread( target=print_time, args=("Thread-2", ) ).start() threading.Thread( target=print_time, args=("Thread-3", ) ).start() except Exception as e: print("Error: unable to start thread")

RLOCK和LOCK的区别

1.2 死锁

Lock在下面的情形下会发生死锁

Lock.acquire()

Lock.acquire()

Lock.release()

Lock.release()

连续两次acquire请求，会导致死锁，因为第一次获得锁之后还没有释放，第二次再来申请，程序就阻塞在这里，导致第一次申请到的锁无法释放

1.3 可重入锁

RLock就不存在1.2中所提到的死锁

RLock.acquire()

RLock.acquire()

RLock.release()

RLock.release()

但是要保证，有多少次acquire就有多少次release