Question

我正在浏览信号量小册子＆＃34;现在，我遇到了第一个障碍问题。在下面的代码中，我尝试在继续之前有3个线程集合点。这部分工作正常 - 我总是得到3＆＃34;在推送到队列之前。但是，在推送到队列之后，我并不总是得到3＆＃34;有时候我会，但并非总是这样。我做错了什么？

import threading
import random
import Queue
import time

num_loops = 1
class myThread(threading.Thread):
    def __init__(self, id, count, n, q, locks):
        threading.Thread.__init__(self)
        self.id = id
        self.q = q
        self.n = n
        self.locks = locks
        self.count = count
        return

    def run(self):
        time.sleep(random.random()/100)
        self.q.put("before")
        with self.locks['mutex']:
            self.count[0] += 1
            if self.count[0] == self.n:
                locks['barrier'].release()
        locks['barrier'].acquire()
        locks['barrier'].release()
        time.sleep(random.random()/100)
        self.q.put("after")


if __name__ == '__main__':
    total = 10
    incorrect = 0
    num_threads = 3
    for _ in range(total):
        q = Queue.Queue()
        locks = {'mutex': threading.Semaphore(1),
                 'barrier': threading.Semaphore(0),
                }
        threads = []
        count = [0]
        for i in range(num_threads):
            t = myThread(i, count, num_threads, q, locks)
            t.start()
            threads.append(t)

        for i in threads:
            t.join()
            print "join"

        one_loop = ['before']*num_threads + ['after']*num_threads

        total_loop = one_loop * num_loops
        result = []
        while not q.empty():
            result.append(q.get())
        print result
        if result != total_loop:
            incorrect += 1
    print "%s out of %s is wrong" % (incorrect, total)

Answer 1

我发现了问题。你没有加入所有的线程。这一行：

for i in threads:
    t.join()
    print "join"

应该是：

for i in threads:
    i.join()  # changed line
    print "join"

加入t首先只是等待创建的最后一个线程，然后在其余的迭代中等待无操作。

Rendezvous线程 - 当join（）取消阻塞时，线程没有完成处理

1 个答案: