使用信号量实现 N 个进程屏障 [英] Implementing an N process barrier using semaphores

问题描述

我目前正在为之前迭代的操作系统考试进行培训，我遇到了这个问题:

I'm currently training for an OS exam with previous iterations and I came across this:

实施N 流程屏障"，即是，确保每个过程出来一群人在等待，在某些点在其各自的执行，对于其他进程达到他们的给定点.

Implement a "N Process Barrier", that is, making sure that each process out of a group of them waits, at some point in its respective execution, for the other processes to reach their given point.

你有以下可用的操作:

init(sem,value)、wait(sem)和signal(sem)

N 是一个任意数字.我可以使它适用于给定数量的进程，但不适用于任何数量.

N is an arbitrary number. I can make it so that it works for a given number of processes, but not for any number.

有什么想法吗?用伪代码回复就可以了，这不是作业，只是个人学习.

Any ideas? It's OK to reply with the pseudo-code, this is not an assignment, just personal study.

推荐答案

这在信号量小书.

n = the number of threads
count = 0
mutex = Semaphore(1)
barrier = Semaphore(0)


mutex.wait()
count = count + 1
mutex.signal()

if count == n: barrier.signal() # unblock ONE thread

barrier.wait()
barrier.signal() # once we are unblocked, it's our duty to unblock the next thread

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