muduo网络库学习之MutexLock类、MutexLockGuard类、Condition类、CountDownLatch类封装中的知识点

一、MutexLock 类

class MutexLock : boost::noncopyable



二、MutexLockGuard类



class MutexLockGuard : boost::noncopyable



三、Condition类

class Condition : boost::noncopyable



某个线程：
加锁                                    
     while (条件)
          wait(); //1、解锁；2、等待通知；3、得到通知返回前重新加锁
解锁

另一个线程：
加锁
     更改条件
     通知notify（可以移到锁外）
解锁

四、CountDownLatch类

class CountDownLatch : boost::noncopyable



既可以用于所有子线程等待主线程发起 “起跑”
也可以用于主线程等待子线程初始化完毕才开始工作

下面写两个程序测试一下CountDownLatch 的作用：

CountDownLatch_test1:

 C++ Code 

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71

#include <muduo/base/CountDownLatch.h> #include <muduo/base/Thread.h> #include <boost/bind.hpp> #include <boost/ptr_container/ptr_vector.hpp> #include <string> #include <stdio.h> using namespace muduo; class Test { public:     Test(int numThreads)         : latch_(1),           threads_(numThreads)     {         for (int i = 0; i < numThreads; ++i)         {             char name[32];             snprintf(name, sizeof name, "work thread %d", i);             threads_.push_back(new muduo::Thread(                                    boost::bind(&Test::threadFunc, this), muduo::string(name)));         }         for_each(threads_.begin(), threads_.end(), boost::bind(&Thread::start, _1));     }     void run()     {         latch_.countDown();     }     void joinAll()     {         for_each(threads_.begin(), threads_.end(), boost::bind(&Thread::join, _1));     } private:     void threadFunc()     {         latch_.wait();         printf("tid=%d, %s started\n",                CurrentThread::tid(),                CurrentThread::name());         printf("tid=%d, %s stopped\n",                CurrentThread::tid(),                CurrentThread::name());     }     CountDownLatch latch_;     boost::ptr_vector<Thread> threads_; }; int main() {     printf("pid=%d, tid=%d\n", ::getpid(), CurrentThread::tid());     Test t(3);     sleep(3);     printf("pid=%d, tid=%d %s running ...\n", ::getpid(), CurrentThread::tid(), CurrentThread::name());     t.run();     t.joinAll();     printf("number of created threads %d\n", Thread::numCreated()); }

执行结果如下：

simba@ubuntu:~/Documents/build/debug/bin$ ./countdownlatch_test1

pid=2994, tid=2994

pid=2994, tid=2994 main running ...

tid=2997, work thread 2 started

tid=2997, work thread 2 stopped

tid=2996, work thread 1 started

tid=2996, work thread 1 stopped

tid=2995, work thread 0 started

tid=2995, work thread 0 stopped

number of created threads 3

simba@ubuntu:~/Documents/build/debug/bin$ 

可以看到其他三个线程一直等到主线程睡眠完执行run()，在里面执行latch_.countDown() 将计数减为0，进而执行notifyall 唤醒后，才开始执行下来。

CountDownLatch_test2:

 C++ Code 

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71

#include <muduo/base/CountDownLatch.h> #include <muduo/base/Thread.h> #include <boost/bind.hpp> #include <boost/ptr_container/ptr_vector.hpp> #include <string> #include <stdio.h> using namespace muduo; class Test { public:     Test(int numThreads)         : latch_(numThreads),           threads_(numThreads)     {         for (int i = 0; i < numThreads; ++i)         {             char name[32];             snprintf(name, sizeof name, "work thread %d", i);             threads_.push_back(new muduo::Thread(                                    boost::bind(&Test::threadFunc, this), muduo::string(name)));         }         for_each(threads_.begin(), threads_.end(), boost::bind(&muduo::Thread::start, _1));     }     void wait()     {         latch_.wait();     }     void joinAll()     {         for_each(threads_.begin(), threads_.end(), boost::bind(&Thread::join, _1));     } private:     void threadFunc()     {         sleep(3);        printf("tid=%d, %s started\n",                CurrentThread::tid(),                CurrentThread::name());         latch_.countDown();               printf("tid=%d, %s stopped\n",                CurrentThread::tid(),                CurrentThread::name());     }     CountDownLatch latch_;     boost::ptr_vector<Thread> threads_; }; int main() {     printf("pid=%d, tid=%d\n", ::getpid(), CurrentThread::tid());     Test t(3);     t.wait();     printf("pid=%d, tid=%d %s running ...\n", ::getpid(), CurrentThread::tid(), CurrentThread::name());     t.joinAll();     printf("number of created threads %d\n", Thread::numCreated()); }

执行结果输出如下：

simba@ubuntu:~/Documents/build/debug/bin$ ./countdownlatch_test2

pid=4488, tid=4488

tid=4491, work thread 2 started

tid=4491, work thread 2 stopped

tid=4490, work thread 1 started

tid=4490, work thread 1 stopped

tid=4489, work thread 0 started

pid=4488, tid=4488 main running ...

tid=4489, work thread 0 stopped

number of created threads 3

可以看出当其他三个线程都启动后，各自执行一次 latch_.countDown()，主线程wait() 返回继续执行下去。

参考：

muduo manual.pdf

《linux 多线程服务器编程：使用muduo c++网络库》