c++ - boost::this_thread::sleep_用于使整个程序休眠

Question

C++ 98和Boost 1.54

我在弄清楚为什么使用boost::this_thread::sleep_for会使我的整个程序处于休眠状态时遇到了麻烦。调用Wait()函数的唯一时间和地点是在此线程内，并且该线程的唯一目的是读取目录中的文件名并触发上载。

但是由于某种原因，当它到达boost::this_thread::sleep_for函数中的Wait()行时，它卡在那里并且还休眠所有其他线程。我不确定自己缺少什么，因此我们将不胜感激。

代码:

void Upload::ReadFileNames()
{
    cout << "[DEBUG] ReadFileNames -> A " << endl;
    Wait();  
    cout << "[DEBUG] ReadFileNames -> B " << endl;


    // read filename stuff
}

void Upload::Wait()
{
    typedef boost::chrono::duration<long, boost::ratio<60> > seconds;
    int randomWaitTime = 0;
    try{   
        randomWaitTime = lexical_cast<unsigned int>(getId());
        randomWaitTime = randomWaitTime * 10;
    }
    catch ( const boost::bad_lexical_cast & e){
        // cout << "[LOG] FileUpLoad : Wait : bad_lexical_cast : "  << e.what() << endl ;
        randomWaitTime = 0;
    }

    seconds testTimeToWait(randomWaitTime);

    cout << "[DEBUG] Wait() -> A" << endl;
    boost::this_thread::sleep_for(testTimeToWait);
    cout << "[DEBUG] Wait() -> B" << endl;

    cout << "RANDOM WAIT TIME = " << randomWaitTime << endl;
}

main.cpp

int  main()
{   
    pthread_t threadA; 
    pthread_create(&threadA,NULL,threadAfn,NULL);

    pthread_t threadB;
    pthread_create(&threadB,NULL,threadBfn,NULL);

    pthread_t Upload;    //  <--- Thread in question
    pthread_create(&Upload,NULL,Uploadfn,NULL);

    pthread_join(threadA,NULL);
    pthread_join(threadB,NULL);
    pthread_join(Upload,NULL); // <--- Thread in question

    return 0; 
}

输出

[DEBUG] ReadFileNames -> A 
[DEBUG] Wait() -> A
// hangs here and rest of the threads are locked/slept as well?

Answer 1

it hangs there and sleeps all the other threads as well

不，不是。如果那样 似乎是，那是因为其他线程已经卡住或结束。

查找阻塞的事物(mutex.lock，条件等待，IO操作等)或检查线程是否未退出。

笔记

您的seconds计算已关闭。在我的系统上，以下内容:

Live On Coliru

#include <boost/chrono.hpp>
#include <iostream>

int main() {
    std::cout << boost::chrono::duration<long, boost::ratio<60> >(1)/boost::chrono::seconds(1) << std::endl;
}

版画

60

因此，您命名的seconds实际上是几分钟。只需这样做:

using boost::chrono::seconds;
int delay = std::strtoul(getId().c_str(), NULL, 10)*10;
sleep_for(seconds(delay));

如果getId返回是，则您的随机延迟是随机的。使用boost/random.hpp，可以通过良好的范围控制使其真正随机化。例如。休眠1000到3000毫秒之间:

int random_gen(int low，int high){//不是线程安全的
静态boost::random_device rdev;
静态升压:: mt19937 prng(rdev);
返回boost::uniform_int <>(low，high)(prng);
}

无效上传:: Wait(){
int const ms_delay = random_gen(1000，3000);
cout <<“RANDOM WAIT TIME =” << ms_delay << endl;
sleep_for(毫秒(ms_delay));
}

Note to seed using random_device as shown (so true random seed) you need to link the random library. Otherwise, you can "stoop" to a time-based seed:

 static boost::mt19937 prng(std::time(NULL));

这是代码的独立版本，其中应用了各种建议，表明没有死锁/软锁:

Live On Coliru

#include <boost/asio.hpp>
#include <boost/chrono.hpp>
#include <boost/lexical_cast.hpp>
#include <boost/thread.hpp>
#include <iostream>
#include <boost/random.hpp>

using boost::this_thread::sleep_for;
using boost::chrono::seconds;
using boost::chrono::milliseconds;

using boost::lexical_cast;
using std::cout;
using std::endl;

struct Upload {
    std::string getId() const { return "42"; }
    void Wait();
    void ReadFileNames();
};

void Upload::ReadFileNames() {
    cout << "[DEBUG] ReadFileNames -> A " << endl;
    Wait();
    cout << "[DEBUG] ReadFileNames -> B " << endl;

    // read filename stuff
}

int random_gen(int low, int high) { // not threadsafe
    static boost::mt19937 prng(std::time(NULL));
    return boost::uniform_int<>(low, high)(prng);
}

void Upload::Wait() {
    int const ms_delay = random_gen(1000, 3000);
    cout << "RANDOM WAIT TIME = " << ms_delay << endl;
    sleep_for(milliseconds(ms_delay));
}

void background(char const* name) {
    // desync different background threads
    sleep_for(milliseconds(boost::hash_value(name) % 1000));

    for (int i=0; i<5; ++i) {
        sleep_for(seconds(1));
        std::clog << name << " " << i << std::endl;
    }
}

void threadAfn() { background("thread A"); }
void threadBfn() { background("thread B"); }

void Uploadfn() {
    Upload u;
    u.ReadFileNames();
}

int main() {
    boost::thread threadA(threadAfn);
    boost::thread threadB(threadBfn);
    boost::thread Upload(Uploadfn);

    threadA.join();
    threadB.join();
    Upload.join();
}

打印品，例如:

[DEBUG] ReadFileNames -> A 
RANDOM WAIT TIME = 1150
[DEBUG] ReadFileNames -> B 
thread A 0
thread B 0
thread A 1
thread B 1
thread A 2
thread B 2
thread A 3
thread B 3
thread A 4
thread B 4