Question

作为项目的一部分，我正在编写记录器功能。当程序想要记录某些内容时，此记录器功能会发送电子邮件。由于SMTP服务器没有响应，我决定在单独的线程中发送邮件。该线程从std :: deque读取消息，该消息由日志记录函数填充。线程设置如下：

while (!boost::this_thread::interruption_requested())
{
  EmailItem emailItem;
  {
    boost::unique_lock<boost::mutex> lock(mMutex);
    while (mEmailBuffer.empty())
      mCond.wait(lock);

    bufferOverflow = mBufferOverflow;
    mBufferOverflow = false;
    nrOfItems = mEmailBuffer.size();

    if (nrOfItems > 0)
    {
      emailItem = mEmailBuffer.front();
      mEmailBuffer.pop_front();
    }
  }

  if (nrOfItems > 0)
  {
      bool sent = false;
      while(!sent)
      {
          try
          {
             ..... Do something with the message .....
            {
                boost::this_thread::disable_interruption di;
                boost::lock_guard<boost::mutex> lock(mLoggerMutex);
                mLogFile << emailItem.mMessage << std::endl;
            }
            sent = true;
          }
          catch (const std::exception &e)
          {
            // Unable to send mail, an exception occurred. Retry sending it after some time
            sent = false;
            boost::this_thread::sleep(boost::posix_time::seconds(LOG_WAITBEFORE_RETRY));
          }
      }
  }
}

函数log（）向deque（mEmailBuffer）添加一条新消息，如下所示：

{
  boost::lock_guard<boost::mutex> lock(mMutex);
  mEmailBuffer.push_back(e);
  mCond.notify_one();
}

当主程序退出时，将调用logger对象的析构函数。这是出错的地方，应用程序崩溃时出现错误：

/usr/include/boost/thread/pthread/mutex.hpp:45: boost::mutex::~mutex(): Assertion `!pthread_mutex_destroy(&m)' failed.

析构函数只是在线程上调用一个中断然后加入它：

mQueueThread.interrupt();
mQueueThread.join();

在主程序中，我使用了多个不同的类，这些类也使用了增强线程和互斥，这会导致这种行为吗？不调用logger对象的析构函数不会导致错误，就像使用logger对象而不执行任何其他操作一样。

我的猜测是我做了一些非常错误的事情，或者在使用分散在多个类的多个线程时，线程库中存在一个错误。有谁知道这个错误的原因是什么？

编辑：我做了@Andy T提议并尽可能地删除了代码。我删除了在不同线程中运行的函数中的几乎所有内容。线程现在看起来像：

void Vi::Logger::ThreadedQueue()
{
  bool bufferOverflow = false;
  time_t last_overflow = 0;
  unsigned int nrOfItems = 0;

  while (!boost::this_thread::interruption_requested())
  {
    EmailItem emailItem;
    // Check for new log entries
    {
      boost::unique_lock<boost::mutex> lock(mMutex);
      while (mEmailBuffer.empty())
        mCond.wait(lock);
    }
  }
}

问题仍然存在。然而，回溯问题显示我与初始代码有所不同：

#0  0x00007ffff53e9ba5 in raise (sig=<value optimized out>) at ../nptl/sysdeps/unix/sysv/linux/raise.c:64
#1  0x00007ffff53ed6b0 in abort () at abort.c:92
#2  0x00007ffff53e2a71 in __assert_fail (assertion=0x7ffff7bb6407 "!pthread_mutex_lock(&m)", file=<value optimized out>, line=50, function=0x7ffff7bb7130 "void boost::mutex::lock()") at assert.c:81
#3  0x00007ffff7b930f3 in boost::mutex::lock (this=0x7fffe2c1b0b8) at /usr/include/boost/thread/pthread/mutex.hpp:50
#4  0x00007ffff7b9596c in boost::unique_lock<boost::mutex>::lock (this=0x7fffe48b3b40) at /usr/include/boost/thread/locks.hpp:349
#5  0x00007ffff7b958db in boost::unique_lock<boost::mutex>::unique_lock (this=0x7fffe48b3b40, m_=...) at /usr/include/boost/thread/locks.hpp:227
#6  0x00007ffff6ac2bb7 in Vi::Logger::ThreadedQueue (this=0x7fffe2c1ade0) at /data/repos_ViNotion/stdcomp/Logging/trunk/src/Logger.cpp:198
#7  0x00007ffff6acf2b2 in boost::_mfi::mf0<void, Vi::Logger>::operator() (this=0x7fffe2c1d890, p=0x7fffe2c1ade0) at /usr/include/boost/bind/mem_fn_template.hpp:49
#8  0x00007ffff6acf222 in boost::_bi::list1<boost::_bi::value<Vi::Logger*> >::operator()<boost::_mfi::mf0<void, Vi::Logger>, boost::_bi::list0> (this=0x7fffe2c1d8a0, f=..., a=...) at /usr/include/boost/bind/bind.hpp:253
#9  0x00007ffff6acf1bd in boost::_bi::bind_t<void, boost::_mfi::mf0<void, Vi::Logger>, boost::_bi::list1<boost::_bi::value<Vi::Logger*> > >::operator() (this=0x7fffe2c1d890) at /usr/include/boost/bind/bind_template.hpp:20
#10 0x00007ffff6aceff2 in boost::detail::thread_data<boost::_bi::bind_t<void, boost::_mfi::mf0<void, Vi::Logger>, boost::_bi::list1<boost::_bi::value<Vi::Logger*> > > >::run (this=0x7fffe2c1d760)
    at /usr/include/boost/thread/detail/thread.hpp:56
#11 0x00007ffff2cc5230 in thread_proxy () from /usr/lib/libboost_thread.so.1.42.0
#12 0x00007ffff4d87971 in start_thread (arg=<value optimized out>) at pthread_create.c:304
#13 0x00007ffff549c92d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:112
#14 0x0000000000000000 in ?? ()

在使用unique_lock（）然后中断线程的组合中，有可能没有解锁mMutex吗？

Answer 1

你退出前加入你的主题吗？如tyz所示，当mutex被破坏时，你的线程仍可以锁定它。

[编辑]

你没有提供可以编译和运行的完整示例，很难提供帮助。

检查这个与你的例子类似的简单示例：

#include <boost/thread.hpp>
#include <boost/bind.hpp>
#include <queue>

class Test
{
public:
    Test()
    {
        thread = boost::thread(boost::bind(&Test::thread_func, this));
    }

    ~Test()
    {
        thread.interrupt();
        thread.join();
    }

    void run()
    {
        for (size_t i = 0; i != 10000; ++i) {
            boost::lock_guard<boost::mutex> lock(mutex);
            queue.push(i);
            condition_var.notify_one();
        }
    }

private:
    void thread_func()
    {
        while (!boost::this_thread::interruption_requested())
        {
            {
                boost::unique_lock<boost::mutex> lock(mutex);
                while (queue.empty())
                    condition_var.wait(lock);
                queue.pop();
            }
        }
    }

private:
    boost::thread thread;
    boost::mutex mutex;
    boost::condition_variable condition_var;
    std::queue<int> queue;
};

int main()
{
    Test test;
    test.run();

    return 0;
}

与您的案例进行比较

Answer 2

您应该在删除互斥锁之前解锁互斥锁。

使用多个线程和互斥锁时断言互斥锁

2 个答案: