c++ - 在消费者进程中 boost 共享内存和同步队列问题/崩溃

Question

我正在尝试从子进程使用 C++ 中的同步队列。我在 C++ () ( http://www.internetmosquito.com/2011/04/making-thread-safe-queue-in-c-i.html ) 中使用这个同步队列

我将队列修改为可在 boost 中序列化，还替换了使用过的 boost::mutex io_mutex_改为使用进程间互斥锁(感谢@Sehe)boost::interprocess::interprocess_mutex io_mutex_锁定时我改变了每一行 boost::mutex::scoped_lock lock(io_mutex_);至 scoped_lock<interprocess_mutex> lock(io_mutex_);

template<class T>
class SynchronizedQueue
{
    friend class boost::serialization::access;
    template<class Archive>
    void serialize(Archive & ar, const unsigned int version)
    {
        ar & sQueue;
        ar & io_mutex_;
        ar & waitCondition;
    }
    ... // queue implementation (see [http://www.internetmosquito.com/2011/04/making-thread-safe-queue-in-c-i.html][2])

在我的测试应用程序中，我正在创建同步队列并在其中存储该类的 100 个实例:

class gps_position
{
    friend class boost::serialization::access;
    template<class Archive>
    void serialize(Archive & ar, const unsigned int version)
    {
        ar & degrees;
        ar & minutes;
        ar & seconds;
    }
public:
 int degrees;
 int minutes;
 float seconds;

 gps_position() {};
 gps_position(int d, int m, float s) :
 degrees(d), minutes(m), seconds(s)
 {}
};

消费者和生产者之间的通用定义:

 char *SHARED_MEMORY_NAME = "MySharedMemory";
 char *SHARED_QUEUE_NAME  =  "MyQueue";
 typedef SynchronizedQueue<gps_position> MySynchronisedQueue;

生产者流程代码:

    // Remove shared memory if it was created before
    shared_memory_object::remove(SHARED_MEMORY_NAME);
    // Create a new segment with given name and size
    managed_shared_memory mysegment(create_only,SHARED_MEMORY_NAME, 65536);
    MySynchronisedQueue *myQueue = mysegment.construct<MySynchronisedQueue>(SHARED_QUEUE_NAME)();
    //Insert data in the queue
    for(int i = 0; i < 100; ++i)  {
        gps_position position(i, 2, 3);
        myQueue->push(position);
    }
    // Start 1 process (for testing for now)
    STARTUPINFO info1={sizeof(info1)};
    PROCESS_INFORMATION processInfo1;
    ZeroMemory(&info1, sizeof(info1));
    info1.cb = sizeof info1 ; //Only compulsory field
    ZeroMemory(&processInfo1, sizeof(processInfo1));
    // Launch child process
    LPTSTR szCmdline = _tcsdup(TEXT("ClientTest.exe"));
    CreateProcess(NULL, szCmdline, NULL, NULL, TRUE, 0, NULL, NULL, &info1, &processInfo1);
    // Wait a little bit ( 5 seconds) for the started client process to load
    WaitForSingleObject(processInfo1.hProcess, 5000);

    /* THIS TESTING CODE WORK HERE AT PARENT PROCESS BUT NOT IN CLIENT PROCESS
    // Open the managed segment memory
    managed_shared_memory openedSegment(open_only, SHARED_MEMORY_NAME);
    //Find the synchronized queue using it's name
    MySynchronisedQueue *openedQueue = openedSegment.find<MySynchronisedQueue>(SHARED_QUEUE_NAME).first;
    gps_position position;
    while (true) {
        if (myQueue->pop(position)) {
            std::cout << "Degrees= " << position.degrees << " Minutes= " << position.minutes << " Seconds= " << position.seconds;
            std::cout << "\n";
        }
        else
            break;
    }*/


    // Wait until the queue is empty: has been processed by client(s)
    while(myQueue->sizeOfQueue() > 0) continue;

    // Close process and thread handles. 
    CloseHandle( processInfo1.hThread );

我的消费者代码如下:

    //Open the managed segment memory
    managed_shared_memory segment(open_only, SHARED_MEMORY_NAME);
    //Find the vector using it's name
    MySynchronisedQueue *myQueue = segment.find<MySynchronisedQueue>(SHARED_QUEUE_NAME).first;
    gps_position position;
    // Pop each position until the queue become empty and output its values
    while (true)
    {
        if (myQueue->pop(position)) { // CRASH HERE
            std::cout << "Degrees= " << position.degrees << " Minutes= " << position.minutes << " Seconds= " << position.seconds;
            std::cout << "\n";
        }
        else
            break;
    }

当我运行创建队列的父进程(生产者)并创建子(消费者)进程时，子进程在尝试从队列中“弹出”时崩溃。

我在这里做错了什么？任何想法 ？感谢您的任何见解。这是我使用 boost 和共享内存创建的第一个应用程序。

我的目标是能够从多个进程中使用这个队列。在上面的示例中，我只创建了一个子进程，以确保在创建其他子进程之前首先它可以工作。这个想法是队列将由项目提前填充，并且多个创建的进程将从队列中“弹出”项目而不会相互冲突。

Answer 1

更新后的代码:

• 如果你要共享队列，你应该使用 interprocess_mutex；这意味着许多相关的变化。
• 如果您要共享队列，您的队列应该使用共享内存分配器
• 应该在互斥量下提出条件以在所有平台上实现可靠的行为
• 你锁里面失败toString() .即使您复制了集合，这还远远不够，因为容器可能会在复制过程中被修改。
• 队列设计很有意义(返回 empty() 的“线程安全”函数有什么用？在处理返回值之前它可能不再为空/只是空...这些被称为 竞争条件并导致真正难以跟踪的错误
• Boost Serialization 与什么有什么关系？它似乎只是为了混淆画面，因为它不是必需的，也没有被使用。
• 同样适用于 Boost Any。为什么是any用于 toString() ？由于队列的设计，typeid 始终为 gpsposition 无论如何。
• 同样适用于 boost::lexical_cast<> (如果你已经有了字符串流，为什么还要进行字符串连接？)
• 为什么是empty() , toString() , sizeOfQueue()不是const ？

我强烈推荐使用 boost::interprocess::message_queue .这似乎是您实际想要使用的。

这是一个修改后的版本，将容器放在共享内存中并且可以正常工作:

#include <boost/interprocess/allocators/allocator.hpp>
#include <boost/interprocess/containers/deque.hpp>
#include <boost/interprocess/managed_shared_memory.hpp>
#include <boost/interprocess/sync/interprocess_condition.hpp>
#include <boost/interprocess/sync/interprocess_mutex.hpp>
#include <boost/thread/lock_guard.hpp>
#include <sstream>

namespace bip = boost::interprocess;

template <class T> class SynchronizedQueue {

  public:
    typedef bip::allocator<T, bip::managed_shared_memory::segment_manager> allocator_type;
  private:
    bip::deque<T, allocator_type> sQueue;
    mutable bip::interprocess_mutex io_mutex_;
    mutable bip::interprocess_condition waitCondition;
  public:
    SynchronizedQueue(allocator_type alloc) : sQueue(alloc) {} 

    void push(T element) {
        boost::lock_guard<bip::interprocess_mutex> lock(io_mutex_);
        sQueue.push_back(element);
        waitCondition.notify_one();
    }
    bool empty() const {
        boost::lock_guard<bip::interprocess_mutex> lock(io_mutex_);
        return sQueue.empty();
    }
    bool pop(T &element) {
        boost::lock_guard<bip::interprocess_mutex> lock(io_mutex_);

        if (sQueue.empty()) {
            return false;
        }

        element = sQueue.front();
        sQueue.pop_front();

        return true;
    }
    unsigned int sizeOfQueue() const {
        // try to lock the mutex
        boost::lock_guard<bip::interprocess_mutex> lock(io_mutex_);
        return sQueue.size();
    }
    void waitAndPop(T &element) {
        boost::lock_guard<bip::interprocess_mutex> lock(io_mutex_);

        while (sQueue.empty()) {
            waitCondition.wait(lock);
        }

        element = sQueue.front();
        sQueue.pop();
    }

    std::string toString() const {
        bip::deque<T> copy;
        // make a copy of the class queue, to reduce time locked
        {
            boost::lock_guard<bip::interprocess_mutex> lock(io_mutex_);
            copy.insert(copy.end(), sQueue.begin(), sQueue.end());
        }

        if (copy.empty()) {
            return "Queue is empty";
        } else {
            std::stringstream os;
            int counter = 0;

            os << "Elements in the Synchronized queue are as follows:" << std::endl;
            os << "**************************************************" << std::endl;

            while (!copy.empty()) {
                T object = copy.front();
                copy.pop_front();
                os << "Element at position " << counter << " is: [" << typeid(object).name()  << "]\n";
            }
            return os.str();
        }
    }
};

struct gps_position {
    int degrees;
    int minutes;
    float seconds;

    gps_position(int d=0, int m=0, float s=0) : degrees(d), minutes(m), seconds(s) {}
};

static char const *SHARED_MEMORY_NAME = "MySharedMemory";
static char const *SHARED_QUEUE_NAME  =  "MyQueue";
typedef SynchronizedQueue<gps_position> MySynchronisedQueue;

#include <boost/interprocess/shared_memory_object.hpp>
#include <iostream>

void consumer()
{
    bip::managed_shared_memory openedSegment(bip::open_only, SHARED_MEMORY_NAME);
    
    MySynchronisedQueue *openedQueue = openedSegment.find<MySynchronisedQueue>(SHARED_QUEUE_NAME).first;
    gps_position position;

    while (openedQueue->pop(position)) {
        std::cout << "Degrees= " << position.degrees << " Minutes= " << position.minutes << " Seconds= " << position.seconds;
        std::cout << "\n";
    }
}

void producer() {
    bip::shared_memory_object::remove(SHARED_MEMORY_NAME);
    
    bip::managed_shared_memory mysegment(bip::create_only,SHARED_MEMORY_NAME, 65536);

    MySynchronisedQueue::allocator_type alloc(mysegment.get_segment_manager());
    MySynchronisedQueue *myQueue = mysegment.construct<MySynchronisedQueue>(SHARED_QUEUE_NAME)(alloc);

    for(int i = 0; i < 100; ++i)          
        myQueue->push(gps_position(i, 2, 3));

    // Wait until the queue is empty: has been processed by client(s)
    while(myQueue->sizeOfQueue() > 0) 
        continue;
}

int main() {
    producer();
    // or enable the consumer code for client:
    // consumer();
}