pthreads — Как безопасно уничтожить пул потоков Posix в Stack Overflow

Я пытаюсь реализовать пул потоков в C ++, используя pthread. Я хочу заключить логику, связанную с управлением потоками, в один объект, который становится владельцем этих потоков. Это означает, что всякий раз, когда этот объект уничтожается, потоки должны быть остановлены и очищены.

Каков наилучший способ остановить и уничтожить потоки? Является ли отсоединение при запуске и отмена при остановке хорошим решением? Или, может быть, лучше отменить и присоединиться к темам? Смотрите мой код, я буду признателен за любые соответствующие комментарии.

WorkerThreadManager.h:

#include "WorkerThreadManagerInterface.h"#include "utils/mutex.h"#include <queue>
#include <semaphore.h>

#include <iostream>

class WorkerThreadManager : public WorkerThreadManagerInterface
{
public:
WorkerThreadManager(unsigned threadsNumber = 5);
virtual ~WorkerThreadManager();

virtual void    PushTask(thread_function_t A_threadFun, result_function_t A_resultFun);
void    SignalResults();

private:
static void*    WorkerThread(void* A_data);

void    PushResult(int A_result, result_function_t A_resultFun);

typedef boost::function<void ()> signal_function_t;

struct worker_thread_data_t
{
worker_thread_data_t(thread_function_t A_threadFun, result_function_t A_resultFun) :
threadFun(A_threadFun), resultFun(A_resultFun) {}
worker_thread_data_t() {}

thread_function_t       threadFun;
result_function_t       resultFun;
};const unsigned                      m_threadsNumber;
pthread_t*                          m_pthreads;

utils::Mutex                        m_tasksMutex;
sem_t                               m_tasksSem;
std::queue<worker_thread_data_t>    m_tasks;

utils::Mutex                        m_resultsMutex;
std::queue<signal_function_t>       m_results;
};

WorkerThreadManager.cpp:

#include "WorkerThreadManager.h"#include "gateway_log.h"#include <pthread.h>

/**
* @brief Creates semaphore and starts threads.
*/
WorkerThreadManager::WorkerThreadManager(unsigned threadsNumber) : m_threadsNumber(threadsNumber)
{
if ( sem_init(&m_tasksSem, 0, 0) )
{
std::stringstream ss;
ss << "Semaphore could not be initialized: " << errno << " - " << strerror(errno);
LOG_FATAL(ss);
throw std::runtime_error(ss.str());
}

m_pthreads = new pthread_t[m_threadsNumber];
for (unsigned i = 0; i < m_threadsNumber; ++i)
{
int rc = pthread_create(&m_pthreads[i], NULL, WorkerThreadManager::WorkerThread, (void*) this );
if(rc)
{
std::stringstream ss;
ss << "Pthread could not be started: " << errno << " - " << strerror(errno);
LOG_FATAL(ss.str());

if ( sem_destroy(&m_tasksSem) )
LOG_ERROR("Semaphore could not be destroyed: " << errno << " - " << strerror(errno));

delete [] m_pthreads;

throw std::runtime_error(ss.str());
}
else
{
LOG_DEBUG("Worker thread started " << m_pthreads[i]);

if(pthread_detach(m_pthreads[i]))
LOG_WARN("Failed to detach worker thread");
}
}
}

/**
* @brief Cancels all threads, destroys semaphore
*/
WorkerThreadManager::~WorkerThreadManager()
{
LOG_DEBUG("~WorkerThreadManager()");

for(unsigned i = 0; i < m_threadsNumber; ++i)
{
if ( pthread_cancel(m_pthreads[i]) )
LOG_ERROR("Worker thread cancellation failed");
}

if ( sem_destroy(&m_tasksSem) )
LOG_ERROR("Semaphore could not be destroyed: " << errno << " - " << strerror(errno));

delete [] m_pthreads;
}

/**
* @brief Adds new task to queue, so worker threads can
* @param A_threadFun function which will be executed by thread
* @param A_resultFun function which will be enqueued for calling with return value of A_threadFun as parameter
*          after worker thread executes A_threadFun.
*/
void WorkerThreadManager::PushTask(thread_function_t A_threadFun, result_function_t A_resultFun)
{
utils::ScopedLock mutex(m_tasksMutex);

worker_thread_data_t    data(A_threadFun, A_resultFun);
m_tasks.push( data );
sem_post(&m_tasksSem);
LOG_DEBUG("Task for worker threads has been added to queue");
}

/**
* @brief   Executes result functions (if there are any) to give feedback
*  to classes which requested task execution in worker thread.
*/
void WorkerThreadManager::SignalResults()
{
while(true)
{
signal_function_t signal;
{
utils::ScopedLock mutex(m_resultsMutex);
if(m_results.size())
{
signal = m_results.front();
m_results.pop();
}
else
return;
}

signal();
}
}

/**
* @brief Enqueues result of function executed in worker thread.
* @param A_result return value of function executed in worker thread
* @param A_resultFun function which will be enqueued for calling with A_result as a parameter.
*/
void WorkerThreadManager::PushResult(int A_result, result_function_t A_resultFun)
{
utils::ScopedLock mutex(m_resultsMutex);

signal_function_t signal = boost::bind(A_resultFun, A_result);
m_results.push( signal );
}/**
* @brief   worker thread body
* @param A_data pointer to WorkerThreadManager instance
*/
void* WorkerThreadManager::WorkerThread(void* A_data)
{
WorkerThreadManager* manager = reinterpret_cast<WorkerThreadManager*>(A_data);
LOG_DEBUG("Starting worker thread loop");
while (1)
{
if ( -1 == sem_wait(&manager->m_tasksSem) && errno == EINTR )
{
LOG_DEBUG("sem_wait interrupted with signal");
continue;
}
LOG_DEBUG("WorkerThread:::::: about to call lock mutex");

worker_thread_data_t data;
{
utils::ScopedLock mutex(manager->m_tasksMutex);
data = manager->m_tasks.front();
manager->m_results.pop();
}

LOG_DEBUG("WorkerThread:::::: about to call resultFun");
int result  = data.threadFun();
LOG_DEBUG("WorkerThread:::::: after call resultFun");
pthread_testcancel();

manager->PushResult(result, data.resultFun);
}

return NULL;
}

main.cpp:

#include "gateway_log.h"#include "WorkerThreadManager.h"#include <memory>

class A {
public:
int Fun() { LOG_DEBUG("Fun before sleep"); sleep(8); LOG_DEBUG("Fun after sleep");return 0; }
void Result(int a) { LOG_DEBUG("Result: " << a); }
};int main()
{
sd::auto_ptr<WorkerThreadManager> workerThreadManager = new WorkerThreadManager;
A a;
workerThreadManager->PushTask(boost::bind(&A::Fun, &a), boost::bind(&A::Result, &a, _1));
sleep(3);
LOG_DEBUG("deleting workerThreadManager");
workerThreadManager.reset();                    // <<<--- CRASH
LOG_DEBUG("deleted workerThreadManager");
sleep(10);
LOG_DEBUG("after sleep");

return 0;
}

Обратите внимание, что существует проблема с этим кодом, описанным Вот.