CAThreadPool.cpp

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/********************************************************
 * A Thread pool class inspired by:
 * "Using POSIX Threads: Programming with Pthreads"
 *     by Brad nichols, Dick Buttlar, Jackie Farrell
 *     O'Reilly & Associates, Inc.
 */
#include "StdAfx.h"
#ifndef ONLY_LOCAL_PROXY
#include "CAThreadPool.hpp"
#include "CAMsg.hpp"
void *tpool_thread(void *);

CAThreadPool::CAThreadPool( UINT32 num_worker_threads, 
                            UINT32 max_queue_size,
                            bool   b_do_not_block_when_full)
  {
    UINT i;
    
    /* initialize fields */
    m_NumThreads = num_worker_threads;
    m_MaxQueueSize = max_queue_size;
    m_bDoNotBlockWhenFull = b_do_not_block_when_full;
    m_parThreads=new CAThread*[num_worker_threads];
    m_CurQueueSize = 0;
    m_pQueueHead = NULL; 
    m_pQueueTail = NULL;
    m_bQueueClosed = false;  
    m_bShutdown = false; 
    m_pmutexQueue=new CAMutex();
    m_pcondEmpty=new CAConditionVariable();
    m_pcondNotEmpty=new CAConditionVariable();
    m_pcondNotFull=new CAConditionVariable();

    char thread_str[24];
    
    /* create threads */
    for (i = 0; i != num_worker_threads; i++) 
      {
        snprintf(thread_str, 16, "Pool Thread %3d", i);
        m_parThreads[i]=new CAThread((UINT8*)thread_str);
        m_parThreads[i]->setMainLoop(worker_thread_main_loop);
        m_parThreads[i]->start(this);
      }
  }

SINT32 CAThreadPool::addRequest(THREAD_MAIN_TYP routine, void *args)
{
  m_pmutexQueue->lock();
  tpool_work_t *workp;

  // no space and this caller doesn't want to wait 
  if ((m_CurQueueSize == m_MaxQueueSize) && m_bDoNotBlockWhenFull) 
    {
      m_pmutexQueue->unlock();
      return E_SPACE;
    }

  while((m_CurQueueSize == m_MaxQueueSize) && 
        (!(m_bShutdown || m_bQueueClosed))  )
    {
      CAMsg::printMsg(LOG_INFO,"CAThreadPool::addRequest() -the Thread pool is full...waiting!\n");
      m_pcondNotFull->wait(m_pmutexQueue);
    }

  // the pool is in the process of being destroyed 
  if (m_bShutdown || m_bQueueClosed)
    {
      m_pmutexQueue->unlock();
      return E_UNKNOWN;
    }

  // allocate work structure 
  workp = new tpool_work_t;
  workp->routine = routine;
  workp->arg = args;
  workp->next = NULL;

  if (m_CurQueueSize == 0)
    {
      m_pQueueTail = m_pQueueHead = workp;
      m_pcondNotEmpty->broadcast();
    }
  else
    {
      m_pQueueTail->next = workp;
      m_pQueueTail = workp;
    }

  m_CurQueueSize++; 
  m_pmutexQueue->unlock();
  return E_SUCCESS;
}

SINT32 CAThreadPool::destroy(bool bWaitForFinish)
  {
    tpool_work_t *cur_nodep;
    // Is a shutdown already in progress?
    if (m_bQueueClosed || m_bShutdown)
      {
        return E_SUCCESS;
      }

    m_pmutexQueue->lock();
    m_bQueueClosed = true;
    // If the finish flag is set, wait for workers to 
    //   drain queue  
    if (bWaitForFinish)
      {
        while (m_CurQueueSize != 0)
          {
            m_pcondEmpty->wait(m_pmutexQueue);
          }
      }

    m_bShutdown = true;
    m_pmutexQueue->unlock();

    // Wake up any workers so they recheck shutdown flag 
    m_pcondNotEmpty->broadcast();
    m_pcondNotFull->broadcast();

    // Wait for workers to exit 
    for(UINT32 i=0; i < m_NumThreads; i++) 
      {
        m_parThreads[i]->join();
        delete m_parThreads[i];
        m_parThreads[i] = NULL;
      }
    // Now free pool structures 
    delete[] m_parThreads;
    m_parThreads = NULL;
    while(m_pQueueHead != NULL)
    {
      cur_nodep = m_pQueueHead->next;
      delete m_pQueueHead; 
      m_pQueueHead = cur_nodep;     
    }
    delete m_pmutexQueue;
    m_pmutexQueue = NULL;
    delete m_pcondEmpty;
    m_pcondEmpty = NULL;
    delete m_pcondNotEmpty;
    m_pcondNotEmpty = NULL;
    delete m_pcondNotFull;
    m_pcondNotFull = NULL;

    return E_SUCCESS;
  }

THREAD_RETURN worker_thread_main_loop(void *arg)
{
  CAThreadPool* pPool = (CAThreadPool*)arg; 
  tpool_work_t  *my_workp;
  
  for(;;)
    {
    // Check queue for work  
      pPool->m_pmutexQueue->lock();
      while ((pPool->m_CurQueueSize == 0) && (!pPool->m_bShutdown))
        {
          pPool->m_pcondNotEmpty->wait(pPool->m_pmutexQueue);
        }
      //sSleep(5); 
      // Has a shutdown started while i was sleeping? 
      if (pPool->m_bShutdown)
        {
          pPool->m_pmutexQueue->unlock();
          THREAD_RETURN_SUCCESS;
        }

      // Get to work, dequeue the next item  
      my_workp = pPool->m_pQueueHead;
      pPool->m_CurQueueSize--;
      if (pPool->m_CurQueueSize == 0)
        pPool->m_pQueueHead = pPool->m_pQueueTail = NULL;
      else
        pPool->m_pQueueHead = my_workp->next;
 
      // Handle waiting add_work threads 
      if ((!pPool->m_bDoNotBlockWhenFull) &&
          (pPool->m_CurQueueSize ==  (pPool->m_MaxQueueSize - 1))) 
          pPool->m_pcondNotFull->broadcast();
      // Handle waiting destroyer threads 
      if (pPool->m_CurQueueSize == 0)
        pPool->m_pcondEmpty->signal();
      pPool->m_pmutexQueue->unlock();
      
      // Do this work item 
      (*(my_workp->routine))(my_workp->arg);
      delete my_workp;
      my_workp = NULL;
  } 
}
#endif //ONLY_LOCAL_PROXY