342 lines
11 KiB
C++
342 lines
11 KiB
C++
/* Copyright (C) 2012 J.F.Dockes
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the
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* Free Software Foundation, Inc.,
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* 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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*/
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#ifndef _WORKQUEUE_H_INCLUDED_
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#define _WORKQUEUE_H_INCLUDED_
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#include <pthread.h>
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#include <time.h>
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#include <string>
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#include <queue>
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#include <list>
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#include "debuglog.h"
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#include "ptmutex.h"
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/**
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* A WorkQueue manages the synchronisation around a queue of work items,
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* where a number of client threads queue tasks and a number of worker
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* threads take and execute them. The goal is to introduce some level
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* of parallelism between the successive steps of a previously single
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* threaded pipeline. For example data extraction / data preparation / index
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* update, but this could have other uses.
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*
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* There is no individual task status return. In case of fatal error,
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* the client or worker sets an end condition on the queue. A second
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* queue could conceivably be used for returning individual task
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* status.
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*/
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template <class T> class WorkQueue {
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public:
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/** Create a WorkQueue
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* @param name for message printing
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* @param hi number of tasks on queue before clients blocks. Default 0
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* meaning no limit. hi == -1 means that the queue is disabled.
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* @param lo minimum count of tasks before worker starts. Default 1.
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*/
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WorkQueue(const std::string& name, size_t hi = 0, size_t lo = 1)
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: m_name(name), m_high(hi), m_low(lo),
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m_workers_exited(0), m_clients_waiting(0), m_workers_waiting(0),
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m_tottasks(0), m_nowake(0), m_workersleeps(0), m_clientsleeps(0)
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{
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m_ok = (pthread_cond_init(&m_ccond, 0) == 0) &&
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(pthread_cond_init(&m_wcond, 0) == 0);
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}
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~WorkQueue()
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{
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LOGDEB2(("WorkQueue::~WorkQueue:%s\n", m_name.c_str()));
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if (!m_worker_threads.empty())
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setTerminateAndWait();
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}
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/** Start the worker threads.
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*
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* @param nworkers number of threads copies to start.
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* @param start_routine thread function. It should loop
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* taking (QueueWorker::take()) and executing tasks.
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* @param arg initial parameter to thread function.
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* @return true if ok.
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*/
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bool start(int nworkers, void *(*start_routine)(void *), void *arg)
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{
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PTMutexLocker lock(m_mutex);
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for (int i = 0; i < nworkers; i++) {
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int err;
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pthread_t thr;
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if ((err = pthread_create(&thr, 0, start_routine, arg))) {
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LOGERR(("WorkQueue:%s: pthread_create failed, err %d\n",
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m_name.c_str(), err));
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return false;
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}
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m_worker_threads.push_back(thr);
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}
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return true;
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}
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/** Add item to work queue, called from client.
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*
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* Sleeps if there are already too many.
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*/
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bool put(T t)
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{
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PTMutexLocker lock(m_mutex);
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if (!lock.ok() || !ok()) {
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LOGERR(("WorkQueue::put:%s: !ok or mutex_lock failed\n",
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m_name.c_str()));
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return false;
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}
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while (ok() && m_high > 0 && m_queue.size() >= m_high) {
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m_clientsleeps++;
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// Keep the order: we test ok() AFTER the sleep...
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m_clients_waiting++;
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if (pthread_cond_wait(&m_ccond, lock.getMutex()) || !ok()) {
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m_clients_waiting--;
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return false;
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}
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m_clients_waiting--;
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}
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m_queue.push(t);
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if (m_workers_waiting > 0) {
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// Just wake one worker, there is only one new task.
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pthread_cond_signal(&m_wcond);
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} else {
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m_nowake++;
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}
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return true;
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}
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/** Wait until the queue is inactive. Called from client.
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*
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* Waits until the task queue is empty and the workers are all
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* back sleeping. Used by the client to wait for all current work
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* to be completed, when it needs to perform work that couldn't be
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* done in parallel with the worker's tasks, or before shutting
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* down. Work can be resumed after calling this. Note that the
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* only thread which can call it safely is the client just above
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* (which can control the task flow), else there could be
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* tasks in the intermediate queues.
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* To rephrase: there is no warranty on return that the queue is actually
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* idle EXCEPT if the caller knows that no jobs are still being created.
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* It would be possible to transform this into a safe call if some kind
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* of suspend condition was set on the queue by waitIdle(), to be reset by
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* some kind of "resume" call. Not currently the case.
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*/
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bool waitIdle()
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{
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PTMutexLocker lock(m_mutex);
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if (!lock.ok() || !ok()) {
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LOGERR(("WorkQueue::waitIdle:%s: not ok or can't lock\n",
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m_name.c_str()));
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return false;
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}
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// We're done when the queue is empty AND all workers are back
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// waiting for a task.
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while (ok() && (m_queue.size() > 0 ||
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m_workers_waiting != m_worker_threads.size())) {
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m_clients_waiting++;
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if (pthread_cond_wait(&m_ccond, lock.getMutex())) {
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m_clients_waiting--;
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m_ok = false;
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LOGERR(("WorkQueue::waitIdle:%s: cond_wait failed\n",
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m_name.c_str()));
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return false;
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}
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m_clients_waiting--;
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}
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return ok();
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}
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/** Tell the workers to exit, and wait for them.
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*
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* Does not bother about tasks possibly remaining on the queue, so
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* should be called after waitIdle() for an orderly shutdown.
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*/
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void* setTerminateAndWait()
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{
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PTMutexLocker lock(m_mutex);
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LOGDEB(("setTerminateAndWait:%s\n", m_name.c_str()));
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if (m_worker_threads.empty()) {
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// Already called ?
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return (void*)0;
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}
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// Wait for all worker threads to have called workerExit()
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m_ok = false;
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while (m_workers_exited < m_worker_threads.size()) {
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pthread_cond_broadcast(&m_wcond);
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m_clients_waiting++;
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if (pthread_cond_wait(&m_ccond, lock.getMutex())) {
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LOGERR(("WorkQueue::setTerminate:%s: cond_wait failed\n",
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m_name.c_str()));
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m_clients_waiting--;
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return (void*)0;
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}
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m_clients_waiting--;
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}
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LOGINFO(("%s: tasks %u nowakes %u wsleeps %u csleeps %u\n",
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m_name.c_str(), m_tottasks, m_nowake, m_workersleeps,
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m_clientsleeps));
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// Perform the thread joins and compute overall status
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// Workers return (void*)1 if ok
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void *statusall = (void*)1;
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std::list<pthread_t>::iterator it;
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while (!m_worker_threads.empty()) {
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void *status;
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it = m_worker_threads.begin();
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pthread_join(*it, &status);
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if (status == (void *)0)
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statusall = status;
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m_worker_threads.erase(it);
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}
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// Reset to start state.
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m_workers_exited = m_clients_waiting = m_workers_waiting =
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m_tottasks = m_nowake = m_workersleeps = m_clientsleeps = 0;
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m_ok = true;
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LOGDEB(("setTerminateAndWait:%s done\n", m_name.c_str()));
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return statusall;
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}
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/** Take task from queue. Called from worker.
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*
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* Sleeps if there are not enough. Signal if we go to sleep on empty
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* queue: client may be waiting for our going idle.
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*/
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bool take(T* tp, size_t *szp = 0)
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{
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PTMutexLocker lock(m_mutex);
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if (!lock.ok() || !ok()) {
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LOGDEB(("WorkQueue::take:%s: not ok\n", m_name.c_str()));
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return false;
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}
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while (ok() && m_queue.size() < m_low) {
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m_workersleeps++;
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m_workers_waiting++;
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if (m_queue.empty())
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pthread_cond_broadcast(&m_ccond);
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if (pthread_cond_wait(&m_wcond, lock.getMutex()) || !ok()) {
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// !ok is a normal condition when shutting down
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if (ok())
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LOGERR(("WorkQueue::take:%s: cond_wait failed or !ok\n",
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m_name.c_str()));
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m_workers_waiting--;
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return false;
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}
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m_workers_waiting--;
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}
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m_tottasks++;
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*tp = m_queue.front();
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if (szp)
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*szp = m_queue.size();
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m_queue.pop();
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if (m_clients_waiting > 0) {
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// No reason to wake up more than one client thread
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pthread_cond_signal(&m_ccond);
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} else {
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m_nowake++;
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}
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return true;
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}
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/** Advertise exit and abort queue. Called from worker
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*
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* This would happen after an unrecoverable error, or when
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* the queue is terminated by the client. Workers never exit normally,
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* except when the queue is shut down (at which point m_ok is set to
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* false by the shutdown code anyway). The thread must return/exit
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* immediately after calling this.
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*/
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void workerExit()
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{
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LOGDEB(("workerExit:%s\n", m_name.c_str()));
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PTMutexLocker lock(m_mutex);
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m_workers_exited++;
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m_ok = false;
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pthread_cond_broadcast(&m_ccond);
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}
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size_t qsize()
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{
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PTMutexLocker lock(m_mutex);
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size_t sz = m_queue.size();
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return sz;
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}
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private:
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bool ok()
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{
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bool isok = m_ok && m_workers_exited == 0 && !m_worker_threads.empty();
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if (!isok) {
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LOGDEB(("WorkQueue:ok:%s: not ok m_ok %d m_workers_exited %d "
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"m_worker_threads size %d\n", m_name.c_str(),
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m_ok, m_workers_exited, int(m_worker_threads.size())));
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}
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return isok;
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}
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long long nanodiff(const struct timespec& older,
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const struct timespec& newer)
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{
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return (newer.tv_sec - older.tv_sec) * 1000000000LL
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+ newer.tv_nsec - older.tv_nsec;
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}
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// Configuration
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std::string m_name;
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size_t m_high;
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size_t m_low;
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// Status
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// Worker threads having called exit
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unsigned int m_workers_exited;
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bool m_ok;
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// Per-thread data. The data is not used currently, this could be
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// a set<pthread_t>
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std::list<pthread_t> m_worker_threads;
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// Synchronization
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std::queue<T> m_queue;
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pthread_cond_t m_ccond;
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pthread_cond_t m_wcond;
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PTMutexInit m_mutex;
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// Client/Worker threads currently waiting for a job
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unsigned int m_clients_waiting;
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unsigned int m_workers_waiting;
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// Statistics
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unsigned int m_tottasks;
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unsigned int m_nowake;
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unsigned int m_workersleeps;
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unsigned int m_clientsleeps;
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};
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#endif /* _WORKQUEUE_H_INCLUDED_ */
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