--- a
+++ b/src/workqueue.hxx
@@ -0,0 +1,328 @@
+/* Copyright (C) 2012 J.F.Dockes
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the
+ * Free Software Foundation, Inc.,
+ * 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ */
+#ifndef _WORKQUEUE_H_INCLUDED_
+#define _WORKQUEUE_H_INCLUDED_
+
+#include <pthread.h>
+#include <time.h>
+
+#include <string>
+#include <queue>
+#include <unordered_map>
+
+#include "ptmutex.hxx"
+
+namespace UPnPP {
+
+/// Store per-worker-thread data. Just an initialized timespec, and
+/// used at the moment.
+class WQTData {
+public:
+ WQTData() {wstart.tv_sec = 0; wstart.tv_nsec = 0;}
+ struct timespec wstart;
+};
+
+/**
+ * A WorkQueue manages the synchronisation around a queue of work items,
+ * where a number of client threads queue tasks and a number of worker
+ * threads take and execute them. The goal is to introduce some level
+ * of parallelism between the successive steps of a previously single
+ * threaded pipeline. For example data extraction / data preparation / index
+ * update, but this could have other uses.
+ *
+ * There is no individual task status return. In case of fatal error,
+ * the client or worker sets an end condition on the queue. A second
+ * queue could conceivably be used for returning individual task
+ * status.
+ */
+template <class T> class WorkQueue {
+public:
+
+ /** Create a WorkQueue
+ * @param name for message printing
+ * @param hi number of tasks on queue before clients blocks. Default 0
+ * meaning no limit. hi == -1 means that the queue is disabled.
+ * @param lo minimum count of tasks before worker starts. Default 1.
+ */
+ WorkQueue(const std::string& name, size_t hi = 0, size_t lo = 1)
+ : m_name(name), m_high(hi), m_low(lo),
+ m_workers_exited(0), m_clients_waiting(0), m_workers_waiting(0),
+ m_tottasks(0), m_nowake(0), m_workersleeps(0), m_clientsleeps(0)
+ {
+ m_ok = (pthread_cond_init(&m_ccond, 0) == 0) &&
+ (pthread_cond_init(&m_wcond, 0) == 0);
+ }
+
+ ~WorkQueue()
+ {
+ if (!m_worker_threads.empty())
+ setTerminateAndWait();
+ }
+
+ /** Start the worker threads.
+ *
+ * @param nworkers number of threads copies to start.
+ * @param start_routine thread function. It should loop
+ * taking (QueueWorker::take()) and executing tasks.
+ * @param arg initial parameter to thread function.
+ * @return true if ok.
+ */
+ bool start(int nworkers, void *(*workproc)(void *), void *arg)
+ {
+ PTMutexLocker lock(m_mutex);
+ for (int i = 0; i < nworkers; i++) {
+ int err;
+ pthread_t thr;
+ if ((err = pthread_create(&thr, 0, workproc, arg))) {
+ return false;
+ }
+ m_worker_threads.insert(std::pair<pthread_t, WQTData>(thr, WQTData()));
+ }
+ return true;
+ }
+
+ /** Add item to work queue, called from client.
+ *
+ * Sleeps if there are already too many.
+ */
+ bool put(T t, bool flushprevious = false)
+ {
+ PTMutexLocker lock(m_mutex);
+ if (!lock.ok() || !ok()) {
+ return false;
+ }
+
+ while (ok() && m_high > 0 && m_queue.size() >= m_high) {
+ m_clientsleeps++;
+ // Keep the order: we test ok() AFTER the sleep...
+ m_clients_waiting++;
+ if (pthread_cond_wait(&m_ccond, lock.getMutex()) || !ok()) {
+ m_clients_waiting--;
+ return false;
+ }
+ m_clients_waiting--;
+ }
+ if (flushprevious) {
+ while (!m_queue.empty())
+ m_queue.pop();
+ }
+ m_queue.push(t);
+ if (m_workers_waiting > 0) {
+ // Just wake one worker, there is only one new task.
+ pthread_cond_signal(&m_wcond);
+ } else {
+ m_nowake++;
+ }
+
+ return true;
+ }
+
+ /** Wait until the queue is inactive. Called from client.
+ *
+ * Waits until the task queue is empty and the workers are all
+ * back sleeping. Used by the client to wait for all current work
+ * to be completed, when it needs to perform work that couldn't be
+ * done in parallel with the worker's tasks, or before shutting
+ * down. Work can be resumed after calling this. Note that the
+ * only thread which can call it safely is the client just above
+ * (which can control the task flow), else there could be
+ * tasks in the intermediate queues.
+ * To rephrase: there is no warranty on return that the queue is actually
+ * idle EXCEPT if the caller knows that no jobs are still being created.
+ * It would be possible to transform this into a safe call if some kind
+ * of suspend condition was set on the queue by waitIdle(), to be reset by
+ * some kind of "resume" call. Not currently the case.
+ */
+ bool waitIdle()
+ {
+ PTMutexLocker lock(m_mutex);
+ if (!lock.ok() || !ok()) {
+ return false;
+ }
+
+ // We're done when the queue is empty AND all workers are back
+ // waiting for a task.
+ while (ok() && (m_queue.size() > 0 ||
+ m_workers_waiting != m_worker_threads.size())) {
+ m_clients_waiting++;
+ if (pthread_cond_wait(&m_ccond, lock.getMutex())) {
+ m_clients_waiting--;
+ m_ok = false;
+ return false;
+ }
+ m_clients_waiting--;
+ }
+
+ return ok();
+ }
+
+
+ /** Tell the workers to exit, and wait for them.
+ *
+ * Does not bother about tasks possibly remaining on the queue, so
+ * should be called after waitIdle() for an orderly shutdown.
+ */
+ void* setTerminateAndWait()
+ {
+ PTMutexLocker lock(m_mutex);
+
+ if (m_worker_threads.empty()) {
+ // Already called ?
+ return (void*)0;
+ }
+
+ // Wait for all worker threads to have called workerExit()
+ m_ok = false;
+ while (m_workers_exited < m_worker_threads.size()) {
+ pthread_cond_broadcast(&m_wcond);
+ m_clients_waiting++;
+ if (pthread_cond_wait(&m_ccond, lock.getMutex())) {
+ m_clients_waiting--;
+ return (void*)0;
+ }
+ m_clients_waiting--;
+ }
+
+ // Perform the thread joins and compute overall status
+ // Workers return (void*)1 if ok
+ void *statusall = (void*)1;
+ std::unordered_map<pthread_t, WQTData>::iterator it;
+ while (!m_worker_threads.empty()) {
+ void *status;
+ it = m_worker_threads.begin();
+ pthread_join(it->first, &status);
+ if (status == (void *)0)
+ statusall = status;
+ m_worker_threads.erase(it);
+ }
+
+ // Reset to start state.
+ m_workers_exited = m_clients_waiting = m_workers_waiting =
+ m_tottasks = m_nowake = m_workersleeps = m_clientsleeps = 0;
+ m_ok = true;
+
+ return statusall;
+ }
+
+ /** Take task from queue. Called from worker.
+ *
+ * Sleeps if there are not enough. Signal if we go to sleep on empty
+ * queue: client may be waiting for our going idle.
+ */
+ bool take(T* tp, size_t *szp = 0)
+ {
+ PTMutexLocker lock(m_mutex);
+ if (!lock.ok() || !ok()) {
+ return false;
+ }
+
+ while (ok() && m_queue.size() < m_low) {
+ m_workersleeps++;
+ m_workers_waiting++;
+ if (m_queue.empty())
+ pthread_cond_broadcast(&m_ccond);
+ if (pthread_cond_wait(&m_wcond, lock.getMutex()) || !ok()) {
+ m_workers_waiting--;
+ return false;
+ }
+ m_workers_waiting--;
+ }
+
+ m_tottasks++;
+ *tp = m_queue.front();
+ if (szp)
+ *szp = m_queue.size();
+ m_queue.pop();
+ if (m_clients_waiting > 0) {
+ // No reason to wake up more than one client thread
+ pthread_cond_signal(&m_ccond);
+ } else {
+ m_nowake++;
+ }
+ return true;
+ }
+
+ /** Advertise exit and abort queue. Called from worker
+ *
+ * This would happen after an unrecoverable error, or when
+ * the queue is terminated by the client. Workers never exit normally,
+ * except when the queue is shut down (at which point m_ok is set to
+ * false by the shutdown code anyway). The thread must return/exit
+ * immediately after calling this.
+ */
+ void workerExit()
+ {
+ PTMutexLocker lock(m_mutex);
+ m_workers_exited++;
+ m_ok = false;
+ pthread_cond_broadcast(&m_ccond);
+ }
+
+ size_t qsize()
+ {
+ PTMutexLocker lock(m_mutex);
+ size_t sz = m_queue.size();
+ return sz;
+ }
+
+private:
+ bool ok()
+ {
+ bool isok = m_ok && m_workers_exited == 0 && !m_worker_threads.empty();
+ return isok;
+ }
+
+ long long nanodiff(const struct timespec& older,
+ const struct timespec& newer)
+ {
+ return (newer.tv_sec - older.tv_sec) * 1000000000LL
+ + newer.tv_nsec - older.tv_nsec;
+ }
+
+ // Configuration
+ std::string m_name;
+ size_t m_high;
+ size_t m_low;
+
+ // Status
+ // Worker threads having called exit
+ unsigned int m_workers_exited;
+ bool m_ok;
+
+ // Per-thread data. The data is not used currently, this could be
+ // a set<pthread_t>
+ std::unordered_map<pthread_t, WQTData> m_worker_threads;
+
+ // Synchronization
+ std::queue<T> m_queue;
+ pthread_cond_t m_ccond;
+ pthread_cond_t m_wcond;
+ PTMutexInit m_mutex;
+ // Client/Worker threads currently waiting for a job
+ unsigned int m_clients_waiting;
+ unsigned int m_workers_waiting;
+
+ // Statistics
+ unsigned int m_tottasks;
+ unsigned int m_nowake;
+ unsigned int m_workersleeps;
+ unsigned int m_clientsleeps;
+};
+
+} // namespace
+
+#endif /* _WORKQUEUE_H_INCLUDED_ */