libqb/lib/wthread.c

/*
 * Copyright (C) 2006, 2010 Red Hat, Inc.
 *
 * Author: Steven Dake <sdake@redhat.com>
 *
 * This file is part of libqb.
 *
 * libqb is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 2.1 of the License, or
 * (at your option) any later version.
 *
 * libqb 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 Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with libqb.  If not, see <http://www.gnu.org/licenses/>.
 */

/*
 * Add work to a work group and have threads process the work
 * Provide blocking for all work to complete
 */

#include <config.h>

#include <stdlib.h>
#include <pthread.h>
#include <errno.h>
#include <qb/qbqueue.h>
#include <qb/qbwthread.h>

struct thread_data {
	void *thread_state;
	void *data;
};

struct qb_wthread_t {
	struct qb_wthread_group *worker_thread_group;
	pthread_mutex_t new_work_mutex;
	pthread_cond_t new_work_cond;
	pthread_cond_t cond;
	pthread_mutex_t done_work_mutex;
	pthread_cond_t done_work_cond;
	pthread_t thread_id;
	struct qb_queue queue;
	void *thread_state;
	struct thread_data thread_data;
};

static void *start_worker_thread (void *thread_data_in) {
	struct thread_data *thread_data = (struct thread_data *)thread_data_in;
	struct qb_wthread_t *worker_thread =
		(struct qb_wthread_t *)thread_data->data;
	void *data_for_worker_fn;

	for (;;) {
		pthread_mutex_lock (&worker_thread->new_work_mutex);
		if (qb_queue_is_empty (&worker_thread->queue) == 1) {
		pthread_cond_wait (&worker_thread->new_work_cond,
			&worker_thread->new_work_mutex);
		}

		/*
		 * We unlock then relock the new_work_mutex to allow the
		 * worker function to execute and also allow new work to be
		 * added to the work queue
		 */
		data_for_worker_fn = qb_queue_item_get (&worker_thread->queue);
		pthread_mutex_unlock (&worker_thread->new_work_mutex);
		worker_thread->worker_thread_group->worker_fn (worker_thread->thread_state, data_for_worker_fn);
		pthread_mutex_lock (&worker_thread->new_work_mutex);
		qb_queue_item_remove (&worker_thread->queue);
		pthread_mutex_unlock (&worker_thread->new_work_mutex);
		pthread_mutex_lock (&worker_thread->done_work_mutex);
		if (qb_queue_is_empty (&worker_thread->queue) == 1) {
			pthread_cond_signal (&worker_thread->done_work_cond);
		}
		pthread_mutex_unlock (&worker_thread->done_work_mutex);
	}
	return (NULL);
}

int qb_wthread_group_init (
	struct qb_wthread_group *worker_thread_group,
	int threads,
	int items_max,
	int item_size,
	int thread_state_size,
	void (*thread_state_constructor)(void *),
	void (*worker_fn)(void *thread_state, void *work_item))
{
	int i;

	worker_thread_group->threadcount = threads;
	worker_thread_group->last_scheduled = 0;
	worker_thread_group->worker_fn = worker_fn;
	worker_thread_group->threads = malloc (sizeof (struct qb_wthread_t) *
		threads);
	if (worker_thread_group->threads == 0) {
		return (-1);
	}

	for (i = 0; i < threads; i++) {
		if (thread_state_size) {
			worker_thread_group->threads[i].thread_state = malloc (thread_state_size);
		} else {
			worker_thread_group->threads[i].thread_state = NULL;
		}
		if (thread_state_constructor) {
			thread_state_constructor (worker_thread_group->threads[i].thread_state);
		}
		worker_thread_group->threads[i].worker_thread_group = worker_thread_group;
		pthread_mutex_init (&worker_thread_group->threads[i].new_work_mutex, NULL);
		pthread_cond_init (&worker_thread_group->threads[i].new_work_cond, NULL);
		pthread_mutex_init (&worker_thread_group->threads[i].done_work_mutex, NULL);
		pthread_cond_init (&worker_thread_group->threads[i].done_work_cond, NULL);
		qb_queue_init (&worker_thread_group->threads[i].queue, items_max,
			item_size);

		worker_thread_group->threads[i].thread_data.thread_state =
			worker_thread_group->threads[i].thread_state;
		worker_thread_group->threads[i].thread_data.data = &worker_thread_group->threads[i];
		pthread_create (&worker_thread_group->threads[i].thread_id,
			NULL, start_worker_thread, &worker_thread_group->threads[i].thread_data);
	}
	return (0);
}

int qb_wthread_group_work_add (
	struct qb_wthread_group *worker_thread_group,
	void *item)
{
	int schedule;

	schedule = (worker_thread_group->last_scheduled + 1) % (worker_thread_group->threadcount);
	worker_thread_group->last_scheduled = schedule;

	pthread_mutex_lock (&worker_thread_group->threads[schedule].new_work_mutex);
	if (qb_queue_is_full (&worker_thread_group->threads[schedule].queue)) {
		pthread_mutex_unlock (&worker_thread_group->threads[schedule].new_work_mutex);
		return (-1);
	}
	qb_queue_item_add (&worker_thread_group->threads[schedule].queue, item);
	pthread_cond_signal (&worker_thread_group->threads[schedule].new_work_cond);
	pthread_mutex_unlock (&worker_thread_group->threads[schedule].new_work_mutex);
	return (0);
}

void qb_wthread_group_wait (
	struct qb_wthread_group *worker_thread_group)
{
	int i;

	for (i = 0; i < worker_thread_group->threadcount; i++) {
		pthread_mutex_lock (&worker_thread_group->threads[i].done_work_mutex);
		if (qb_queue_is_empty (&worker_thread_group->threads[i].queue) == 0) {
			pthread_cond_wait (&worker_thread_group->threads[i].done_work_cond,
				&worker_thread_group->threads[i].done_work_mutex);
		}
		pthread_mutex_unlock (&worker_thread_group->threads[i].done_work_mutex);
	}
}

void qb_wthread_group_exit (
	struct qb_wthread_group *worker_thread_group)
{
	int i;

	for (i = 0; i < worker_thread_group->threadcount; i++) {
		pthread_cancel (worker_thread_group->threads[i].thread_id);

		/* Wait for worker thread to exit gracefully before destroying
		 * mutexes and processing items in the queue etc.
		 */
		pthread_join (worker_thread_group->threads[i].thread_id, NULL);
		pthread_mutex_destroy (&worker_thread_group->threads[i].new_work_mutex);
		pthread_cond_destroy (&worker_thread_group->threads[i].new_work_cond);
		pthread_mutex_destroy (&worker_thread_group->threads[i].done_work_mutex);
		pthread_cond_destroy (&worker_thread_group->threads[i].done_work_cond);
	}
}

void qb_wthread_group_atsegv (
	struct qb_wthread_group *worker_thread_group)
{
	void *data_for_worker_fn;
	struct qb_wthread_t *worker_thread;
	unsigned int i;

	for (i = 0; i < worker_thread_group->threadcount; i++) {
		worker_thread = &worker_thread_group->threads[i];
		while (qb_queue_is_empty (&worker_thread->queue) == 0) {
			data_for_worker_fn = qb_queue_item_get (&worker_thread->queue);
			worker_thread->worker_thread_group->worker_fn (worker_thread->thread_state, data_for_worker_fn);
			qb_queue_item_remove (&worker_thread->queue);
		}
	}
}