Commit some progress towards threadpools.

Does this compile? Not even close.
But I figure I don't want to lose this all in the case
of some catastrophe.



git-svn-id: https://origsvn.digium.com/svn/asterisk/team/mmichelson/threadpool@376833 65c4cc65-6c06-0410-ace0-fbb531ad65f3

include/asterisk/threadpool.h

@@ -0,0 +1,96 @@
+/*
+ * Asterisk -- An open source telephony toolkit.
+ *
+ * Copyright (C) 2012, Digium, Inc.
+ *
+ * Mark Michelson <mmmichelson@digium.com>
+ *
+ * See http://www.asterisk.org for more information about
+ * the Asterisk project. Please do not directly contact
+ * any of the maintainers of this project for assistance;
+ * the project provides a web site, mailing lists and IRC
+ * channels for your use.
+ *
+ * This program is free software, distributed under the terms of
+ * the GNU General Public License Version 2. See the LICENSE file
+ * at the top of the source tree.
+ */
+
+
+#ifndef _ASTERISK_THREADPOOL_H
+#define _ASTERISK_THREADPOOL_H
+
+struct ast_threadpool;
+struct ast_taskprocessor;
+struct ast_threadpool_listener;
+
+struct ast_threadpool_listener_callbacks {
+	/*!
+	 * \brief Indicates that the state of threads in the pool has changed
+	 *
+	 * \param listener The threadpool listener
+	 * \param active_threads The number of active threads in the pool
+	 * \param idle_threads The number of idle threads in the pool
+	 * \param zombie_threads The number of zombie threads in the pool
+	 */
+	void (*state_changed)(struct ast_threadpool_listener *listener,
+			int active_threads,
+			int idle_threads,
+			int zombie_threads);
+	/*!
+	 * \brief Indicates that a task was pushed to the threadpool's taskprocessor
+	 *
+	 * \param listener The threadpool listener
+	 * \param was_empty Indicates whether the taskprocessor was empty prior to adding the task
+	 */
+	void (*tps_task_pushed)(struct ast_threadpool_listener *listener,
+			int was_empty);
+	/*!
+	 * \brief Indicates the threadpoo's taskprocessor has become empty
+	 * 
+	 * \param listener The threadpool's listener
+	 */
+	void (*emptied)(struct ast_threadpool_listener *listener);
+};
+
+/*!
+ * \brief listener for a threadpool
+ *
+ * The listener is notified of changes in a threadpool. It can
+ * react by doing things like increasing the number of threads
+ * in the pool
+ */
+struct ast_threadpool_listener {
+	/*! Callbacks called by the threadpool */
+	struct ast_threadpool_listener_callbacks *callbacks;
+	/*! Handle to the threadpool */
+	struct ast_threadpool *threadpool;
+	/*! User data for the listener */
+	void *private_data;
+};
+
+/*!
+ * \brief Create a new threadpool
+ *
+ * This function creates a threadpool and returns a taskprocessor. Tasks pushed
+ * to this taskprocessor will be handled by the threadpool and will be reported
+ * on the threadpool's listener.
+ *
+ * \param listener The listener the threadpool will notify of changes
+ * \retval NULL Failed to create the threadpool
+ * \retval non-NULL The associated taskprocessor
+ */
+struct ast_threadpool *ast_threadpool_create(struct ast_threadpool_listener *listener);
+
+/*!
+ * \brief Set the number of threads for the thread pool
+ *
+ * This number may be more or less than the current number of
+ * threads in the threadpool.
+ * 
+ * \param threadpool The threadpool to adjust
+ * \param size The new desired size of the threadpool
+ */
+void ast_threadpool_set_size(struct ast_threadpool *threadpool, unsigned int size);
+
+#endif /* ASTERISK_THREADPOOL_H */

main/threadpool.c

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+/*
+ * Asterisk -- An open source telephony toolkit.
+ *
+ * Copyright (C) 2012, Digium, Inc.
+ *
+ * Mark Michelson <mmmichelson@digium.com>
+ *
+ * See http://www.asterisk.org for more information about
+ * the Asterisk project. Please do not directly contact
+ * any of the maintainers of this project for assistance;
+ * the project provides a web site, mailing lists and IRC
+ * channels for your use.
+ *
+ * This program is free software, distributed under the terms of
+ * the GNU General Public License Version 2. See the LICENSE file
+ * at the top of the source tree.
+ */
+
+
+#include "asterisk.h"
+
+#include "asterisk/threadpool.h"
+#include "asterisk/taskprocessor.h"
+
+struct ast_threadpool;
+
+enum worker_state {
+	ALIVE,
+	ZOMBIE,
+	DEAD,
+};
+
+struct worker_thread {
+	ast_cond_t cond;
+	ast_mutex_t lock;
+	pthread_t thread;
+	struct ast_threadpool *pool;
+	AST_LIST_ENTRY(struct worker_thread) next;
+	int wake_up;
+	enum worker_state state;
+};
+
+static int worker_idle(struct worker_thread *worker)
+{
+	SCOPED_MUTEX(lock, &worker->lock);
+	if (worker->state != ALIVE) {
+		return false;
+	}
+	threadpool_active_thread_idle(worker->pool, worker);
+	while (!worker->wake_up) {
+		ast_cond_wait(&worker->cond, lock);
+	}
+	worker->wake_up = false;
+	return worker->state == ALIVE;
+}
+
+static int worker_active(struct worker_thread *worker)
+{
+	int alive = 1;
+	while (alive) {
+		if (threadpool_execute(worker->pool)) {
+			alive = worker_idle(worker);
+		}
+	}
+
+	/* Reaching this portion means the thread is
+	 * on death's door. It may have been killed while
+	 * it was idle, in which case it can just die
+	 * peacefully. If it's a zombie, though, then
+	 * it needs to let the pool know so
+	 * that the thread can be removed from the
+	 * list of zombie threads.
+	 */
+	if (worker->state == ZOMBIE) {
+		threadpool_zombie_thread_dead(worker->pool, worker);
+	}
+
+	return 0;
+}
+
+struct ast_threadpool {
+	struct ast_threadpool_listener *threadpool_listener;
+	int active_threads;
+	int idle_threads;
+	int zombie_threads;
+}
+
+static void *threadpool_tps_listener_alloc(struct ast_taskprocessor_listener *listener)
+{
+	RAII_VAR(ast_threadpool *, threadpool,
+			ao2_alloc(sizeof(*threadpool), threadpool_destroy), ao2_cleanup);
+
+	return threadpool;
+}
+
+static void threadpool_tps_task_pushed(struct ast_taskprocessor_listener *listener)
+{
+	/* XXX stub */
+}
+
+static void threadpool_tps_emptied(struct ast_taskprocessor_listener *listener)
+{
+	/* XXX stub */
+}
+
+static void threadpool_tps_shutdown(struct ast_taskprocessor_listener *listener)
+{
+	/* XXX stub */
+}
+
+static void threadpool_tps_listener_destroy(struct ast_taskprocessor_listener *listener)
+{
+	/* XXX stub */
+}
+
+static struct ast_taskprocessor_listener_callbacks threadpool_tps_listener_callbacks = {
+	.alloc = threadpool_tps_listener_alloc,
+	.task_pushed = threadpool_tps_task_pushed,
+	.emptied = threadpool_tps_emptied,
+	.shutdown = threadpool_tps_shutdown,
+	.destroy = threadpool_tps_listener_destroy,
+};
+
+/*!
+ * \brief Allocate the taskprocessor to be used for the threadpool
+ *
+ * We use a custom taskprocessor listener. We allocate our custom
+ * listener and then create a taskprocessor.
+ */
+static struct ast_taskprocessor_listener *threadpool_tps_alloc(void)
+{
+	RAII_VAR(struct threadpool_tps_listener *, tps_listener,
+			ast_taskprocessor_listener_alloc(&threadpool_tps_listener_callbacks),
+			ao2_cleanup);
+
+	if (!tps_listener) {
+		return NULL;
+	}
+
+	return ast_taskprocessor_create_with_listener(tps_listener);
+}
+
+void ast_threadpool_set_size(struct ast_threadpool *pool, int size)
+{
+}
+
+struct ast_threadpool *ast_threadpool_create(struct ast_threadpool_listener *listener, int initial_size)
+{
+	struct ast_threadpool *pool;
+	RAII_VAR(ast_taskprocessor *, tps, threadpool_tps_alloc(), ast_taskprocessor_unreference);
+
+	if (!tps) {
+		return NULL;
+	}
+
+	pool = tps->listener->private_data;
+	pool->tps = tps;
+	ast_threadpool_set_size(pool, initial_size);
+
+	return pool;
+}