/*****************************************************************************

Copyright (c) 1996, 2009, Innobase Oy. All Rights Reserved.

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; version 2 of the License.

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

*****************************************************************************/

/**************************************************//**
@file srv/srv0que.c
Server query execution

Created 6/5/1996 Heikki Tuuri
*******************************************************/

#include "srv0que.h"

#include "srv0srv.h"
#include "sync0sync.h"
#include "os0thread.h"
#include "usr0sess.h"
#include "que0que.h"

/**********************************************************************//**
Checks if there is work to do in the server task queue. If there is, the
thread starts processing a task. Before leaving, it again checks the task
queue and picks a new task if any exists. This is called by a SRV_WORKER
thread. */
UNIV_INTERN
void
srv_que_task_queue_check(void)
/*==========================*/
{
	que_thr_t*	thr;

	for (;;) {
		mutex_enter(&kernel_mutex);

		thr = UT_LIST_GET_FIRST(srv_sys->tasks);

		if (thr == NULL) {
			mutex_exit(&kernel_mutex);

			return;
		}

		UT_LIST_REMOVE(queue, srv_sys->tasks, thr);

		mutex_exit(&kernel_mutex);

		que_run_threads(thr);
	}
}

/**********************************************************************//**
Performs round-robin on the server tasks. This is called by a SRV_WORKER
thread every second or so.
@return	the new (may be == thr) query thread to run */
UNIV_INTERN
que_thr_t*
srv_que_round_robin(
/*================*/
	que_thr_t*	thr)	/*!< in: query thread */
{
	que_thr_t*	new_thr;

	ut_ad(thr);
	ut_ad(thr->state == QUE_THR_RUNNING);

	mutex_enter(&kernel_mutex);

	UT_LIST_ADD_LAST(queue, srv_sys->tasks, thr);

	new_thr = UT_LIST_GET_FIRST(srv_sys->tasks);

	mutex_exit(&kernel_mutex);

	return(new_thr);
}

/**********************************************************************//**
Enqueues a task to server task queue and releases a worker thread, if there
is a suspended one. */
UNIV_INTERN
void
srv_que_task_enqueue_low(
/*=====================*/
	que_thr_t*	thr)	/*!< in: query thread */
{
	ut_ad(thr);
	ut_ad(mutex_own(&kernel_mutex));

	UT_LIST_ADD_LAST(queue, srv_sys->tasks, thr);

	srv_release_threads(SRV_WORKER, 1);
}

/**********************************************************************//**
Enqueues a task to server task queue and releases a worker thread, if there
is a suspended one. */
UNIV_INTERN
void
srv_que_task_enqueue(
/*=================*/
	que_thr_t*	thr)	/*!< in: query thread */
{
	ut_ad(thr);

	ut_a(0);	/* Under MySQL this is never called */

	mutex_enter(&kernel_mutex);

	srv_que_task_enqueue_low(thr);

	mutex_exit(&kernel_mutex);
}