/*
 * Copyright (c) 2005 The DragonFly Project.  All rights reserved.
 * 
 * This code is derived from software contributed to The DragonFly Project
 * by Sergey Glushchenko <deen@smz.com.ua>
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 3. Neither the name of The DragonFly Project nor the names of its
 *    contributors may be used to endorse or promote products derived
 *    from this software without specific, prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * 
 * $DragonFly: src/sys/kern/kern_usched.c,v 1.2 2006/03/23 14:04:24 drhodus Exp $
 */

#include <sys/errno.h>
#include <sys/globaldata.h>		/* curthread */
#include <sys/proc.h>
#include <sys/sysproto.h>		/* struct usched_set_args */
#include <sys/systm.h>			/* strcmp() */
#include <sys/usched.h>	

static TAILQ_HEAD(, usched) usched_list = TAILQ_HEAD_INITIALIZER(usched_list);

/*
 * Called from very low level boot code, i386/i386/machdep.c/init386().
 * We cannot do anything fancy.  no malloc's, no nothing other then 
 * static initialization.
 */
struct usched *
usched_init(void)
{
	/*
	 * Add the bsd4 userland scheduler to the system.
	 */
	usched_ctl(&usched_bsd4, USCH_ADD);
	return(&usched_bsd4);
}

/*
 * USCHED_CTL
 *
 * SYNOPSIS:
 * 	Add/remove usched to/from list.
 * 	
 * ARGUMENTS:
 * 	usched - pointer to target scheduler
 * 	action - addition or removal ?
 *
 * RETURN VALUES:
 * 	0 - success
 * 	EINVAL - error
 */
int
usched_ctl(struct usched *usched, int action)
{
	struct usched *item;	/* temporaly for TAILQ processing */
	int error = 0;

	switch(action) {
	case USCH_ADD:
		/*
		 * Make sure it isn't already on the list
		 */
#ifdef INVARIANTS
		TAILQ_FOREACH(item, &usched_list, entry) {
			KKASSERT(item != usched);
		}
#endif
		/*
		 * Optional callback to the scheduler before we officially
		 * add it to the list.
		 */
		if (usched->usched_register)
			usched->usched_register();
		TAILQ_INSERT_TAIL(&usched_list, usched, entry);
		break;
	case USCH_REM:
		/*
		 * Do not allow the default scheduler to be removed
		 */
		if (strcmp(usched->name, "bsd4") == 0) {
			error = EINVAL;
			break;
		}
		TAILQ_FOREACH(item, &usched_list, entry) {
			if (item == usched)
				break;
		}
		if (item) {
			if (item->usched_unregister)
				item->usched_unregister();
			TAILQ_REMOVE(&usched_list, item, entry);
		} else {
			error = EINVAL;
		}
		break;
	default:
		error = EINVAL;
		break;
	}
	return (error);
}

/*
 * USCHED_SET(syscall)
 *
 * SYNOPSIS:
 * 	Setting up a proc's usched.
 *
 * ARGUMENTS:
 * 	name - usched's name
 *
 * RETURN VALUES:
 * 	0 - success
 * 	EINVAL - error
 */
int
usched_set(struct usched_set_args *uap)
{
	struct proc *p = curthread->td_proc;
	struct usched *item;	/* temporaly for TAILQ processing */
	int error;
	char buffer[NAME_LENGTH];

	if ((error = suser(curthread)) != 0)
		return (error);

	if ((error = copyinstr(uap->name, buffer, sizeof(buffer), NULL)) != 0)
		return (error);
	
	TAILQ_FOREACH(item, &usched_list, entry) {
		if ((strcmp(item->name, buffer) == 0))
			break;
	}

	/*
	 * If the scheduler for a process is being changed, disassociate
	 * the old scheduler before switching to the new one.  
	 *
	 * XXX we might have to add an additional ABI call to do a 'full
	 * disassociation' and another ABI call to do a 'full reassociation'
	 */
	if (item && item != p->p_usched) {
		p->p_usched->release_curproc(&p->p_lwp);
		p->p_usched = item;
	} else if (item == NULL) {
		error = EINVAL;
	}
	return (error);
}