/*

 * CDDL HEADER START

 *

 * The contents of this file are subject to the terms of the

 * Common Development and Distribution License (the "License").

 * You may not use this file except in compliance with the License.

 *

 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE

 * or http://www.opensolaris.org/os/licensing.

 * See the License for the specific language governing permissions

 * and limitations under the License.

 *

 * When distributing Covered Code, include this CDDL HEADER in each

 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.

 * If applicable, add the following below this CDDL HEADER, with the

 * fields enclosed by brackets "[]" replaced with your own identifying

 * information: Portions Copyright [yyyy] [name of copyright owner]

 *

 * CDDL HEADER END

 */

/*

 * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.

 * Use is subject to license terms.

 */

/*	Copyright (c) 1988 AT&T	*/

/*	  All Rights Reserved  	*/

/*

 * University Copyright- Copyright (c) 1982, 1986, 1988

 * The Regents of the University of California

 * All Rights Reserved

 *

 * University Acknowledgment- Portions of this document are derived from

 * software developed by the University of California, Berkeley, and its

 * contributors.

 */

#pragma ident	"%Z%%M%	%I%	%E% SMI"

#include "lint.h"

#include "thr_uberdata.h"

#include <stdlib.h>

#include <atomic.h>

/*

 * We need atomic_cas_uint() protection because a multithreaded process

 * may be calling rand() from different threads and because multiple

 * threads may be calling rand_r() using a pointer to the same seed.

 */

static uint_t rand_seed = 1;

#define	NEXT_SEED(s)	((s) * 1103515245 + 12345)

#define	NEXT_VALUE(s)	(((s) >> 16) & 0x7fff)

static int

rand_mt(uint_t *seed)

{

	uint_t old_seed;

	uint_t new_seed;

	for (;;) {

		/* force reload on every iteration */

		old_seed = *(volatile uint_t *)seed;

		new_seed = NEXT_SEED(old_seed);

		if (atomic_cas_uint(seed, old_seed, new_seed) == old_seed)

			return (NEXT_VALUE(new_seed));

		SMT_PAUSE();

	}

}

int

rand_r(uint_t *seed)

{

	if (curthread->ul_uberdata->uberflags.uf_mt)

		return (rand_mt(seed));

	return (NEXT_VALUE(*seed = NEXT_SEED(*seed)));

}

void

srand(uint_t seed)

{

	rand_seed = seed;

}

int

rand(void)

{

	return (rand_r(&rand_seed));

}