17c478bd9Sstevel@tonic-gate /*
27c478bd9Sstevel@tonic-gate * CDDL HEADER START
37c478bd9Sstevel@tonic-gate *
47c478bd9Sstevel@tonic-gate * The contents of this file are subject to the terms of the
5*7257d1b4Sraf * Common Development and Distribution License (the "License").
6*7257d1b4Sraf * You may not use this file except in compliance with the License.
77c478bd9Sstevel@tonic-gate *
87c478bd9Sstevel@tonic-gate * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
97c478bd9Sstevel@tonic-gate * or http://www.opensolaris.org/os/licensing.
107c478bd9Sstevel@tonic-gate * See the License for the specific language governing permissions
117c478bd9Sstevel@tonic-gate * and limitations under the License.
127c478bd9Sstevel@tonic-gate *
137c478bd9Sstevel@tonic-gate * When distributing Covered Code, include this CDDL HEADER in each
147c478bd9Sstevel@tonic-gate * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
157c478bd9Sstevel@tonic-gate * If applicable, add the following below this CDDL HEADER, with the
167c478bd9Sstevel@tonic-gate * fields enclosed by brackets "[]" replaced with your own identifying
177c478bd9Sstevel@tonic-gate * information: Portions Copyright [yyyy] [name of copyright owner]
187c478bd9Sstevel@tonic-gate *
197c478bd9Sstevel@tonic-gate * CDDL HEADER END
207c478bd9Sstevel@tonic-gate */
21*7257d1b4Sraf
227c478bd9Sstevel@tonic-gate /*
23*7257d1b4Sraf * Copyright 2008 Sun Microsystems, Inc. All rights reserved.
247c478bd9Sstevel@tonic-gate * Use is subject to license terms.
257c478bd9Sstevel@tonic-gate */
267c478bd9Sstevel@tonic-gate
277c478bd9Sstevel@tonic-gate /* Copyright (c) 1988 AT&T */
287c478bd9Sstevel@tonic-gate /* All Rights Reserved */
297c478bd9Sstevel@tonic-gate
307c478bd9Sstevel@tonic-gate /*
317c478bd9Sstevel@tonic-gate * University Copyright- Copyright (c) 1982, 1986, 1988
327c478bd9Sstevel@tonic-gate * The Regents of the University of California
337c478bd9Sstevel@tonic-gate * All Rights Reserved
347c478bd9Sstevel@tonic-gate *
357c478bd9Sstevel@tonic-gate * University Acknowledgment- Portions of this document are derived from
367c478bd9Sstevel@tonic-gate * software developed by the University of California, Berkeley, and its
377c478bd9Sstevel@tonic-gate * contributors.
387c478bd9Sstevel@tonic-gate */
397c478bd9Sstevel@tonic-gate
40*7257d1b4Sraf #include "lint.h"
417c478bd9Sstevel@tonic-gate #include "thr_uberdata.h"
427c478bd9Sstevel@tonic-gate #include <stdlib.h>
437c478bd9Sstevel@tonic-gate #include <atomic.h>
447c478bd9Sstevel@tonic-gate
457c478bd9Sstevel@tonic-gate /*
467c478bd9Sstevel@tonic-gate * We need atomic_cas_uint() protection because a multithreaded process
477c478bd9Sstevel@tonic-gate * may be calling rand() from different threads and because multiple
487c478bd9Sstevel@tonic-gate * threads may be calling rand_r() using a pointer to the same seed.
497c478bd9Sstevel@tonic-gate */
507c478bd9Sstevel@tonic-gate
517c478bd9Sstevel@tonic-gate static uint_t rand_seed = 1;
527c478bd9Sstevel@tonic-gate
537c478bd9Sstevel@tonic-gate #define NEXT_SEED(s) ((s) * 1103515245 + 12345)
547c478bd9Sstevel@tonic-gate #define NEXT_VALUE(s) (((s) >> 16) & 0x7fff)
557c478bd9Sstevel@tonic-gate
567c478bd9Sstevel@tonic-gate static int
rand_mt(uint_t * seed)577c478bd9Sstevel@tonic-gate rand_mt(uint_t *seed)
587c478bd9Sstevel@tonic-gate {
597c478bd9Sstevel@tonic-gate uint_t old_seed;
607c478bd9Sstevel@tonic-gate uint_t new_seed;
617c478bd9Sstevel@tonic-gate
627c478bd9Sstevel@tonic-gate for (;;) {
637c478bd9Sstevel@tonic-gate /* force reload on every iteration */
647c478bd9Sstevel@tonic-gate old_seed = *(volatile uint_t *)seed;
657c478bd9Sstevel@tonic-gate new_seed = NEXT_SEED(old_seed);
667c478bd9Sstevel@tonic-gate if (atomic_cas_uint(seed, old_seed, new_seed) == old_seed)
677c478bd9Sstevel@tonic-gate return (NEXT_VALUE(new_seed));
687c478bd9Sstevel@tonic-gate SMT_PAUSE();
697c478bd9Sstevel@tonic-gate }
707c478bd9Sstevel@tonic-gate }
717c478bd9Sstevel@tonic-gate
727c478bd9Sstevel@tonic-gate int
rand_r(uint_t * seed)737c478bd9Sstevel@tonic-gate rand_r(uint_t *seed)
747c478bd9Sstevel@tonic-gate {
757c478bd9Sstevel@tonic-gate if (curthread->ul_uberdata->uberflags.uf_mt)
767c478bd9Sstevel@tonic-gate return (rand_mt(seed));
777c478bd9Sstevel@tonic-gate return (NEXT_VALUE(*seed = NEXT_SEED(*seed)));
787c478bd9Sstevel@tonic-gate }
797c478bd9Sstevel@tonic-gate
807c478bd9Sstevel@tonic-gate void
srand(uint_t seed)817c478bd9Sstevel@tonic-gate srand(uint_t seed)
827c478bd9Sstevel@tonic-gate {
837c478bd9Sstevel@tonic-gate rand_seed = seed;
847c478bd9Sstevel@tonic-gate }
857c478bd9Sstevel@tonic-gate
867c478bd9Sstevel@tonic-gate int
rand(void)877c478bd9Sstevel@tonic-gate rand(void)
887c478bd9Sstevel@tonic-gate {
897c478bd9Sstevel@tonic-gate return (rand_r(&rand_seed));
907c478bd9Sstevel@tonic-gate }
91