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/*
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* CDDL HEADER START
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*
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* The contents of this file are subject to the terms of the
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* Common Development and Distribution License, Version 1.0 only
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* (the "License"). You may not use this file except in compliance
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* with the License.
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*
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* You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
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* or http://www.opensolaris.org/os/licensing.
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* See the License for the specific language governing permissions
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* and limitations under the License.
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*
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* When distributing Covered Code, include this CDDL HEADER in each
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* file and include the License file at usr/src/OPENSOLARIS.LICENSE.
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* If applicable, add the following below this CDDL HEADER, with the
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* fields enclosed by brackets "[]" replaced with your own identifying
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* information: Portions Copyright [yyyy] [name of copyright owner]
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*
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* CDDL HEADER END
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*/
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/*
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* Copyright 2005 Sun Microsystems, Inc. All rights reserved.
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* Use is subject to license terms.
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*/
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/* Copyright (c) 1988 AT&T */
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/* All Rights Reserved */
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/*
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* University Copyright- Copyright (c) 1982, 1986, 1988
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* The Regents of the University of California
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* All Rights Reserved
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*
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* University Acknowledgment- Portions of this document are derived from
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* software developed by the University of California, Berkeley, and its
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* contributors.
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*/
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#pragma ident "%Z%%M% %I% %E% SMI"
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#pragma weak rand_r = _rand_r
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#include "synonyms.h"
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#include "thr_uberdata.h"
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#include <stdlib.h>
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#include <atomic.h>
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/*
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* We need atomic_cas_uint() protection because a multithreaded process
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* may be calling rand() from different threads and because multiple
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* threads may be calling rand_r() using a pointer to the same seed.
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*/
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static uint_t rand_seed = 1;
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#define NEXT_SEED(s) ((s) * 1103515245 + 12345)
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#define NEXT_VALUE(s) (((s) >> 16) & 0x7fff)
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static int
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rand_mt(uint_t *seed)
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{
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uint_t old_seed;
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uint_t new_seed;
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for (;;) {
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/* force reload on every iteration */
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old_seed = *(volatile uint_t *)seed;
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new_seed = NEXT_SEED(old_seed);
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if (atomic_cas_uint(seed, old_seed, new_seed) == old_seed)
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return (NEXT_VALUE(new_seed));
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SMT_PAUSE();
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}
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}
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int
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rand_r(uint_t *seed)
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{
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if (curthread->ul_uberdata->uberflags.uf_mt)
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return (rand_mt(seed));
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return (NEXT_VALUE(*seed = NEXT_SEED(*seed)));
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}
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void
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srand(uint_t seed)
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{
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rand_seed = seed;
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}
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int
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rand(void)
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{
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return (rand_r(&rand_seed));
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}
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