1 /* 2 * CDDL HEADER START 3 * 4 * The contents of this file are subject to the terms of the 5 * Common Development and Distribution License, Version 1.0 only 6 * (the "License"). You may not use this file except in compliance 7 * with the License. 8 * 9 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE 10 * or http://www.opensolaris.org/os/licensing. 11 * See the License for the specific language governing permissions 12 * and limitations under the License. 13 * 14 * When distributing Covered Code, include this CDDL HEADER in each 15 * file and include the License file at usr/src/OPENSOLARIS.LICENSE. 16 * If applicable, add the following below this CDDL HEADER, with the 17 * fields enclosed by brackets "[]" replaced with your own identifying 18 * information: Portions Copyright [yyyy] [name of copyright owner] 19 * 20 * CDDL HEADER END 21 */ 22 /* 23 * Copyright 2005 Sun Microsystems, Inc. All rights reserved. 24 * Use is subject to license terms. 25 */ 26 27 /* Copyright (c) 1988 AT&T */ 28 /* All Rights Reserved */ 29 30 /* 31 * University Copyright- Copyright (c) 1982, 1986, 1988 32 * The Regents of the University of California 33 * All Rights Reserved 34 * 35 * University Acknowledgment- Portions of this document are derived from 36 * software developed by the University of California, Berkeley, and its 37 * contributors. 38 */ 39 40 #pragma ident "%Z%%M% %I% %E% SMI" 41 42 #pragma weak rand_r = _rand_r 43 44 #include "synonyms.h" 45 #include "thr_uberdata.h" 46 #include <stdlib.h> 47 #include <atomic.h> 48 49 /* 50 * We need atomic_cas_uint() protection because a multithreaded process 51 * may be calling rand() from different threads and because multiple 52 * threads may be calling rand_r() using a pointer to the same seed. 53 */ 54 55 static uint_t rand_seed = 1; 56 57 #define NEXT_SEED(s) ((s) * 1103515245 + 12345) 58 #define NEXT_VALUE(s) (((s) >> 16) & 0x7fff) 59 60 static int 61 rand_mt(uint_t *seed) 62 { 63 uint_t old_seed; 64 uint_t new_seed; 65 66 for (;;) { 67 /* force reload on every iteration */ 68 old_seed = *(volatile uint_t *)seed; 69 new_seed = NEXT_SEED(old_seed); 70 if (atomic_cas_uint(seed, old_seed, new_seed) == old_seed) 71 return (NEXT_VALUE(new_seed)); 72 SMT_PAUSE(); 73 } 74 } 75 76 int 77 rand_r(uint_t *seed) 78 { 79 if (curthread->ul_uberdata->uberflags.uf_mt) 80 return (rand_mt(seed)); 81 return (NEXT_VALUE(*seed = NEXT_SEED(*seed))); 82 } 83 84 void 85 srand(uint_t seed) 86 { 87 rand_seed = seed; 88 } 89 90 int 91 rand(void) 92 { 93 return (rand_r(&rand_seed)); 94 } 95