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 (the "License"). 6 * You may not use this file except in compliance with the License. 7 * 8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE 9 * or http://www.opensolaris.org/os/licensing. 10 * See the License for the specific language governing permissions 11 * and limitations under the License. 12 * 13 * When distributing Covered Code, include this CDDL HEADER in each 14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE. 15 * If applicable, add the following below this CDDL HEADER, with the 16 * fields enclosed by brackets "[]" replaced with your own identifying 17 * information: Portions Copyright [yyyy] [name of copyright owner] 18 * 19 * CDDL HEADER END 20 */ 21 22 /* 23 * Copyright 2008 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 #include "lint.h" 41 #include "thr_uberdata.h" 42 #include <stdlib.h> 43 #include <atomic.h> 44 45 /* 46 * We need atomic_cas_uint() protection because a multithreaded process 47 * may be calling rand() from different threads and because multiple 48 * threads may be calling rand_r() using a pointer to the same seed. 49 */ 50 51 static uint_t rand_seed = 1; 52 53 #define NEXT_SEED(s) ((s) * 1103515245 + 12345) 54 #define NEXT_VALUE(s) (((s) >> 16) & 0x7fff) 55 56 static int 57 rand_mt(uint_t *seed) 58 { 59 uint_t old_seed; 60 uint_t new_seed; 61 62 for (;;) { 63 /* force reload on every iteration */ 64 old_seed = *(volatile uint_t *)seed; 65 new_seed = NEXT_SEED(old_seed); 66 if (atomic_cas_uint(seed, old_seed, new_seed) == old_seed) 67 return (NEXT_VALUE(new_seed)); 68 SMT_PAUSE(); 69 } 70 } 71 72 int 73 rand_r(uint_t *seed) 74 { 75 if (curthread->ul_uberdata->uberflags.uf_mt) 76 return (rand_mt(seed)); 77 return (NEXT_VALUE(*seed = NEXT_SEED(*seed))); 78 } 79 80 void 81 srand(uint_t seed) 82 { 83 rand_seed = seed; 84 } 85 86 int 87 rand(void) 88 { 89 return (rand_r(&rand_seed)); 90 } 91