thr_once.c revision 256281
1/* 2 * Copyright (c) 2005, David Xu <davidxu@freebsd.org> 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice unmodified, this list of conditions, and the following 10 * disclaimer. 11 * 2. Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 16 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 17 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 18 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 20 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 22 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 24 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 25 * 26 * $FreeBSD: stable/10/lib/libthr/thread/thr_once.c 220888 2011-04-20 14:19:34Z rstone $ 27 * 28 */ 29 30#include "namespace.h" 31#include <pthread.h> 32#include "un-namespace.h" 33 34#include "thr_private.h" 35 36__weak_reference(_pthread_once, pthread_once); 37 38#define ONCE_NEVER_DONE PTHREAD_NEEDS_INIT 39#define ONCE_DONE PTHREAD_DONE_INIT 40#define ONCE_IN_PROGRESS 0x02 41#define ONCE_WAIT 0x03 42 43/* 44 * POSIX: 45 * The pthread_once() function is not a cancellation point. However, 46 * if init_routine is a cancellation point and is canceled, the effect 47 * on once_control shall be as if pthread_once() was never called. 48 */ 49 50static void 51once_cancel_handler(void *arg) 52{ 53 pthread_once_t *once_control = arg; 54 55 if (atomic_cmpset_rel_int(&once_control->state, ONCE_IN_PROGRESS, ONCE_NEVER_DONE)) 56 return; 57 atomic_store_rel_int(&once_control->state, ONCE_NEVER_DONE); 58 _thr_umtx_wake(&once_control->state, INT_MAX, 0); 59} 60 61int 62_pthread_once(pthread_once_t *once_control, void (*init_routine) (void)) 63{ 64 struct pthread *curthread; 65 int state; 66 67 _thr_check_init(); 68 69 for (;;) { 70 state = once_control->state; 71 if (state == ONCE_DONE) 72 return (0); 73 if (state == ONCE_NEVER_DONE) { 74 if (atomic_cmpset_acq_int(&once_control->state, state, ONCE_IN_PROGRESS)) 75 break; 76 } else if (state == ONCE_IN_PROGRESS) { 77 if (atomic_cmpset_acq_int(&once_control->state, state, ONCE_WAIT)) 78 _thr_umtx_wait_uint(&once_control->state, ONCE_WAIT, NULL, 0); 79 } else if (state == ONCE_WAIT) { 80 _thr_umtx_wait_uint(&once_control->state, state, NULL, 0); 81 } else 82 return (EINVAL); 83 } 84 85 curthread = _get_curthread(); 86 THR_CLEANUP_PUSH(curthread, once_cancel_handler, once_control); 87 init_routine(); 88 THR_CLEANUP_POP(curthread, 0); 89 if (atomic_cmpset_rel_int(&once_control->state, ONCE_IN_PROGRESS, ONCE_DONE)) 90 return (0); 91 atomic_store_rel_int(&once_control->state, ONCE_DONE); 92 _thr_umtx_wake(&once_control->state, INT_MAX, 0); 93 return (0); 94} 95 96void 97_thr_once_init() 98{ 99} 100