thr_once.c revision 155739
1112918Sjeff/* 2153496Sdavidxu * Copyright (c) 2005, David Xu <davidxu@freebsd.org> 3112918Sjeff * All rights reserved. 4112918Sjeff * 5112918Sjeff * Redistribution and use in source and binary forms, with or without 6112918Sjeff * modification, are permitted provided that the following conditions 7112918Sjeff * are met: 8112918Sjeff * 1. Redistributions of source code must retain the above copyright 9153496Sdavidxu * notice unmodified, this list of conditions, and the following 10153496Sdavidxu * disclaimer. 11112918Sjeff * 2. Redistributions in binary form must reproduce the above copyright 12112918Sjeff * notice, this list of conditions and the following disclaimer in the 13112918Sjeff * documentation and/or other materials provided with the distribution. 14112918Sjeff * 15153496Sdavidxu * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 16153496Sdavidxu * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 17153496Sdavidxu * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 18153496Sdavidxu * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 19153496Sdavidxu * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 20153496Sdavidxu * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 21153496Sdavidxu * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 22153496Sdavidxu * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 23153496Sdavidxu * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 24153496Sdavidxu * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 25112918Sjeff * 26112918Sjeff * $FreeBSD: head/lib/libthr/thread/thr_once.c 155739 2006-02-15 23:05:03Z davidxu $ 27153496Sdavidxu * 28112918Sjeff */ 29144518Sdavidxu 30144518Sdavidxu#include "namespace.h" 31112918Sjeff#include <pthread.h> 32144518Sdavidxu#include "un-namespace.h" 33144518Sdavidxu 34112918Sjeff#include "thr_private.h" 35112918Sjeff 36112918Sjeff__weak_reference(_pthread_once, pthread_once); 37112918Sjeff 38144518Sdavidxu#define ONCE_NEVER_DONE PTHREAD_NEEDS_INIT 39144518Sdavidxu#define ONCE_DONE PTHREAD_DONE_INIT 40144518Sdavidxu#define ONCE_IN_PROGRESS 0x02 41144518Sdavidxu#define ONCE_MASK 0x03 42144518Sdavidxu 43155739Sdavidxustatic pthread_mutex_t _thr_once_lock = PTHREAD_MUTEX_INITIALIZER; 44155739Sdavidxustatic pthread_cond_t _thr_once_cv = PTHREAD_COND_INITIALIZER; 45144518Sdavidxu 46144518Sdavidxu/* 47144518Sdavidxu * POSIX: 48144518Sdavidxu * The pthread_once() function is not a cancellation point. However, 49144518Sdavidxu * if init_routine is a cancellation point and is canceled, the effect 50144518Sdavidxu * on once_control shall be as if pthread_once() was never called. 51144518Sdavidxu */ 52144518Sdavidxu 53144518Sdavidxustatic void 54144518Sdavidxuonce_cancel_handler(void *arg) 55144518Sdavidxu{ 56144518Sdavidxu pthread_once_t *once_control = arg; 57144518Sdavidxu 58155714Sdavidxu _pthread_mutex_lock(&_thr_once_lock); 59144518Sdavidxu once_control->state = ONCE_NEVER_DONE; 60155714Sdavidxu _pthread_mutex_unlock(&_thr_once_lock); 61155714Sdavidxu _pthread_cond_broadcast(&_thr_once_cv); 62144518Sdavidxu} 63144518Sdavidxu 64112918Sjeffint 65144518Sdavidxu_pthread_once(pthread_once_t *once_control, void (*init_routine) (void)) 66112918Sjeff{ 67144518Sdavidxu int wakeup = 0; 68144518Sdavidxu 69144518Sdavidxu if (once_control->state == ONCE_DONE) 70144518Sdavidxu return (0); 71155714Sdavidxu _pthread_mutex_lock(&_thr_once_lock); 72144518Sdavidxu while (*(volatile int *)&(once_control->state) == ONCE_IN_PROGRESS) 73155714Sdavidxu _pthread_cond_wait(&_thr_once_cv, &_thr_once_lock); 74144518Sdavidxu /* 75144518Sdavidxu * If previous thread was canceled, then the state still 76144518Sdavidxu * could be ONCE_NEVER_DONE, we need to check it again. 77144518Sdavidxu */ 78144518Sdavidxu if (*(volatile int *)&(once_control->state) == ONCE_NEVER_DONE) { 79144518Sdavidxu once_control->state = ONCE_IN_PROGRESS; 80155714Sdavidxu _pthread_mutex_unlock(&_thr_once_lock); 81144518Sdavidxu _pthread_cleanup_push(once_cancel_handler, once_control); 82144518Sdavidxu init_routine(); 83144518Sdavidxu _pthread_cleanup_pop(0); 84155714Sdavidxu _pthread_mutex_lock(&_thr_once_lock); 85144518Sdavidxu once_control->state = ONCE_DONE; 86144518Sdavidxu wakeup = 1; 87112918Sjeff } 88155714Sdavidxu _pthread_mutex_unlock(&_thr_once_lock); 89144518Sdavidxu if (wakeup) 90155714Sdavidxu _pthread_cond_broadcast(&_thr_once_cv); 91112918Sjeff return (0); 92112918Sjeff} 93144518Sdavidxu 94155739Sdavidxuvoid 95155739Sdavidxu_thr_once_init() 96155739Sdavidxu{ 97155739Sdavidxu _thr_once_lock = PTHREAD_MUTEX_INITIALIZER; 98155739Sdavidxu _thr_once_cv = PTHREAD_COND_INITIALIZER; 99155739Sdavidxu} 100