thr_once.c revision 139023
1/* 2 * Copyright (c) 1995 John Birrell <jb@cimlogic.com.au>. 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, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 3. All advertising materials mentioning features or use of this software 14 * must display the following acknowledgement: 15 * This product includes software developed by John Birrell. 16 * 4. Neither the name of the author nor the names of any co-contributors 17 * may be used to endorse or promote products derived from this software 18 * without specific prior written permission. 19 * 20 * THIS SOFTWARE IS PROVIDED BY JOHN BIRRELL AND CONTRIBUTORS ``AS IS'' AND 21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30 * SUCH DAMAGE. 31 * 32 * $FreeBSD: head/lib/libkse/thread/thr_once.c 139023 2004-12-18 18:07:37Z deischen $ 33 */ 34#include "namespace.h" 35#include <pthread.h> 36#include "un-namespace.h" 37#include "thr_private.h" 38 39__weak_reference(_pthread_once, pthread_once); 40 41#define ONCE_NEVER_DONE PTHREAD_NEEDS_INIT 42#define ONCE_DONE PTHREAD_DONE_INIT 43#define ONCE_IN_PROGRESS 0x02 44#define ONCE_MASK 0x03 45 46static pthread_mutex_t once_lock = PTHREAD_MUTEX_INITIALIZER; 47static pthread_cond_t once_cv = PTHREAD_COND_INITIALIZER; 48 49/* 50 * POSIX: 51 * The pthread_once() function is not a cancellation point. However, 52 * if init_routine is a cancellation point and is canceled, the effect 53 * on once_control shall be as if pthread_once() was never called. 54 */ 55 56static void 57once_cancel_handler(void *arg) 58{ 59 pthread_once_t *once_control = arg; 60 61 _pthread_mutex_lock(&once_lock); 62 once_control->state = ONCE_NEVER_DONE; 63 _pthread_mutex_unlock(&once_lock); 64 _pthread_cond_broadcast(&once_cv); 65} 66 67int 68_pthread_once(pthread_once_t *once_control, void (*init_routine) (void)) 69{ 70 struct pthread *curthread; 71 int wakeup = 0; 72 73 if (once_control->state == ONCE_DONE) 74 return (0); 75 _pthread_mutex_lock(&once_lock); 76 while (*(volatile int *)&(once_control->state) == ONCE_IN_PROGRESS) 77 _pthread_cond_wait(&once_cv, &once_lock); 78 /* 79 * If previous thread was canceled, then the state still 80 * could be ONCE_NEVER_DONE, we need to check it again. 81 */ 82 if (*(volatile int *)&(once_control->state) == ONCE_NEVER_DONE) { 83 once_control->state = ONCE_IN_PROGRESS; 84 _pthread_mutex_unlock(&once_lock); 85 curthread = _get_curthread(); 86 THR_CLEANUP_PUSH(curthread, once_cancel_handler, once_control); 87 init_routine(); 88 THR_CLEANUP_POP(curthread, 0); 89 _pthread_mutex_lock(&once_lock); 90 once_control->state = ONCE_DONE; 91 wakeup = 1; 92 } 93 _pthread_mutex_unlock(&once_lock); 94 if (wakeup) 95 _pthread_cond_broadcast(&once_cv); 96 return (0); 97} 98 99