thr_once.c revision 174689
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. Neither the name of the author nor the names of any co-contributors 14 * may be used to endorse or promote products derived from this software 15 * without specific prior written permission. 16 * 17 * THIS SOFTWARE IS PROVIDED BY JOHN BIRRELL AND CONTRIBUTORS ``AS IS'' AND 18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 27 * SUCH DAMAGE. 28 * 29 * $FreeBSD: head/lib/libkse/thread/thr_once.c 174689 2007-12-16 23:29:57Z deischen $ 30 */ 31 32#include "namespace.h" 33#include <pthread.h> 34#include "un-namespace.h" 35#include "thr_private.h" 36 37__weak_reference(_pthread_once, pthread_once); 38 39#define ONCE_NEVER_DONE PTHREAD_NEEDS_INIT 40#define ONCE_DONE PTHREAD_DONE_INIT 41#define ONCE_IN_PROGRESS 0x02 42#define ONCE_MASK 0x03 43 44static pthread_mutex_t once_lock = PTHREAD_MUTEX_INITIALIZER; 45static pthread_cond_t once_cv = PTHREAD_COND_INITIALIZER; 46 47/* 48 * POSIX: 49 * The pthread_once() function is not a cancellation point. However, 50 * if init_routine is a cancellation point and is canceled, the effect 51 * on once_control shall be as if pthread_once() was never called. 52 */ 53 54static void 55once_cancel_handler(void *arg) 56{ 57 pthread_once_t *once_control = arg; 58 59 _pthread_mutex_lock(&once_lock); 60 once_control->state = ONCE_NEVER_DONE; 61 _pthread_mutex_unlock(&once_lock); 62 _pthread_cond_broadcast(&once_cv); 63} 64 65int 66_pthread_once(pthread_once_t *once_control, void (*init_routine) (void)) 67{ 68 struct pthread *curthread; 69 int wakeup = 0; 70 71 if (once_control->state == ONCE_DONE) 72 return (0); 73 _pthread_mutex_lock(&once_lock); 74 while (*(volatile int *)&(once_control->state) == ONCE_IN_PROGRESS) 75 _pthread_cond_wait(&once_cv, &once_lock); 76 /* 77 * If previous thread was canceled, then the state still 78 * could be ONCE_NEVER_DONE, we need to check it again. 79 */ 80 if (*(volatile int *)&(once_control->state) == ONCE_NEVER_DONE) { 81 once_control->state = ONCE_IN_PROGRESS; 82 _pthread_mutex_unlock(&once_lock); 83 curthread = _get_curthread(); 84 THR_CLEANUP_PUSH(curthread, once_cancel_handler, once_control); 85 init_routine(); 86 THR_CLEANUP_POP(curthread, 0); 87 _pthread_mutex_lock(&once_lock); 88 once_control->state = ONCE_DONE; 89 wakeup = 1; 90 } 91 _pthread_mutex_unlock(&once_lock); 92 if (wakeup) 93 _pthread_cond_broadcast(&once_cv); 94 return (0); 95} 96 97