thr_once.c revision 156611
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 156611 2006-03-13 00:59:51Z deischen $ 33 */ 34#include "namespace.h" 35#include <pthread.h> 36#include "un-namespace.h" 37#include "thr_private.h" 38 39LT10_COMPAT_PRIVATE(_pthread_once); 40LT10_COMPAT_DEFAULT(pthread_once); 41 42__weak_reference(_pthread_once, pthread_once); 43 44#define ONCE_NEVER_DONE PTHREAD_NEEDS_INIT 45#define ONCE_DONE PTHREAD_DONE_INIT 46#define ONCE_IN_PROGRESS 0x02 47#define ONCE_MASK 0x03 48 49static pthread_mutex_t once_lock = PTHREAD_MUTEX_INITIALIZER; 50static pthread_cond_t once_cv = PTHREAD_COND_INITIALIZER; 51 52/* 53 * POSIX: 54 * The pthread_once() function is not a cancellation point. However, 55 * if init_routine is a cancellation point and is canceled, the effect 56 * on once_control shall be as if pthread_once() was never called. 57 */ 58 59static void 60once_cancel_handler(void *arg) 61{ 62 pthread_once_t *once_control = arg; 63 64 _pthread_mutex_lock(&once_lock); 65 once_control->state = ONCE_NEVER_DONE; 66 _pthread_mutex_unlock(&once_lock); 67 _pthread_cond_broadcast(&once_cv); 68} 69 70int 71_pthread_once(pthread_once_t *once_control, void (*init_routine) (void)) 72{ 73 struct pthread *curthread; 74 int wakeup = 0; 75 76 if (once_control->state == ONCE_DONE) 77 return (0); 78 _pthread_mutex_lock(&once_lock); 79 while (*(volatile int *)&(once_control->state) == ONCE_IN_PROGRESS) 80 _pthread_cond_wait(&once_cv, &once_lock); 81 /* 82 * If previous thread was canceled, then the state still 83 * could be ONCE_NEVER_DONE, we need to check it again. 84 */ 85 if (*(volatile int *)&(once_control->state) == ONCE_NEVER_DONE) { 86 once_control->state = ONCE_IN_PROGRESS; 87 _pthread_mutex_unlock(&once_lock); 88 curthread = _get_curthread(); 89 THR_CLEANUP_PUSH(curthread, once_cancel_handler, once_control); 90 init_routine(); 91 THR_CLEANUP_POP(curthread, 0); 92 _pthread_mutex_lock(&once_lock); 93 once_control->state = ONCE_DONE; 94 wakeup = 1; 95 } 96 _pthread_mutex_unlock(&once_lock); 97 if (wakeup) 98 _pthread_cond_broadcast(&once_cv); 99 return (0); 100} 101 102