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