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 * $DragonFly: src/lib/libthread_xu/thread/thr_once.c,v 1.3 2006/04/06 13:03:09 davidxu Exp $ 33 */ 34 35 #include "namespace.h" 36 #include <pthread.h> 37 #include "un-namespace.h" 38 39 #include "thr_private.h" 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 46 static pthread_mutex_t once_lock = PTHREAD_MUTEX_INITIALIZER; 47 static 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 56 static void 57 once_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 67 int 68 _pthread_once(pthread_once_t *once_control, void (*init_routine) (void)) 69 { 70 int wakeup = 0; 71 72 if (once_control->state == ONCE_DONE) 73 return (0); 74 _pthread_mutex_lock(&once_lock); 75 while (*(volatile int *)&(once_control->state) == ONCE_IN_PROGRESS) 76 _pthread_cond_wait(&once_cv, &once_lock); 77 /* 78 * If previous thread was canceled, then the state still 79 * could be ONCE_NEVER_DONE, we need to check it again. 80 */ 81 if (*(volatile int *)&(once_control->state) == ONCE_NEVER_DONE) { 82 once_control->state = ONCE_IN_PROGRESS; 83 _pthread_mutex_unlock(&once_lock); 84 _pthread_cleanup_push(once_cancel_handler, once_control); 85 init_routine(); 86 _pthread_cleanup_pop(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 __strong_reference(_pthread_once, pthread_once); 98