1 /* 2 * Copyright (c) 2005, David Xu <davidxu@freebsd.org> 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 unmodified, this list of conditions, and the following 10 * disclaimer. 11 * 2. Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 16 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 17 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 18 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 20 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 22 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 24 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 25 * 26 * $FreeBSD$ 27 * 28 */ 29 30 #include "namespace.h" 31 #include <pthread.h> 32 #include "un-namespace.h" 33 34 #include "thr_private.h" 35 36 __weak_reference(_pthread_once, pthread_once); 37 38 #define ONCE_NEVER_DONE PTHREAD_NEEDS_INIT 39 #define ONCE_DONE PTHREAD_DONE_INIT 40 #define ONCE_IN_PROGRESS 0x02 41 #define ONCE_MASK 0x03 42 43 static pthread_mutex_t _thr_once_lock = PTHREAD_MUTEX_INITIALIZER; 44 static pthread_cond_t _thr_once_cv = PTHREAD_COND_INITIALIZER; 45 46 /* 47 * POSIX: 48 * The pthread_once() function is not a cancellation point. However, 49 * if init_routine is a cancellation point and is canceled, the effect 50 * on once_control shall be as if pthread_once() was never called. 51 */ 52 53 static void 54 once_cancel_handler(void *arg) 55 { 56 pthread_once_t *once_control = arg; 57 58 _pthread_mutex_lock(&_thr_once_lock); 59 once_control->state = ONCE_NEVER_DONE; 60 _pthread_mutex_unlock(&_thr_once_lock); 61 _pthread_cond_broadcast(&_thr_once_cv); 62 } 63 64 int 65 _pthread_once(pthread_once_t *once_control, void (*init_routine) (void)) 66 { 67 struct pthread *curthread; 68 int wakeup = 0; 69 70 if (once_control->state == ONCE_DONE) 71 return (0); 72 _pthread_mutex_lock(&_thr_once_lock); 73 while (*(volatile int *)&(once_control->state) == ONCE_IN_PROGRESS) 74 _pthread_cond_wait(&_thr_once_cv, &_thr_once_lock); 75 /* 76 * If previous thread was canceled, then the state still 77 * could be ONCE_NEVER_DONE, we need to check it again. 78 */ 79 if (*(volatile int *)&(once_control->state) == ONCE_NEVER_DONE) { 80 once_control->state = ONCE_IN_PROGRESS; 81 _pthread_mutex_unlock(&_thr_once_lock); 82 curthread = _get_curthread(); 83 THR_CLEANUP_PUSH(curthread, once_cancel_handler, once_control); 84 init_routine(); 85 THR_CLEANUP_POP(curthread, 0); 86 _pthread_mutex_lock(&_thr_once_lock); 87 once_control->state = ONCE_DONE; 88 wakeup = 1; 89 } 90 _pthread_mutex_unlock(&_thr_once_lock); 91 if (wakeup) 92 _pthread_cond_broadcast(&_thr_once_cv); 93 return (0); 94 } 95 96 void 97 _thr_once_init() 98 { 99 _thr_once_lock = PTHREAD_MUTEX_INITIALIZER; 100 _thr_once_cv = PTHREAD_COND_INITIALIZER; 101 } 102