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, 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 * 14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 15 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 16 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 17 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 18 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 19 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 20 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 21 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 23 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 24 * 25 */ 26 27 #include "namespace.h" 28 #include <pthread.h> 29 #include "un-namespace.h" 30 31 #include "thr_private.h" 32 33 #define ONCE_NEVER_DONE PTHREAD_NEEDS_INIT 34 #define ONCE_DONE PTHREAD_DONE_INIT 35 #define ONCE_IN_PROGRESS 0x02 36 #define ONCE_MASK 0x03 37 38 static pthread_mutex_t once_lock = PTHREAD_MUTEX_INITIALIZER; 39 static pthread_cond_t once_cv = PTHREAD_COND_INITIALIZER; 40 41 /* 42 * POSIX: 43 * The pthread_once() function is not a cancellation point. However, 44 * if init_routine is a cancellation point and is canceled, the effect 45 * on once_control shall be as if pthread_once() was never called. 46 */ 47 48 static void 49 once_cancel_handler(void *arg) 50 { 51 pthread_once_t *once_control = arg; 52 53 _pthread_mutex_lock(&once_lock); 54 once_control->__state = ONCE_NEVER_DONE; 55 _pthread_mutex_unlock(&once_lock); 56 _pthread_cond_broadcast(&once_cv); 57 } 58 59 int 60 _pthread_once(pthread_once_t *once_control, void (*init_routine) (void)) 61 { 62 int wakeup = 0; 63 64 _thr_check_init(); 65 66 if (once_control->__state == ONCE_DONE) 67 return (0); 68 _pthread_mutex_lock(&once_lock); 69 while (*(volatile int *)&(once_control->__state) == ONCE_IN_PROGRESS) 70 _pthread_cond_wait(&once_cv, &once_lock); 71 /* 72 * If previous thread was canceled, then the state still 73 * could be ONCE_NEVER_DONE, we need to check it again. 74 */ 75 if (*(volatile int *)&(once_control->__state) == ONCE_NEVER_DONE) { 76 once_control->__state = ONCE_IN_PROGRESS; 77 _pthread_mutex_unlock(&once_lock); 78 _pthread_cleanup_push(once_cancel_handler, once_control); 79 init_routine(); 80 _pthread_cleanup_pop(0); 81 _pthread_mutex_lock(&once_lock); 82 once_control->__state = ONCE_DONE; 83 wakeup = 1; 84 } 85 _pthread_mutex_unlock(&once_lock); 86 if (wakeup) 87 _pthread_cond_broadcast(&once_cv); 88 return (0); 89 } 90 91 __strong_reference(_pthread_once, pthread_once); 92