thr_once.c revision 303975
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 27#include <sys/cdefs.h> 28__FBSDID("$FreeBSD: releng/11.0/lib/libthr/thread/thr_once.c 303708 2016-08-03 10:18:52Z kib $"); 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_WAIT 0x03 42 43/* 44 * POSIX: 45 * The pthread_once() function is not a cancellation point. However, 46 * if init_routine is a cancellation point and is canceled, the effect 47 * on once_control shall be as if pthread_once() was never called. 48 */ 49 50static void 51once_cancel_handler(void *arg) 52{ 53 pthread_once_t *once_control; 54 55 once_control = arg; 56 if (atomic_cmpset_rel_int(&once_control->state, ONCE_IN_PROGRESS, 57 ONCE_NEVER_DONE)) 58 return; 59 atomic_store_rel_int(&once_control->state, ONCE_NEVER_DONE); 60 _thr_umtx_wake(&once_control->state, INT_MAX, 0); 61} 62 63int 64_pthread_once(pthread_once_t *once_control, void (*init_routine) (void)) 65{ 66 struct pthread *curthread; 67 int state; 68 69 _thr_check_init(); 70 71 for (;;) { 72 state = once_control->state; 73 if (state == ONCE_DONE) { 74 atomic_thread_fence_acq(); 75 return (0); 76 } 77 if (state == ONCE_NEVER_DONE) { 78 if (atomic_cmpset_int(&once_control->state, state, 79 ONCE_IN_PROGRESS)) 80 break; 81 } else if (state == ONCE_IN_PROGRESS) { 82 if (atomic_cmpset_int(&once_control->state, state, 83 ONCE_WAIT)) 84 _thr_umtx_wait_uint(&once_control->state, 85 ONCE_WAIT, NULL, 0); 86 } else if (state == ONCE_WAIT) { 87 _thr_umtx_wait_uint(&once_control->state, state, 88 NULL, 0); 89 } else 90 return (EINVAL); 91 } 92 93 curthread = _get_curthread(); 94 THR_CLEANUP_PUSH(curthread, once_cancel_handler, once_control); 95 init_routine(); 96 THR_CLEANUP_POP(curthread, 0); 97 if (atomic_cmpset_rel_int(&once_control->state, ONCE_IN_PROGRESS, 98 ONCE_DONE)) 99 return (0); 100 atomic_store_rel_int(&once_control->state, ONCE_DONE); 101 _thr_umtx_wake(&once_control->state, INT_MAX, 0); 102 return (0); 103} 104