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 #include <errno.h> 35 #include <pthread.h> 36 #include <stdlib.h> 37 #include "thr_private.h" 38 39 __weak_reference(_pthread_join, pthread_join); 40 41 int 42 _pthread_join(pthread_t pthread, void **thread_return) 43 { 44 int ret = 0; 45 pthread_t thread; 46 47 _thread_enter_cancellation_point(); 48 49 /* Check if the caller has specified an invalid thread: */ 50 if (pthread->magic != PTHREAD_MAGIC) { 51 /* Invalid thread: */ 52 _thread_leave_cancellation_point(); 53 return(EINVAL); 54 } 55 56 /* Check if the caller has specified itself: */ 57 if (pthread == curthread) { 58 /* Avoid a deadlock condition: */ 59 _thread_leave_cancellation_point(); 60 return(EDEADLK); 61 } 62 63 /* 64 * Search for the specified thread in the list of active threads. This 65 * is done manually here rather than calling _find_thread() because 66 * the searches in _thread_list and _dead_list (as well as setting up 67 * join/detach state) have to be done atomically. 68 */ 69 DEAD_LIST_LOCK; 70 THREAD_LIST_LOCK; 71 TAILQ_FOREACH(thread, &_thread_list, tle) 72 if (thread == pthread) { 73 UMTX_LOCK(&pthread->lock); 74 break; 75 } 76 77 if (thread == NULL) 78 /* 79 * Search for the specified thread in the list of dead threads: 80 */ 81 TAILQ_FOREACH(thread, &_dead_list, dle) 82 if (thread == pthread) { 83 UMTX_LOCK(&pthread->lock); 84 break; 85 } 86 87 /* Check if the thread was not found or has been detached: */ 88 if (thread == NULL) { 89 THREAD_LIST_UNLOCK; 90 DEAD_LIST_UNLOCK; 91 ret = ESRCH; 92 goto out; 93 } 94 if ((pthread->attr.flags & PTHREAD_DETACHED) != 0) { 95 UMTX_UNLOCK(&pthread->lock); 96 THREAD_LIST_UNLOCK; 97 DEAD_LIST_UNLOCK; 98 ret = EINVAL; 99 goto out; 100 } 101 102 if (pthread->joiner != NULL) { 103 /* Multiple joiners are not supported. */ 104 /* XXXTHR - support multiple joiners. */ 105 UMTX_UNLOCK(&pthread->lock); 106 THREAD_LIST_UNLOCK; 107 DEAD_LIST_UNLOCK; 108 ret = ENOTSUP; 109 goto out; 110 111 } 112 113 /* Check if the thread is not dead: */ 114 if (pthread->state != PS_DEAD) { 115 /* Set the running thread to be the joiner: */ 116 pthread->joiner = curthread; 117 UMTX_UNLOCK(&pthread->lock); 118 _thread_critical_enter(curthread); 119 120 /* Keep track of which thread we're joining to: */ 121 curthread->join_status.thread = pthread; 122 123 while (curthread->join_status.thread == pthread) { 124 PTHREAD_SET_STATE(curthread, PS_JOIN); 125 /* Wait for our signal to wake up. */ 126 _thread_critical_exit(curthread); 127 THREAD_LIST_UNLOCK; 128 DEAD_LIST_UNLOCK; 129 ret = _thread_suspend(curthread, NULL); 130 if (ret != 0 && ret != EAGAIN && ret != EINTR) 131 PANIC("Unable to suspend in join."); 132 133 /* 134 * XXX - For correctness reasons. 135 * We must aquire these in the same order and also 136 * importantly, release in the same order, order because 137 * otherwise we might deadlock with the joined thread 138 * when we attempt to release one of these locks. 139 */ 140 DEAD_LIST_LOCK; 141 THREAD_LIST_LOCK; 142 _thread_critical_enter(curthread); 143 } 144 145 /* 146 * The thread return value and error are set by the thread we're 147 * joining to when it exits or detaches: 148 */ 149 ret = curthread->join_status.error; 150 if ((ret == 0) && (thread_return != NULL)) 151 *thread_return = curthread->join_status.ret; 152 _thread_critical_exit(curthread); 153 THREAD_LIST_UNLOCK; 154 DEAD_LIST_UNLOCK; 155 } else { 156 /* 157 * The thread exited (is dead) without being detached, and no 158 * thread has joined it. 159 */ 160 161 /* Check if the return value is required: */ 162 if (thread_return != NULL) { 163 /* Return the thread's return value: */ 164 *thread_return = pthread->ret; 165 } 166 167 /* Free all remaining memory allocated to the thread. */ 168 pthread->attr.flags |= PTHREAD_DETACHED; 169 UMTX_UNLOCK(&pthread->lock); 170 TAILQ_REMOVE(&_dead_list, pthread, dle); 171 deadlist_free_onethread(pthread); 172 THREAD_LIST_UNLOCK; 173 DEAD_LIST_UNLOCK; 174 } 175 176 out: 177 _thread_leave_cancellation_point(); 178 179 /* Return the completion status: */ 180 return (ret); 181 } 182