thr_join.c revision 113658 
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: head/lib/libkse/thread/thr_join.c 113658 2003-04-18 05:04:16Z deischen $
33 */
34#include <errno.h>
35#include <pthread.h>
36#include "thr_private.h"
37
38__weak_reference(_pthread_join, pthread_join);
39
40int
41_pthread_join(pthread_t pthread, void **thread_return)
42{
43	struct pthread	*curthread = _get_curthread();
44	int		ret = 0;
45
46	_thr_enter_cancellation_point(curthread);
47
48	/* Check if the caller has specified an invalid thread: */
49	if (pthread == NULL || pthread->magic != THR_MAGIC) {
50		/* Invalid thread: */
51		_thr_leave_cancellation_point(curthread);
52		return (EINVAL);
53	}
54
55	/* Check if the caller has specified itself: */
56	if (pthread == curthread) {
57		/* Avoid a deadlock condition: */
58		_thr_leave_cancellation_point(curthread);
59		return (EDEADLK);
60	}
61
62	/*
63	 * Find the thread in the list of active threads or in the
64	 * list of dead threads:
65	 */
66	if ((ret = _thr_ref_add(curthread, pthread, /*include dead*/1)) != 0) {
67		/* Return an error: */
68		_thr_leave_cancellation_point(curthread);
69		return (ESRCH);
70	}
71
72	/* Check if this thread has been detached: */
73	if ((pthread->attr.flags & PTHREAD_DETACHED) != 0) {
74		/* Remove the reference and return an error: */
75		_thr_ref_delete(curthread, pthread);
76		ret = ESRCH;
77	} else {
78		/* Lock the target thread while checking its state. */
79		THR_SCHED_LOCK(curthread, pthread);
80		if ((pthread->state == PS_DEAD) ||
81		    ((pthread->flags & THR_FLAGS_EXITING) != 0)) {
82			if (thread_return != NULL)
83				/* Return the thread's return value: */
84				*thread_return = pthread->ret;
85
86			/* Unlock the thread and remove the reference. */
87			THR_SCHED_UNLOCK(curthread, pthread);
88			_thr_ref_delete(curthread, pthread);
89		}
90		else if (pthread->joiner != NULL) {
91			/* Unlock the thread and remove the reference. */
92			THR_SCHED_UNLOCK(curthread, pthread);
93			_thr_ref_delete(curthread, pthread);
94
95			/* Multiple joiners are not supported. */
96			ret = ENOTSUP;
97		}
98		else {
99			/* Set the running thread to be the joiner: */
100			pthread->joiner = curthread;
101
102			/* Keep track of which thread we're joining to: */
103			curthread->join_status.thread = pthread;
104
105			/* Unlock the thread and remove the reference. */
106			THR_SCHED_UNLOCK(curthread, pthread);
107			_thr_ref_delete(curthread, pthread);
108
109			THR_SCHED_LOCK(curthread, curthread);
110			if (curthread->join_status.thread == pthread)
111				THR_SET_STATE(curthread, PS_JOIN);
112			THR_SCHED_UNLOCK(curthread, curthread);
113
114			while (curthread->join_status.thread == pthread) {
115				/* Schedule the next thread: */
116				_thr_sched_switch(curthread);
117			}
118
119			/*
120			 * The thread return value and error are set by the
121			 * thread we're joining to when it exits or detaches:
122			 */
123			ret = curthread->join_status.error;
124			if ((ret == 0) && (thread_return != NULL))
125				*thread_return = curthread->join_status.ret;
126		}
127	}
128	_thr_leave_cancellation_point(curthread);
129
130	/* Return the completion status: */
131	return (ret);
132}
133