1 /*-
2  * Copyright (c) 2003 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 AND CONTRIBUTORS ``AS IS'' AND
15  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
18  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
24  * SUCH DAMAGE.
25  *
26  * $FreeBSD: src/lib/libpthread/thread/thr_barrier.c,v 1.1 2003/09/04 14:06:43 davidxu Exp $
27  */
28 
29 #include "namespace.h"
30 #include <machine/tls.h>
31 #include <errno.h>
32 #include <stdlib.h>
33 #include <pthread.h>
34 #include "un-namespace.h"
35 
36 #include "thr_private.h"
37 
38 int
39 _pthread_barrier_destroy(pthread_barrier_t *barrier)
40 {
41 	pthread_barrier_t bar;
42 
43 	if (barrier == NULL || *barrier == NULL)
44 		return (EINVAL);
45 
46 	bar = *barrier;
47 	if (bar->b_waiters > 0)
48 		return (EBUSY);
49 	*barrier = NULL;
50 	__free(bar);
51 	return (0);
52 }
53 
54 int
55 _pthread_barrier_init(pthread_barrier_t * __restrict barrier,
56 		      const pthread_barrierattr_t * __restrict attr __unused,
57 		      unsigned count)
58 {
59 	pthread_barrier_t bar;
60 
61 	if (barrier == NULL || count == 0 || count > INT_MAX)
62 		return (EINVAL);
63 
64 	bar = __malloc(sizeof(struct __pthread_barrier_s));
65 	if (bar == NULL)
66 		return (ENOMEM);
67 
68 	_thr_umtx_init(&bar->b_lock);
69 	bar->b_cycle	= 0;
70 	bar->b_waiters	= 0;
71 	bar->b_count	= count;
72 	*barrier	= bar;
73 
74 	return (0);
75 }
76 
77 int
78 _pthread_barrier_wait(pthread_barrier_t *barrier)
79 {
80 	pthread_t curthread;
81 	pthread_barrier_t bar;
82 	int64_t cycle;
83 	int ret;
84 
85 	if (barrier == NULL || *barrier == NULL)
86 		return (EINVAL);
87 
88 	bar = *barrier;
89 	curthread = tls_get_curthread();
90 	THR_UMTX_LOCK(curthread, &bar->b_lock);
91 	if (++bar->b_waiters == bar->b_count) {
92 		/* Current thread is lastest thread */
93 		bar->b_waiters = 0;
94 		bar->b_cycle++;
95 		_thr_umtx_wake(&bar->b_cycle, 0);
96 		THR_UMTX_UNLOCK(curthread, &bar->b_lock);
97 		ret = PTHREAD_BARRIER_SERIAL_THREAD;
98 	} else {
99 		cycle = bar->b_cycle;
100 		THR_UMTX_UNLOCK(curthread, &bar->b_lock);
101 		do {
102 			_thr_umtx_wait(&bar->b_cycle, cycle, NULL, 0);
103 			/* test cycle to avoid bogus wakeup */
104 		} while (cycle == bar->b_cycle);
105 		ret = 0;
106 	}
107 	return (ret);
108 }
109 
110 __strong_reference(_pthread_barrier_init,	pthread_barrier_init);
111 __strong_reference(_pthread_barrier_wait,	pthread_barrier_wait);
112 __strong_reference(_pthread_barrier_destroy,	pthread_barrier_destroy);
113