1/*
2 * Copyright 2011-2015 Samy Al Bahra.
3 * Copyright 2011 David Joseph.
4 * All rights reserved.
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 * 1. Redistributions of source code must retain the above copyright
10 *    notice, this list of conditions and the following 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 AND CONTRIBUTORS ``AS IS'' AND
16 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
17 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
18 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
19 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
20 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
21 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
22 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
23 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
24 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
25 * SUCH DAMAGE.
26 */
27
28#include <ck_barrier.h>
29#include <ck_pr.h>
30
31void
32ck_barrier_centralized(struct ck_barrier_centralized *barrier,
33    struct ck_barrier_centralized_state *state,
34    unsigned int n_threads)
35{
36	unsigned int sense, value;
37
38	/*
39	 * Every execution context has a sense associated with it.
40	 * This sense is reversed when the barrier is entered. Every
41	 * thread will spin on the global sense until the last thread
42	 * reverses it.
43	 */
44	sense = state->sense = ~state->sense;
45	value = ck_pr_faa_uint(&barrier->value, 1);
46	if (value == n_threads - 1) {
47		ck_pr_store_uint(&barrier->value, 0);
48		ck_pr_fence_memory();
49		ck_pr_store_uint(&barrier->sense, sense);
50		return;
51	}
52
53	ck_pr_fence_atomic_load();
54	while (sense != ck_pr_load_uint(&barrier->sense))
55		ck_pr_stall();
56
57	ck_pr_fence_acquire();
58	return;
59}
60