1/*	$NetBSD: membar_ops.S,v 1.9 2022/04/09 23:32:52 riastradh Exp $	*/
2
3/*-
4 * Copyright (c) 2007 The NetBSD Foundation, Inc.
5 * All rights reserved.
6 *
7 * This code is derived from software contributed to The NetBSD Foundation
8 * by Jason R. Thorpe, and by Andrew Doran.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 *    notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 *    notice, this list of conditions and the following disclaimer in the
17 *    documentation and/or other materials provided with the distribution.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
20 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
21 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
22 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
23 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
24 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
25 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
26 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
27 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
28 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
29 * POSSIBILITY OF SUCH DAMAGE.
30 */
31
32#include "atomic_op_asm.h"
33
34	.text
35
36/*
37 * These assume Total Store Order (TSO), which may reorder
38 * store-before-load but nothing else.  Hence, only membar_sync (and
39 * its deprecated alias membar_enter) must issue anything -- namely,
40 * membar #StoreLoad.
41 *
42 * If we ran with Partial Store Order (PSO), we would also need to
43 * issue membar #StoreStore for membar_exit (load/store-before-store)
44 * and membar_producer (store-before-store).
45 */
46
47ENTRY(_membar_acquire)
48	retl
49	 nop
50END(_membar_acquire)
51ATOMIC_OP_ALIAS(membar_acquire,_membar_acquire)
52
53ENTRY(_membar_release)
54	retl
55	 nop
56END(_membar_release)
57ATOMIC_OP_ALIAS(membar_release,_membar_release)
58
59ENTRY(_membar_sync)
60	/*
61	 * Some SPARC CPUs have errata with MEMBAR in the delay slot of
62	 * a branch, such as the UltraSPARC-IIi:
63	 *
64	 *	`Apparently, the deadlock is most easily caused if the
65	 *	 delay slot of the JMPL is a MEMBAR #Sync, or any
66	 *	 instruction that synchronizes on the load or store
67	 *	 buffers being empty.'
68	 *
69	 *	UltraSPARC-IIi User's Manual, Part No. 805-0087-01, Sun
70	 *	Microsystems, October 1997, Appendix K.2 `Errata
71	 *	Created by UltraSPARC-I', Erratum 51, p. 476.
72	 *	https://www.oracle.com/technetwork/server-storage/sun-sparc-enterprise/documentation/sparc-2i-usersmanual-2516677.pdf#page=518
73	 *
74	 * So let's avoid doing that.
75	 */
76	membar	#StoreLoad
77	retl
78	 nop
79END(_membar_sync)
80ATOMIC_OP_ALIAS(membar_sync,_membar_sync)
81
82ATOMIC_OP_ALIAS(membar_producer,_membar_release)
83STRONG_ALIAS(_membar_producer,_membar_release)
84ATOMIC_OP_ALIAS(membar_consumer,_membar_acquire)
85STRONG_ALIAS(_membar_consumer,_membar_acquire)
86ATOMIC_OP_ALIAS(membar_enter,_membar_sync)
87STRONG_ALIAS(_membar_enter,_membar_sync)
88ATOMIC_OP_ALIAS(membar_exit,_membar_release)
89STRONG_ALIAS(_membar_exit,_membar_release)
90