1/*	$NetBSD: pthread_lock.c,v 1.36 2022/04/10 10:38:33 riastradh Exp $	*/
2
3/*-
4 * Copyright (c) 2001, 2006, 2007 The NetBSD Foundation, Inc.
5 * All rights reserved.
6 *
7 * This code is derived from software contributed to The NetBSD Foundation
8 * by Nathan J. Williams and 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/*
33 * libpthread internal spinlock routines.
34 */
35
36#include <sys/cdefs.h>
37__RCSID("$NetBSD: pthread_lock.c,v 1.36 2022/04/10 10:38:33 riastradh Exp $");
38
39/* Need to use libc-private names for atomic operations. */
40#include "../../common/lib/libc/atomic/atomic_op_namespace.h"
41
42#include <sys/types.h>
43#include <sys/ras.h>
44
45#include <machine/lock.h>
46
47#include <errno.h>
48#include <unistd.h>
49#include <stdio.h>
50#include <stdlib.h>
51
52#include "pthread.h"
53#include "pthread_int.h"
54
55/* How many times to try acquiring spin locks on MP systems. */
56#define	PTHREAD__NSPINS         64
57
58RAS_DECL(pthread__lock);
59
60static void 	pthread__spinlock_slow(pthread_spin_t *);
61
62#ifdef PTHREAD__ASM_RASOPS
63
64void pthread__ras_simple_lock_init(__cpu_simple_lock_t *);
65int pthread__ras_simple_lock_try(__cpu_simple_lock_t *);
66void pthread__ras_simple_unlock(__cpu_simple_lock_t *);
67
68#else
69
70static void
71pthread__ras_simple_lock_init(__cpu_simple_lock_t *alp)
72{
73
74	__cpu_simple_lock_clear(alp);
75}
76
77static int
78pthread__ras_simple_lock_try(__cpu_simple_lock_t *alp)
79{
80	int locked;
81
82	RAS_START(pthread__lock);
83	locked = __SIMPLELOCK_LOCKED_P(alp);
84	__cpu_simple_lock_set(alp);
85	RAS_END(pthread__lock);
86
87	return !locked;
88}
89
90static void
91pthread__ras_simple_unlock(__cpu_simple_lock_t *alp)
92{
93
94	__cpu_simple_lock_clear(alp);
95}
96
97#endif /* PTHREAD__ASM_RASOPS */
98
99static const struct pthread_lock_ops pthread__lock_ops_ras = {
100	pthread__ras_simple_lock_init,
101	pthread__ras_simple_lock_try,
102	pthread__ras_simple_unlock,
103	pthread__spinlock_slow,
104};
105
106static void
107pthread__atomic_simple_lock_init(__cpu_simple_lock_t *alp)
108{
109
110	__cpu_simple_lock_init(alp);
111}
112
113static int
114pthread__atomic_simple_lock_try(__cpu_simple_lock_t *alp)
115{
116
117	return (__cpu_simple_lock_try(alp));
118}
119
120static void
121pthread__atomic_simple_unlock(__cpu_simple_lock_t *alp)
122{
123
124	__cpu_simple_unlock(alp);
125}
126
127static const struct pthread_lock_ops pthread__lock_ops_atomic = {
128	pthread__atomic_simple_lock_init,
129	pthread__atomic_simple_lock_try,
130	pthread__atomic_simple_unlock,
131	pthread__spinlock_slow,
132};
133
134/*
135 * We default to pointing to the RAS primitives; we might need to use
136 * locks early, but before main() starts.  This is safe, since no other
137 * threads will be active for the process, so atomicity will not be
138 * required.
139 */
140const struct pthread_lock_ops *pthread__lock_ops = &pthread__lock_ops_ras;
141
142/*
143 * Prevent this routine from being inlined.  The common case is no
144 * contention and it's better to not burden the instruction decoder.
145 */
146static void
147pthread__spinlock_slow(pthread_spin_t *lock)
148{
149	pthread_t self;
150	int count;
151
152	self = pthread__self();
153
154	do {
155		count = pthread__nspins;
156		while (__SIMPLELOCK_LOCKED_P(lock) && --count > 0)
157			pthread__smt_pause();
158		if (count > 0) {
159			if ((*self->pt_lockops.plo_try)(lock))
160				break;
161			continue;
162		}
163		sched_yield();
164	} while (/*CONSTCOND*/ 1);
165}
166
167/*
168 * Initialize the locking primitives.  On uniprocessors, we always
169 * use Restartable Atomic Sequences if they are available.  Otherwise,
170 * we fall back onto machine-dependent atomic lock primitives.
171 */
172void
173pthread__lockprim_init(void)
174{
175	char *p;
176
177	if ((p = pthread__getenv("PTHREAD_NSPINS")) != NULL)
178		pthread__nspins = atoi(p);
179	else if (pthread__concurrency != 1)
180		pthread__nspins = PTHREAD__NSPINS;
181	else
182		pthread__nspins = 1;
183
184	if (pthread__concurrency != 1) {
185		pthread__lock_ops = &pthread__lock_ops_atomic;
186		return;
187	}
188
189	if (rasctl(RAS_ADDR(pthread__lock), RAS_SIZE(pthread__lock),
190	    RAS_INSTALL) != 0) {
191		pthread__lock_ops = &pthread__lock_ops_atomic;
192		return;
193	}
194}
195
196void
197pthread_lockinit(pthread_spin_t *lock)
198{
199
200	pthread__simple_lock_init(lock);
201}
202