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
58 RAS_DECL(pthread__lock);
59
60 static void pthread__spinlock_slow(pthread_spin_t *);
61
62 #ifdef PTHREAD__ASM_RASOPS
63
64 void pthread__ras_simple_lock_init(__cpu_simple_lock_t *);
65 int pthread__ras_simple_lock_try(__cpu_simple_lock_t *);
66 void pthread__ras_simple_unlock(__cpu_simple_lock_t *);
67
68 #else
69
70 static void
pthread__ras_simple_lock_init(__cpu_simple_lock_t * alp)71 pthread__ras_simple_lock_init(__cpu_simple_lock_t *alp)
72 {
73
74 __cpu_simple_lock_clear(alp);
75 }
76
77 static int
pthread__ras_simple_lock_try(__cpu_simple_lock_t * alp)78 pthread__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
90 static void
pthread__ras_simple_unlock(__cpu_simple_lock_t * alp)91 pthread__ras_simple_unlock(__cpu_simple_lock_t *alp)
92 {
93
94 __cpu_simple_lock_clear(alp);
95 }
96
97 #endif /* PTHREAD__ASM_RASOPS */
98
99 static 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
106 static void
pthread__atomic_simple_lock_init(__cpu_simple_lock_t * alp)107 pthread__atomic_simple_lock_init(__cpu_simple_lock_t *alp)
108 {
109
110 __cpu_simple_lock_init(alp);
111 }
112
113 static int
pthread__atomic_simple_lock_try(__cpu_simple_lock_t * alp)114 pthread__atomic_simple_lock_try(__cpu_simple_lock_t *alp)
115 {
116
117 return (__cpu_simple_lock_try(alp));
118 }
119
120 static void
pthread__atomic_simple_unlock(__cpu_simple_lock_t * alp)121 pthread__atomic_simple_unlock(__cpu_simple_lock_t *alp)
122 {
123
124 __cpu_simple_unlock(alp);
125 }
126
127 static 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 */
140 const 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 */
146 static void
pthread__spinlock_slow(pthread_spin_t * lock)147 pthread__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 */
172 void
pthread__lockprim_init(void)173 pthread__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
196 void
pthread_lockinit(pthread_spin_t * lock)197 pthread_lockinit(pthread_spin_t *lock)
198 {
199
200 pthread__simple_lock_init(lock);
201 }
202