1 /*
2 * Copyright (c) 1997 John Birrell <jb@cimlogic.com.au>.
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 * 3. Neither the name of the author nor the names of any co-contributors
14 * may be used to endorse or promote products derived from this software
15 * without specific prior written permission.
16 *
17 * THIS SOFTWARE IS PROVIDED BY JOHN BIRRELL AND CONTRIBUTORS ``AS IS'' AND
18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27 * SUCH DAMAGE.
28 *
29 */
30
31 #include <sys/types.h>
32 #include <machine/atomic.h>
33 #include <machine/tls.h>
34 #include <pthread.h>
35 #include <libc_private.h>
36 #include "spinlock.h"
37
38 #include "thr_private.h"
39
40 #define MAX_SPINLOCKS 256
41
42 /*
43 * These data structures are used to trace all spinlocks
44 * in libc.
45 */
46 struct spinlock_extra {
47 spinlock_t *owner;
48 };
49
50 static umtx_t spinlock_static_lock;
51 static struct spinlock_extra extra[MAX_SPINLOCKS];
52 static int spinlock_count;
53 static int initialized;
54
55 static void init_spinlock(spinlock_t *lck);
56
57 /*
58 * These functions implement temporary spinlocks as used by libc.
59 * these are not persistent spinlocks, so we use the API for
60 * temporary locks which block all signals for the duration.
61 */
62 void
_spinunlock(spinlock_t * lck)63 _spinunlock(spinlock_t *lck)
64 {
65 pthread_t curthread = tls_get_curthread();
66
67 THR_UMTX_UNLOCK(curthread, (volatile umtx_t *)&lck->access_lock);
68 }
69
70 void
_spinlock(spinlock_t * lck)71 _spinlock(spinlock_t *lck)
72 {
73 pthread_t curthread;
74
75 if (!__isthreaded)
76 PANIC("Spinlock called when not threaded.");
77 if (!initialized)
78 PANIC("Spinlocks not initialized.");
79 if (lck->fname == NULL)
80 init_spinlock(lck);
81
82 curthread = tls_get_curthread();
83 THR_UMTX_LOCK(curthread, (volatile umtx_t *)&lck->access_lock);
84 }
85
86 /*
87 * Returns 0 on success, else EBUSY
88 */
89 int
_spintrylock(spinlock_t * lck)90 _spintrylock(spinlock_t *lck)
91 {
92 pthread_t curthread;
93
94 if (!__isthreaded)
95 PANIC("Spinlock called when not threaded.");
96 if (!initialized)
97 PANIC("Spinlocks not initialized.");
98 if (lck->fname == NULL)
99 init_spinlock(lck);
100
101 curthread = tls_get_curthread();
102 return(THR_UMTX_TRYLOCK(curthread,
103 (volatile umtx_t *)&lck->access_lock));
104 }
105
106 void
_spinlock_debug(spinlock_t * lck,char * fname __unused,int lineno __unused)107 _spinlock_debug(spinlock_t *lck, char *fname __unused, int lineno __unused)
108 {
109 _spinlock(lck);
110 }
111
112 static void
init_spinlock(spinlock_t * lck)113 init_spinlock(spinlock_t *lck)
114 {
115 static int count = 0;
116 pthread_t curthread = tls_get_curthread();
117
118 THR_UMTX_LOCK(curthread, &spinlock_static_lock);
119 if ((lck->fname == NULL) && (spinlock_count < MAX_SPINLOCKS)) {
120 lck->fname = (char *)&extra[spinlock_count];
121 extra[spinlock_count].owner = lck;
122 spinlock_count++;
123 }
124 THR_UMTX_UNLOCK(curthread, &spinlock_static_lock);
125 if (lck->fname == NULL && ++count < 5)
126 stderr_debug("Warning: exceeded max spinlocks");
127 }
128
129 void
_thr_spinlock_init(void)130 _thr_spinlock_init(void)
131 {
132 int i;
133
134 _thr_umtx_init(&spinlock_static_lock);
135 if (initialized != 0) {
136 /*
137 * called after fork() to reset state of libc spin locks,
138 * it is not quite right since libc may be in inconsistent
139 * state, resetting the locks to allow current thread to be
140 * able to hold them may not help things too much, but
141 * anyway, we do our best.
142 * it is better to do pthread_atfork in libc.
143 */
144 for (i = 0; i < spinlock_count; i++)
145 _thr_umtx_init((volatile umtx_t *)
146 &extra[i].owner->access_lock);
147 } else {
148 initialized = 1;
149 }
150 }
151