Reduce lock contention for simple cases in stdtime.
[dragonfly.git] / lib / libc / stdlib / atexit.c
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1/*-
2 * Copyright (c) 1990, 1993
3 * The Regents of the University of California. All rights reserved.
4 *
5 * This code is derived from software contributed to Berkeley by
6 * Chris Torek.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in the
15 * documentation and/or other materials provided with the distribution.
16 * 3. All advertising materials mentioning features or use of this software
17 * must display the following acknowledgement:
18 * This product includes software developed by the University of
19 * California, Berkeley and its contributors.
20 * 4. Neither the name of the University nor the names of its contributors
21 * may be used to endorse or promote products derived from this software
22 * without specific prior written permission.
23 *
24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
27 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
34 * SUCH DAMAGE.
35 *
36 * $FreeBSD: src/lib/libc/stdlib/atexit.c,v 1.3.6.1 2002/03/10 20:28:40 tegge Exp $
fc6d0222 37 * $DragonFly: src/lib/libc/stdlib/atexit.c,v 1.7 2006/08/03 16:40:46 swildner Exp $
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38 *
39 * @(#)atexit.c 8.2 (Berkeley) 7/3/94
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40 */
41
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42#include <stddef.h>
43#include <stdlib.h>
44#include <unistd.h>
45#include "atexit.h"
46
47#include "libc_private.h"
48#include "spinlock.h"
49
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50#define ATEXIT_FN_EMPTY 0
51#define ATEXIT_FN_STD 1
52#define ATEXIT_FN_CXA 2
53
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54static spinlock_t thread_lock = _SPINLOCK_INITIALIZER;
55
56#define THREAD_LOCK() if (__isthreaded) _SPINLOCK(&thread_lock);
57#define THREAD_UNLOCK() if (__isthreaded) _SPINUNLOCK(&thread_lock);
58
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59struct atexit {
60 struct atexit *next; /* next in list */
61 int ind; /* next index in this table */
62 struct atexit_fn {
63 int fn_type; /* ATEXIT_? from above */
64 union {
65 void (*std_func)(void);
66 void (*cxa_func)(void *);
67 } fn_ptr; /* function pointer */
68 void *fn_arg; /* argument for CXA callback */
69 void *fn_dso; /* shared module handle */
70 } fns[ATEXIT_SIZE]; /* the table itself */
71};
72
73static struct atexit *__atexit; /* points to head of LIFO stack */
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74
75/*
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76 * Register the function described by 'fptr' to be called at application
77 * exit or owning shared object unload time. This is a helper function
78 * for atexit and __cxa_atexit.
984263bc 79 */
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80static int
81atexit_register(struct atexit_fn *fptr)
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82{
83 static struct atexit __atexit0; /* one guaranteed table */
3b0357f0 84 struct atexit *p;
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85
86 THREAD_LOCK();
87 if ((p = __atexit) == NULL)
88 __atexit = p = &__atexit0;
89 else while (p->ind >= ATEXIT_SIZE) {
90 struct atexit *old__atexit;
91 old__atexit = __atexit;
92 THREAD_UNLOCK();
93 if ((p = (struct atexit *)malloc(sizeof(*p))) == NULL)
94 return (-1);
95 THREAD_LOCK();
96 if (old__atexit != __atexit) {
97 /* Lost race, retry operation */
98 THREAD_UNLOCK();
99 free(p);
100 THREAD_LOCK();
101 p = __atexit;
102 continue;
103 }
104 p->ind = 0;
105 p->next = __atexit;
106 __atexit = p;
107 }
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108 p->fns[p->ind++] = *fptr;
109 THREAD_UNLOCK();
110 return (0);
111}
112
113/*
114 * Register a function to be performed at exit.
115 */
116int
117atexit(void (*func)(void))
118{
119 struct atexit_fn fn;
120 int error;
121
122 fn.fn_type = ATEXIT_FN_STD;
fc6d0222 123 fn.fn_ptr.std_func = func;
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124 fn.fn_arg = NULL;
125 fn.fn_dso = NULL;
126
127 error = atexit_register(&fn);
128 return (error);
129}
130
131/*
132 * Register a function to be performed at exit or when an shared object
133 * with given dso handle is unloaded dynamically.
134 */
135int
136__cxa_atexit(void (*func)(void *), void *arg, void *dso)
137{
138 struct atexit_fn fn;
139 int error;
140
141 fn.fn_type = ATEXIT_FN_CXA;
fc6d0222 142 fn.fn_ptr.cxa_func = func;
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143 fn.fn_arg = arg;
144 fn.fn_dso = dso;
145
146 error = atexit_register(&fn);
147 return (error);
148}
149
150/*
151 * Call all handlers registered with __cxa_atexit for the shared
152 * object owning 'dso'. Note: if 'dso' is NULL, then all remaining
153 * handlers are called.
154 */
155void
156__cxa_finalize(void *dso)
157{
158 struct atexit *p;
159 struct atexit_fn fn;
160 int n;
161
162 THREAD_LOCK();
163 for (p = __atexit; p; p = p->next) {
164 for (n = p->ind; --n >= 0;) {
165 if (p->fns[n].fn_type == ATEXIT_FN_EMPTY)
166 continue; /* already been called */
167 if (dso != NULL && dso != p->fns[n].fn_dso)
168 continue; /* wrong DSO */
169 fn = p->fns[n];
170 /*
171 Mark entry to indicate that this particular handler
172 has already been called.
173 */
174 p->fns[n].fn_type = ATEXIT_FN_EMPTY;
175 THREAD_UNLOCK();
176
177 /* Call the function of correct type. */
178 if (fn.fn_type == ATEXIT_FN_CXA)
179 fn.fn_ptr.cxa_func(fn.fn_arg);
180 else if (fn.fn_type == ATEXIT_FN_STD)
181 fn.fn_ptr.std_func();
182 THREAD_LOCK();
183 }
184 }
984263bc 185 THREAD_UNLOCK();
984263bc 186}