1 /*
2 * Copyright (C) 2008 The Android Open Source Project
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 * * Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * * Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in
12 * the documentation and/or other materials provided with the
13 * distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
16 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
17 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
18 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
19 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
21 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
22 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
23 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
24 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
25 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26 * SUCH DAMAGE.
27 */
28
29 #include <errno.h>
30 #include <pthread.h>
31
32 struct atfork_t {
33 atfork_t* next;
34 atfork_t* prev;
35
36 void (*prepare)(void);
37 void (*child)(void);
38 void (*parent)(void);
39 };
40
41 struct atfork_list_t {
42 atfork_t* first;
43 atfork_t* last;
44 };
45
46 static pthread_mutex_t g_atfork_list_mutex = PTHREAD_RECURSIVE_MUTEX_INITIALIZER;
47 static atfork_list_t g_atfork_list = { NULL, NULL };
48
__bionic_atfork_run_prepare()49 void __bionic_atfork_run_prepare() {
50 // We lock the atfork list here, unlock it in the parent, and reset it in the child.
51 // This ensures that nobody can modify the handler array between the calls
52 // to the prepare and parent/child handlers.
53 //
54 // TODO: If a handler tries to mutate the list, they'll block. We should probably copy
55 // the list before forking, and have prepare, parent, and child all work on the consistent copy.
56 pthread_mutex_lock(&g_atfork_list_mutex);
57
58 // Call pthread_atfork() prepare handlers. POSIX states that the prepare
59 // handlers should be called in the reverse order of the parent/child
60 // handlers, so we iterate backwards.
61 for (atfork_t* it = g_atfork_list.last; it != NULL; it = it->prev) {
62 if (it->prepare != NULL) {
63 it->prepare();
64 }
65 }
66 }
67
__bionic_atfork_run_child()68 void __bionic_atfork_run_child() {
69 for (atfork_t* it = g_atfork_list.first; it != NULL; it = it->next) {
70 if (it->child != NULL) {
71 it->child();
72 }
73 }
74
75 g_atfork_list_mutex = PTHREAD_RECURSIVE_MUTEX_INITIALIZER;
76 }
77
__bionic_atfork_run_parent()78 void __bionic_atfork_run_parent() {
79 for (atfork_t* it = g_atfork_list.first; it != NULL; it = it->next) {
80 if (it->parent != NULL) {
81 it->parent();
82 }
83 }
84
85 pthread_mutex_unlock(&g_atfork_list_mutex);
86 }
87
pthread_atfork(void (* prepare)(void),void (* parent)(void),void (* child)(void))88 int pthread_atfork(void (*prepare)(void), void (*parent)(void), void(*child)(void)) {
89 atfork_t* entry = reinterpret_cast<atfork_t*>(malloc(sizeof(atfork_t)));
90 if (entry == NULL) {
91 return ENOMEM;
92 }
93
94 entry->prepare = prepare;
95 entry->parent = parent;
96 entry->child = child;
97
98 pthread_mutex_lock(&g_atfork_list_mutex);
99
100 // Append 'entry' to the list.
101 entry->next = NULL;
102 entry->prev = g_atfork_list.last;
103 if (entry->prev != NULL) {
104 entry->prev->next = entry;
105 }
106 if (g_atfork_list.first == NULL) {
107 g_atfork_list.first = entry;
108 }
109 g_atfork_list.last = entry;
110
111 pthread_mutex_unlock(&g_atfork_list_mutex);
112
113 return 0;
114 }
115