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
32struct 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
41struct atfork_list_t {
42  atfork_t* first;
43  atfork_t* last;
44};
45
46static pthread_mutex_t g_atfork_list_mutex = PTHREAD_RECURSIVE_MUTEX_INITIALIZER;
47static atfork_list_t g_atfork_list = { NULL, NULL };
48
49void __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
68void __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
78void __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
88int 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