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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 #include <stdlib.h>
29 #include <errno.h>
30 #include <pthread.h>
31 #include <sys/queue.h>
32 
33 static pthread_mutex_t handler_mutex = PTHREAD_RECURSIVE_MUTEX_INITIALIZER;
34 
35 struct atfork_t
36 {
37     CIRCLEQ_ENTRY(atfork_t) entries;
38 
39     void (*prepare)(void);
40     void (*child)(void);
41     void (*parent)(void);
42 };
43 static CIRCLEQ_HEAD(atfork_head_t, atfork_t) atfork_head = \
44     CIRCLEQ_HEAD_INITIALIZER(atfork_head);
45 
__bionic_atfork_run_prepare()46 void __bionic_atfork_run_prepare()
47 {
48     struct atfork_t *cursor;
49 
50     /* We will lock this here, and unlock it in the parent and child functions.
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 mucks with the list, it could cause problems.  Right
55      *       now it's ok because all they can do is add new items to the end
56      *       of the list, but if/when we implement cleanup in dlclose() things
57      *       will get more interesting...
58      */
59     pthread_mutex_lock(&handler_mutex);
60 
61     /* Call pthread_atfork() prepare handlers.  Posix states that the prepare
62      * handlers should be called in the reverse order of the parent/child
63      * handlers, so we iterate backwards.
64      */
65     for (cursor = atfork_head.cqh_last;
66          cursor != (void*)&atfork_head;
67          cursor = cursor->entries.cqe_prev) {
68         if (cursor->prepare != NULL) {
69             cursor->prepare();
70         }
71     }
72 }
73 
__bionic_atfork_run_child()74 void __bionic_atfork_run_child()
75 {
76     struct atfork_t *cursor;
77     pthread_mutexattr_t  attr;
78 
79     /* Call pthread_atfork() child handlers */
80     for (cursor = atfork_head.cqh_first;
81          cursor != (void*)&atfork_head;
82          cursor = cursor->entries.cqe_next) {
83         if (cursor->child != NULL) {
84             cursor->child();
85         }
86     }
87 
88     pthread_mutexattr_init(&attr);
89     pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_RECURSIVE);
90     pthread_mutex_init(&handler_mutex, &attr);
91 }
92 
__bionic_atfork_run_parent()93 void __bionic_atfork_run_parent()
94 {
95     struct atfork_t *cursor;
96 
97     /* Call pthread_atfork() parent handlers */
98     for (cursor = atfork_head.cqh_first;
99          cursor != (void*)&atfork_head;
100          cursor = cursor->entries.cqe_next) {
101         if (cursor->parent != NULL) {
102             cursor->parent();
103         }
104     }
105 
106     pthread_mutex_unlock(&handler_mutex);
107 }
108 
pthread_atfork(void (* prepare)(void),void (* parent)(void),void (* child)(void))109 int pthread_atfork(void (*prepare)(void), void (*parent)(void), void(*child)(void))
110 {
111     struct atfork_t *entry = malloc(sizeof(struct atfork_t));
112 
113     if (entry == NULL) {
114         return ENOMEM;
115     }
116 
117     entry->prepare = prepare;
118     entry->parent = parent;
119     entry->child = child;
120 
121     pthread_mutex_lock(&handler_mutex);
122     CIRCLEQ_INSERT_TAIL(&atfork_head, entry, entries);
123     pthread_mutex_unlock(&handler_mutex);
124 
125     return 0;
126 }
127