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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 
     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 
     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 
     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 
    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