linuxthreads/ptfork.c

   1 /* Linuxthreads - a simple clone()-based implementation of Posix        */
   2 /* threads for Linux.                                                   */
   3 /* Copyright (C) 1996 Xavier Leroy (Xavier.Leroy@inria.fr)              */
   4 /*                                                                      */
   5 /* This program is free software; you can redistribute it and/or        */
   6 /* modify it under the terms of the GNU Library General Public License  */
   7 /* as published by the Free Software Foundation; either version 2       */
   8 /* of the License, or (at your option) any later version.               */
   9 /*                                                                      */
  10 /* This program is distributed in the hope that it will be useful,      */
  11 /* but WITHOUT ANY WARRANTY; without even the implied warranty of       */
  12 /* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the        */
  13 /* GNU Library General Public License for more details.                 */
  14
  15 /* The "atfork" stuff */
  16
  17 #include <errno.h>
  18 #include <stddef.h>
  19 #include <stdlib.h>
  20 #include <unistd.h>
  21 #include "pthread.h"
  22 #include "internals.h"
  23 #include <bits/libc-lock.h>
  24
  25 struct handler_list {
  26   void (*handler)(void);
  27   struct handler_list * next;
  28 };
  29
  30 static pthread_mutex_t pthread_atfork_lock = PTHREAD_MUTEX_INITIALIZER;
  31 static struct handler_list * pthread_atfork_prepare = NULL;
  32 static struct handler_list * pthread_atfork_parent = NULL;
  33 static struct handler_list * pthread_atfork_child = NULL;
  34
  35 static void pthread_insert_list(struct handler_list ** list,
  36                                 void (*handler)(void),
  37                                 struct handler_list * newlist,
  38                                 int at_end)
  39 {
  40   if (handler == NULL) return;
  41   if (at_end) {
  42     while(*list != NULL) list = &((*list)->next);
  43   }
  44   newlist->handler = handler;
  45   newlist->next = *list;
  46   *list = newlist;
  47 }
  48
  49 struct handler_list_block {
  50   struct handler_list prepare, parent, child;
  51 };
  52
  53 int __pthread_atfork(void (*prepare)(void),
  54                      void (*parent)(void),
  55                      void (*child)(void))
  56 {
  57   struct handler_list_block * block =
  58     (struct handler_list_block *) malloc(sizeof(struct handler_list_block));
  59   if (block == NULL) return ENOMEM;
  60   pthread_mutex_lock(&pthread_atfork_lock);
  61   /* "prepare" handlers are called in LIFO */
  62   pthread_insert_list(&pthread_atfork_prepare, prepare, &block->prepare, 0);
  63   /* "parent" handlers are called in FIFO */
  64   pthread_insert_list(&pthread_atfork_parent, parent, &block->parent, 1);
  65   /* "child" handlers are called in FIFO */
  66   pthread_insert_list(&pthread_atfork_child, child, &block->child, 1);
  67   pthread_mutex_unlock(&pthread_atfork_lock);
  68   return 0;
  69 }
  70 strong_alias (__pthread_atfork, pthread_atfork)
  71
  72 static inline void pthread_call_handlers(struct handler_list * list)
  73 {
  74   for (/*nothing*/; list != NULL; list = list->next) (list->handler)();
  75 }
  76
  77 extern int __libc_fork(void);
  78
  79 pid_t __fork(void)
  80 {
  81   pid_t pid;
  82
  83   pthread_mutex_lock(&pthread_atfork_lock);
  84
  85   pthread_call_handlers(pthread_atfork_prepare);
  86   __pthread_once_fork_prepare();
  87   __flockfilelist();
  88
  89   pid = __libc_fork();
  90
  91   if (pid == 0) {
  92     __pthread_reset_main_thread();
  93
  94     __fresetlockfiles();
  95     __pthread_once_fork_child();
  96     pthread_call_handlers(pthread_atfork_child);
  97
  98     pthread_mutex_init(&pthread_atfork_lock, NULL);
  99   } else {
 100     __funlockfilelist();
 101     __pthread_once_fork_parent();
 102     pthread_call_handlers(pthread_atfork_parent);
 103
 104     pthread_mutex_unlock(&pthread_atfork_lock);
 105   }
 106
 107   return pid;
 108 }
 109
 110 weak_alias (__fork, fork);
 111
 112 pid_t __vfork(void)
 113 {
 114   return __fork();
 115 }
 116 weak_alias (__vfork, vfork);