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
  24 struct handler_list {
  25   void (*handler)(void);
  26   struct handler_list * next;
  27 };
  28
  29 static pthread_mutex_t pthread_atfork_lock = PTHREAD_MUTEX_INITIALIZER;
  30 static struct handler_list * pthread_atfork_prepare = NULL;
  31 static struct handler_list * pthread_atfork_parent = NULL;
  32 static struct handler_list * pthread_atfork_child = NULL;
  33
  34 static void pthread_insert_list(struct handler_list ** list,
  35                                 void (*handler)(void),
  36                                 struct handler_list * newlist,
  37                                 int at_end)
  38 {
  39   if (handler == NULL) return;
  40   if (at_end) {
  41     while(*list != NULL) list = &((*list)->next);
  42   }
  43   newlist->handler = handler;
  44   newlist->next = *list;
  45   *list = newlist;
  46 }
  47
  48 struct handler_list_block {
  49   struct handler_list prepare, parent, child;
  50 };
  51
  52 int __pthread_atfork(void (*prepare)(void),
  53                      void (*parent)(void),
  54                      void (*child)(void))
  55 {
  56   struct handler_list_block * block =
  57     (struct handler_list_block *) malloc(sizeof(struct handler_list_block));
  58   if (block == NULL) return ENOMEM;
  59   pthread_mutex_lock(&pthread_atfork_lock);
  60   /* "prepare" handlers are called in LIFO */
  61   pthread_insert_list(&pthread_atfork_prepare, prepare, &block->prepare, 0);
  62   /* "parent" handlers are called in FIFO */
  63   pthread_insert_list(&pthread_atfork_parent, parent, &block->parent, 1);
  64   /* "child" handlers are called in FIFO */
  65   pthread_insert_list(&pthread_atfork_child, child, &block->child, 1);
  66   pthread_mutex_unlock(&pthread_atfork_lock);
  67   return 0;
  68 }
  69 strong_alias (__pthread_atfork, pthread_atfork)
  70
  71 static inline void pthread_call_handlers(struct handler_list * list)
  72 {
  73   for (/*nothing*/; list != NULL; list = list->next) (list->handler)();
  74 }
  75
  76 extern int __libc_fork(void);
  77
  78 pid_t __fork(void)
  79 {
  80   pid_t pid;
  81
  82   pthread_mutex_lock(&pthread_atfork_lock);
  83
  84   pthread_call_handlers(pthread_atfork_prepare);
  85   __pthread_once_fork_prepare();
  86   __flockfilelist();
  87
  88   pid = __libc_fork();
  89
  90   if (pid == 0) {
  91     __pthread_reset_main_thread();
  92
  93     __fresetlockfiles();
  94     __pthread_once_fork_child();
  95     pthread_call_handlers(pthread_atfork_child);
  96
  97     pthread_mutex_init(&pthread_atfork_lock, NULL);
  98   } else {
  99     __funlockfilelist();
 100     __pthread_once_fork_parent();
 101     pthread_call_handlers(pthread_atfork_parent);
 102
 103     pthread_mutex_unlock(&pthread_atfork_lock);
 104   }
 105
 106   return pid;
 107 }
 108
 109 weak_alias (__fork, fork);
 110
 111 pid_t __vfork(void)
 112 {
 113   return __fork();
 114 }
 115 weak_alias (__vfork, vfork);