/* Copyright (C) 2002, 2003, 2007 Free Software Foundation, Inc.   This file is part of the GNU C Library.   Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.   The GNU C Library is free software; you can redistribute it and/or   modify it under the terms of the GNU Lesser General Public   License as published by the Free Software Foundation; either   version 2.1 of the License, or (at your option) any later version.   The GNU C Library is distributed in the hope that it will be useful,   but WITHOUT ANY WARRANTY; without even the implied warranty of   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU   Lesser General Public License for more details.   You should have received a copy of the GNU Lesser General Public   License along with the GNU C Library; if not, write to the Free   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA   02111-1307 USA.  */#include <assert.h>#include <stdlib.h>#include <unistd.h>#include <sys/types.h>#include <sysdep.h>#include <libio/libioP.h>#include <tls.h>#include "fork.h"#include <hp-timing.h>#include <ldsodefs.h>#include <bits/stdio-lock.h>#include <atomic.h>unsigned long int *__fork_generation_pointer;/* The single linked list of all currently registered for handlers.  */struct fork_handler *__fork_handlers;static voidfresetlockfiles (void){  _IO_ITER i;  for (i = _IO_iter_begin(); i != _IO_iter_end(); i = _IO_iter_next(i))    _IO_lock_init (*((_IO_lock_t *) _IO_iter_file(i)->_lock));}pid_t__libc_fork (void){  pid_t pid;  struct used_handler  {    struct fork_handler *handler;    struct used_handler *next;  } *allp = NULL;  /* Run all the registered preparation handlers.  In reverse order.     While doing this we build up a list of all the entries.  */  struct fork_handler *runp;  while ((runp = __fork_handlers) != NULL)    {      unsigned int oldval = runp->refcntr;      if (oldval == 0)	/* This means some other thread removed the list just after	   the pointer has been loaded.  Try again.  Either the list	   is empty or we can retry it.  */	continue;      /* Bump the reference counter.  */      if (atomic_compare_and_exchange_bool_acq (&__fork_handlers->refcntr,						oldval + 1, oldval))	/* The value changed, try again.  */	continue;      /* We bumped the reference counter for the first entry in the	 list.  That means that none of the following entries will	 just go away.  The unloading code works in the order of the	 list.         While executing the registered handlers we are building a         list of all the entries so that we can go backward later on.  */      while (1)	{	  /* Execute the handler if there is one.  */	  if (runp->prepare_handler != NULL)	    runp->prepare_handler ();	  /* Create a new element for the list.  */	  struct used_handler *newp	    = (struct used_handler *) alloca (sizeof (*newp));	  newp->handler = runp;	  newp->next = allp;	  allp = newp;	  /* Advance to the next handler.  */	  runp = runp->next;	  if (runp == NULL)	    break;	  /* Bump the reference counter for the next entry.  */	  atomic_increment (&runp->refcntr);	}      /* We are done.  */      break;    }  _IO_list_lock ();#ifndef NDEBUG  pid_t ppid = THREAD_GETMEM (THREAD_SELF, tid);#endif  /* We need to prevent the getpid() code to update the PID field so     that, if a signal arrives in the child very early and the signal     handler uses getpid(), the value returned is correct.  */  pid_t parentpid = THREAD_GETMEM (THREAD_SELF, pid);  THREAD_SETMEM (THREAD_SELF, pid, -parentpid);#ifdef ARCH_FORK  pid = ARCH_FORK ();#else# error "ARCH_FORK must be defined so that the CLONE_SETTID flag is used"  pid = INLINE_SYSCALL (fork, 0);#endif  if (pid == 0)    {      struct pthread *self = THREAD_SELF;      assert (THREAD_GETMEM (self, tid) != ppid);      if (__fork_generation_pointer != NULL)	*__fork_generation_pointer += 4;      /* Adjust the PID field for the new process.  */      THREAD_SETMEM (self, pid, THREAD_GETMEM (self, tid));#if HP_TIMING_AVAIL      /* The CPU clock of the thread and process have to be set to zero.  */      hp_timing_t now;      HP_TIMING_NOW (now);      THREAD_SETMEM (self, cpuclock_offset, now);      GL(dl_cpuclock_offset) = now;#endif      /* Reset the file list.  These are recursive mutexes.  */      fresetlockfiles ();      /* Reset locks in the I/O code.  */      _IO_list_resetlock ();      /* Reset the lock the dynamic loader uses to protect its data.  */      __rtld_lock_initialize (GL(dl_load_lock));      /* Run the handlers registered for the child.  */      while (allp != NULL)	{	  if (allp->handler->child_handler != NULL)	    allp->handler->child_handler ();	  /* Note that we do not have to wake any possible waiter. 	     This is the only thread in the new process.  The count 	     may have been bumped up by other threads doing a fork. 	     We reset it to 1, to avoid waiting for non-existing 	     thread(s) to release the count.  */	  allp->handler->refcntr = 1;	  /* XXX We could at this point look through the object pool	     and mark all objects not on the __fork_handlers list as	     unused.  This is necessary in case the fork() happened	     while another thread called dlclose() and that call had	     to create a new list.  */	  allp = allp->next;	}      /* Initialize the fork lock.  */      __fork_lock = LLL_LOCK_INITIALIZER;    }  else    {      assert (THREAD_GETMEM (THREAD_SELF, tid) == ppid);      /* Restore the PID value.  */      THREAD_SETMEM (THREAD_SELF, pid, parentpid);      /* We execute this even if the 'fork' call failed.  */      _IO_list_unlock ();      /* Run the handlers registered for the parent.  */      while (allp != NULL)	{	  if (allp->handler->parent_handler != NULL)	    allp->handler->parent_handler ();	  if (atomic_decrement_and_test (&allp->handler->refcntr)	      && allp->handler->need_signal)	    lll_futex_wake (allp->handler->refcntr, 1, LLL_PRIVATE);	  allp = allp->next;	}    }  return pid;}weak_alias (__libc_fork, __fork)libc_hidden_def (__fork)weak_alias (__libc_fork, fork)