/* Copyright (C) 2002, 2003, 2005, 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 <errno.h>#include <stdlib.h>#include <fork.h>#include <atomic.h>void__unregister_atfork (dso_handle)     void *dso_handle;{  /* Check whether there is any entry in the list which we have to     remove.  It is likely that this is not the case so don't bother     getting the lock.     We do not worry about other threads adding entries for this DSO     right this moment.  If this happens this is a race and we can do     whatever we please.  The program will crash anyway seen.  */  struct fork_handler *runp = __fork_handlers;  struct fork_handler *lastp = NULL;  while (runp != NULL)    if (runp->dso_handle == dso_handle)      break;    else      {	lastp = runp;	runp = runp->next;      }  if (runp == NULL)    /* Nothing to do.  */    return;  /* Get the lock to not conflict with additions or deletions.  Note     that there couldn't have been another thread deleting something.     The __unregister_atfork function is only called from the     dlclose() code which itself serializes the operations.  */  lll_lock (__fork_lock, LLL_PRIVATE);  /* We have to create a new list with all the entries we don't remove.  */  struct deleted_handler  {    struct fork_handler *handler;    struct deleted_handler *next;  } *deleted = NULL;  /* Remove the entries for the DSO which is unloaded from the list.     It's a single linked list so readers are.  */  do    {      if (runp->dso_handle == dso_handle)	{	  if (lastp == NULL)	    __fork_handlers = runp->next;	  else	    lastp->next = runp->next;	  /* We cannot overwrite the ->next element now.  Put the deleted	     entries in a separate list.  */	  struct deleted_handler *newp = alloca (sizeof (*newp));	  newp->handler = runp;	  newp->next = deleted;	  deleted = newp;	}      else	lastp = runp;      runp = runp->next;    }  while (runp != NULL);  /* Release the lock.  */  lll_unlock (__fork_lock, LLL_PRIVATE);  /* Walk the list of all entries which have to be deleted.  */  while (deleted != NULL)    {      /* We need to be informed by possible current users.  */      deleted->handler->need_signal = 1;      /* Make sure this gets written out first.  */      atomic_write_barrier ();      /* Decrement the reference counter.  If it does not reach zero	 wait for the last user.  */      atomic_decrement (&deleted->handler->refcntr);      unsigned int val;      while ((val = deleted->handler->refcntr) != 0)	lll_futex_wait (&deleted->handler->refcntr, val, LLL_PRIVATE);      deleted = deleted->next;    }}