gcc/config/vxlib.c

/* Copyright (C) 2002, 2003, 2004, 2005 Free Software Foundation, Inc.
   Contributed by Zack Weinberg <zack@codesourcery.com>

This file is part of GCC.

GCC is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free
Software Foundation; either version 2, or (at your option) any later
version.

GCC 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 General Public License
for more details.

You should have received a copy of the GNU General Public License
along with GCC; see the file COPYING.  If not, write to the Free
Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA
02110-1301, USA.  */

/* As a special exception, if you link this library with other files,
   some of which are compiled with GCC, to produce an executable,
   this library does not by itself cause the resulting executable
   to be covered by the GNU General Public License.
   This exception does not however invalidate any other reasons why
   the executable file might be covered by the GNU General Public License.  */

/* Threads compatibility routines for libgcc2 for VxWorks.
   These are out-of-line routines called from gthr-vxworks.h.  */

#include "tconfig.h"
#include "tsystem.h"
#include "gthr.h"

#if defined(__GTHREADS)
#include <vxWorks.h>
#ifndef __RTP__
#include <vxLib.h>
#endif
#include <taskLib.h>
#ifndef __RTP__
#include <taskHookLib.h>
#else
# include <errno.h>
#endif

/* Init-once operation.

   This would be a clone of the implementation from gthr-solaris.h,
   except that we have a bootstrap problem - the whole point of this
   exercise is to prevent double initialization, but if two threads
   are racing with each other, once->mutex is liable to be initialized
   by both.  Then each thread will lock its own mutex, and proceed to
   call the initialization routine.

   So instead we use a bare atomic primitive (vxTas()) to handle
   mutual exclusion.  Threads losing the race then busy-wait, calling
   taskDelay() to yield the processor, until the initialization is
   completed.  Inefficient, but reliable.  */

int
__gthread_once (__gthread_once_t *guard, void (*func)(void))
{
  if (guard->done)
    return 0;

#ifdef __RTP__
  __gthread_lock_library ();
#else
  while (!vxTas ((void *)&guard->busy))
    taskDelay (1);
#endif

  /* Only one thread at a time gets here.  Check ->done again, then
     go ahead and call func() if no one has done it yet.  */
  if (!guard->done)
    {
      func ();
      guard->done = 1;
    }

#ifdef __RTP__
  __gthread_unlock_library ();
#else
  guard->busy = 0;
#endif
  return 0;
}

#endif /* __GTHREADS */