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/* Copyright (C) 2002-2017 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 3, 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.
Under Section 7 of GPL version 3, you are granted additional
permissions described in the GCC Runtime Library Exception, version
3.1, as published by the Free Software Foundation.
You should have received a copy of the GNU General Public License and
a copy of the GCC Runtime Library Exception along with this program;
see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
<http://www.gnu.org/licenses/>. */
/* 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))
{
#ifdef __PPC__
/* This can happen on powerpc, which is using all 32 bits
of the gthread_once_t structure. */
if (guard->done)
return;
#endif
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 */
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