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jeremybenn |
/* Copyright (C) 2002, 2003, 2004, 2005, 2009 Free Software Foundation, Inc.
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Contributed by Zack Weinberg <zack@codesourcery.com>
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This file is part of GCC.
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GCC is free software; you can redistribute it and/or modify it under
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the terms of the GNU General Public License as published by the Free
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Software Foundation; either version 3, or (at your option) any later
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version.
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GCC is distributed in the hope that it will be useful, but WITHOUT ANY
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WARRANTY; without even the implied warranty of MERCHANTABILITY or
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FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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for more details.
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Under Section 7 of GPL version 3, you are granted additional
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permissions described in the GCC Runtime Library Exception, version
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3.1, as published by the Free Software Foundation.
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You should have received a copy of the GNU General Public License and
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a copy of the GCC Runtime Library Exception along with this program;
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see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
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<http://www.gnu.org/licenses/>. */
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/* Threads compatibility routines for libgcc2 for VxWorks.
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These are out-of-line routines called from gthr-vxworks.h. */
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#include "tconfig.h"
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#include "tsystem.h"
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#include "gthr.h"
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#if defined(__GTHREADS)
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#include <vxWorks.h>
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#ifndef __RTP__
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#include <vxLib.h>
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#endif
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#include <taskLib.h>
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#ifndef __RTP__
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#include <taskHookLib.h>
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#else
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# include <errno.h>
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#endif
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/* Init-once operation.
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This would be a clone of the implementation from gthr-solaris.h,
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except that we have a bootstrap problem - the whole point of this
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exercise is to prevent double initialization, but if two threads
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are racing with each other, once->mutex is liable to be initialized
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by both. Then each thread will lock its own mutex, and proceed to
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call the initialization routine.
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So instead we use a bare atomic primitive (vxTas()) to handle
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mutual exclusion. Threads losing the race then busy-wait, calling
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taskDelay() to yield the processor, until the initialization is
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completed. Inefficient, but reliable. */
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int
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__gthread_once (__gthread_once_t *guard, void (*func)(void))
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{
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if (guard->done)
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return 0;
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#ifdef __RTP__
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__gthread_lock_library ();
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#else
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while (!vxTas ((void *)&guard->busy))
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{
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#ifdef __PPC__
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/* This can happen on powerpc, which is using all 32 bits
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of the gthread_once_t structure. */
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if (guard->done)
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return;
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#endif
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taskDelay (1);
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}
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#endif
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/* Only one thread at a time gets here. Check ->done again, then
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go ahead and call func() if no one has done it yet. */
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if (!guard->done)
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{
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func ();
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guard->done = 1;
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}
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#ifdef __RTP__
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__gthread_unlock_library ();
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#else
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guard->busy = 0;
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#endif
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return 0;
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}
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#endif /* __GTHREADS */
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