gcc/config/vxlib.c

   1 /* Copyright (C) 2002, 2003, 2004, 2005 Free Software Foundation, Inc.
   2    Contributed by Zack Weinberg <zack@codesourcery.com>
   3
   4 This file is part of GCC.
   5
   6 GCC is free software; you can redistribute it and/or modify it under
   7 the terms of the GNU General Public License as published by the Free
   8 Software Foundation; either version 2, or (at your option) any later
   9 version.
  10
  11 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
  12 WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13 FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14 for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GCC; see the file COPYING.  If not, write to the Free
  18 Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA
  19 02110-1301, USA.  */
  20
  21 /* As a special exception, if you link this library with other files,
  22    some of which are compiled with GCC, to produce an executable,
  23    this library does not by itself cause the resulting executable
  24    to be covered by the GNU General Public License.
  25    This exception does not however invalidate any other reasons why
  26    the executable file might be covered by the GNU General Public License.  */
  27
  28 /* Threads compatibility routines for libgcc2 for VxWorks.
  29    These are out-of-line routines called from gthr-vxworks.h.  */
  30
  31 #include "tconfig.h"
  32 #include "tsystem.h"
  33 #include "gthr.h"
  34
  35 #if defined(__GTHREADS)
  36 #include <vxWorks.h>
  37 #ifndef __RTP__
  38 #include <vxLib.h>
  39 #endif
  40 #include <taskLib.h>
  41 #ifndef __RTP__
  42 #include <taskHookLib.h>
  43 #else
  44 # include <errno.h>
  45 #endif
  46
  47 /* Init-once operation.
  48
  49    This would be a clone of the implementation from gthr-solaris.h,
  50    except that we have a bootstrap problem - the whole point of this
  51    exercise is to prevent double initialization, but if two threads
  52    are racing with each other, once->mutex is liable to be initialized
  53    by both.  Then each thread will lock its own mutex, and proceed to
  54    call the initialization routine.
  55
  56    So instead we use a bare atomic primitive (vxTas()) to handle
  57    mutual exclusion.  Threads losing the race then busy-wait, calling
  58    taskDelay() to yield the processor, until the initialization is
  59    completed.  Inefficient, but reliable.  */
  60
  61 int
  62 __gthread_once (__gthread_once_t *guard, void (*func)(void))
  63 {
  64   if (guard->done)
  65     return 0;
  66
  67 #ifdef __RTP__
  68   __gthread_lock_library ();
  69 #else
  70   while (!vxTas ((void *)&guard->busy))
  71     taskDelay (1);
  72 #endif
  73
  74   /* Only one thread at a time gets here.  Check ->done again, then
  75      go ahead and call func() if no one has done it yet.  */
  76   if (!guard->done)
  77     {
  78       func ();
  79       guard->done = 1;
  80     }
  81
  82 #ifdef __RTP__
  83   __gthread_unlock_library ();
  84 #else
  85   guard->busy = 0;
  86 #endif
  87   return 0;
  88 }
  89
  90 #endif /* __GTHREADS */