atomicity.h

基于LWVCL开发的库

/* Low-level functions for atomic operations.  ARM version.
   Copyright (C) 1997, 1998, 1999, 2000 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   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., 51 Franklin Street, Fifth Floor, Boston, MA
   02110-1301 USA.  */

#ifndef _ATOMICITY_H
#define _ATOMICITY_H    1


/* Kaffe: Modified by Guilhem Lavaux to return the oldval */

static inline long int
__attribute__ ((unused))
compare_and_swap (volatile long int *p, long int oldval, long int newval)
{
  long int result, tmp;
  __asm__ ("\n"
 	   "0:\tldr\t%1,[%2]\n\t"
   	   "mov\t%0,#0\n\t"
   	   "cmp\t%1,%4\n\t"
   	   "bne\t1f\n\t"
   	   "swp\t%0,%3,[%2]\n\t"
   	   "cmp\t%1,%0\n\t"
   	   "swpne\t%1,%0,[%2]\n\t"
  	   "bne\t0b\n\t"
	   "mov\t%0,%4\n\t"
	   "b\t2f\n\t"
   	   "1:"
 	   "mov\t%0,%1\n"
	   "2:"
	: "=&r" (result), "=&r" (tmp)
	: "r" (p), "r" (newval), "r" (oldval)
	: "cc", "memory");
  return result;
}

#define atomic_compare_and_exchange_val_acq(mem, newval, oldval)  \
    ({ __typeof (*mem) result;                                    \
           if (sizeof(*mem) == 4)                                 \
	     result = compare_and_swap((long int*)(mem), (long int)(oldval), (long int)(newval));      \
	   else                                                   \
	     {                                                    \
	       result = (__typeof(*mem))0;                        \
	       abort();                                           \
	     }                                                    \
	   result;                                                \
    })

#endif /* atomicity.h */