LXR linux/tools/testing/selftests/futex/include/atomic.h

   1/******************************************************************************
   2 *
   3 *   Copyright © International Business Machines  Corp., 2009
   4 *
   5 *   This program is free software;  you can redistribute it and/or modify
   6 *   it under the terms of the GNU General Public License as published by
   7 *   the Free Software Foundation; either version 2 of the License, or
   8 *   (at your option) any later version.
   9 *
  10 * DESCRIPTION
  11 *      GCC atomic builtin wrappers
  12 *      http://gcc.gnu.org/onlinedocs/gcc-4.1.0/gcc/Atomic-Builtins.html
  13 *
  14 * AUTHOR
  15 *      Darren Hart <dvhart@linux.intel.com>
  16 *
  17 * HISTORY
  18 *      2009-Nov-17: Initial version by Darren Hart <dvhart@linux.intel.com>
  19 *
  20 *****************************************************************************/
  21
  22#ifndef _ATOMIC_H
  23#define _ATOMIC_H
  24
  25typedef struct {
  26        volatile int val;
  27} atomic_t;
  28
  29#define ATOMIC_INITIALIZER { 0 }
  30
  31/**
  32 * atomic_cmpxchg() - Atomic compare and exchange
  33 * @uaddr:      The address of the futex to be modified
  34 * @oldval:     The expected value of the futex
  35 * @newval:     The new value to try and assign the futex
  36 *
  37 * Return the old value of addr->val.
  38 */
  39static inline int
  40atomic_cmpxchg(atomic_t *addr, int oldval, int newval)
  41{
  42        return __sync_val_compare_and_swap(&addr->val, oldval, newval);
  43}
  44
  45/**
  46 * atomic_inc() - Atomic incrememnt
  47 * @addr:       Address of the variable to increment
  48 *
  49 * Return the new value of addr->val.
  50 */
  51static inline int
  52atomic_inc(atomic_t *addr)
  53{
  54        return __sync_add_and_fetch(&addr->val, 1);
  55}
  56
  57/**
  58 * atomic_dec() - Atomic decrement
  59 * @addr:       Address of the variable to decrement
  60 *
  61 * Return the new value of addr-val.
  62 */
  63static inline int
  64atomic_dec(atomic_t *addr)
  65{
  66        return __sync_sub_and_fetch(&addr->val, 1);
  67}
  68
  69/**
  70 * atomic_set() - Atomic set
  71 * @addr:       Address of the variable to set
  72 * @newval:     New value for the atomic_t
  73 *
  74 * Return the new value of addr->val.
  75 */
  76static inline int
  77atomic_set(atomic_t *addr, int newval)
  78{
  79        addr->val = newval;
  80        return newval;
  81}
  82
  83#endif
  84