lib/windows-spin.c

   1 /* Spin locks (native Windows implementation).
   2    Copyright (C) 2019-2020 Free Software Foundation, Inc.
   3
   4    This program is free software; you can redistribute it and/or modify
   5    it under the terms of the GNU General Public License as published by
   6    the Free Software Foundation; either version 2, or (at your option)
   7    any later version.
   8
   9    This program is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12    GNU General Public License for more details.
  13
  14    You should have received a copy of the GNU General Public License
  15    along with this program; if not, see <https://www.gnu.org/licenses/>.  */
  16
  17 /* Written by Bruno Haible <bruno@clisp.org>, 2019.  */
  18
  19 #include <config.h>
  20
  21 /* Specification.  */
  22 #include "windows-spin.h"
  23
  24 #include <errno.h>
  25
  26 void
  27 glwthread_spin_init (glwthread_spinlock_t *lock)
  28 {
  29   lock->word = 0;
  30 }
  31
  32 int
  33 glwthread_spin_lock (glwthread_spinlock_t *lock)
  34 {
  35   /* Wait until lock->word becomes 0, then replace it with 1.  */
  36   /* InterlockedCompareExchange
  37      <https://docs.microsoft.com/en-us/windows/win32/api/winnt/nf-winnt-interlockedcompareexchange> */
  38   while (InterlockedCompareExchange (&lock->word, 1, 0))
  39     ;
  40   return 0;
  41 }
  42
  43 int
  44 glwthread_spin_trylock (glwthread_spinlock_t *lock)
  45 {
  46   /* If lock->word is 0, then replace it with 1.  */
  47   /* InterlockedCompareExchange
  48      <https://docs.microsoft.com/en-us/windows/win32/api/winnt/nf-winnt-interlockedcompareexchange> */
  49   if (InterlockedCompareExchange (&lock->word, 1, 0))
  50     return EBUSY;
  51   return 0;
  52 }
  53
  54 int
  55 glwthread_spin_unlock (glwthread_spinlock_t *lock)
  56 {
  57   /* If lock->word is 1, then replace it with 0.  */
  58   /* InterlockedCompareExchange
  59      <https://docs.microsoft.com/en-us/windows/win32/api/winnt/nf-winnt-interlockedcompareexchange> */
  60   if (!InterlockedCompareExchange (&lock->word, 0, 1))
  61     return EINVAL;
  62   return 0;
  63 }
  64
  65 int
  66 glwthread_spin_destroy (glwthread_spinlock_t *lock)
  67 {
  68   return 0;
  69 }