lib/windows-spin.c

   1 /* Spin locks (native Windows implementation).
   2    Copyright (C) 2019-2025 Free Software Foundation, Inc.
   3
   4    This file is free software: you can redistribute it and/or modify
   5    it under the terms of the GNU Lesser General Public License as
   6    published by the Free Software Foundation; either version 2.1 of the
   7    License, or (at your option) any later version.
   8
   9    This file 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 Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser 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   MemoryBarrier ();
  31 }
  32
  33 int
  34 glwthread_spin_lock (glwthread_spinlock_t *lock)
  35 {
  36   /* Wait until lock->word becomes 0, then replace it with 1.  */
  37   /* InterlockedCompareExchange
  38      <https://docs.microsoft.com/en-us/windows/win32/api/winnt/nf-winnt-interlockedcompareexchange> */
  39   while (InterlockedCompareExchange (&lock->word, 1, 0))
  40     ;
  41   return 0;
  42 }
  43
  44 int
  45 glwthread_spin_trylock (glwthread_spinlock_t *lock)
  46 {
  47   /* If lock->word is 0, then replace it with 1.  */
  48   /* InterlockedCompareExchange
  49      <https://docs.microsoft.com/en-us/windows/win32/api/winnt/nf-winnt-interlockedcompareexchange> */
  50   if (InterlockedCompareExchange (&lock->word, 1, 0))
  51     return EBUSY;
  52   return 0;
  53 }
  54
  55 int
  56 glwthread_spin_unlock (glwthread_spinlock_t *lock)
  57 {
  58   /* If lock->word is 1, then replace it with 0.  */
  59   /* InterlockedCompareExchange
  60      <https://docs.microsoft.com/en-us/windows/win32/api/winnt/nf-winnt-interlockedcompareexchange> */
  61   if (!InterlockedCompareExchange (&lock->word, 0, 1))
  62     return EINVAL;
  63   return 0;
  64 }
  65
  66 int
  67 glwthread_spin_destroy (glwthread_spinlock_t *lock)
  68 {
  69   return 0;
  70 }