1  /* Spin locks (native Windows implementation).
       2     Copyright (C) 2019-2021 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 3, 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    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  }