File: windows-recmutex.c

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/* Plain recursive mutexes (native Windows implementation).
   Copyright (C) 2005-2020 Free Software Foundation, Inc.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 3, or (at your option)
   any later version.

   This program 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 General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, see <https://www.gnu.org/licenses/>.  */

/* Written by Bruno Haible <bruno@clisp.org>, 2005.
   Based on GCC's gthr-win32.h.  */

#include <config.h>

/* Specification.  */
#include "windows-recmutex.h"

#include <errno.h>

void
glwthread_recmutex_init (glwthread_recmutex_t *mutex)
{
  mutex->owner = 0;
  mutex->depth = 0;
  InitializeCriticalSection (&mutex->lock);
  mutex->guard.done = 1;
}

int
glwthread_recmutex_lock (glwthread_recmutex_t *mutex)
{
  if (!mutex->guard.done)
    {
      if (InterlockedIncrement (&mutex->guard.started) == 0)
        /* This thread is the first one to need this mutex.  Initialize it.  */
        glwthread_recmutex_init (mutex);
      else
        {
          /* Don't let mutex->guard.started grow and wrap around.  */
          InterlockedDecrement (&mutex->guard.started);
          /* Yield the CPU while waiting for another thread to finish
             initializing this mutex.  */
          while (!mutex->guard.done)
            Sleep (0);
        }
    }
  {
    DWORD self = GetCurrentThreadId ();
    if (mutex->owner != self)
      {
        EnterCriticalSection (&mutex->lock);
        mutex->owner = self;
      }
    if (++(mutex->depth) == 0) /* wraparound? */
      {
        mutex->depth--;
        return EAGAIN;
      }
  }
  return 0;
}

int
glwthread_recmutex_trylock (glwthread_recmutex_t *mutex)
{
  if (!mutex->guard.done)
    {
      if (InterlockedIncrement (&mutex->guard.started) == 0)
        /* This thread is the first one to need this mutex.  Initialize it.  */
        glwthread_recmutex_init (mutex);
      else
        {
          /* Don't let mutex->guard.started grow and wrap around.  */
          InterlockedDecrement (&mutex->guard.started);
          /* Let another thread finish initializing this mutex, and let it also
             lock this mutex.  */
          return EBUSY;
        }
    }
  {
    DWORD self = GetCurrentThreadId ();
    if (mutex->owner != self)
      {
        if (!TryEnterCriticalSection (&mutex->lock))
          return EBUSY;
        mutex->owner = self;
      }
    if (++(mutex->depth) == 0) /* wraparound? */
      {
        mutex->depth--;
        return EAGAIN;
      }
  }
  return 0;
}

int
glwthread_recmutex_unlock (glwthread_recmutex_t *mutex)
{
  if (mutex->owner != GetCurrentThreadId ())
    return EPERM;
  if (mutex->depth == 0)
    return EINVAL;
  if (--(mutex->depth) == 0)
    {
      mutex->owner = 0;
      LeaveCriticalSection (&mutex->lock);
    }
  return 0;
}

int
glwthread_recmutex_destroy (glwthread_recmutex_t *mutex)
{
  if (mutex->owner != 0)
    return EBUSY;
  DeleteCriticalSection (&mutex->lock);
  mutex->guard.done = 0;
  return 0;
}