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/* Plain mutexes (native Windows implementation).
Copyright (C) 2005-2024 Free Software Foundation, Inc.
This file is free software: you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as
published by the Free Software Foundation; either version 2.1 of the
License, or (at your option) any later version.
This file 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 Lesser General Public License for more details.
You should have received a copy of the GNU Lesser 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-mutex.h"
#include <errno.h>
#include <stdlib.h>
void
glwthread_mutex_init (glwthread_mutex_t *mutex)
{
mutex->owner = 0;
InitializeCriticalSection (&mutex->lock);
mutex->guard.done = 1;
}
int
glwthread_mutex_lock (glwthread_mutex_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_mutex_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);
}
}
/* If this thread already owns the mutex, POSIX pthread_mutex_lock() is
required to deadlock here. But let's not do that on purpose. */
EnterCriticalSection (&mutex->lock);
{
DWORD self = GetCurrentThreadId ();
mutex->owner = self;
}
return 0;
}
int
glwthread_mutex_trylock (glwthread_mutex_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_mutex_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;
}
}
if (!TryEnterCriticalSection (&mutex->lock))
return EBUSY;
{
DWORD self = GetCurrentThreadId ();
/* TryEnterCriticalSection succeeded. This means that the mutex was either
previously unlocked (and thus mutex->owner == 0) or previously locked by
this thread (and thus mutex->owner == self). Since the mutex is meant to
be plain, we need to fail in the latter case. */
if (mutex->owner == self)
{
LeaveCriticalSection (&mutex->lock);
return EBUSY;
}
if (mutex->owner != 0)
abort ();
mutex->owner = self;
}
return 0;
}
int
glwthread_mutex_unlock (glwthread_mutex_t *mutex)
{
if (!mutex->guard.done)
return EINVAL;
mutex->owner = 0;
LeaveCriticalSection (&mutex->lock);
return 0;
}
int
glwthread_mutex_destroy (glwthread_mutex_t *mutex)
{
if (!mutex->guard.done)
return EINVAL;
DeleteCriticalSection (&mutex->lock);
mutex->guard.done = 0;
return 0;
}
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