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/* Timed mutexes (native Windows implementation).
Copyright (C) 2005-2023 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, 2019.
Based on GCC's gthr-win32.h. */
#include <config.h>
/* Specification. */
#include "windows-timedmutex.h"
#include <errno.h>
#include <stdlib.h>
#include <sys/time.h>
/* Don't assume that UNICODE is not defined. */
#undef CreateEvent
#define CreateEvent CreateEventA
int
glwthread_timedmutex_init (glwthread_timedmutex_t *mutex)
{
/* Attempt to allocate an auto-reset event object. */
/* CreateEvent
<https://docs.microsoft.com/en-us/windows/desktop/api/synchapi/nf-synchapi-createeventa> */
HANDLE event = CreateEvent (NULL, FALSE, FALSE, NULL);
if (event == INVALID_HANDLE_VALUE)
return EAGAIN;
mutex->event = event;
InitializeCriticalSection (&mutex->lock);
mutex->guard.done = 1;
return 0;
}
int
glwthread_timedmutex_lock (glwthread_timedmutex_t *mutex)
{
if (!mutex->guard.done)
{
if (InterlockedIncrement (&mutex->guard.started) == 0)
{
/* This thread is the first one to need this mutex.
Initialize it. */
int err = glwthread_timedmutex_init (mutex);
if (err != 0)
{
/* Undo increment. */
InterlockedDecrement (&mutex->guard.started);
return err;
}
}
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);
}
}
EnterCriticalSection (&mutex->lock);
return 0;
}
int
glwthread_timedmutex_trylock (glwthread_timedmutex_t *mutex)
{
if (!mutex->guard.done)
{
if (InterlockedIncrement (&mutex->guard.started) == 0)
{
/* This thread is the first one to need this mutex.
Initialize it. */
int err = glwthread_timedmutex_init (mutex);
if (err != 0)
{
/* Undo increment. */
InterlockedDecrement (&mutex->guard.started);
return err;
}
}
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;
return 0;
}
int
glwthread_timedmutex_timedlock (glwthread_timedmutex_t *mutex,
const struct timespec *abstime)
{
if (!mutex->guard.done)
{
if (InterlockedIncrement (&mutex->guard.started) == 0)
{
/* This thread is the first one to need this mutex.
Initialize it. */
int err = glwthread_timedmutex_init (mutex);
if (err != 0)
{
/* Undo increment. */
InterlockedDecrement (&mutex->guard.started);
return err;
}
}
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);
}
}
/* POSIX says:
"Under no circumstance shall the function fail with a timeout if
the mutex can be locked immediately. The validity of the abstime
parameter need not be checked if the mutex can be locked
immediately."
Therefore start the loop with a TryEnterCriticalSection call. */
for (;;)
{
if (TryEnterCriticalSection (&mutex->lock))
break;
{
struct timeval currtime;
DWORD timeout;
DWORD result;
gettimeofday (&currtime, NULL);
/* Wait until another thread signals the event or until the
abstime passes. */
if (currtime.tv_sec > abstime->tv_sec)
timeout = 0;
else
{
unsigned long seconds = abstime->tv_sec - currtime.tv_sec;
timeout = seconds * 1000;
if (timeout / 1000 != seconds) /* overflow? */
timeout = INFINITE;
else
{
long milliseconds =
abstime->tv_nsec / 1000000 - currtime.tv_usec / 1000;
if (milliseconds >= 0)
{
timeout += milliseconds;
if (timeout < milliseconds) /* overflow? */
timeout = INFINITE;
}
else
{
if (timeout >= - milliseconds)
timeout -= (- milliseconds);
else
timeout = 0;
}
}
}
if (timeout == 0)
return ETIMEDOUT;
/* WaitForSingleObject
<https://docs.microsoft.com/en-us/windows/desktop/api/synchapi/nf-synchapi-waitforsingleobject> */
result = WaitForSingleObject (mutex->event, timeout);
if (result == WAIT_FAILED)
abort ();
if (result == WAIT_TIMEOUT)
return ETIMEDOUT;
/* Another thread has just unlocked the mutex. We have good chances at
locking it now. */
}
}
return 0;
}
int
glwthread_timedmutex_unlock (glwthread_timedmutex_t *mutex)
{
if (!mutex->guard.done)
return EINVAL;
LeaveCriticalSection (&mutex->lock);
/* Notify one of the threads that were waiting with a timeout. */
/* SetEvent
<https://docs.microsoft.com/en-us/windows/desktop/api/synchapi/nf-synchapi-setevent> */
SetEvent (mutex->event);
return 0;
}
int
glwthread_timedmutex_destroy (glwthread_timedmutex_t *mutex)
{
if (!mutex->guard.done)
return EINVAL;
DeleteCriticalSection (&mutex->lock);
/* CloseHandle
<https://docs.microsoft.com/en-us/windows/desktop/api/handleapi/nf-handleapi-closehandle> */
CloseHandle (mutex->event);
mutex->guard.done = 0;
return 0;
}
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