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/****************************************************************************
**
** Copyright (C) 2015 Konstantin Ritt <ritt.ks@gmail.com>
** Copyright (C) 2015 The Qt Company Ltd.
** Copyright (C) 2015 Klarälvdalens Datakonsult AB, a KDAB Group company, info@kdab.com, author Tobias Koenig <tobias.koenig@kdab.com>
** Contact: http://www.qt.io/licensing/
**
** This file is part of the QtCore module of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:LGPL21$
** Commercial License Usage
** Licensees holding valid commercial Qt licenses may use this file in
** accordance with the commercial license agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and The Qt Company. For licensing terms
** and conditions see http://www.qt.io/terms-conditions. For further
** information use the contact form at http://www.qt.io/contact-us.
**
** GNU Lesser General Public License Usage
** Alternatively, this file may be used under the terms of the GNU Lesser
** General Public License version 2.1 or version 3 as published by the Free
** Software Foundation and appearing in the file LICENSE.LGPLv21 and
** LICENSE.LGPLv3 included in the packaging of this file. Please review the
** following information to ensure the GNU Lesser General Public License
** requirements will be met: https://www.gnu.org/licenses/lgpl.html and
** http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
**
** As a special exception, The Qt Company gives you certain additional
** rights. These rights are described in The Qt Company LGPL Exception
** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
**
** $QT_END_LICENSE$
**
****************************************************************************/
#include "qsystemsemaphore.h"
#include "qsystemsemaphore_p.h"
#include <qdebug.h>
#include <qfile.h>
#include <qcoreapplication.h>
#ifdef QT_POSIX_IPC
#ifndef QT_NO_SYSTEMSEMAPHORE
#include <sys/types.h>
#include <fcntl.h>
#include <errno.h>
#include "private/qcore_unix_p.h"
// OpenBSD 4.2 doesn't define EIDRM, see BUGS section:
// http://www.openbsd.org/cgi-bin/man.cgi?query=semop&manpath=OpenBSD+4.2
#if defined(Q_OS_OPENBSD) && !defined(EIDRM)
#define EIDRM EINVAL
#endif
QT_BEGIN_NAMESPACE
bool QSystemSemaphorePrivate::handle(QSystemSemaphore::AccessMode mode)
{
if (semaphore != SEM_FAILED)
return true; // we already have a semaphore
if (fileName.isEmpty()) {
errorString = QCoreApplication::tr("%1: key is empty", "QSystemSemaphore").arg(QLatin1String("QSystemSemaphore::handle"));
error = QSystemSemaphore::KeyError;
return false;
}
const QByteArray semName = QFile::encodeName(fileName);
// Always try with O_EXCL so we know whether we created the semaphore.
int oflag = O_CREAT | O_EXCL;
for (int tryNum = 0, maxTries = 1; tryNum < maxTries; ++tryNum) {
do {
semaphore = ::sem_open(semName.constData(), oflag, 0600, initialValue);
} while (semaphore == SEM_FAILED && errno == EINTR);
if (semaphore == SEM_FAILED && errno == EEXIST) {
if (mode == QSystemSemaphore::Create) {
if (::sem_unlink(semName.constData()) == -1 && errno != ENOENT) {
setErrorString(QLatin1String("QSystemSemaphore::handle (sem_unlink)"));
return false;
}
// Race condition: the semaphore might be recreated before
// we call sem_open again, so we'll retry several times.
maxTries = 3;
} else {
// Race condition: if it no longer exists at the next sem_open
// call, we won't realize we created it, so we'll leak it later.
oflag &= ~O_EXCL;
maxTries = 2;
}
} else {
break;
}
}
if (semaphore == SEM_FAILED) {
setErrorString(QLatin1String("QSystemSemaphore::handle"));
return false;
}
createdSemaphore = (oflag & O_EXCL) != 0;
return true;
}
void QSystemSemaphorePrivate::cleanHandle()
{
if (semaphore != SEM_FAILED) {
if (::sem_close(semaphore) == -1) {
setErrorString(QLatin1String("QSystemSemaphore::cleanHandle (sem_close)"));
#if defined QSYSTEMSEMAPHORE_DEBUG
qDebug() << QLatin1String("QSystemSemaphore::cleanHandle sem_close failed.");
#endif
}
semaphore = SEM_FAILED;
}
if (createdSemaphore) {
if (::sem_unlink(QFile::encodeName(fileName).constData()) == -1 && errno != ENOENT) {
setErrorString(QLatin1String("QSystemSemaphore::cleanHandle (sem_unlink)"));
#if defined QSYSTEMSEMAPHORE_DEBUG
qDebug() << QLatin1String("QSystemSemaphore::cleanHandle sem_unlink failed.");
#endif
}
createdSemaphore = false;
}
}
bool QSystemSemaphorePrivate::modifySemaphore(int count)
{
if (!handle())
return false;
if (count > 0) {
int cnt = count;
do {
if (::sem_post(semaphore) == -1) {
setErrorString(QLatin1String("QSystemSemaphore::modifySemaphore (sem_post)"));
#if defined QSYSTEMSEMAPHORE_DEBUG
qDebug() << QLatin1String("QSystemSemaphore::modify sem_post failed") << count << errno;
#endif
// rollback changes to preserve the SysV semaphore behavior
for ( ; cnt < count; ++cnt) {
int res;
EINTR_LOOP(res, ::sem_wait(semaphore));
}
return false;
}
--cnt;
} while (cnt > 0);
} else {
int res;
EINTR_LOOP(res, ::sem_wait(semaphore));
if (res == -1) {
// If the semaphore was removed be nice and create it and then modifySemaphore again
if (errno == EINVAL || errno == EIDRM) {
semaphore = SEM_FAILED;
return modifySemaphore(count);
}
setErrorString(QLatin1String("QSystemSemaphore::modifySemaphore (sem_wait)"));
#if defined QSYSTEMSEMAPHORE_DEBUG
qDebug() << QLatin1String("QSystemSemaphore::modify sem_wait failed") << count << errno;
#endif
return false;
}
}
clearError();
return true;
}
QT_END_NAMESPACE
#endif // QT_NO_SYSTEMSEMAPHORE
#endif // QT_POSIX_IPC
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