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/****************************************************************************
**
** Copyright (C) 2012 Digia Plc and/or its subsidiary(-ies).
** Contact: http://www.qt-project.org/legal
**
** This file is part of the QtGui module of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:LGPL$
** 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 Digia. For licensing terms and
** conditions see http://qt.digia.com/licensing. For further information
** use the contact form at http://qt.digia.com/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 as published by the Free Software
** Foundation and appearing in the file LICENSE.LGPL included in the
** packaging of this file. Please review the following information to
** ensure the GNU Lesser General Public License version 2.1 requirements
** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
**
** In addition, as a special exception, Digia gives you certain additional
** rights. These rights are described in the Digia Qt LGPL Exception
** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
**
** GNU General Public License Usage
** Alternatively, this file may be used under the terms of the GNU
** General Public License version 3.0 as published by the Free Software
** Foundation and appearing in the file LICENSE.GPL included in the
** packaging of this file. Please review the following information to
** ensure the GNU General Public License version 3.0 requirements will be
** met: http://www.gnu.org/copyleft/gpl.html.
**
**
** $QT_END_LICENSE$
**
****************************************************************************/
#include "qwslock_p.h"
#ifndef QT_NO_QWS_MULTIPROCESS
#include "qwssignalhandler_p.h"
#include <qglobal.h>
#include <qdebug.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/sem.h>
#include <sys/time.h>
#include <time.h>
#ifdef Q_OS_LINUX
#include <linux/version.h>
#endif
#include <unistd.h>
QT_BEGIN_NAMESPACE
#ifdef QT_NO_SEMAPHORE
#error QWSLock currently requires semaphores
#endif
#ifndef Q_OS_BSD4
union semun {
int val;
struct semid_ds *buf;
unsigned short *array;
struct seminfo *__buf;
};
#endif
QWSLock::QWSLock()
{
semId = semget(IPC_PRIVATE, 3, IPC_CREAT | 0666);
if (semId == -1) {
perror("QWSLock::QWSLock");
qFatal("Unable to create semaphore");
}
QWSSignalHandler::instance()->addSemaphore(semId);
semun semval;
semval.val = 1;
if (semctl(semId, BackingStore, SETVAL, semval) == -1) {
perror("QWSLock::QWSLock");
qFatal("Unable to initialize backingstore semaphore");
}
lockCount[BackingStore] = 0;
if (semctl(semId, Communication, SETVAL, semval) == -1) {
perror("QWSLock::QWSLock");
qFatal("Unable to initialize communication semaphore");
}
lockCount[Communication] = 0;
semval.val = 0;
if (semctl(semId, RegionEvent, SETVAL, semval) == -1) {
perror("QWSLock::QWSLock");
qFatal("Unable to initialize region event semaphore");
}
}
QWSLock::QWSLock(int id)
{
semId = id;
QWSSignalHandler::instance()->addSemaphore(semId);
lockCount[0] = lockCount[1] = 0;
}
QWSLock::~QWSLock()
{
if (semId == -1)
return;
QWSSignalHandler::instance()->removeSemaphore(semId);
}
static bool forceLock(int semId, int semNum, int)
{
int ret;
do {
sembuf sops = { semNum, -1, 0 };
// As the BackingStore lock is a mutex, and only one process may own
// the lock, it's safe to use SEM_UNDO. On the other hand, the
// Communication lock is locked by the client but unlocked by the
// server and therefore can't use SEM_UNDO.
if (semNum == QWSLock::BackingStore)
sops.sem_flg |= SEM_UNDO;
ret = semop(semId, &sops, 1);
if (ret == -1 && errno != EINTR)
qDebug("QWSLock::lock: %s", strerror(errno));
} while (ret == -1 && errno == EINTR);
return (ret != -1);
}
static bool up(int semId, int semNum)
{
int ret;
do {
sembuf sops = { semNum, 1, 0 };
ret = semop(semId, &sops, 1);
if (ret == -1 && errno != EINTR)
qDebug("QWSLock::up: %s", strerror(errno));
} while (ret == -1 && errno == EINTR);
return (ret != -1);
}
static bool down(int semId, int semNum)
{
int ret;
do {
sembuf sops = { semNum, -1, 0 };
ret = semop(semId, &sops, 1);
if (ret == -1 && errno != EINTR)
qDebug("QWSLock::down: %s", strerror(errno));
} while (ret == -1 && errno == EINTR);
return (ret != -1);
}
static int getValue(int semId, int semNum)
{
int ret;
do {
ret = semctl(semId, semNum, GETVAL, 0);
if (ret == -1 && errno != EINTR)
qDebug("QWSLock::getValue: %s", strerror(errno));
} while (ret == -1 && errno == EINTR);
return ret;
}
bool QWSLock::lock(LockType type, int timeout)
{
if (type == RegionEvent)
return up(semId, RegionEvent);
if (hasLock(type)) {
++lockCount[type];
return true;
}
if (!forceLock(semId, type, timeout))
return false;
++lockCount[type];
return true;
}
bool QWSLock::hasLock(LockType type)
{
if (type == RegionEvent)
return (getValue(semId, RegionEvent) == 0);
return (lockCount[type] > 0);
}
void QWSLock::unlock(LockType type)
{
if (type == RegionEvent) {
down(semId, RegionEvent);
return;
}
if (hasLock(type)) {
--lockCount[type];
if (hasLock(type))
return;
}
const int semNum = type;
int ret;
do {
sembuf sops = {semNum, 1, 0};
if (semNum == QWSLock::BackingStore)
sops.sem_flg |= SEM_UNDO;
ret = semop(semId, &sops, 1);
if (ret == -1 && errno != EINTR)
qDebug("QWSLock::unlock: %s", strerror(errno));
} while (ret == -1 && errno == EINTR);
}
bool QWSLock::wait(LockType type, int timeout)
{
bool ok = forceLock(semId, type, timeout);
if (ok)
unlock(type);
return ok;
}
QT_END_NAMESPACE
#endif // QT_NO_QWS_MULTIPROCESS
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