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diff --git a/src/gui/embedded/qwslock.cpp b/src/gui/embedded/qwslock.cpp
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+/****************************************************************************
+**
+** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).
+** Contact: Qt Software Information (qt-info@nokia.com)
+**
+** This file is part of the QtGui module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** No Commercial Usage
+** This file contains pre-release code and may not be distributed.
+** You may use this file in accordance with the terms and conditions
+** contained in the either Technology Preview License Agreement or the
+** Beta Release License Agreement.
+**
+** 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, Nokia gives you certain
+** additional rights. These rights are described in the Nokia Qt LGPL
+** Exception version 1.0, 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.
+**
+** If you are unsure which license is appropriate for your use, please
+** contact the sales department at qt-sales@nokia.com.
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#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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