| /**************************************************************************** |
| ** |
| ** Copyright (C) 2015 Konstantin Ritt <ritt.ks@gmail.com> |
| ** Copyright (C) 2016 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: https://www.qt.io/licensing/ |
| ** |
| ** This file is part of the QtCore 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 The Qt Company. For licensing terms |
| ** and conditions see https://www.qt.io/terms-conditions. For further |
| ** information use the contact form at https://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 3 as published by the Free Software |
| ** Foundation and appearing in the file LICENSE.LGPL3 included in the |
| ** packaging of this file. Please review the following information to |
| ** ensure the GNU Lesser General Public License version 3 requirements |
| ** will be met: https://www.gnu.org/licenses/lgpl-3.0.html. |
| ** |
| ** GNU General Public License Usage |
| ** Alternatively, this file may be used under the terms of the GNU |
| ** General Public License version 2.0 or (at your option) the GNU General |
| ** Public license version 3 or any later version approved by the KDE Free |
| ** Qt Foundation. The licenses are as published by the Free Software |
| ** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3 |
| ** included in the packaging of this file. Please review the following |
| ** information to ensure the GNU General Public License requirements will |
| ** be met: https://www.gnu.org/licenses/gpl-2.0.html and |
| ** https://www.gnu.org/licenses/gpl-3.0.html. |
| ** |
| ** $QT_END_LICENSE$ |
| ** |
| ****************************************************************************/ |
| |
| #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("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("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("QSystemSemaphore::modify sem_post failed %d %d", 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("QSystemSemaphore::modify sem_wait failed %d %d", count, errno); |
| #endif |
| return false; |
| } |
| } |
| |
| clearError(); |
| return true; |
| } |
| |
| QT_END_NAMESPACE |
| |
| #endif // QT_NO_SYSTEMSEMAPHORE |
| |
| #endif // QT_POSIX_IPC |