qthread.cpp

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// Copyright (C) 2016 The Qt Company Ltd.
// Copyright (C) 2016 Intel Corporation.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
 
#include "qthread.h"
#include "qthreadstorage.h"
#include "qmutex.h"
#include "qreadwritelock.h"
#include "qabstracteventdispatcher.h"
#include "qbindingstorage.h"
 
#include <qeventloop.h>
 
#include "qthread_p.h"
#include "private/qcoreapplication_p.h"
 
#include <limits>
 
QT_BEGIN_NAMESPACE
 
/*
    QPostEventList
*/
 
void QPostEventList::addEvent(const QPostEvent &ev)
{
    int priority = ev.priority;
    if (isEmpty() ||
            constLast().priority >= priority ||
            insertionOffset >= size()) {
        // optimization: we can simply append if the last event in
        // the queue has higher or equal priority
        append(ev);
    } else {
        // insert event in descending priority order, using upper
        // bound for a given priority (to ensure proper ordering
        // of events with the same priority)
        QPostEventList::iterator at = std::upper_bound(begin() + insertionOffset, end(), ev);
        insert(at, ev);
    }
}
 
 
/*
  QThreadData
*/
 
QThreadData::QThreadData(int initialRefCount)
    : _ref(initialRefCount), loopLevel(0), scopeLevel(0),
      eventDispatcher(nullptr),
      quitNow(false), canWait(true), isAdopted(false), requiresCoreApplication(true)
{
    // fprintf(stderr, "QThreadData %p created\n", this);
}
 
QThreadData::~QThreadData()
{
#if QT_CONFIG(thread)
    Q_ASSERT(_ref.loadRelaxed() == 0);
#endif
 
    // In the odd case that Qt is running on a secondary thread, the main
    // thread instance will have been dereffed asunder because of the deref in
    // QThreadData::current() and the deref in the pthread_destroy. To avoid
    // crashing during QCoreApplicationData's global static cleanup we need to
    // safeguard the main thread here.. This fix is a bit crude, but it solves
    // the problem...
    if (this->thread.loadAcquire() == QCoreApplicationPrivate::theMainThread.loadAcquire()) {
       QCoreApplicationPrivate::theMainThread.storeRelease(nullptr);
       QThreadData::clearCurrentThreadData();
    }
 
    // ~QThread() sets thread to nullptr, so if it isn't null here, it's
    // because we're being run before the main object itself. This can only
    // happen for QAdoptedThread. Note that both ~QThreadPrivate() and
    // ~QObjectPrivate() will deref this object again, but that is acceptable
    // because this destructor is still running (the _ref sub-object has not
    // been destroyed) and there's no reentrancy. The refcount will become
    // negative, but that's acceptable.
    QThread *t = thread.loadAcquire();
    thread.storeRelease(nullptr);
    delete t;
 
    for (int i = 0; i < postEventList.size(); ++i) {
        const QPostEvent &pe = postEventList.at(i);
        if (pe.event) {
            --pe.receiver->d_func()->postedEvents;
            pe.event->m_posted = false;
            delete pe.event;
        }
    }
 
    // fprintf(stderr, "QThreadData %p destroyed\n", this);
}
 
void QThreadData::ref()
{
#if QT_CONFIG(thread)
    (void) _ref.ref();
    Q_ASSERT(_ref.loadRelaxed() != 0);
#endif
}
 
void QThreadData::deref()
{
#if QT_CONFIG(thread)
    if (!_ref.deref())
        delete this;
#endif
}
 
QAbstractEventDispatcher *QThreadData::createEventDispatcher()
{
    QAbstractEventDispatcher *ed = QThreadPrivate::createEventDispatcher(this);
    eventDispatcher.storeRelease(ed);
    return ed;
}
 
/*
  QAdoptedThread
*/
 
QAdoptedThread::QAdoptedThread(QThreadData *data)
    : QThread(*new QThreadPrivate(data))
{
    // thread should be running and not finished for the lifetime
    // of the application (even if QCoreApplication goes away)
#if QT_CONFIG(thread)
    d_func()->running = true;
    d_func()->finished = false;
    init();
    d_func()->m_statusOrPendingObjects.setStatusAndClearList(
                QtPrivate::getBindingStatus({}));
#endif
    // fprintf(stderr, "new QAdoptedThread = %p\n", this);
}
 
QAdoptedThread::~QAdoptedThread()
{
    // fprintf(stderr, "~QAdoptedThread = %p\n", this);
}
 
#if QT_CONFIG(thread)
void QAdoptedThread::run()
{
    // this function should never be called
    qFatal("QAdoptedThread::run(): Internal error, this implementation should never be called.");
}
 
/*
  QThreadPrivate
*/
 
QThreadPrivate::QThreadPrivate(QThreadData *d)
    : QObjectPrivate(), running(false), finished(false),
      isInFinish(false), interruptionRequested(false),
      exited(false), returnCode(-1),
      stackSize(0), priority(QThread::InheritPriority), data(d)
{
 
// INTEGRITY doesn't support self-extending stack. The default stack size for
// a pthread on INTEGRITY is too small so we have to increase the default size
// to 128K.
#ifdef Q_OS_INTEGRITY
    stackSize = 128 * 1024;
#elif defined(Q_OS_RTEMS)
    Q_CONSTINIT static bool envStackSizeOk = false;
    static const int envStackSize = qEnvironmentVariableIntValue("QT_DEFAULT_THREAD_STACK_SIZE", &envStackSizeOk);
    if (envStackSizeOk)
        stackSize = envStackSize;
#endif
 
#if defined (Q_OS_WIN)
    handle = 0;
    id = 0;
    waiters = 0;
    terminationEnabled = true;
    terminatePending = false;
#endif
 
    if (!data)
        data = new QThreadData;
}
 
QThreadPrivate::~QThreadPrivate()
{
    // access to m_statusOrPendingObjects cannot race with anything
    // unless there is already a potential use-after-free bug, as the
    // thread is in the process of being destroyed
    delete m_statusOrPendingObjects.list();
    data->deref();
}
 
QThread *QThread::currentThread()
{
    QThreadData *data = QThreadData::current();
    Q_ASSERT(data != nullptr);
    return data->thread.loadAcquire();
}
 
QThread::QThread(QObject *parent)
    : QObject(*(new QThreadPrivate), parent)
{
    Q_D(QThread);
    // fprintf(stderr, "QThreadData %p created for thread %p\n", d->data, this);
    d->data->thread.storeRelaxed(this);
}
 
QThread::QThread(QThreadPrivate &dd, QObject *parent)
    : QObject(dd, parent)
{
    Q_D(QThread);
    // fprintf(stderr, "QThreadData %p taken from private data for thread %p\n", d->data, this);
    d->data->thread.storeRelaxed(this);
}
 
QThread::~QThread()
{
    Q_D(QThread);
    {
        QMutexLocker locker(&d->mutex);
        if (d->isInFinish) {
            locker.unlock();
            wait();
            locker.relock();
        }
        if (d->running && !d->finished && !d->data->isAdopted)
            qFatal("QThread: Destroyed while thread is still running");
 
        d->data->thread.storeRelease(nullptr);
    }
}
 
bool QThread::isFinished() const
{
    Q_D(const QThread);
    QMutexLocker locker(&d->mutex);
    return d->finished || d->isInFinish;
}
 
bool QThread::isRunning() const
{
    Q_D(const QThread);
    QMutexLocker locker(&d->mutex);
    return d->running && !d->isInFinish;
}
 
void QThread::setStackSize(uint stackSize)
{
    Q_D(QThread);
    QMutexLocker locker(&d->mutex);
    Q_ASSERT_X(!d->running, "QThread::setStackSize",
               "cannot change stack size while the thread is running");
    d->stackSize = stackSize;
}
 
uint QThread::stackSize() const
{
    Q_D(const QThread);
    QMutexLocker locker(&d->mutex);
    return d->stackSize;
}
 
void QtPrivate::BindingStatusOrList::setStatusAndClearList(QBindingStatus *status) noexcept
{
 
    if (auto pendingObjects = list()) {
        for (auto obj: *pendingObjects)
            QObjectPrivate::get(obj)->reinitBindingStorageAfterThreadMove();
        delete pendingObjects;
    }
    // synchronizes-with the load-acquire in bindingStatus():
    data.store(encodeBindingStatus(status), std::memory_order_release);
}
 
int QThread::exec()
{
    Q_D(QThread);
    const auto status = QtPrivate::getBindingStatus(QtPrivate::QBindingStatusAccessToken{});
 
    QMutexLocker locker(&d->mutex);
    d->m_statusOrPendingObjects.setStatusAndClearList(status);
    d->data->quitNow = false;
    if (d->exited) {
        d->exited = false;
        return d->returnCode;
    }
    locker.unlock();
 
    QEventLoop eventLoop;
    int returnCode = eventLoop.exec();
 
    locker.relock();
    d->exited = false;
    d->returnCode = -1;
    return returnCode;
}
 
 
QBindingStatus *QtPrivate::BindingStatusOrList::addObjectUnlessAlreadyStatus(QObject *object)
{
    if (auto status = bindingStatus())
        return status;
    List *objectList = list();
    if (!objectList) {
        objectList = new List();
        objectList->reserve(8);
        data.store(encodeList(objectList), std::memory_order_relaxed);
    }
    objectList->push_back(object);
    return nullptr;
}
 
void QtPrivate::BindingStatusOrList::removeObject(QObject *object)
{
    List *objectList = list();
    if (!objectList)
        return;
    auto it = std::remove(objectList->begin(), objectList->end(), object);
    objectList->erase(it, objectList->end());
}
 
QBindingStatus *QThreadPrivate::addObjectWithPendingBindingStatusChange(QObject *obj)
{
    if (auto status = m_statusOrPendingObjects.bindingStatus())
        return status;
    QMutexLocker lock(&mutex);
    return m_statusOrPendingObjects.addObjectUnlessAlreadyStatus(obj);
}
 
void QThreadPrivate::removeObjectWithPendingBindingStatusChange(QObject *obj)
{
    if (m_statusOrPendingObjects.bindingStatus())
        return;
    QMutexLocker lock(&mutex);
    m_statusOrPendingObjects.removeObject(obj);
}
 
 
void QThread::exit(int returnCode)
{
    Q_D(QThread);
    QMutexLocker locker(&d->mutex);
    d->exited = true;
    d->returnCode = returnCode;
    d->data->quitNow = true;
    for (int i = 0; i < d->data->eventLoops.size(); ++i) {
        QEventLoop *eventLoop = d->data->eventLoops.at(i);
        eventLoop->exit(returnCode);
    }
}
 
void QThread::quit()
{ exit(); }
 
void QThread::run()
{
    (void) exec();
}
 
void QThread::setPriority(Priority priority)
{
    if (priority == QThread::InheritPriority) {
        qWarning("QThread::setPriority: Argument cannot be InheritPriority");
        return;
    }
    Q_D(QThread);
    QMutexLocker locker(&d->mutex);
    if (!d->running) {
        qWarning("QThread::setPriority: Cannot set priority, thread is not running");
        return;
    }
    d->setPriority(priority);
}
 
QThread::Priority QThread::priority() const
{
    Q_D(const QThread);
    QMutexLocker locker(&d->mutex);
 
    // mask off the high bits that are used for flags
    return Priority(d->priority & 0xffff);
}
 
int QThread::loopLevel() const
{
    Q_D(const QThread);
    return d->data->eventLoops.size();
}
 
#else // QT_CONFIG(thread)
 
QThread::QThread(QObject *parent)
    : QObject(*(new QThreadPrivate), parent)
{
    Q_D(QThread);
    d->data->thread.storeRelaxed(this);
}
 
QThread::~QThread()
{
 
}
 
void QThread::run()
{
 
}
 
int QThread::exec()
{
    return 0;
}
 
void QThread::start(Priority priority)
{
    Q_D(QThread);
    Q_UNUSED(priority);
    d->running = true;
}
 
void QThread::terminate()
{
 
}
 
void QThread::quit()
{
 
}
 
void QThread::exit(int returnCode)
{
    Q_D(QThread);
    d->data->quitNow = true;
    for (int i = 0; i < d->data->eventLoops.size(); ++i) {
        QEventLoop *eventLoop = d->data->eventLoops.at(i);
        eventLoop->exit(returnCode);
    }
}
 
bool QThread::wait(QDeadlineTimer deadline)
{
    Q_UNUSED(deadline);
    return false;
}
 
bool QThread::event(QEvent *event)
{
    return QObject::event(event);
}
 
Qt::HANDLE QThread::currentThreadIdImpl() noexcept
{
    return Qt::HANDLE(currentThread());
}
 
QThread *QThread::currentThread()
{
    return QThreadData::current()->thread.loadAcquire();
}
 
int QThread::idealThreadCount() noexcept
{
    return 1;
}
 
void QThread::yieldCurrentThread()
{
 
}
 
bool QThread::isFinished() const
{
    return false;
}
 
bool QThread::isRunning() const
{
    Q_D(const QThread);
    return d->running;
}
 
void QThread::requestInterruption()
{
 
}
 
bool QThread::isInterruptionRequested() const
{
    return false;
}
 
// No threads: so we can just use static variables
Q_CONSTINIT static QThreadData *data = nullptr;
 
QThreadData *QThreadData::current(bool createIfNecessary)
{
    if (!data && createIfNecessary) {
        data = new QThreadData;
        data->thread = new QAdoptedThread(data);
        data->threadId.storeRelaxed(Qt::HANDLE(data->thread.loadAcquire()));
        data->deref();
        data->isAdopted = true;
        if (!QCoreApplicationPrivate::theMainThread.loadAcquire())
            QCoreApplicationPrivate::theMainThread.storeRelease(data->thread.loadRelaxed());
    }
    return data;
}
 
void QThreadData::clearCurrentThreadData()
{
    delete data;
    data = 0;
}
 
QThread::QThread(QThreadPrivate &dd, QObject *parent)
    : QObject(dd, parent)
{
    Q_D(QThread);
    // fprintf(stderr, "QThreadData %p taken from private data for thread %p\n", d->data, this);
    d->data->thread.storeRelaxed(this);
}
 
QThreadPrivate::QThreadPrivate(QThreadData *d) : data(d ? d : new QThreadData)
{
}
 
QThreadPrivate::~QThreadPrivate()
{
    data->thread.storeRelease(nullptr); // prevent QThreadData from deleting the QThreadPrivate (again).
    delete data;
}
 
void QThread::setStackSize(uint stackSize)
{
    Q_UNUSED(stackSize);
}
 
uint QThread::stackSize() const
{
    return 0;
}
 
#endif // QT_CONFIG(thread)
 
QAbstractEventDispatcher *QThread::eventDispatcher() const
{
    Q_D(const QThread);
    return d->data->eventDispatcher.loadRelaxed();
}
 
void QThread::setEventDispatcher(QAbstractEventDispatcher *eventDispatcher)
{
    Q_D(QThread);
    if (d->data->hasEventDispatcher()) {
        qWarning("QThread::setEventDispatcher: An event dispatcher has already been created for this thread");
    } else {
        eventDispatcher->moveToThread(this);
        if (eventDispatcher->thread() == this) // was the move successful?
            d->data->eventDispatcher = eventDispatcher;
        else
            qWarning("QThread::setEventDispatcher: Could not move event dispatcher to target thread");
    }
}
 
#if QT_CONFIG(thread)
 
bool QThread::event(QEvent *event)
{
    if (event->type() == QEvent::Quit) {
        quit();
        return true;
    } else {
        return QObject::event(event);
    }
}
 
void QThread::requestInterruption()
{
    if (this == QCoreApplicationPrivate::theMainThread.loadAcquire()) {
        qWarning("QThread::requestInterruption has no effect on the main thread");
        return;
    }
    Q_D(QThread);
    QMutexLocker locker(&d->mutex);
    if (!d->running || d->finished || d->isInFinish)
        return;
    d->interruptionRequested.store(true, std::memory_order_relaxed);
}
 
bool QThread::isInterruptionRequested() const
{
    Q_D(const QThread);
    // fast path: check that the flag is not set:
    if (!d->interruptionRequested.load(std::memory_order_relaxed))
        return false;
    // slow path: if the flag is set, take into account run status:
    QMutexLocker locker(&d->mutex);
    return d->running && !d->finished && !d->isInFinish;
}
 
#if QT_CONFIG(cxx11_future)
class QThreadCreateThread : public QThread
{
public:
    explicit QThreadCreateThread(std::future<void> &&future)
        : m_future(std::move(future))
    {
    }
 
    ~QThreadCreateThread()
    {
        requestInterruption();
        quit();
        wait();
    }
 
private:
    void run() override
    {
        m_future.get();
    }
 
    std::future<void> m_future;
};
 
QThread *QThread::createThreadImpl(std::future<void> &&future)
{
    return new QThreadCreateThread(std::move(future));
}
#endif // QT_CONFIG(cxx11_future)
 
QDaemonThread::QDaemonThread(QObject *parent)
    : QThread(parent)
{
    // QThread::started() is emitted from the thread we start
    connect(this, &QThread::started,
            this,
            [](){ QThreadData::current()->requiresCoreApplication = false; },
            Qt::DirectConnection);
}
 
QDaemonThread::~QDaemonThread()
{
}
 
#endif // QT_CONFIG(thread)
 
QT_END_NAMESPACE
 
#include "moc_qthread.cpp"