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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 "qthread.h" #include "qthreadstorage.h" #include "qmutex.h" #include "qreadwritelock.h" #include "qabstracteventdispatcher.h" #include #include #include "qthread_p.h" #include "private/qcoreapplication_p.h" QT_BEGIN_NAMESPACE /* QThreadData */ QThreadData::QThreadData(int initialRefCount) : _ref(initialRefCount), loopLevel(0), thread(0), threadId(0), eventDispatcher(0), quitNow(false), canWait(true), isAdopted(false) { // fprintf(stderr, "QThreadData %p created\n", this); } QThreadData::~QThreadData() { Q_ASSERT(_ref.load() == 0); // 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 == QCoreApplicationPrivate::theMainThread) { QCoreApplicationPrivate::theMainThread = 0; QThreadData::clearCurrentThreadData(); } QThread *t = thread; thread = 0; 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->posted = false; delete pe.event; } } // fprintf(stderr, "QThreadData %p destroyed\n", this); } void QThreadData::ref() { #ifndef QT_NO_THREAD (void) _ref.ref(); Q_ASSERT(_ref.load() != 0); #endif } void QThreadData::deref() { #ifndef QT_NO_THREAD if (!_ref.deref()) delete this; #endif } /* 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) #ifndef QT_NO_THREAD d_func()->running = true; d_func()->finished = false; init(); #endif // fprintf(stderr, "new QAdoptedThread = %p\n", this); } QAdoptedThread::~QAdoptedThread() { // fprintf(stderr, "~QAdoptedThread = %p\n", this); } void QAdoptedThread::run() { // this function should never be called qFatal("QAdoptedThread::run(): Internal error, this implementation should never be called."); } #ifndef QT_NO_THREAD /* 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) { #if defined (Q_OS_UNIX) thread_id = 0; #elif defined (Q_OS_WIN) handle = 0; # ifndef Q_OS_WINRT id = 0; # endif waiters = 0; #endif #if defined (Q_OS_WIN) terminationEnabled = true; terminatePending = false; #endif if (!data) data = new QThreadData; } QThreadPrivate::~QThreadPrivate() { data->deref(); } /*! \class QThread \inmodule QtCore \brief The QThread class provides a platform-independent way to manage threads. \ingroup thread A QThread object manages one thread of control within the program. QThreads begin executing in run(). By default, run() starts the event loop by calling exec() and runs a Qt event loop inside the thread. You can use worker objects by moving them to the thread using QObject::moveToThread. \snippet code/src_corelib_thread_qthread.cpp worker The code inside the Worker's slot would then execute in a separate thread. However, you are free to connect the Worker's slots to any signal, from any object, in any thread. It is safe to connect signals and slots across different threads, thanks to a mechanism called \l{Qt::QueuedConnection}{queued connections}. Another way to make code run in a separate thread, is to subclass QThread and reimplement run(). For example: \snippet code/src_corelib_thread_qthread.cpp reimpl-run In that example, the thread will exit after the run function has returned. There will not be any event loop running in the thread unless you call exec(). It is important to remember that a QThread instance \l{QObject#Thread Affinity}{lives in} the old thread that instantiated it, not in the new thread that calls run(). This means that all of QThread's queued slots will execute in the old thread. Thus, a developer who wishes to invoke slots in the new thread must use the worker-object approach; new slots should not be implemented directly into a subclassed QThread. When subclassing QThread, keep in mind that the constructor executes in the old thread while run() executes in the new thread. If a member variable is accessed from both functions, then the variable is accessed from two different threads. Check that it is safe to do so. \note Care must be taken when interacting with objects across different threads. See \l{Synchronizing Threads} for details. \section1 Managing threads QThread will notifiy you via a signal when the thread is started() and finished(), or you can use isFinished() and isRunning() to query the state of the thread. You can stop the thread by calling exit() or quit(). In extreme cases, you may want to forcibly terminate() an executing thread. However, doing so is dangerous and discouraged. Please read the documentation for terminate() and setTerminationEnabled() for detailed information. From Qt 4.8 onwards, it is possible to deallocate objects that live in a thread that has just ended, by connecting the finished() signal to QObject::deleteLater(). Use wait() to block the calling thread, until the other thread has finished execution (or until a specified time has passed). QThread also provides static, platform independent sleep functions: sleep(), msleep(), and usleep() allow full second, millisecond, and microsecond resolution respectively. These functions were made public in Qt 5.0. \note wait() and the sleep() functions should be unnecessary in general, since Qt is an event-driven framework. Instead of wait(), consider listening for the finished() signal. Instead of the sleep() functions, consider using QTimer. The static functions currentThreadId() and currentThread() return identifiers for the currently executing thread. The former returns a platform specific ID for the thread; the latter returns a QThread pointer. To choose the name that your thread will be given (as identified by the command \c{ps -L} on Linux, for example), you can call \l{QObject::setObjectName()}{setObjectName()} before starting the thread. If you don't call \l{QObject::setObjectName()}{setObjectName()}, the name given to your thread will be the class name of the runtime type of your thread object (for example, \c "RenderThread" in the case of the \l{Mandelbrot Example}, as that is the name of the QThread subclass). Note that this is currently not available with release builds on Windows. \sa {Thread Support in Qt}, QThreadStorage, {Synchronizing Threads} {Mandelbrot Example}, {Semaphores Example}, {Wait Conditions Example} */ /*! \fn Qt::HANDLE QThread::currentThreadId() Returns the thread handle of the currently executing thread. \warning The handle returned by this function is used for internal purposes and should not be used in any application code. \warning On Windows, the returned value is a pseudo-handle for the current thread. It can't be used for numerical comparison. i.e., this function returns the DWORD (Windows-Thread ID) returned by the Win32 function getCurrentThreadId(), not the HANDLE (Windows-Thread HANDLE) returned by the Win32 function getCurrentThread(). */ /*! \fn int QThread::idealThreadCount() Returns the ideal number of threads that can be run on the system. This is done querying the number of processor cores, both real and logical, in the system. This function returns -1 if the number of processor cores could not be detected. */ /*! \fn void QThread::yieldCurrentThread() Yields execution of the current thread to another runnable thread, if any. Note that the operating system decides to which thread to switch. */ /*! \fn void QThread::start(Priority priority) Begins execution of the thread by calling run(). The operating system will schedule the thread according to the \a priority parameter. If the thread is already running, this function does nothing. The effect of the \a priority parameter is dependent on the operating system's scheduling policy. In particular, the \a priority will be ignored on systems that do not support thread priorities (such as on Linux, see http://linux.die.net/man/2/sched_setscheduler for more details). \sa run(), terminate() */ /*! \fn void QThread::started() This signal is emitted from the associated thread when it starts executing, before the run() function is called. \sa finished() */ /*! \fn void QThread::finished() This signal is emitted from the associated thread right before it finishes executing. When this signal is emitted, the event loop has already stopped running. No more events will be processed in the thread, except for deferred deletion events. This signal can be connected to QObject::deleteLater(), to free objects in that thread. \note If the associated thread was terminated using terminate(), it is undefined from which thread this signal is emitted. \sa started() */ /*! \enum QThread::Priority This enum type indicates how the operating system should schedule newly created threads. \value IdlePriority scheduled only when no other threads are running. \value LowestPriority scheduled less often than LowPriority. \value LowPriority scheduled less often than NormalPriority. \value NormalPriority the default priority of the operating system. \value HighPriority scheduled more often than NormalPriority. \value HighestPriority scheduled more often than HighPriority. \value TimeCriticalPriority scheduled as often as possible. \value InheritPriority use the same priority as the creating thread. This is the default. */ /*! Returns a pointer to a QThread which manages the currently executing thread. */ QThread *QThread::currentThread() { QThreadData *data = QThreadData::current(); Q_ASSERT(data != 0); return data->thread; } /*! Constructs a new QThread to manage a new thread. The \a parent takes ownership of the QThread. The thread does not begin executing until start() is called. \sa start() */ 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 = this; } /*! \internal */ 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 = this; } /*! Destroys the QThread. Note that deleting a QThread object will not stop the execution of the thread it manages. Deleting a running QThread (i.e. isFinished() returns \c false) will probably result in a program crash. Wait for the finished() signal before deleting the QThread. */ 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) qWarning("QThread: Destroyed while thread is still running"); d->data->thread = 0; } } /*! Returns \c true if the thread is finished; otherwise returns \c false. \sa isRunning() */ bool QThread::isFinished() const { Q_D(const QThread); QMutexLocker locker(&d->mutex); return d->finished || d->isInFinish; } /*! Returns \c true if the thread is running; otherwise returns \c false. \sa isFinished() */ bool QThread::isRunning() const { Q_D(const QThread); QMutexLocker locker(&d->mutex); return d->running && !d->isInFinish; } /*! Sets the maximum stack size for the thread to \a stackSize. If \a stackSize is greater than zero, the maximum stack size is set to \a stackSize bytes, otherwise the maximum stack size is automatically determined by the operating system. \warning Most operating systems place minimum and maximum limits on thread stack sizes. The thread will fail to start if the stack size is outside these limits. \sa stackSize() */ 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; } /*! Returns the maximum stack size for the thread (if set with setStackSize()); otherwise returns zero. \sa setStackSize() */ uint QThread::stackSize() const { Q_D(const QThread); QMutexLocker locker(&d->mutex); return d->stackSize; } /*! Enters the event loop and waits until exit() is called, returning the value that was passed to exit(). The value returned is 0 if exit() is called via quit(). This function is meant to be called from within run(). It is necessary to call this function to start event handling. \sa quit(), exit() */ int QThread::exec() { Q_D(QThread); QMutexLocker locker(&d->mutex); 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; } /*! Tells the thread's event loop to exit with a return code. After calling this function, the thread leaves the event loop and returns from the call to QEventLoop::exec(). The QEventLoop::exec() function returns \a returnCode. By convention, a \a returnCode of 0 means success, any non-zero value indicates an error. Note that unlike the C library function of the same name, this function \e does return to the caller -- it is event processing that stops. No QEventLoops will be started anymore in this thread until QThread::exec() has been called again. If the eventloop in QThread::exec() is not running then the next call to QThread::exec() will also return immediately. \sa quit(), QEventLoop */ 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); } } /*! Tells the thread's event loop to exit with return code 0 (success). Equivalent to calling QThread::exit(0). This function does nothing if the thread does not have an event loop. \sa exit(), QEventLoop */ void QThread::quit() { exit(); } /*! The starting point for the thread. After calling start(), the newly created thread calls this function. The default implementation simply calls exec(). You can reimplement this function to facilitate advanced thread management. Returning from this method will end the execution of the thread. \sa start(), wait() */ void QThread::run() { (void) exec(); } /*! \fn void QThread::setPriority(Priority priority) \since 4.1 This function sets the \a priority for a running thread. If the thread is not running, this function does nothing and returns immediately. Use start() to start a thread with a specific priority. The \a priority argument can be any value in the \c QThread::Priority enum except for \c InheritPriorty. The effect of the \a priority parameter is dependent on the operating system's scheduling policy. In particular, the \a priority will be ignored on systems that do not support thread priorities (such as on Linux, see http://linux.die.net/man/2/sched_setscheduler for more details). \sa Priority, priority(), start() */ void QThread::setPriority(Priority priority) { Q_D(QThread); QMutexLocker locker(&d->mutex); if (!d->running) { qWarning("QThread::setPriority: Cannot set priority, thread is not running"); return; } d->setPriority(priority); } /*! \since 4.1 Returns the priority for a running thread. If the thread is not running, this function returns \c InheritPriority. \sa Priority, setPriority(), start() */ 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); } /*! \fn void QThread::sleep(unsigned long secs) Forces the current thread to sleep for \a secs seconds. \sa msleep(), usleep() */ /*! \fn void QThread::msleep(unsigned long msecs) Forces the current thread to sleep for \a msecs milliseconds. \sa sleep(), usleep() */ /*! \fn void QThread::usleep(unsigned long usecs) Forces the current thread to sleep for \a usecs microseconds. \sa sleep(), msleep() */ /*! \fn void QThread::terminate() Terminates the execution of the thread. The thread may or may not be terminated immediately, depending on the operating system's scheduling policies. Use QThread::wait() after terminate(), to be sure. When the thread is terminated, all threads waiting for the thread to finish will be woken up. \warning This function is dangerous and its use is discouraged. The thread can be terminated at any point in its code path. Threads can be terminated while modifying data. There is no chance for the thread to clean up after itself, unlock any held mutexes, etc. In short, use this function only if absolutely necessary. Termination can be explicitly enabled or disabled by calling QThread::setTerminationEnabled(). Calling this function while termination is disabled results in the termination being deferred, until termination is re-enabled. See the documentation of QThread::setTerminationEnabled() for more information. \sa setTerminationEnabled() */ /*! \fn bool QThread::wait(unsigned long time) Blocks the thread until either of these conditions is met: \list \li The thread associated with this QThread object has finished execution (i.e. when it returns from \l{run()}). This function will return true if the thread has finished. It also returns true if the thread has not been started yet. \li \a time milliseconds has elapsed. If \a time is ULONG_MAX (the default), then the wait will never timeout (the thread must return from \l{run()}). This function will return false if the wait timed out. \endlist This provides similar functionality to the POSIX \c pthread_join() function. \sa sleep(), terminate() */ /*! \fn void QThread::setTerminationEnabled(bool enabled) Enables or disables termination of the current thread based on the \a enabled parameter. The thread must have been started by QThread. When \a enabled is false, termination is disabled. Future calls to QThread::terminate() will return immediately without effect. Instead, the termination is deferred until termination is enabled. When \a enabled is true, termination is enabled. Future calls to QThread::terminate() will terminate the thread normally. If termination has been deferred (i.e. QThread::terminate() was called with termination disabled), this function will terminate the calling thread \e immediately. Note that this function will not return in this case. \sa terminate() */ #else // QT_NO_THREAD QThread::QThread(QObject *parent) : QObject(*(new QThreadPrivate), (QObject*)0){ Q_D(QThread); d->data->thread = this; } QThread *QThread::currentThread() { return QThreadData::current()->thread; } QThreadData* QThreadData::current() { static QThreadData *data = 0; // reinterpret_cast(pthread_getspecific(current_thread_data_key)); if (!data) { QScopedPointer newdata(new QThreadData); newdata->thread = new QAdoptedThread(newdata.data()); data = newdata.take(); data->deref(); } return data; } /*! \internal */ 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 = this; } #endif // QT_NO_THREAD /*! \since 5.0 Returns a pointer to the event dispatcher object for the thread. If no event dispatcher exists for the thread, this function returns 0. */ QAbstractEventDispatcher *QThread::eventDispatcher() const { Q_D(const QThread); return d->data->eventDispatcher.load(); } /*! \since 5.0 Sets the event dispatcher for the thread to \a eventDispatcher. This is only possible as long as there is no event dispatcher installed for the thread yet. That is, before the thread has been started with start() or, in case of the main thread, before QCoreApplication has been instantiated. This method takes ownership of the object. */ 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"); } } /*! \reimp */ bool QThread::event(QEvent *event) { if (event->type() == QEvent::Quit) { quit(); return true; } else { return QObject::event(event); } } /*! \since 5.2 Request the interruption of the thread. That request is advisory and it is up to code running on the thread to decide if and how it should act upon such request. This function does not stop any event loop running on the thread and does not terminate it in any way. \sa isInterruptionRequested() */ void QThread::requestInterruption() { Q_D(QThread); QMutexLocker locker(&d->mutex); if (!d->running || d->finished || d->isInFinish) return; if (this == QCoreApplicationPrivate::theMainThread) { qWarning("QThread::requestInterruption has no effect on the main thread"); return; } d->interruptionRequested = true; } /*! \since 5.2 Return true if the task running on this thread should be stopped. An interruption can be requested by requestInterruption(). This function can be used to make long running tasks cleanly interruptible. Never checking or acting on the value returned by this function is safe, however it is advisable do so regularly in long running functions. Take care not to call it too often, to keep the overhead low. \code void long_task() { forever { if ( QThread::currentThread()->isInterruptionRequested() ) { return; } } } \endcode \sa currentThread() requestInterruption() */ bool QThread::isInterruptionRequested() const { Q_D(const QThread); QMutexLocker locker(&d->mutex); if (!d->running || d->finished || d->isInFinish) return false; return d->interruptionRequested; } QT_END_NAMESPACE