| /**************************************************************************** |
| ** |
| ** Copyright (C) 2016 The Qt Company Ltd. |
| ** 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 |
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| ** packaging of this file. Please review the following information to |
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| ** GNU General Public License Usage |
| ** Alternatively, this file may be used under the terms of the GNU |
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| ** Public license version 3 or any later version approved by the KDE Free |
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| ** $QT_END_LICENSE$ |
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| ****************************************************************************/ |
| |
| #include "qthreadstorage.h" |
| |
| #include "qthread.h" |
| #include "qthread_p.h" |
| #include "qmutex.h" |
| |
| #include <string.h> |
| |
| QT_BEGIN_NAMESPACE |
| |
| // #define THREADSTORAGE_DEBUG |
| #ifdef THREADSTORAGE_DEBUG |
| # define DEBUG_MSG qtsDebug |
| |
| # include <stdio.h> |
| # include <stdarg.h> |
| void qtsDebug(const char *fmt, ...) |
| { |
| va_list va; |
| va_start(va, fmt); |
| |
| fprintf(stderr, "QThreadStorage: "); |
| vfprintf(stderr, fmt, va); |
| fprintf(stderr, "\n"); |
| |
| va_end(va); |
| } |
| #else |
| # define DEBUG_MSG if(false)qDebug |
| #endif |
| |
| static QBasicMutex destructorsMutex; |
| typedef QVector<void (*)(void *)> DestructorMap; |
| Q_GLOBAL_STATIC(DestructorMap, destructors) |
| |
| QThreadStorageData::QThreadStorageData(void (*func)(void *)) |
| { |
| QMutexLocker locker(&destructorsMutex); |
| DestructorMap *destr = destructors(); |
| if (!destr) { |
| /* |
| the destructors vector has already been destroyed, yet a new |
| QThreadStorage is being allocated. this can only happen during global |
| destruction, at which point we assume that there is only one thread. |
| in order to keep QThreadStorage working, we need somewhere to store |
| the data, best place we have in this situation is at the tail of the |
| current thread's tls vector. the destructor is ignored, since we have |
| no where to store it, and no way to actually call it. |
| */ |
| QThreadData *data = QThreadData::current(); |
| id = data->tls.count(); |
| DEBUG_MSG("QThreadStorageData: Allocated id %d, destructor %p cannot be stored", id, func); |
| return; |
| } |
| for (id = 0; id < destr->count(); id++) { |
| if (destr->at(id) == 0) |
| break; |
| } |
| if (id == destr->count()) { |
| destr->append(func); |
| } else { |
| (*destr)[id] = func; |
| } |
| DEBUG_MSG("QThreadStorageData: Allocated id %d, destructor %p", id, func); |
| } |
| |
| QThreadStorageData::~QThreadStorageData() |
| { |
| DEBUG_MSG("QThreadStorageData: Released id %d", id); |
| QMutexLocker locker(&destructorsMutex); |
| if (destructors()) |
| (*destructors())[id] = 0; |
| } |
| |
| void **QThreadStorageData::get() const |
| { |
| QThreadData *data = QThreadData::current(); |
| if (!data) { |
| qWarning("QThreadStorage::get: QThreadStorage can only be used with threads started with QThread"); |
| return 0; |
| } |
| QVector<void *> &tls = data->tls; |
| if (tls.size() <= id) |
| tls.resize(id + 1); |
| void **v = &tls[id]; |
| |
| DEBUG_MSG("QThreadStorageData: Returning storage %d, data %p, for thread %p", |
| id, |
| *v, |
| data->thread.loadRelaxed()); |
| |
| return *v ? v : 0; |
| } |
| |
| void **QThreadStorageData::set(void *p) |
| { |
| QThreadData *data = QThreadData::current(); |
| if (!data) { |
| qWarning("QThreadStorage::set: QThreadStorage can only be used with threads started with QThread"); |
| return 0; |
| } |
| QVector<void *> &tls = data->tls; |
| if (tls.size() <= id) |
| tls.resize(id + 1); |
| |
| void *&value = tls[id]; |
| // delete any previous data |
| if (value != 0) { |
| DEBUG_MSG("QThreadStorageData: Deleting previous storage %d, data %p, for thread %p", |
| id, |
| value, |
| data->thread.loadRelaxed()); |
| |
| QMutexLocker locker(&destructorsMutex); |
| DestructorMap *destr = destructors(); |
| void (*destructor)(void *) = destr ? destr->value(id) : 0; |
| locker.unlock(); |
| |
| void *q = value; |
| value = 0; |
| |
| if (destructor) |
| destructor(q); |
| } |
| |
| // store new data |
| value = p; |
| DEBUG_MSG("QThreadStorageData: Set storage %d for thread %p to %p", id, data->thread.loadRelaxed(), p); |
| return &value; |
| } |
| |
| void QThreadStorageData::finish(void **p) |
| { |
| QVector<void *> *tls = reinterpret_cast<QVector<void *> *>(p); |
| if (!tls || tls->isEmpty() || !destructors()) |
| return; // nothing to do |
| |
| DEBUG_MSG("QThreadStorageData: Destroying storage for thread %p", QThread::currentThread()); |
| while (!tls->isEmpty()) { |
| void *&value = tls->last(); |
| void *q = value; |
| value = 0; |
| int i = tls->size() - 1; |
| tls->resize(i); |
| |
| if (!q) { |
| // data already deleted |
| continue; |
| } |
| |
| QMutexLocker locker(&destructorsMutex); |
| void (*destructor)(void *) = destructors()->value(i); |
| locker.unlock(); |
| |
| if (!destructor) { |
| if (QThread::currentThread()) |
| qWarning("QThreadStorage: Thread %p exited after QThreadStorage %d destroyed", |
| QThread::currentThread(), i); |
| continue; |
| } |
| destructor(q); //crash here might mean the thread exited after qthreadstorage was destroyed |
| |
| if (tls->size() > i) { |
| //re reset the tls in case it has been recreated by its own destructor. |
| (*tls)[i] = 0; |
| } |
| } |
| tls->clear(); |
| } |
| |
| /*! |
| \class QThreadStorage |
| \inmodule QtCore |
| \brief The QThreadStorage class provides per-thread data storage. |
| |
| \threadsafe |
| |
| \ingroup thread |
| |
| QThreadStorage is a template class that provides per-thread data |
| storage. |
| |
| The setLocalData() function stores a single thread-specific value |
| for the calling thread. The data can be accessed later using |
| localData(). |
| |
| The hasLocalData() function allows the programmer to determine if |
| data has previously been set using the setLocalData() function. |
| This is also useful for lazy initializiation. |
| |
| If T is a pointer type, QThreadStorage takes ownership of the data |
| (which must be created on the heap with \c new) and deletes it when |
| the thread exits, either normally or via termination. |
| |
| For example, the following code uses QThreadStorage to store a |
| single cache for each thread that calls the cacheObject() and |
| removeFromCache() functions. The cache is automatically |
| deleted when the calling thread exits. |
| |
| \snippet threads/threads.cpp 7 |
| \snippet threads/threads.cpp 8 |
| \snippet threads/threads.cpp 9 |
| |
| \section1 Caveats |
| |
| \list |
| |
| \li The QThreadStorage destructor does not delete per-thread data. |
| QThreadStorage only deletes per-thread data when the thread exits |
| or when setLocalData() is called multiple times. |
| |
| \li QThreadStorage can be used to store data for the \c main() |
| thread. QThreadStorage deletes all data set for the \c main() |
| thread when QApplication is destroyed, regardless of whether or |
| not the \c main() thread has actually finished. |
| |
| \endlist |
| |
| \sa QThread |
| */ |
| |
| /*! |
| \fn template <class T> QThreadStorage<T>::QThreadStorage() |
| |
| Constructs a new per-thread data storage object. |
| */ |
| |
| /*! |
| \fn template <class T> QThreadStorage<T>::~QThreadStorage() |
| |
| Destroys the per-thread data storage object. |
| |
| Note: The per-thread data stored is not deleted. Any data left |
| in QThreadStorage is leaked. Make sure that all threads using |
| QThreadStorage have exited before deleting the QThreadStorage. |
| |
| \sa hasLocalData() |
| */ |
| |
| /*! |
| \fn template <class T> bool QThreadStorage<T>::hasLocalData() const |
| |
| If T is a pointer type, returns \c true if the calling thread has |
| non-zero data available. |
| |
| If T is a value type, returns whether the data has already been |
| constructed by calling setLocalData or localData. |
| |
| \sa localData() |
| */ |
| |
| /*! |
| \fn template <class T> T &QThreadStorage<T>::localData() |
| |
| Returns a reference to the data that was set by the calling |
| thread. |
| |
| If no data has been set, this will create a default constructed |
| instance of type T. |
| |
| \sa hasLocalData() |
| */ |
| |
| /*! |
| \fn template <class T> const T QThreadStorage<T>::localData() const |
| \overload |
| |
| Returns a copy of the data that was set by the calling thread. |
| |
| \sa hasLocalData() |
| */ |
| |
| /*! |
| \fn template <class T> void QThreadStorage<T>::setLocalData(T data) |
| |
| Sets the local data for the calling thread to \a data. It can be |
| accessed later using the localData() functions. |
| |
| If T is a pointer type, QThreadStorage takes ownership of the data |
| and deletes it automatically either when the thread exits (either |
| normally or via termination) or when setLocalData() is called again. |
| |
| \sa localData(), hasLocalData() |
| */ |
| |
| QT_END_NAMESPACE |