diff options
Diffstat (limited to 'src/corelib/thread/qmutex.cpp')
| -rw-r--r-- | src/corelib/thread/qmutex.cpp | 100 |
1 files changed, 89 insertions, 11 deletions
diff --git a/src/corelib/thread/qmutex.cpp b/src/corelib/thread/qmutex.cpp index bd3a0fa7ba..9e52f286ee 100644 --- a/src/corelib/thread/qmutex.cpp +++ b/src/corelib/thread/qmutex.cpp @@ -147,7 +147,7 @@ public: It is constructed and destroyed with almost no overhead, which means it is fine to have many mutexes as part of other classes. - \sa QMutexLocker, QReadWriteLock, QSemaphore, QWaitCondition + \sa QRecursiveMutex, QMutexLocker, QReadWriteLock, QSemaphore, QWaitCondition */ /*! @@ -156,12 +156,19 @@ public: \value Recursive In this mode, a thread can lock the same mutex multiple times and the mutex won't be unlocked until a corresponding number of unlock() calls - have been made. + have been made. You should use QRecursiveMutex + for this use-case. \value NonRecursive In this mode, a thread may only lock a mutex once. - \sa QMutex() + \sa QMutex(), QRecursiveMutex +*/ + +/*! + \fn QMutex::QMutex() + + Constructs a new mutex. The mutex is created in an unlocked state. */ /*! @@ -205,13 +212,15 @@ QMutex::~QMutex() } /*! \fn void QMutex::lock() + \fn QRecursiveMutex::lock() + Locks the mutex. If another thread has locked the mutex then this call will block until that thread has unlocked it. Calling this function multiple times on the same mutex from the same thread is allowed if this mutex is a - \l{QMutex::Recursive}{recursive mutex}. If this mutex is a - \l{QMutex::NonRecursive}{non-recursive mutex}, this function will + \l{QRecursiveMutex}{recursive mutex}. If this mutex is a + \l{QMutex}{non-recursive mutex}, this function will \e dead-lock when the mutex is locked recursively. \sa unlock() @@ -228,6 +237,7 @@ void QMutex::lock() QT_MUTEX_LOCK_NOEXCEPT } /*! \fn bool QMutex::tryLock(int timeout) + \fn bool QRecursiveMutex::tryLock(int timeout) Attempts to lock the mutex. This function returns \c true if the lock was obtained; otherwise it returns \c false. If another thread has @@ -243,8 +253,8 @@ void QMutex::lock() QT_MUTEX_LOCK_NOEXCEPT Calling this function multiple times on the same mutex from the same thread is allowed if this mutex is a - \l{QMutex::Recursive}{recursive mutex}. If this mutex is a - \l{QMutex::NonRecursive}{non-recursive mutex}, this function will + \l{QRecursiveMutex}{recursive mutex}. If this mutex is a + \l{QMutex}{non-recursive mutex}, this function will \e always return false when attempting to lock the mutex recursively. @@ -262,6 +272,7 @@ bool QMutex::tryLock(int timeout) QT_MUTEX_LOCK_NOEXCEPT } /*! \fn bool QMutex::try_lock() + \fn bool QRecursiveMutex::try_lock() \since 5.8 Attempts to lock the mutex. This function returns \c true if the lock @@ -275,6 +286,7 @@ bool QMutex::tryLock(int timeout) QT_MUTEX_LOCK_NOEXCEPT */ /*! \fn template <class Rep, class Period> bool QMutex::try_lock_for(std::chrono::duration<Rep, Period> duration) + \fn template <class Rep, class Period> bool QRecursiveMutex::try_lock_for(std::chrono::duration<Rep, Period> duration) \since 5.8 Attempts to lock the mutex. This function returns \c true if the lock @@ -290,8 +302,8 @@ bool QMutex::tryLock(int timeout) QT_MUTEX_LOCK_NOEXCEPT Calling this function multiple times on the same mutex from the same thread is allowed if this mutex is a - \l{QMutex::Recursive}{recursive mutex}. If this mutex is a - \l{QMutex::NonRecursive}{non-recursive mutex}, this function will + \l{QRecursiveMutex}{recursive mutex}. If this mutex is a + \l{QMutex}{non-recursive mutex}, this function will \e always return false when attempting to lock the mutex recursively. @@ -299,6 +311,7 @@ bool QMutex::tryLock(int timeout) QT_MUTEX_LOCK_NOEXCEPT */ /*! \fn template<class Clock, class Duration> bool QMutex::try_lock_until(std::chrono::time_point<Clock, Duration> timePoint) + \fn template<class Clock, class Duration> bool QRecursiveMutex::try_lock_until(std::chrono::time_point<Clock, Duration> timePoint) \since 5.8 Attempts to lock the mutex. This function returns \c true if the lock @@ -314,8 +327,8 @@ bool QMutex::tryLock(int timeout) QT_MUTEX_LOCK_NOEXCEPT Calling this function multiple times on the same mutex from the same thread is allowed if this mutex is a - \l{QMutex::Recursive}{recursive mutex}. If this mutex is a - \l{QMutex::NonRecursive}{non-recursive mutex}, this function will + \l{QRecursiveMutex}{recursive mutex}. If this mutex is a + \l{QMutex}{non-recursive mutex}, this function will \e always return false when attempting to lock the mutex recursively. @@ -323,6 +336,8 @@ bool QMutex::tryLock(int timeout) QT_MUTEX_LOCK_NOEXCEPT */ /*! \fn void QMutex::unlock() + \fn void QRecursiveMutex::unlock() + Unlocks the mutex. Attempting to unlock a mutex in a different thread to the one that locked it results in an error. Unlocking a mutex that is not locked results in undefined behavior. @@ -364,6 +379,58 @@ bool QBasicMutex::isRecursive() const noexcept } /*! + \class QRecursiveMutex + \inmodule QtCore + \since 5.14 + \brief The QRecursiveMutex class provides access serialization between threads. + + \threadsafe + + \ingroup thread + + The QRecursiveMutex class is a mutex, like QMutex, with which it is + API-compatible. It differs from QMutex by accepting lock() calls from + the same thread any number of times. QMutex would deadlock in this situation. + + QRecursiveMutex is much more expensive to construct and operate on, so + use a plain QMutex whenever you can. Sometimes, one public function, + however, calls another public function, and they both need to lock the + same mutex. In this case, you have two options: + + \list + \li Factor the code that needs mutex protection into private functions, + which assume that the mutex is held when they are called, and lock a + plain QMutex in the public functions before you call the private + implementation ones. + \li Or use a recursive mutex, so it doesn't matter that the first public + function has already locked the mutex when the second one wishes to do so. + \endlist + + \sa QMutex, QMutexLocker, QReadWriteLock, QSemaphore, QWaitCondition +*/ + +/*! + Constructs a new recursive mutex. The mutex is created in an unlocked state. + + \sa lock(), unlock() +*/ +QRecursiveMutex::QRecursiveMutex() + : QMutex() +{ + d_ptr.storeRelaxed(new QRecursiveMutexPrivate); +} + +/*! + Destroys the mutex. + + \warning Destroying a locked mutex may result in undefined behavior. +*/ +QRecursiveMutex::~QRecursiveMutex() +{ + delete static_cast<QRecursiveMutexPrivate*>(d_ptr.fetchAndStoreAcquire(nullptr)); +} + +/*! \class QMutexLocker \inmodule QtCore \brief The QMutexLocker class is a convenience class that simplifies @@ -427,6 +494,17 @@ bool QBasicMutex::isRecursive() const noexcept */ /*! + \fn QMutexLocker::QMutexLocker(QRecursiveMutex *mutex) + \since 5.14 + + Constructs a QMutexLocker and locks \a mutex. The mutex will be + unlocked (unlock() called) when the QMutexLocker is destroyed. + If \a mutex is \nullptr, QMutexLocker does nothing. + + \sa QMutex::lock() +*/ + +/*! \fn QMutexLocker::~QMutexLocker() Destroys the QMutexLocker and unlocks the mutex that was locked |