When to use QMutexLocker?
QMutexLocker should be used in such situations to ensure that the state of the mutex is well defined and always locked and unlocked properly. QMutexLocker should be created within a function where a QMutex needs to be locked. The mutex is locked when QMutexLocker is created, and unlocked when QMutexLocker is destroyed.
Q. What does QMutex do?
The purpose of a QMutex is to protect an object, data structure or section of code so that only one thread can access it at a time (this is similar to the Java synchronized keyword).
Q. Is mutex locked?
A mutex is a lock. Only one state (locked/unlocked) is associated with it. However, a recursive mutex can be locked more than once (POSIX compliant systems), in which a count is associated with it, yet retains only one state (locked/unlocked). The programmer must unlock the mutex as many number times as it was locked.
Q. What is a mutex in CPP?
The mutex class is a synchronization primitive that can be used to protect shared data from being simultaneously accessed by multiple threads. A calling thread owns a mutex from the time that it successfully calls either lock or try_lock until it calls unlock .
Q. When to use qmutexlocker in a function?
Locking and unlocking a QMutex in complex functions and statements or in exception handling code is error-prone and difficult to debug. QMutexLocker can be used in such situations to ensure that the state of the mutex is always well-defined. QMutexLocker should be created within a function where a QMutex needs to be locked.
Q. Can you call qmutex multiple times on the same mutex?
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 recursive mutex. If this mutex is a non-recursive mutex, this function will dead-lock when the mutex is locked recursively.
Q. When is the mutex unlocked in Qt core?
Using QMutexLocker greatly simplifies the code, and makes it more readable: Now, the mutex will always be unlocked when the QMutexLocker object is destroyed (when the function returns since locker is an auto variable). The same principle applies to code that throws and catches exceptions.
Q. Which is the default mode for qmutex non recursive?
If mode is QMutex::Recursive, 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. Otherwise a thread may only lock a mutex once. The default is QMutex::NonRecursive. Recursive mutexes are slower and take more memory than non-recursive ones.
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