On terça-feira, 19 de março de 2013 10.37.56, Hugo Drumond Jacob wrote: > Hi folks! > > Today some doubt has ocurred on my office. Suppose that for some > reason we need to sleep a thread (not the main thread) for some time
Suppose that you're wrong and you came to the wrong solution that sleeping is the way to go. Try to find a solution that makes you do what you need to do and not sleep. > (eg. 100 ms). The QThread::wait(int) "provides similar functionality > to the POSIX pthread_join()" and this don't will sleep the target > thread, but the caller thread. > > Call the QThread::wait(int) from the target thread is forbidden > (according to line 651 of qthread_unix.cpp). You were looking for QThread::sleep, not wait. The latter is used to wait for a thread to finish, with a given timeout. The former suspends and blocks execution of the calling thread for a given time. > Furthermore, is "wrong" call QThread::wait(int) except for > synchronously thread termination with QThread::terminate() ? ( I know, > isn't so healthy use QThread::terminate() ) QThread::wait(int) is a > busy wait, right? No, it isn't. It's like a pthread_join: it will suspend the execution of the calling thread until the other thread exits or the timeout happens, whichever comes first. QThread::wait() is normal use and is, in fact, used even by the QThread destructor. QThread::sleep() is, more often than not, a bad choice. Avoid it if you can. If you can't, redesign your code so you don't need to use it. > The attached code illustrate the question. Your example has the main thread waiting for 100 ms for the auxiliary thread to exit. But your auxiliary thread is busy-looping doing a qDebug and will never exit. Since it doesn't exit, QThread::wait() will always timeout. > My immediate solution is: create some MyThread class inherited of > QThread just for expose the QThread::*sleep(unsigned long) methods and > create some slot or Q_INVOKABLE method on Worker to call these exposed > methods. Anyone propose some more elegant solution? Yes: don't sleep. -- Thiago Macieira - thiago.macieira (AT) intel.com Software Architect - Intel Open Source Technology Center
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