Image Scaling Example freezes (qt concurrent issue)

[caesun]

I built and run the official Image Scaling Example, it freezes if 12 or more files were selected.

My env:
Desktop_Qt_5_15_0_MSVC2019_64bit

the debug call stack show

[caesun]

Found some clues.

My CPU is AMD Ryzen 5 1600, 6 cores, 12 logical cores.

When AMD SMT is enabled, there are 12 logical cores available, and QFutureWatcher::setFuture() will freeze if 12 or more concurrent tasks are queued.
When SMT feature is disabled, setFuture() will freeze when 6 tasks or more are queued.

The qt freezes when 12 (or 6 w/o SMT) tasks complete.

OS: Windows 10 Pro, 1903, 18362.1016

[caesun]

Is it possible to use qtconcurrent function without OpenGL involved? It seems that qt blocks in OpenGL relative calls.

[caesun]

This bug has been resolved in Qt 5.15.1.