[Development] QTimer question

[Thiago Macieira]

On Tuesday, 30 May 2023 17:10:11 PDT Ilya Fedin wrote:
> On Tue, 30 May 2023 16:55:51 -0700
> 
> Thiago Macieira <thiago.macieira at intel.com> wrote:
> > After trying myself, it turns out the problem is not QTimer or the
> > 
> > event dispatcher, but the Windows API. The following test:
> >   https://codereview.qt-project.org/c/qt/qtbase/+/480705
> > 
> > passes on Linux (glib and native), macOS but fails on Windows, all of
> > them Core and Gui.
> 
> While talking about Windows timer bugs, want to remind about
> QTBUG-95034 which causes crashes in highly concurrent applications
> since at least 2 years already.

If we choose to use a single timer source per thread and keep changing its 
timeout, like we do everywhere else, then it would get fixed.

It might be as simple as replacing that INFINITE in:

            emit aboutToBlock();
            MsgWaitForMultipleObjectsEx(0, NULL, INFINITE, QS_ALLINPUT, 
MWMO_ALERTABLE | MWMO_INPUTAVAILABLE);
            emit awake();

with a value obtained from QTimerInfoList::timerWait, then calling 
QTimerInfoList::activateTimers().

This should be easier after the work by Ahmad to use <chrono> in 
QTimerInfoList lands. QDeadlineTimer is already using 
std::chrono::steady_clock on Windows.

-- 
Thiago Macieira - thiago.macieira (AT) intel.com
  Cloud Software Architect - Intel DCAI Cloud Engineering
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