breaking yield loops on forced quit.

Jan-Marek Glogowski glogow at
Fri Mar 12 12:23:35 UTC 2021

Hi *,

Am 12.03.21 um 12:16 schrieb Michael Meeks:
> 	We've recently had problems with dialogs running in Online Kit
> processes that are not cleaning up properly when the process is asked
> to quit by the core.
> 	The proximate fix is/was to hard kill the remote process =)
> but - I'd love to do better if possible.

... regression?

> 	If you see vcl's:
> Dialog::Execute () ...
>      // Yield util EndDialog is called or dialog gets destroyed
>      // (the latter should not happen, but better safe than sorry
>      while ( !xWindow->IsDisposed() && mbInExecute )
>          Application::Yield();
> 	You see one of these:
> 	while (condition)
> 		Application::Yield();
> 	archetypes. Of which there a dozen+ scattered around the code eg.
> sfx2/source/doc/printhelper.cxx-                while( m_pPrinter->IsPrinting() )
> sfx2/source/doc/printhelper.cxx:                    Application::Yield();
> 	etc. etc.
> 	Not least because Application:Yield becomes an instant-return when
> we're trying to quit. So - we could add a flag:
> 	while (condition && !(new Application::mbAppQuit accessor))
> 	to all suspicious looking call-sites.
> 	Perhaps it'd be nicer to have a:
> 	Application::YieldWhile([]{ return m_pPrinter->IsPrinting(); });
> 	or somesuch - so we can add that this just once (?)

There is also:

static void Quit();
static void EndYield();

so we can add

bool Application::IsQuit()
     return ImplGetSVData()->maAppData.mbAppQuit;

 From my POV and your example, whatever IsPrinting is testing (I assume 
some thread or OS API), should return earlier / cancel processing / 
check IsQuit / imply called EndYield. I don't think trying to "beef up" 
Application::Yield in whatever direction will help, but might introduce 
other problems, like un-joined threads, missing cleanup and whatnot.

Adding a !Application::IsQuit to a yield loop, might be the right fix in 
some cases, but not generally. Application::Quit already sets mbAppQuit 
and calls PostUserEvent to wake up yield.


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