Fixing krunner's threading

[Andreas Hartmetz]

Hi,

Now that many of the more prominent crashes in krunner have been fixed
I think it's time to attack something more "theoretic": runners run in
threads and often don't pay any attention to thread-safety of API they
use. Two weeks ago I've added a warning to KIO::Scheduler() to warn
about its use from non-main threads, but so far nobody paid attention.
The offending runner here is the places runner.
This is a real problem, and it has to be fixed if krunner is ever
supposed to become *really* stable.
So I'd like to hear from the Plasma team where they can fix things,
and maybe some things can be made thread-safe in kdelibs and friends
without too much effort. But most of all we have to talk about the
problem instead of ignoring it. I'm not even sure who to talk to
because runners are made by different people.
I get the impression that krunner and/or most runners take the "put
things into threads now, ask questions later" approach. It may very
well be that runner authors don't even know that there is a problem -
or the problems are being ignored.
I'm a big fan of the krunner concept, but krunner has to stop crashing so much.

Cheers,
Andreas