r212281 breaks KDE

For the last week, on and off, I've been looking for something that
caused KDE to be horridly unstable, i.e. machine freezes with and
without a core-dump.

Removing r212281 (and r212282) restores that stability. Is there a race
condition that this update exposes by reducing lock strength?

The most common failure with this code included produces a back-trace
similar to the one attached,

	imb