The deadlocked process is sometimes unkillable, and although it does not use much CPU or memory it retains a display and hogs the event loop, slowing down all other interactive applications on the machine (e.g. it takes a minute to open a terminal). It can be terminated only by a reboot.
I am sorry to create a duplicate bug for this; however comments have been disabled for 3608904 which makes it impossible to add this information there.
IMHO "Wont Fix" bugs should not be closed or have comments disabled - if we are lucky someone else might provide useful information or even a fix.