(In reply to Andy Furniss from comment #38)
> (In reply to Andy Furniss from comment #32)
> 
> > I'll try over the weekend - no locks so far.
> 
> Still good, I've also tried to hang with Unreal demos and mplayer+uvd, no
> hangs and no vm faults so far.

Assuming you tried it with the scheduler enabled? Just tried it with the
scheduler enabled and semaphores disabled on drm-fixes-4.3, and it also seems
to work.

Is the scheduler going to be left enabled from now on? If so we could probably
say that this issue has been solved (though more testing is probably required).
However, something is causing all of those vm faults when the scheduler is
disabled, so it might still be worth looking into if it's going to be possible
to disable it using a module parameter.