CATiledLayer and setNeedsDisplayInRect update problems

Question

I have a view where I add a CATiledLayer as a sublayer. The view is inserted in a scroll view.

When specifically requesting an update by sending setNeedsDisplayInRect: to the sublayer, my application hangs. Anyone more knowledgable on the why?

EDIT: If I have a UIView explicitly using a CATiledLayer as a backing layer, calling the UIView's setNeedsDisplayInRect: also makes the app hang (both on device as in simulator). BTB setNeedsDisplay works fine.