"The most exciting (well, for me personally - my life is apparently too boring for words) was how we had some stack overflows that totally corrupted some basic thread data structures. That's exciting because we haven't had those in a long time. The cause turned out to be a somewhat overly optimistic increase in the maximum NR_CPUS value, but it also caused some introspection about our stack usage in general. Including things like a patch to gcc to fix insane stack usage for vararg functions on x86-64. But that one would only hit anybody who was a bit too adventurous and selected the big 4096 CPU configuration. The rest of the regressions fixed are a bit more pedestrian."