Hi Paul, While reading the discussion at:
https://marc.info/?l=linux-kernel&m=148044253400769 I figured we might use this fact to save some extra checks in RCU core code, currently we iterate over all the possible CPUs on a leaf node, check whether they were masked in a certain mask and do something. However, given the fact that the masks on a leaf node should always be sparse than the corresponding part of cpu_possible_mask, we'd better iterate over all bits in a mask and check whether the corresponding CPU is possible or not. So I made this RFC, I did a simple build/boot/rcutorture test on my box with SMP=4, nothing bad happens. Currently I'm waiting for the 0day and trying to test this one a bigger system, in the meanwhile, looking forwards to any comment and suggestion. So thoughts? Regards, Boqun
