On Fri, Dec 09, 2016 at 03:49:45PM -0800, Paul E. McKenney wrote: > On Fri, Dec 09, 2016 at 04:48:22PM +0800, Boqun Feng wrote: > > Hi Paul, > > > > While reading the discussion at: > > > > https://marc.info/?l=linux-kernel&m=148044253400769 > > This discussion was for stalls specifically, rather than for routine > scans of the bitmasks. > > But it does look to save some code, so worth looking into. > > > 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? > > By analogy with for_each_cpu() and for_each_possible_cpu(), the name > should instead be for_each_leaf_node_cpu(), the tradition of excessively > long names in RCU notwithstanding. ;-) >
Make sense ;-) I think it's more appropriate to call it for_each_leaf_node_mask_cpu(), because we don't iterate all cpus of a leaf node. The word "possible" could be dropped because obviously we won't iterate over "impossible" cpus in a leaf node ;-) Will modify that in next version. Regards, Boqun > Thanx, Paul >
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