Messages in this thread | | | Date | Fri, 13 May 2016 02:27:01 +0100 | From | Mark Rutland <> | Subject | Re: [PATCHv2] rcu: tree: correctly handle sparse possible CPUs |
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On Tue, May 17, 2016 at 12:01:06PM -0700, Paul E. McKenney wrote: > On Tue, May 17, 2016 at 11:22:10AM +0100, Mark Rutland wrote: > > /* > > + * Iterate over all possible CPUs in a leaf RCU node. > > + */ > > +#define for_each_leaf_node_possible_cpu(rnp, cpu) \ > > + for ((cpu) = rnp->grplo; \ > > + cpu <= rnp->grphi; \ > > + cpu = cpumask_next((cpu), cpu_possible_mask)) > > What if the rnp->grplo corresponds to a non-existent CPU?
Good point, I had evidently not considered that.
> Would something like this handle that possibility? > > +#define for_each_leaf_node_possible_cpu(rnp, cpu) \ > + for ((cpu) = cpumask_next(rnp->grplo - 1, cpu_possible_mask); \ > + cpu <= rnp->grphi; \ > + cpu = cpumask_next((cpu), cpu_possible_mask)) > > Or maybe like this, with less duplicated code but very strange style: > > +#define for_each_leaf_node_possible_cpu(rnp, cpu) \ > + for ((cpu) = rnp->grplo - 1; \ > + cpu = cpumask_next((cpu), cpu_possible_mask), cpu <= rnp->grphi; 1) > > The first one is probably far better, assuming that it works, but I could > not resist inflicting the second one on you. ;-)
:)
Those both look like they should work, I'll fold the former in.
> > +/* > > + * Iterate over all possible CPUs in a leaf RCU node, at each step providing a > > + * bit for comparison against rcu_node bitmasks. > > + */ > > +#define for_each_leaf_node_possible_cpu_bit(rnp, cpu, bit) \ > > + for ((cpu) = rnp->grplo, (bit) = 1; \ > > + cpu <= rnp->grphi; \ > > + cpu = cpumask_next((cpu), cpu_possible_mask), \ > > + (bit) = 1UL << (cpu - rnp->grplo)) > > Same question here.
Likewise.
I'll also see about fixing the build issue you spotted in the other reply; that appears to be a typo (missing 'possible_' in the macro invocation).
I'm away from my development machine at the moment, so that may not appear until next week.
Thanks, Mark.
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