Messages in this thread Patch in this message | | | Date | Fri, 4 Mar 2022 14:49:23 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH] sched/topology: Remove redundant variable and fix incorrect type in build_sched_domains |
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On Fri, Mar 04, 2022 at 12:56:44PM +0000, Valentin Schneider wrote: > On 18/02/22 21:57, K Prateek Nayak wrote: > > While investigating the sparse warning reported by the LKP bot [1], > > observed that we have a redundant variable "top" in the function > > build_sched_domains that was introduced in the recent commit > > e496132ebedd ("sched/fair: Adjust the allowed NUMA imbalance when > > SD_NUMA spans multiple LLCs") > > > > The existing variable "sd" suffices which allows us to remove the > > redundant variable "top" while annotating the other variable "top_p" > > with the "__rcu" annotation to silence the sparse warning. > > > > [1] https://lore.kernel.org/lkml/202202170853.9vofgC3O-lkp@intel.com/ > > > > Fixes: e496132ebedd ("sched/fair: Adjust the allowed NUMA imbalance when SD_NUMA spans multiple LLCs") > > Reported-by: kernel test robot <lkp@intel.com> > > Signed-off-by: K Prateek Nayak <kprateek.nayak@amd.com> > > --- > > kernel/sched/topology.c | 8 +++----- > > 1 file changed, 3 insertions(+), 5 deletions(-) > > > > diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c > > index e6cd55951304..4b757fb8f661 100644 > > --- a/kernel/sched/topology.c > > +++ b/kernel/sched/topology.c > > @@ -2255,7 +2255,7 @@ build_sched_domains(const struct cpumask *cpu_map, struct sched_domain_attr *att > > > > if (!(sd->flags & SD_SHARE_PKG_RESOURCES) && child && > > (child->flags & SD_SHARE_PKG_RESOURCES)) { > > - struct sched_domain *top, *top_p; > > + struct sched_domain __rcu *top_p; > > unsigned int nr_llcs; > > > > /* > > @@ -2280,11 +2280,9 @@ build_sched_domains(const struct cpumask *cpu_map, struct sched_domain_attr *att > > sd->imb_numa_nr = imb; > > > > /* Set span based on the first NUMA domain. */ > > - top = sd; > > - top_p = top->parent; > > + top_p = sd->parent; > > while (top_p && !(top_p->flags & SD_NUMA)) { > > - top = top->parent; > > - top_p = top->parent; > > + top_p = top_p->parent; > > } > > imb_span = top_p ? top_p->span_weight : sd->span_weight; > > > So sd starts as the first domain without SD_SHARE_PKG_RESOURCES (but its > direct child has it), and the loop searches upward for a NUMA domain. This > indeed shouldn't require two variables. > > I was going to say that while you're at it, you could init top_p to sd > rather than sd->parent in case someone runs a non-default > sched_domain_topology[], but NODE should have neither > SD_SHARE_PKG_RESOURCES nor SD_NUMA, so that doesn't seem required. > > Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Thanks!
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