Messages in this thread | | | From | Valentin Schneider <> | Subject | Re: [PATCH] sched/topology: Remove redundant variable and fix incorrect type in build_sched_domains | Date | Fri, 04 Mar 2022 12:56:44 +0000 |
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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>
> } else { > -- > 2.25.1
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