linux-kernel - Re: [PATCH] sched/topology: Remove redundant variable and fix incorrect type in build_sched

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Message-ID: <9eedd162-440f-dfb4-e5c6-24ada28fe365@amd.com>
Date:   Fri, 4 Mar 2022 09:18:21 +0530
From:   K Prateek Nayak <kprateek.nayak@....com>
To:     peterz@...radead.org
Cc:     aubrey.li@...ux.intel.com, efault@....de, gautham.shenoy@....com,
        linux-kernel@...r.kernel.org, mgorman@...hsingularity.net,
        mingo@...nel.org, song.bao.hua@...ilicon.com,
        srikar@...ux.vnet.ibm.com, valentin.schneider@....com,
        vincent.guittot@...aro.org
Subject: Re: [PATCH] sched/topology: Remove redundant variable and fix
 incorrect type in build_sched_domains

Hello everyone,

Ping :)

On 2/18/2022 9:57 PM, 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@...el.com>
> Signed-off-by: K Prateek Nayak <kprateek.nayak@....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;
>  			} else {

--
Thanks and Regards,
Prateek