linux-kernel - Re: [PATCH v7 5/8] sched/topology: Unify tl_smt

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Message-ID: <d2ccc708-ab0e-4d25-8fc9-f989cdd0ae55@csgroup.eu>
Date: Tue, 26 Aug 2025 07:13:05 +0200
From: Christophe Leroy <christophe.leroy@...roup.eu>
To: K Prateek Nayak <kprateek.nayak@....com>,
 Madhavan Srinivasan <maddy@...ux.ibm.com>,
 Michael Ellerman <mpe@...erman.id.au>, Nicholas Piggin <npiggin@...il.com>,
 Heiko Carstens <hca@...ux.ibm.com>, Vasily Gorbik <gor@...ux.ibm.com>,
 Alexander Gordeev <agordeev@...ux.ibm.com>,
 Christian Borntraeger <borntraeger@...ux.ibm.com>,
 Sven Schnelle <svens@...ux.ibm.com>, Thomas Gleixner <tglx@...utronix.de>,
 Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
 Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
 "H. Peter Anvin" <hpa@...or.com>, Peter Zijlstra <peterz@...radead.org>,
 Juri Lelli <juri.lelli@...hat.com>,
 Vincent Guittot <vincent.guittot@...aro.org>, linuxppc-dev@...ts.ozlabs.org,
 linux-kernel@...r.kernel.org, linux-s390@...r.kernel.org
Cc: Dietmar Eggemann <dietmar.eggemann@....com>,
 Steven Rostedt <rostedt@...dmis.org>, Ben Segall <bsegall@...gle.com>,
 Mel Gorman <mgorman@...e.de>, Valentin Schneider <vschneid@...hat.com>,
 thomas.weissschuh@...utronix.de, Li Chen <chenl311@...natelecom.cn>,
 Bibo Mao <maobibo@...ngson.cn>, Mete Durlu <meted@...ux.ibm.com>,
 Tobias Huschle <huschle@...ux.ibm.com>,
 Easwar Hariharan <easwar.hariharan@...ux.microsoft.com>,
 Guo Weikang <guoweikang.kernel@...il.com>,
 "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
 Brian Gerst <brgerst@...il.com>,
 Patryk Wlazlyn <patryk.wlazlyn@...ux.intel.com>,
 Swapnil Sapkal <swapnil.sapkal@....com>,
 "Yury Norov [NVIDIA]" <yury.norov@...il.com>,
 Sudeep Holla <sudeep.holla@....com>,
 Jonathan Cameron <Jonathan.Cameron@...wei.com>,
 Andrea Righi <arighi@...dia.com>, Yicong Yang <yangyicong@...ilicon.com>,
 Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>,
 Tim Chen <tim.c.chen@...ux.intel.com>,
 Vinicius Costa Gomes <vinicius.gomes@...el.com>
Subject: Re: [PATCH v7 5/8] sched/topology: Unify tl_smt_mask() across core
 and all arch



Le 26/08/2025 à 06:13, K Prateek Nayak a écrit :
> Unify the tl_smt_mask() wrapper around cpu_smt_mask() across core, x86,
> ppc, and s390.
> 
> On s390, include/linux/topology.c defines an explicit cpu_smt_mask()
> wrapper around topology_sibling_cpumask() when cpu_smt_mask() is not
> defined by the arch/ bits and topology_sibling_cpumask() on s390 returns
> &cpu_topology[cpu].thread_mask.
> 
> No functional changes intended.
> 
> Signed-off-by: K Prateek Nayak <kprateek.nayak@....com>
> ---
>   arch/powerpc/kernel/smp.c      | 5 -----
>   arch/s390/kernel/topology.c    | 8 +-------
>   arch/x86/kernel/smpboot.c      | 5 -----
>   include/linux/sched/topology.h | 8 +++++++-
>   kernel/sched/topology.c        | 7 -------
>   5 files changed, 8 insertions(+), 25 deletions(-)
> 
> diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
> index 7f79b853b221..c58ddf84fe63 100644
> --- a/arch/powerpc/kernel/smp.c
> +++ b/arch/powerpc/kernel/smp.c
> @@ -1038,11 +1038,6 @@ static const struct cpumask *smallcore_smt_mask(struct sched_domain_topology_lev
>   {
>   	return cpu_smallcore_mask(cpu);
>   }
> -
> -static const struct cpumask *tl_smt_mask(struct sched_domain_topology_level *tl, int cpu)
> -{
> -	return cpu_smt_mask(cpu);
> -}
>   #endif
>   
>   static struct cpumask *cpu_corgrp_mask(int cpu)
> diff --git a/arch/s390/kernel/topology.c b/arch/s390/kernel/topology.c
> index 5129e3ffa7f5..c88eda847309 100644
> --- a/arch/s390/kernel/topology.c
> +++ b/arch/s390/kernel/topology.c
> @@ -509,12 +509,6 @@ int topology_cpu_init(struct cpu *cpu)
>   	return rc;
>   }
>   
> -static const struct cpumask *cpu_thread_mask(struct sched_domain_topology_level *tl, int cpu)
> -{
> -	return &cpu_topology[cpu].thread_mask;
> -}
> -
> -
>   const struct cpumask *cpu_coregroup_mask(int cpu)
>   {
>   	return &cpu_topology[cpu].core_mask;
> @@ -541,7 +535,7 @@ static const struct cpumask *cpu_pkg_mask(struct sched_domain_topology_level *tl
>   }
>   
>   static struct sched_domain_topology_level s390_topology[] = {
> -	SDTL_INIT(cpu_thread_mask, cpu_smt_flags, SMT),
> +	SDTL_INIT(tl_smt_mask, cpu_smt_flags, SMT),
>   	SDTL_INIT(cpu_mc_mask, cpu_core_flags, MC),
>   	SDTL_INIT(cpu_book_mask, NULL, BOOK),
>   	SDTL_INIT(cpu_drawer_mask, NULL, DRAWER),
> diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
> index 4cd3d69741cf..03ff6270966a 100644
> --- a/arch/x86/kernel/smpboot.c
> +++ b/arch/x86/kernel/smpboot.c
> @@ -463,11 +463,6 @@ static int x86_core_flags(void)
>   {
>   	return cpu_core_flags() | x86_sched_itmt_flags();
>   }
> -
> -static const struct cpumask *tl_smt_mask(struct sched_domain_topology_level *tl, int cpu)
> -{
> -	return cpu_smt_mask(cpu);
> -}
>   #endif
>   
>   #ifdef CONFIG_SCHED_CLUSTER
> diff --git a/include/linux/sched/topology.h b/include/linux/sched/topology.h
> index 602508130c8a..d75fbb7d9667 100644
> --- a/include/linux/sched/topology.h
> +++ b/include/linux/sched/topology.h
> @@ -37,7 +37,13 @@ static inline int cpu_smt_flags(void)
>   {
>   	return SD_SHARE_CPUCAPACITY | SD_SHARE_LLC;
>   }
> -#endif
> +
> +static const __maybe_unused
> +struct cpumask *tl_smt_mask(struct sched_domain_topology_level *tl, int cpu)

__maybe_unused hides the dust under the carpet.

Leave the function in kernel/sched/topology.c and make it non-static 
with a prototype in linux/sched/topology.h

> +{
> +	return cpu_smt_mask(cpu);
> +}
> +#endif /* CONFIG_SCHED_SMT */
>   
>   #ifdef CONFIG_SCHED_CLUSTER
>   static inline int cpu_cluster_flags(void)
> diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
> index dfc754e0668c..92165fe56a2d 100644
> --- a/kernel/sched/topology.c
> +++ b/kernel/sched/topology.c
> @@ -1724,13 +1724,6 @@ sd_init(struct sched_domain_topology_level *tl,
>   	return sd;
>   }
>   
> -#ifdef CONFIG_SCHED_SMT
> -static const struct cpumask *tl_smt_mask(struct sched_domain_topology_level *tl, int cpu)
> -{
> -	return cpu_smt_mask(cpu);
> -}
> -#endif
> -
>   #ifdef CONFIG_SCHED_CLUSTER
>   static const struct cpumask *tl_cls_mask(struct sched_domain_topology_level *tl, int cpu)
>   {