linux-kernel - Re: [PATCH V2] arch_topology: Clear LLC sibling when cacheinfo teardown

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Date:   Wed, 15 Mar 2023 18:29:37 +0000
From:   Conor Dooley <conor@...nel.org>
To:     Song Shuai <suagrfillet@...il.com>
Cc:     sudeep.holla@....com, gregkh@...uxfoundation.org,
        rafael@...nel.org, conor.dooley@...rochip.com,
        ionela.voinescu@....com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V2] arch_topology: Clear LLC sibling when cacheinfo
 teardown

On Tue, Mar 14, 2023 at 03:53:45PM +0800, Song Shuai wrote:
> The teardown of CPUHP_AP_BASE_CACHEINFO_ONLINE now only invokes
> free_cache_attributes() to clear share_cpu_map of cacheinfo list.
> At the same time, clearing cpu_topology[].llc_sibling is
> called quite late at the teardown code in hotplug STARTING section.
> 
> To avoid the incorrect LLC sibling masks generated, move its clearing
> right after free_cache_attributes().
> 

> Link: https://lore.kernel.org/linux-kernel/20230313102752.1134472-1-suagrfillet@gmail.com/

btw, I think you've added the wrong link here - this seems to be a link
to your previous submission. Was it meant to link to something else?

Cheers,
Conor.

> Fixes: 3fcbf1c77d08 ("arch_topology: Fix cache attributes detection in the CPU hotplug path")
> Signed-off-by: Song Shuai <suagrfillet@...il.com>
> ---
> changes from V1:
>  - fix implicit declaration of clear_llc_topology
> ---
>  drivers/base/arch_topology.c  | 16 ++++++++++++++--
>  drivers/base/cacheinfo.c      |  2 ++
>  include/linux/arch_topology.h |  3 +++
>  3 files changed, 19 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c
> index b1c1dd38ab01..8681654d6c07 100644
> --- a/drivers/base/arch_topology.c
> +++ b/drivers/base/arch_topology.c
> @@ -769,6 +769,20 @@ void update_siblings_masks(unsigned int cpuid)
>  	}
>  }
>  
> +void clear_llc_topology(unsigned int cpu)
> +{
> +	int sib;
> +
> +	for_each_cpu(sib, topology_llc_cpumask(cpu)) {
> +		if (sib == cpu)
> +			continue;
> +		if (last_level_cache_is_shared(cpu, sib)) {
> +			cpumask_clear_cpu(cpu, topology_llc_cpumask(sib));
> +			cpumask_clear_cpu(sib, topology_llc_cpumask(cpu));
> +		}
> +	}
> +}
> +
>  static void clear_cpu_topology(int cpu)
>  {
>  	struct cpu_topology *cpu_topo = &cpu_topology[cpu];
> @@ -811,8 +825,6 @@ void remove_cpu_topology(unsigned int cpu)
>  		cpumask_clear_cpu(cpu, topology_sibling_cpumask(sibling));
>  	for_each_cpu(sibling, topology_cluster_cpumask(cpu))
>  		cpumask_clear_cpu(cpu, topology_cluster_cpumask(sibling));
> -	for_each_cpu(sibling, topology_llc_cpumask(cpu))
> -		cpumask_clear_cpu(cpu, topology_llc_cpumask(sibling));
>  
>  	clear_cpu_topology(cpu);
>  }
> diff --git a/drivers/base/cacheinfo.c b/drivers/base/cacheinfo.c
> index f6573c335f4c..1c276b30fd5a 100644
> --- a/drivers/base/cacheinfo.c
> +++ b/drivers/base/cacheinfo.c
> @@ -19,6 +19,7 @@
>  #include <linux/slab.h>
>  #include <linux/smp.h>
>  #include <linux/sysfs.h>
> +#include <linux/arch_topology.h>
>  
>  /* pointer to per cpu cacheinfo */
>  static DEFINE_PER_CPU(struct cpu_cacheinfo, ci_cpu_cacheinfo);
> @@ -814,6 +815,7 @@ static int cacheinfo_cpu_pre_down(unsigned int cpu)
>  		cpu_cache_sysfs_exit(cpu);
>  
>  	free_cache_attributes(cpu);
> +	clear_llc_topology(cpu);
>  	return 0;
>  }
>  
> diff --git a/include/linux/arch_topology.h b/include/linux/arch_topology.h
> index a07b510e7dc5..569e05607934 100644
> --- a/include/linux/arch_topology.h
> +++ b/include/linux/arch_topology.h
> @@ -89,9 +89,12 @@ void store_cpu_topology(unsigned int cpuid);
>  const struct cpumask *cpu_coregroup_mask(int cpu);
>  const struct cpumask *cpu_clustergroup_mask(int cpu);
>  void update_siblings_masks(unsigned int cpu);
> +void clear_llc_topology(unsigned int cpu);
>  void remove_cpu_topology(unsigned int cpuid);
>  void reset_cpu_topology(void);
>  int parse_acpi_topology(void);
> +#else
> +static inline void clear_llc_topology(unsigned int cpu) { }
>  #endif
>  
>  #endif /* _LINUX_ARCH_TOPOLOGY_H_ */
> -- 
> 2.20.1
> 

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