Subject: Re: [PATCH v8 07/19] cpuset: Honour task_cpu_possible_mask() in guarantee_online_cpus()

From: Valentin Schneider <[email-masked]>
Date: Fri, 04 Jun 2021 18:11:20 +0100

On 02/06/21 17:47, Will Deacon wrote:
> Asymmetric systems may not offer the same level of userspace ISA support
> across all CPUs, meaning that some applications cannot be executed by
> some CPUs. As a concrete example, upcoming arm64 big.LITTLE designs do
> not feature support for 32-bit applications on both clusters.
>
> Modify guarantee_online_cpus() to take task_cpu_possible_mask() into
> account when trying to find a suitable set of online CPUs for a given
> task. This will avoid passing an invalid mask to set_cpus_allowed_ptr()
> during ->attach() and will subsequently allow the cpuset hierarchy to be
> taken into account when forcefully overriding the affinity mask for a
> task which requires migration to a compatible CPU.
>
> Cc: Li Zefan <[email-masked]>
> Cc: Tejun Heo <[email-masked]>
> Cc: Johannes Weiner <[email-masked]>
> Signed-off-by: Will Deacon <[email-masked]>

Reviewed-by: Valentin Schneider <[email-masked]>

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