Re: [PATCH v3 0/2] Fix /proc/cpuinfo cpumask warning

[Yury Norov]

On Fri, Oct 14, 2022 at 05:58:43PM +0200, Andrew Jones wrote:
> Commit 78e5a3399421 ("cpumask: fix checking valid cpu range") has
> started issuing warnings[*] when cpu indices equal to nr_cpu_ids - 1
> are passed to cpumask_next* functions. seq_read_iter() and cpuinfo's
> start and next seq operations implement a pattern like
> 
>   n = cpumask_next(n - 1, mask);
>   show(n);
>   while (1) {
>       ++n;
>       n = cpumask_next(n - 1, mask);
>       if (n >= nr_cpu_ids)
>           break;
>       show(n);
>   }
>     
> which will issue the warning when reading /proc/cpuinfo.
> 
> [*] Warnings will only appear with DEBUG_PER_CPU_MAPS enabled.
> 
> This series address the issue for x86 and riscv, but from a quick
> grep of cpuinfo seq operations, I think at least openrisc, powerpc,
> and s390 also need an equivalent patch. While the test is simple (see
> next paragraph) I'm not equipped to test on each architecture.
> 
> To test, just build a kernel with DEBUG_PER_CPU_MAPS enabled, boot to
> a shell, do 'cat /proc/cpuinfo', and look for a kernel warning.
> 
> While the patches are being posted together in a series since they're
> for two different architectures they don't necessarily need to go
> through the same tree.

Acked-by: Yury Norov <yury.norov@xxxxxxxxx