Re: [PATCH 0/5] kernel/cpu.c: eliminate some indirection

[Rusty Russell]

Rasmus Villemoes <linux@xxxxxxxxxxxxxxxxxx> writes:
> Maybe third time's the charm...
>
> The four cpumasks cpu_{possible,online,present,active}_bits are
> exposed readonly via the corresponding const variables
> cpu_xyz_mask. But they are also accessible for arbitrary writing via
> the exposed functions set_cpu_xyz. There's quite a bit of code
> throughout the kernel which iterates over or otherwise accesses these
> bitmaps, and having the access go via the cpu_xyz_mask variables is
> simply a useless indirection.

Thanks, consider all patches Acked-by: Rusty Russell <rusty@xxxxxxxxxxxxxxx>

But to be clear, it has outlived its usefulness, but it was not useless.

In particular, there used to be a debug config where 'struct cpumask'
wasn't defined, so we could catch people declaring 'struct cpumask' on
the stack (or passing by value).

There was a plan to remove CONFIG_NR_CPUS (ie. having no compile-time
cpu limit), but it seemed overkill and was abandoned.  But avoiding
'struct cpumask' (not struct cpumask *) in the core wherever possible
was a step towards it.

Hope that clarifies,
Rusty.
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