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SubjectRe: [PATCH 09/10] x86: oprofile: remove NR_CPUS arrays in arch/x86/oprofile/nmi_int.c

* Mike Travis <travis@sgi.com> wrote:

> Change the following arrays sized by NR_CPUS to be PERCPU variables:
>
> static struct op_msrs cpu_msrs[NR_CPUS];
> static unsigned long saved_lvtpc[NR_CPUS];
>
> Also some minor complaints from checkpatch.pl fixed.

thanks, applied.

> All changes were transparent except for:
>
> static void nmi_shutdown(void)
> {
> + struct op_msrs *msrs = &__get_cpu_var(cpu_msrs);
> nmi_enabled = 0;
> on_each_cpu(nmi_cpu_shutdown, NULL, 0, 1);
> unregister_die_notifier(&profile_exceptions_nb);
> - model->shutdown(cpu_msrs);
> + model->shutdown(msrs);
> free_msrs();
> }
>
> The existing code passed a reference to cpu 0's instance of struct
> op_msrs to model->shutdown, whilst the other functions are passed a
> reference to <this cpu's> instance of a struct op_msrs. This seemed
> to be a bug to me even though as long as cpu 0 and <this cpu> are of
> the same type it would have the same effect...?

i dont think this has any real effect in practice (the model pointers
are not expected to change across cpus on the same system) - but in any
case i've promoted your observation to the main portion of the changelog
so that we'll have notice of this.

(someone might want to play with simulating a weaker CPU on a secondary
core, but we've got tons of other assumptions on CPU type symmetry.)

Ingo


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