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SubjectRe: [PATCH 1/2] perfcounter: Ignore the nmi call frames in the x86-64 backtraces
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On Wed, 2009-07-01 at 21:02 +0200, Frederic Weisbecker wrote:

> +int x86_is_stack_id(int id, char *name)
> +{
> + return x86_stack_ids[id - 1] == name;
> +}

OK, this bit would need a bit of a comment explaining why this works, as
I don't think the C language guarantees de-duplication of constant
strings.

Therefore the above only works correctly if its passed a pointer from
the x86_stack_ids[] array -- as it indeed is, since the string passed is
obtained through the below method:

> +static unsigned long *in_exception_stack(unsigned cpu, unsigned long stack,
> + unsigned *usedp, char **idp)
> +{
> unsigned k;
>
> /*
> @@ -61,7 +68,7 @@ static unsigned long *in_exception_stack(unsigned cpu, unsigned long stack,
> if (*usedp & (1U << k))
> break;
> *usedp |= 1U << k;
> - *idp = ids[k];
> + *idp = x86_stack_ids[k];
> return (unsigned long *)end;
> }
> /*




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