Re: [this_cpu_xx V6 3/7] Use this_cpu operations in slub

[Christoph Lameter]

On Tue, 13 Oct 2009, Tejun Heo wrote:

> Yeah, widespread use of underscored versions isn't very desirable.
> The underscored versions should notify certain specific exceptional
> conditions instead of being used as general optimization (which
> doesn't make much sense after all as the optimization is only
> meaningful with debug option turned on).  Are you interested in doing
> a sweeping patch to drop underscores from __this_cpu_*() conversions?

Nope. __this_cpu_add/dec cannot be converted.

__this_cpu_ptr could be converted to this_cpu_ptr but I think the __ are
useful there too to show that we are in a preempt section.

The calls to raw_smp_processor_id and smp_processor_id() are only useful
in the fallback case. There is no need for those if the arch has a way to
provide the current percpu offset. So we in effect have two meanings of __
right now.

1. We do not care about the preempt state (thus we call
raw_smp_processor_id so that the preempt state does not trigger)

2. We do not need to disable preempt before the operation.

__this_cpu_ptr only implies 1. __this_cpu_add uses 1 and 2.

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/