Re: local_add_return

Rusty Russell
2008-12-18T22:53:05Z

On Wednesday 17 December 2008 10:31:55 Mathieu Desnoyers wrote:
> I think we have two different use-cases here :
>
> - local_t is useful as-is for things such as a tracer, which need to
> modify an element of data atomically wrt local interrupts. The
> atomic_long_t, in this case, is the correct fallback.
> - local_count_t could be used for fast counters.

Hi Mathieu,

Complete agreement.

I guess I'm biassed towards local_t = counter version, something else
= nmi-safe version because that's what it was originally. Looking through
the tree, there are only 5 users: module, dmaengine and percpu_counter want
a counter, and tracing and x86 nmi.c want nmi-safe. There are several other
places I know of which want local_t-the-counter.

I'll prepare a patch which adds nmi_safe_t, and see how it looks. There's
no amazing hurry on this, so I won't race to hit the merge window.

Thanks!
Rusty.