Re: local_add_return

[Rusty Russell <rusty@rustcorp.com.au>]

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.