Re: local_add_return

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

On Friday 19 December 2008 14:05:14 Mathieu Desnoyers wrote:
> * Rusty Russell (rusty@rustcorp.com.au) wrote:
> But can we turn what you call "nmi_safe_t" into "local_atomic_t" then ?
> Because we have to specify that this type must only be used as part of
> per-cpu data with preemption disabled, and we also specify that it is
> atomic.
> 
> Plus, nmi_safe_t does not make much sense on architectures without NMIs,
> where we sometimes disable interrupts to make the modification "atomic"
> wrt all other interrupts that can happen.

But those archs can use local_t.  I don't like either name local_t nor
atomic_local_t, but renaming sucks too.

OK, how about a different approach?  Since there's really only one case
where we need this local_t property outside arch-specific code, how about
we define ARCH_LOCAL_T_TRACE_SAFE for x86?

Then some trace-specific typedef like "trace_counter_t" which goes to local_t
or atomic_(long?)_t?

Should be a simple patch and pretty clear.

Thanks,
Rusty.