Re: MIPS atomic operations, "sync"

Ralf Baechle
2006-11-10T22:32:47Z

On Fri, Nov 10, 2006 at 01:40:49PM -0500, Mathieu Desnoyers wrote:

> I am currently creating a "LOCK" prefix free and memory barrier free version
> of atomic.h to fulfill my tracer (LTTng) needs, which is to atomically update
> per-cpu data and have a minimal performance loss.
>
> I just came across the MIPS atomic.h and system.h implementations in 2.6.18
> which brings a question :
>
> Why are the primitives in include/asm-mips/atomic.h using the "sync"
> instruction even in the UP case ? system.h cmpxchg only uses the sync in the
> SMP case.

Why are the standard atomic operations insufficient for your needs?

There is an enormous amout of subtilities in those atomic ops for some
architectures you probably do yourself a big favor by avoiding new
variants.

Ralf