Re: [PATCH] memcg: remove unneeded preempt_disable

Peter Zijlstra
2011-08-25T18:50:25Z

On Thu, 2011-08-25 at 13:46 -0500, Christoph Lameter wrote:
>
> RISC cpus have instruction to construct complex atomic actions by the cpu
> as I have shown before for ARM.

Right, but it only makes sense if the whole thing remains cheaper than
the trivial implementation already available.

For instance, the ARM LL/SC constraints pretty much mandate we do
preempt_disable()/preempt_enable() around them, at which point the point
of doing LL/SC is gone (except maybe for the irqsafe_this_cpu_* stuff).