Re: [PATCH] SLUB use cmpxchg_local

Christoph Lameter
2007-08-21T23:14:28Z

On Tue, 21 Aug 2007, Mathieu Desnoyers wrote:

> - Changed smp_rmb() for barrier(). We are not interested in read order
> across cpus, what we want is to be ordered wrt local interrupts only.
> barrier() is much cheaper than a rmb().

But this means a preempt disable is required. RT users do not want that.
Without preemption the processor can be moved after c has been determined.
That is why the smp_rmb() is there.