Re: [RFC][PATCH 0/5] Introduce checks for preemptable code for this_cpu_read/write()

Christoph Lameter
2011-09-20T16:05:20Z

On Tue, 20 Sep 2011, Peter Zijlstra wrote:

> On Tue, 2011-09-20 at 10:03 -0500, Christoph Lameter wrote:
> >
> > Well yes the misunderstanding of per cpu operations was one reason why I
> > proposed the discussion on the subject of esoteric kernel synchronization.
> > I do not think that it was accepted.
>
> I don't think anybody here misunderstands it, we're just all very angry
> that its causing so much problems.

What problems? RT does not work with it? The memcg confusion?

> __this_cpu doesn't have preempt debug checks, and there's a lot of
> this_cpu usage that really should have been __this_cpu.

That only works if preemption is disabled when the this_cpu op is being
invoked.