Re: [RFC patch 08/18] cnt32_to_63 should use smp_rmb()

Nicolas Pitre
2008-11-07T20:03:56Z

On Fri, 7 Nov 2008, Andrew Morton wrote:

> On Fri, 07 Nov 2008 11:47:47 -0500 (EST) Nicolas Pitre <nico@cam.org> wrote:
>
> > > btw, do you know how damned irritating and frustrating it is for a code
> > > reviewer to have his comments deliberately ignored and deleted in
> > > replies?
> >
> > Do you know how irritating and frustrating it is when reviewers don't
> > care reading the damn comments along with the code?
>
> As you still seek to ignore it, I shall repeat my earlier question.
> Please do not delete it again.
>
> It apparently tries to avoid races via ordering tricks, as long
> as it is called with sufficient frequency. But nothing guarantees
> that it _is_ called sufficiently frequently?
>
> Things like tickless kernels and SCHED_RR can surely cause
> sched_clock() to not be called for arbitrary periods.

On the machines this was initially written for, the critical period is
in the order of minutes. And if you're afraid you might lack enough
scheduling activities for that long, you simply have to keep the
algorithm "warm" with a simple kernel timer which only purpose is to
ensure it is called often enough.

> Userspace cli() will definitely do this, but it is expected to break
> stuff and is not as legitiate a thing to do.

Why do you bring it on then?

> I'm just giving up on the tastefulness issue.

Taste is a pretty subjective matter.

Nicolas