On Tue, Oct 11, 2022 at 10:23:27AM -0700, Yury Norov wrote:
> On Tue, Oct 11, 2022 at 10:16:03AM -0700, Yury Norov wrote:
> > > Hi Yury,
> > >
> > > I just wanted to report that the warning fires when doing
> > > 'cat /proc/cpuinfo' on at least x86 and riscv. I don't think
> > > those are false positives. I'm guessing a patch should be
> > > something like the following diff. If you haven't already
> > > addressed this and I'm not off in left field, then I guess
> > > we should integrate it into your series.
> > >
> > > Thanks,
> > > drew
> >
> > Hi Andrew,
> >
> > Can you please send it as a patch with a description?
>
> Also, can you describe why we'd silence the warning this way?
> If the cpu number greater than nr_cpu_ids comes from upper layer,
> we quite probably should investigate what happens there...
Darn, I fired off the patches before reading this. I didn't try to
completely digest seq_read_iter(), but on a quick look I think the
reason is that it implements something like
p = start();
while (1) {
p = next();
if (!p)
break;
show();
}
stop();
where cpuinfo's operators are
start()
{
*pos = cpumask_next(*pos - 1, cpu_online_mask);
if (*pos < nr_cpu_ids)
return ...;
return NULL;
}
next()
{
(*pos)++;
return start(..., pos);
}
So the justification for the patches the way I've written them is
that I think we just need to return NULL from start / next when
we've gone too far, before we first warn and then return NULL.
Thanks,
drew
