* Igor Mammedov <imamm...@redhat.com> wrote:
> On Mon, 14 Apr 2014 12:03:35 +0200
> Ingo Molnar <mi...@kernel.org> wrote:
>
> >
> > * Igor Mammedov <imamm...@redhat.com> wrote:
> >
> > > On Mon, 14 Apr 2014 11:16:00 +0200
> > > Ingo Molnar <mi...@kernel.org> wrote:
> > >
> > > >
> > > > * Igor Mammedov <imamm...@redhat.com> wrote:
> > > >
> > > > > /*
> > > > > + * wait for ACK from master CPU before continuing
> > > > > + * with AP initialization
> > > > > + */
> > > > > + cpumask_set_cpu(cpu, cpu_initialized_mask);
> > > > > + while (!cpumask_test_cpu(cpu, cpu_callout_mask))
> > > > > + cpu_relax();
> > > >
> > > > > + /*
> > > > > + * wait for ACK from master CPU before continuing
> > > > > + * with AP initialization
> > > > > + */
> > > > > + cpumask_set_cpu(cpu, cpu_initialized_mask);
> > > > > + while (!cpumask_test_cpu(cpu, cpu_callout_mask))
> > > > > + cpu_relax();
> > > >
> > > > That repetitive pattern could be stuck into a properly named helper
> > > > inline function.
> > > sure
> > >
> > > > (Also, before the cpumask_set_cpu() we should probably do a WARN_ON()
> > > > if the bit is already set.)
>
> WARN_ON will never be triggered here since bit is always cleared by
> master CPU before AP gets here. There is no harm keeping WARN_ON
> though, do you still want it be here?
The previous code panic()ed on this condition - so it makes sense to
at least keep a WARN_ON(). That it won't ever trigger is good:
> It could be useful to put WARN_ON in do_boot_cpu() before bit is
> cleared, so that user would see that he tries to online AP which has
> failed previous time. It's not really necessary since failed to
> online attempt reported in logs at ERR level now, see patch 2/5.
WARN_ON()s are not used to communicate with users, they are used to
show developers that there's a _bug_ in the code!
So a WARN_ON() not triggering, ever, is a good thing.
Thanks,
Ingo
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