__cpu_up vs. start_secondary race?

[Nathan Lynch]

Benjamin Herrenschmidt wrote:
> On Tue, 2008-12-02 at 20:16 -0600, Nathan Lynch wrote:
> > Apart from barriers (or lack thereof), the fact that __cpu_up gives up
> > after a more-or-less arbitrary period seems... well, arbitrary.  If we
> > get to "Processor X is stuck" then something is seriously wrong:
> > there's either a kernel bug or a platform issue, and the CPU just
> > kicked is in an unknown state.  Polling indefinitely seems safer, no?
> > Especially since some hypervisors allow overcommitting processors and
> > memory, which can introduce latencies in unexpected places.
> 
> I'm pretty happy to keep the timeout :-) Proved useful in many cases
> where we actually fail to bring it up or crash it at bringup. From my
> experience, most of the time, the stuck CPU isn't getting in the way and
> it gets us a chance to move forward.

Fair enough -- thanks.