2.6.15-mm4 failure on power5

[Andrew Morton]

Dave C Boutcher <sleddog at us.ibm.com> wrote:
>
> On Mon, Jan 16, 2006 at 09:37:48AM -0600, Serge E. Hallyn wrote:
> > Quoting Michael Ellerman (michael at ellerman.id.au):
> > > On Mon, 16 Jan 2006 18:05, Andrew Morton wrote:
> > > > "Serge E. Hallyn" <serue at us.ibm.com> wrote:
> > > > > On my power5 partition, 2.6.15-mm4 hangs on boot
> > 
> > boot: quicktest
> > Please wait, loading kernel...
> 
> ...
> 
> > Page orders: linear mapping = 24, others = 12
> >  -> smp_release_cpus()
> >  <- smp_release_cpus()
> >  <- setup_system()
> > 
> > So setup_system() at least finishes, though I don't see the
> > printk's at the bottom of that function.
> 
> 2.6.15-mm4 won't boot on my power5 either.  I tracked it down to the
> following mutex patch from Ingo: kernel-kernel-cpuc-to-mutexes.patch

Thanks for doing that - I know it's a lot of work, but boy it helps.

<mutters something unprintable about mutex patches and work prioritisation>

> If I revert just that patch, mm4 boots fine.  Its really not obvious to
> me at all why that patch is breaking things though...
> 

Yes, that is strange.  I do recall that if something accidentally enables
interrupts too early in boot, ppc64 machines tend to go comatose.  But if
we'd been running that code under local_irq_disable(), down() would have
spat a warning.

Drat, it seems I don't have CPU hotplug in my ppc64 config.