Re: [RFC/PATCH] Make printk work for really early debugging

From: Andi Kleen
Date: Thu May 18 2006 - 11:59:45 EST

On Thursday 18 May 2006 17:41, Michael Ellerman wrote:
> On Thu, 2006-05-18 at 15:55 +0200, Andi Kleen wrote:
> > Michael Ellerman <michael@xxxxxxxxxxxxxx> writes:
> >
> > > Currently printk is no use for early debugging because it refuses to actually
> > > print anything to the console unless cpu_online(smp_processor_id()) is true.
> >
> > On x86-64 this is simply solved by setting the boot processor online very early.
> Yeah, someone suggested that. Unfortunately it doesn't work, we actually
> want to call printk before we even know which cpu we're on :D

You mean smp_processor_id() returns a random value?

Then your patch is broken too because iirc it tested smp_processor_id()
before that other flag

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