Re: Generic kernel fails to boot on Alpha bisected to b38d08f3181c

[Michael Cree]

 On Thu, Dec 13, 2018 at 08:07:24AM -0800, Tejun Heo wrote:
> Hello, Michael.
> 
> On Thu, Dec 13, 2018 at 09:26:12PM +1300, Michael Cree wrote:
> > A kernel built for generic UP Alpha had been noted to fail to boot
> > for quite some time (since the release of 3.18).  The kernel either
> > locks up before printing any messages to the console or just falls
> > back into the SRM with a HALT instruction again before any messages
> > are printed to the console.  A work around is to either use a kernel
> > built for generic SMP or to build a machine specific kernel as these
> > boot correctly.
> > 
> > Because there were other compile errors at the time it proved
> > difficult to bisect, but we are continuing to get complaints about
> > it as it renders the Debian Alpha installer somewhat useless, so I
> > returned to trying to find the problem and managed to bisect it to:
> > 
> > commit b38d08f3181c5025a7ce84646494cc4748492a3b
> > Author: Tejun Heo <tj@xxxxxxxxxx>
> > Date:   Tue Sep 2 14:46:02 2014 -0400
> > 
> >     percpu: restructure locking
> > 
> > Any suggestions as to what might be the problem and a fix?
> 
> So, the only thing I can think of is that it's calling
> spin_unlock_irq() while irq handling isn't set up yet.  Can you please
> try the followings?
> 
> 1. Convert all spin_[un]lock_irq() to
>    spin_lock_irqsave/unlock_irqrestore().

Yes, that's it.  With the attached patch the kernel boots.

Cheers
Michael.