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SubjectRe: Generic kernel fails to boot on Alpha bisected to b38d08f3181c
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@kernel.org>
> 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().

2. If that still doesn't work, just convert all of them to
spin_lock/unlock(), which is obviously broken but still is useful
for debugging.

Thanks.

--
tejun

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