From mboxrd@z Thu Jan  1 00:00:00 1970
From: Keith Owens <kaos@sgi.com>
Date: Tue, 04 May 2004 02:07:25 +0000
Subject: Re: 2.6.5 unwind problem with rp <- r0
Message-Id: <6895.1083636445@kao2.melbourne.sgi.com>
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References: <4885.1083211711@kao2.melbourne.sgi.com>
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To: linux-ia64@vger.kernel.org

On Mon, 3 May 2004 15:28:18 -0700, 
David Mosberger <davidm@napali.hpl.hp.com> wrote:
>>>>>> On Thu, 29 Apr 2004 14:08:31 +1000, Keith Owens <kaos@sgi.com> said:
>
>  Keith> Unwinding through a kernel thread, we hit
>  Keith> kernel_thread_helper which is called from start_kernel_thread
>  Keith> with unwind data
>
>  Keith>         .save rp, r0 // this is the end of the call-chain
>
>  Keith> The kernel unwinder does not handle this correctly, it spits
>  Keith> unwind.pt_regs_off: bad scratch reg r0 and keeps unwinding,
>  Keith> generating garbage.
>
>For now, I think the best solution is to avoid the idiom.  I don't
>want to make too many changes to the existing kernel unwinder anymore.
>That is, I'd rather spend time on a libunwind-based kernel unwinder.

David, you wanted rp <- r0 to get a clean termination of the unwind
chain.  Without that clean termination, unwind wanders off into nowhere
generating garbage.  This has already confused at least two people.