linux-kernel - Re: Lock-up on PPC64

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Message-ID: <Pine.LNX.4.64.0902221126220.3111@linmac.oyster.ru>
Date:	Sun, 22 Feb 2009 11:35:04 +0300 (MSK)
From:	malc <av1474@...tv.ru>
To:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
cc:	linuxppc-dev@...abs.org, linux-kernel@...r.kernel.org
Subject: Re: Lock-up on PPC64

On Wed, 7 Jan 2009, malc wrote:

> On Wed, 7 Jan 2009, Benjamin Herrenschmidt wrote:
> 
> > 
> > > As you wish :) I've written some ad-hoc stuff in the failing path which
> > > manually triggers sysrq and then sends the klogctl output via network
> > > and here it is:
> > 
> > Allright, something's unclear to me. What do you mean by the system goes
> > down then ? The kernel appears to be working at least to a certain
> > extent if you manage to trigger a sysrq from userspace... And from what
> > I see, it looks that all processes are somewhere in schedule.
> > 
> > So what is precisely your symptom here ?

After writing valgrind tool that was simulating Cell XER.SO syscall
(mis)behaviour (pre ab598b6680f1e74c267d1547ee352f3e1e530f89 that is)
and banging my had against the wall for a while trying to figure out
which of the failing syscalls was responsible, i've tried to be simple
and after only ~30 minutes came up with this, rather short, piece of
code that knocks pre XER.SO patched kernels out cold:

gcc -o xer -x assembler /dev/stdin -nostdlib <<eof
.globl _start
_start:
         addis 0,0,0x8000
         mtxer 0
         addi 0,0,1
         sc
eof

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