Date: Sun, 31 Dec 2006 17:27:31 +0100
From: Adrian Bunk <bunk@stusta.de>
To: Alistair John Strachan <s0348365@sms.ed.ac.uk>
Cc: "Zhang, Yanmin" <yanmin_zhang@linux.intel.com>,
       LKML <linux-kernel@vger.kernel.org>, Greg KH <greg@kroah.com>,
       Chuck Ebbert <76306.1226@compuserve.com>
Subject: Re: Oops in 2.6.19.1
Message-ID: <20061231162731.GK20714@stusta.de>
References: <200612201421.03514.s0348365@sms.ed.ac.uk> <200612280402.23474.s0348365@sms.ed.ac.uk> <200612280414.20266.s0348365@sms.ed.ac.uk> <200612301659.35982.s0348365@sms.ed.ac.uk>
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On Sat, Dec 30, 2006 at 04:59:35PM +0000, Alistair John Strachan wrote:
> On Thursday 28 December 2006 04:14, Alistair John Strachan wrote:
> > On Thursday 28 December 2006 04:02, Alistair John Strachan wrote:
> > > On Thursday 28 December 2006 02:41, Zhang, Yanmin wrote:
> > > [snip]
> > >
> > > > > Here's a current decompilation of vmlinux/pipe_poll() from the
> > > > > running kernel, the addresses have changed slightly. There's no xchg
> > > > > there either:
> > > >
> > > > Could you reproduce the bug by the new kernel, so we could get the
> > > > exact address and instruction of the bug?
> > >
> > > It crashed again, but this time with no output (machine locked solid). To
> > > be honest, the disassembly looks right (it's like Chuck said, it's
> > > jumping back half way through an instruction):
> > >
> > > c0156f5f:       3b 87 68 01 00 00       cmp    0x168(%edi),%eax
> > >
> > > So c0156f60 is 87 68 01 00 00..
> > >
> > > This is with the GCC recompile, so it's not a distro problem. It could
> > > still either be GCC 4.x, or a 2.6.19.1 specific bug, but it's serious.
> > > 2.6.19 with GCC 3.4.3 is 100% stable.
> >
> > Looks like a similar crash here:
> >
> > http://ubuntuforums.org/showthread.php?p=1803389
> 
> I've eliminated 2.6.19.1 as the culprit, and also tried toggling "optimize for 
> size", various debug options. 2.6.19 compiled with GCC 4.1.1 on an Via 
> Nehemiah C3-2 seems to crash in pipe_poll reliably, within approximately 12 
> hours.
> 
> The machine passes 6 hours of Prime95 (a CPU stability tester), four memtest86 
> passes, and there are no heat problems.
> 
> I have compiled GCC 3.4.6 and compiled 2.6.19 with an identical config using 
> this compiler (but the same binutils), and will report back if it crashes. My 
> bet is that it won't, however.

There are occasional reports of problems with kernels compiled with 
gcc 4.1 that vanish when using older versions of gcc.

AFAIK, until now noone has ever debugged whether that's a gcc bug, 
gcc exposing a kernel bug or gcc exposing a hardware bug.

Comparing your report and [1], it seems that if these are the same 
problem, it's not a hardware bug but a gcc or kernel bug.

> Cheers,
> Alistair.

cu
Adrian

[1] http://bugzilla.kernel.org/show_bug.cgi?id=7176

-- 

       "Is there not promise of rain?" Ling Tan asked suddenly out
        of the darkness. There had been need of rain for many days.
       "Only a promise," Lao Er said.
                                       Pearl S. Buck - Dragon Seed

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