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Message-ID: <20090115133916.GA3417@elte.hu>
Date: Thu, 15 Jan 2009 14:39:16 +0100
From: Ingo Molnar <mingo@...e.hu>
To: Tejun Heo <tj@...nel.org>
Cc: roel kluin <roel.kluin@...il.com>,
"H. Peter Anvin" <hpa@...or.com>, Brian Gerst <brgerst@...il.com>,
ebiederm@...ssion.com, cl@...ux-foundation.org,
rusty@...tcorp.com.au, travis@....com,
linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
steiner@....com, hugh@...itas.com
Subject: Re: [patch] add optimized generic percpu accessors
* Ingo Molnar <mingo@...e.hu> wrote:
> FYI, -tip testing found the following bug with your percpu stuff:
>
> There's an early exception during bootup, on 64-bit x86:
>
> PANIC: early exception 0e rip 10:ffffffff80276855: error ? cr2 6688
>
> - gcc version 4.3.2 20081007 (Red Hat 4.3.2-6) (GCC)
> - binutils-2.18.50.0.6-2.x86_64
>
> config attached. You can find the disassembly of lock_release_holdtime()
> below - that's where it crashed:
Gut feeling: we must have gotten a window where the PDA is not right. Note
how it crashes in lock_release_holdtime() - that is CONFIG_LOCK_STAT
instrumentation - very lowlevel and pervasive. Function tracing is also
enabled although it should be inactive at the early stages.
So i'd take a good look at the PDA setup portion of the boot code, and see
whether some spinlock acquire/release can slip in while the
PDA/percpu-area is not reliable.
Ingo
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