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Date: Mon, 18 Nov 2013 16:39:41 +0100
From: Ingo Molnar <mingo@kernel.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Stanislaw Gruszka <sgruszka@redhat.com>,
        Christian Engelmayer <cengelma@gmx.at>, Ingo Molnar <mingo@redhat.com>,
        linux-kernel@vger.kernel.org, Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PROBLEM] possible divide by 0 in kernel/sched/cputime.c
 scale_stime()
Message-ID: <20131118153941.GA28699@gmail.com>
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* Peter Zijlstra <peterz@infradead.org> wrote:

> I would be tempted to say you should simply mark the tsc unstable on 
> boot and live with that -- we fully assume the sched_clock stuff is 
> not going backwards in an 'observable' way.

BIOS crap and actual hardware bugs do happen - so kernel code needs to 
consider TSC input with a pinch of salt, assuming that it's untrusted 
external data.

> That said, it might be nice to not crash either..

Indeed, not crashing on weird TSC input is absolutely required!

Thanks,

	Ingo