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From: Thomas Gleixner <tglx@linutronix.de>
To: John Stultz <johnstul@us.ibm.com>
Cc: CAI Qian <caiqian@redhat.com>,
	linux-kernel <linux-kernel@vger.kernel.org>,
	Ingo Molnar <mingo@kernel.org>,
	Peter Zijlstra <a.p.zijlstra@chello.nl>,
	Prarit Bhargava <prarit@redhat.com>,
	Zhouping Liu <zliu@redhat.com>
Subject: Re: boot panic regression introduced in 3.5-rc7
Date: Wed, 1 Aug 2012 08:50:12 +0200 (CEST)	[thread overview]
Message-ID: <alpine.LFD.2.02.1208010847590.32033@ionos> (raw)
In-Reply-To: <501771CA.1090304@us.ibm.com>

On Mon, 30 Jul 2012, John Stultz wrote:
> On 07/29/2012 08:51 PM, CAI Qian wrote:
> Now, one of the reasons Thomas and I changed the logic was that using the
> precalculated realtime_offset was slightly more efficient then re-adding xtime
> and wall_to_monotonic's components separately. But how valuable this
> unmeasured slight efficiency is vs extra robustness for crazy time values is
> questionable.

Well, I guess it unearthed a weakness which has been there forever:

  Trusting random values which are supplied by cmos or whatever.

So the right fix is:
 
> 2) Validate that time values we accept are smaller the ktime_t before using
> them.

I really don't like the magic workaround by nulling out the effect of
crap data with a more expensive calculation.

Thanks,

	tglx

      reply	other threads:[~2012-08-01  6:50 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <1107100725.1273654.1343619920692.JavaMail.root@redhat.com>
2012-07-30  3:51 ` boot panic regression introduced in 3.5-rc7 CAI Qian
2012-07-30 17:53   ` John Stultz
2012-07-31  1:59     ` CAI Qian
2012-07-30 20:59   ` John Stultz
2012-07-31  5:48   ` John Stultz
2012-08-01  6:50     ` Thomas Gleixner [this message]

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