linux-kernel - Re: BUG: using smp_processor_id() in preemptible [00000000] code: icedove-bin/5449

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Date:	Tue, 25 May 2010 12:29:54 +0200
From:	Piotr Hosowicz <piotr@...owicz.com>
To:	piotr@...owicz.com
CC:	Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...e.hu>,
	linux-kernel@...r.kernel.org, Jens Axboe <jens.axboe@...cle.com>,
	Divyesh Shah <dpshah@...gle.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: BUG: using smp_processor_id() in preemptible [00000000] code:
 icedove-bin/5449

On 25.05.2010 12:05, Piotr Hosowicz wrote:
> On 25.05.2010 12:00, Peter Zijlstra wrote:
>> On Tue, 2010-05-25 at 11:57 +0200, Piotr Hosowicz wrote:
>>> On 25.05.2010 11:43, Ingo Molnar wrote:
>>>
>>>> This doesnt fix the whole issue. cpu_clock() is local, while the
>>>> measurements
>>>> done in the blk code are global ...
>>>>
>>>> While the warning is fixed this way, the far more serious issue is
>>>> still
>>>> there: time can go backwards if two points of time measurement are on
>>>> different CPUs and can mess up the statistics with negative values,
>>>> etc...
>>>
>>> How serious is this? Can it damage my data? I ask because the machine is
>>> my private computer, not any test machine.
>>
>> I'm not sure, since I didn't really look what they use the timestamps
>> for, but a guess would say your data is safe, it might schedule the io
>> funny, but it should not compromise integrity. At best its used purely
>> for statistics and not even behaviour is affected.
>
> Thanks.

Seems to work like a charm. I ask my question anew - shall I have to 
apply the patch each time I update my kernel tree?

Regards,

Piotr Hosowicz

-- 
Janusz Korwin-Mikke:
"Idiota z dyplomem to taki sam idiota,
jak przedtem - tylko z pretensjami."
NP: Slash - Ghost (Feat. Ian Astbury)
NB: 2.6.34-20100524-1752-patched
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