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

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Date:	Tue, 25 May 2010 12:05:44 +0200
From:	Piotr Hosowicz <piotr@...owicz.com>
To:	Peter Zijlstra <peterz@...radead.org>
CC:	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 12:00, 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.

Cheers,

Piotr Hosowicz

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