Message-ID: <4D79F92A.20402@canonical.com>
Date:	Fri, 11 Mar 2011 11:27:54 +0100
From:	Stefan Bader <stefan.bader@...onical.com>
To:	Tejun Heo <tj@...nel.org>
CC:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-ide@...r.kernel.org, Jeff Garzik <jgarzik@...ox.com>,
	Andy Whitcroft <apw@...onical.com>
Subject: Re: Some hints needed how to handle SATA ALPM failures

On 02/18/2011 05:51 PM, Stefan Bader wrote:
> On 02/18/2011 05:16 PM, Tejun Heo wrote:
>> Hello,
>>
>> On Fri, Feb 18, 2011 at 04:55:45PM +0100, Stefan Bader wrote:
>>> Sorry that was not specific enough. It is remounting ro, which can
>>> leave the fs in a better or worse state.
>>
>> I see and, nope, that shouldn't lead to corrupted filesystem on a
>> journaled filesystem.  I agree it sucks tho.  This shouldn't be
>> happening with newer kernels unless the hardware completely shuts
>> down, which some very early SATA harddrives did but shouldn't happen
>> with most modern devices.  Backporting the fix isn't difficult.
>>
>>>> Also, the whole LPM thing got revamped several releases ago.  Can you
>>>> please test how the recent kernels behave?  There will be failures as
>>>> not all hardware can handle LPM well but those failures shouldn't lead
>>>> to any catastrophic failures like ro remounting of filesystem.
>>>
>>> The example output given as footnotes in the original post were taken from the
>>> latest re-test someone did on a 2.6.38-rc5 kernel (same user also reported bad
>>> experience with a 2.6.35 based kernel). The comment we got on that was:
>>>
>>> "Here's what i get - the drive led lights continuously for about 10 seconds
>>> during which any hdd access results in hanging process:"
>>>
>>> [12348.040077] ata3.00: exception Emask 0x0 SAct 0x1 SErr 0x150000 action 0x6 frozen
>>> [12348.040086] ata3: SError: { PHYRdyChg CommWake Dispar }
>>> [12348.040091] ata3.00: failed command: READ FPDMA QUEUED
>>> [12348.040099] ata3.00: cmd 60/10:00:b0:94:c5/00:00:03:00:00/40 tag 0 ncq 8192 in
>>> [12348.040101] res 40/00:00:00:4f:c2/00:00:00:00:00/00 Emask 0x4 (timeout)
>>> [12348.040104] ata3.00: status: { DRDY }
>>> [12348.040112] ata3: hard resetting link
>>> [12348.390082] ata3: SATA link up 1.5 Gbps (SStatus 113 SControl 300)
>>> [12348.404414] ata3.00: configured for UDMA/133
>>> [12348.404550] ata3.00: device reported invalid CHS sector 0
>>> [12348.404570] ata3: EH complete
>>>
>>> I believe the details of the failures varied but "READ FPDMA QUEUED" and a
>>> timeout were usually involved.
>>
>> It's on NVIDIA ahci, right?  This shouldn't be happening with intel
>> and jmb ones, which were used while implementing.  The problem is most
>> likely controller dependent.  One possibility is the controller is not
>> happy with DIPM.  Does specifying "medium_power" instead make the
>> problem go away?  Can the bug reporter try some kernel patches?
>>
> 
> Yes, it is an Nvidia MCP67 in ahci mode. I can relay the question about
> medium_power and yes we can try patches. If not the reporter, I can prepare
> kernels and ask for testing.
> One question in general would be whether (if it cannot be said for sure which
> controller is good or not) it may be a good idea to add some whitelisting for
> those known to work and disable (or limit the mode) for the unknown.
> 
> -Stefan
>> Thanks.
>>
> 
Sorry for the delay. So medium power is ok. Only minimum causes the problems
(again this was a relative recent kernel with ndvidia controller). What kind of
information is needed for further debugging?

Stefan
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