linux-kernel - Re: [git patches] libata updates for 2.6.34

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Date:	Mon, 15 Mar 2010 08:33:05 +0100
From:	Zeno Davatz <zdavatz@...il.com>
To:	Jeff Garzik <jeff@...zik.org>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [git patches] libata updates for 2.6.34

On Mon, Mar 15, 2010 at 3:55 AM, Jeff Garzik <jeff@...zik.org> wrote:
> On 03/09/2010 11:26 PM, Tejun Heo wrote:
>>
>> Hello, Linus, Jeff.
>>
>> On 03/10/2010 07:12 AM, Jeff Garzik wrote:
>>>
>>> Coincedentally, it looks like someone else just reported the same
>>> problem, with 2.6.34-rc1.
>>>
>>> It definitely sounds like a race.  READ DMA is a DMA command as the name
>>> implies, so that eliminates the possibility of polling-related paths in
>>> ata_sff_interrupt (libata-sff.c).
>>>
>>> I'll flip some of my machines to the icky slow boring piix mode, rather
>>> than sexy AHCI mode :) to see if I can reproduce.  I have had a feeling
>>> that we needed a more sophisticated IRQ handling setup, this may be what
>>> was needed.  Lost interrupt recovery should occur faster than 30 seconds
>>> in any case, and should not require a hard reset if the hardware
>>> functions just fine outside of the lost-interrupt / race that just
>>> occurred.
>>
>> Yeap, there is a race condition with clearing which I don't think we
>> can solve completely but with some modification I think we can at
>> least cover known failure cases.
>>
>> For longer term, I don't think we can solve this by diddling with the
>> SFF registers.  The interface is just way too ancient and horrid to
>> build anything reliable on top of.  I'm planning on implementing
>> smarter IRQ storm handling and stepped timeouts for ATA commands.
>
> A tester on this bug
>        http://bugzilla.kernel.org/show_bug.cgi?id=15537
> seemed to find success with the patch.

Thanks for the Update!

I will wait some more and then test rc-2.

Best
Zeno
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