From: Jeff Garzik <jeff@garzik.org>
To: Tejun Heo <tj@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Andrew Morton <akpm@linux-foundation.org>,
linux-ide@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>,
Zeno Davatz <zdavatz@gmail.com>, Andrew Benton <b3nton@gmail.com>
Subject: Re: [git patches] libata updates for 2.6.34
Date: Sun, 14 Mar 2010 22:55:55 -0400 [thread overview]
Message-ID: <4B9DA1BB.9010808@garzik.org> (raw)
In-Reply-To: <4B971F83.4030505@kernel.org>
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.
Jeff
prev parent reply other threads:[~2010-03-15 3:02 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-03-01 20:23 [git patches] libata updates for 2.6.34 Jeff Garzik
2010-03-05 18:58 ` Bartlomiej Zolnierkiewicz
2010-03-05 18:37 ` Alan Cox
2010-03-05 19:43 ` Jeff Garzik
2010-03-05 20:12 ` Bartlomiej Zolnierkiewicz
2010-03-09 21:17 ` Linus Torvalds
2010-03-09 22:12 ` Jeff Garzik
2010-03-10 4:26 ` Tejun Heo
2010-03-12 0:16 ` Jeff Garzik
2010-03-15 2:55 ` Jeff Garzik [this message]
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