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    SubjectRe: [git patches] libata updates for 2.6.34
    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




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