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    SubjectRe: [BUG] ide dma_timer_expiry, then hard lockup
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    Hi Sergei,

    On Tue, Jun 19, 2007 at 06:07:07PM +0400, Sergei Shtylyov wrote:
    >
    > Stuart_Hayes@Dell.com wrote:
    > >I think reading the IDE status register clears the interrupt in the IDE
    > >device, which might be causing the drive to think it's OK to generate
    > >another interrupt.
    >
    > This is not how IDE drives are supposed to act -- they won't proceed any
    > further until "interrupt pending" condition is cleared, so these aren't
    > supposed to be "stacked". This behavior however is not strictly specified
    > by ATA standards IIRC, but I can't readily imagine such situaltion anyway
    > unless tagged command queueing (which is not supported by IDE core) and/or
    > ATAPI command overlapping is in action...

    The problem only manifests during high io load; perhaps a missing mutex
    somewhere is blasting one thing too many out to the hard drive?

    > > This could either cause it to get stuck trying to
    > >service an interrupt that is never getting cleared as you suggested, or
    > >possibly when the next IRQ comes in the IDE IRQ handler gets stuck
    > >waiting for a spinlock that the code you're looking at already owns...?
    >
    > I could also imagine the HPT366 chip going mad and stalling the reads if
    > the taskfile regs forever because of the incomplete DMA or even the drive
    > going mad and not replying to I/O cycles with proper -IORDY handshake (i.e.
    > holding it low all the time)...

    In my case, ctrl-alt-sysrq doesn't work, which makes it hard to debug.

    I'm thinking that trying to debug libata is a better idea, rather than
    investing time in ide, right? Although at the moment, libata works even
    less; see other email.

    --linas

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