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    SubjectRe: 2.4.21-pre4: PDC ide driver problems with shared interrupts
    Benjamin Herrenschmidt wrote:

    >>Okay, I had to watch for it a bit longer and it turns out that the kernel PDC driver has a problem in this shared interrupt setup. When loads get high it seems to run into some timing problem which causes things like:
    >>
    >>Feb 4 01:02:22 admin kernel: hde: dma_intr: status=0xd0 { Busy }
    >>
    >>
    >>
    Since the busy bit is set, we know the drive must have received a
    command. Since dma_intr thought the drive was not busy, an interrupt
    must have snuck through between the command being issued and the dma
    being started. I think in my original patch, I had the dma start
    outside of the spinlock, that is a bug. The command to the controller
    to start the dma must be inside of the spinlock.

    I have not looked at 2.4.21-pre4 at all, so I could be entirely off base
    here.

    Ross

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