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SubjectRe: [BUG] ide dma_timer_expiry, then hard lockup

Linas Vepstas wrote:

>> 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?

Hm... not sure about this.

>>>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.

Which makes me think this really is some *hardware* issue.

> --linas

MBR, Sergei
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