Re: [BUG] ide dma_timer_expiry, then hard lockup

[Sergei Shtylyov <sshtylyov@ru.mvista.com>]

Hello.

Linas Vepstas 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?

   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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