Simon Burge wrote:

> For the two panics I've seen so far:
> 
> pc: fffffc00004e27a0 (in pciide_dma_start)
> ra: fffffc00004e2798 (in pciide_dma_start)
> 
> pc: fffffc0000300640 (in idle)
> ra: fffffc000036600c (in mi_switch)

And a third at:

pc: fffffc000036f178 (in _pool_get)
ra: fffffc0000338018 (in wdc_get_xfer)

As per Matt Jacob's suggestion, I tried turning off DMA for the disks
seems to have worked - I've now restored two full tapes and haven't
seen a problem, whereas before I was three from three for panics vs.
restores.

Now the problem is that I get about 4MB/sec with bonnie instead of
18MB/sec.  Is it worth trying lower DMA mode to try to get some
performance back?  It was originally using DMA 2 two - I could try DMA
mode 1...

I'm not cluefull enough to know why DMA would cause the machine checks -
obviously something's getting fratzed on a bus somewhere.  Is this more
likely to be a driver or hardware problem?

Simon.