Messages in this thread | | | Subject | Re: [PATCH 0/16] DMA-API debugging facility v2 | From | David Woodhouse <> | Date | Fri, 06 Feb 2009 07:56:46 +0000 |
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On Thu, 2009-02-05 at 18:05 -0800, Chris Wright wrote: > extra tab
Thanks. Your code to hook it up is better than mine too. I'll steal that.
> Sample output below (2 of ~2500 faults), pages don't appear to be > mapped:
What machine did you get that on?
Yeah, I saw one of those. If could be a driver bug, of course -- it could be unmapping a range before it's actually finished with it. But that's unlikely.
An alternative explanation... The DMA is aborted¹, and the device interrupts us to tell us about it at the _same_ time that the IOMMU interrupts us to tell us about the fault. We process the device interrupt first, unmap that buffer. And then we process the IOMMU interrupt... and the buffer is already gone from the list.
It might be interesting to make this code also remember and print the last range that was unmapped, as well as the currently-mapped ranges.
> (interesting hash_fn spread ;-)
Yeah, that's a little suboptimal, isn't it :)
-- David Woodhouse Open Source Technology Centre David.Woodhouse@intel.com Intel Corporation
¹ due to the bug we're chasing now. The range _is_ supposed to be mapped.
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