Re: [ARM32] panic when sshd responding

["Chris Gilbert" <chris%dokein.co.uk@localhost>]

On Thu, June 19, 2008 10:49 am, Andy Shevchenko wrote:
> The last patch is wrong. There is some kind of lucky.

Yes, it is :)  I discussed this with Matt, and we think the issue is that
pmap_kenter_pa is being a bit too paranoid in trying to avoid cache alias
issues.  And that's what the KASSERT is trying to detect.

We think the right thing to do is assert there are no managed writeable
mappings (which there shouldn't be as the loan switches the pages to read
only, and so flushes the data & write back cache)

However, the current code has a risk that the double pmap_kenter_pa sets
the KENTER flag on the page, and pmap_kremove clears it, as there's no
reference counting.

Commenting out the KASSERT should make it work, but you might also have to
remove the KASSERT about KENTER as well in pmap_kremove.

> The set of experiment with disabled ARM data cache shows stability and
> absence of this new part of bug.

Again probably luck :)

Thanks,
Chris