Panic on boot after upgrade from r320827 -> r320869

[Michael Butler]

On 7/11/17 1:09 PM, Warner Losh wrote:
>> On a machine with SDHCI, a clean rebuild (after "r -rf /usr/obj") refuses
>> to find /dev/ada0 :-(
>>
> 
> Take sdhci out of the kernel and try again. If that works, it tells us one
> thing (need to troubleshoot sdhci stuff more). If not it tells us another
> (need to troubleshoot CAM more), do we get errors with the ATA_IDENTIFY
> command? Does it try multiple times per AHCI port? What AHCI device do you
> have? You may need to scroll back with the screen-lock / pageup keys to see
> these messages.
> 
> Plus we know we have at least one bug in meta-mode rebuilding since not
> everything is being rebuilt that should be across this change.
> 
> The change itself didn't change CAM except for copying one set of data it
> didn't used to, into a structure whose size grew (which is why we're seeing
> crashes / failures for a 'cross-threaded' rebuild). There's nothing else
> that changed (especially after I removed the bogus debug printfs) that I
> can see in auditing the change.
> 
> I was really hoping David's machine would exhibit the behavior since we're
> co-workers and have a shared infrastructure for debugging we can leverage.

I'll try this tonight when I'm back at home. The laptop concerned uses 
the ICH-7M part in "legacy mode" so it doesn't do AHCI at all :-(

	imb