Subject: Re: com rumblings...
To: Bill Studenmund <>
From: David Laight <>
List: tech-kern
Date: 06/21/2006 00:09:58
On Mon, Jun 19, 2006 at 06:45:28PM -0700, Bill Studenmund wrote:
> > (The 'easy' way is to connect the IRQ line from the UART to a logic
> > analiser timing port, set it to trigger on the signal being active
> > for > some_time, connect the trigger-out of the analiser to the systems
> > NMI line, and use the NMI to enter ddb, then look at the traceback.)
> Actually, mac68k has seen the same issue. I've seen anticdotal problems 
> springing up in the 1.5/1.6 time frame.
> Another way to test this is to instrument splx() so that it remembers the 
> IPL it is dropping from. Then when you see an overflow, you ask the IPL 
> code what level splx last left, and you know what IPL is your issue.

The PL level splx() is dropping from isn't relevant.
You need the PC that the ISR interrupted (and if in splx where that
was called from), and the ISR that executed immediately previously.
None of which is actually that hard to get.


David Laight: