Subject: Re: 3.1_STABLE and SMP
To: Andrew Doran <>
From: Stephen Borrill <>
List: port-i386
Date: 04/27/2007 14:29:02
On Fri, 20 Apr 2007, Andrew Doran wrote:
> On Fri, Apr 20, 2007 at 12:46:53PM +0100, Stephen Borrill wrote:
>>> Do you have a DDB stack backtrace, assuming you can get into DDB from
>>> the hung state?
>> I got emailed a screenshot of one:
> I have seen reports of something similar. In addition to what Greg
> mentioned, it's possible that:
> - this CPU holds the kernel lock and is spin waiting on the pmap lock
> - another cpu holds the pmap lock, has taken an interrupt, and is spin
>  waiting on the kernel lock
> That should not happen unless there is a bug somewhere. How many CPUs does
> the machine have? If it happens again, could you ask the custy to do a:
> mach cpu 0
> tr
> mach cpu 1
> tr
> mach cpu ...
> tr
> A dump of the held simplelocks would be good to get too

And to follow up my last mail which linked to:

I had another crash (handwritten backtrace):

CPU 0:
--- interrupt ---
syscall_plain 202

CPU 1:
syscall_plain 59

In common with the first panic, this seems to be on process exit in 

Hope this helps,