[Crash-utility] bt: cannot determine starting stack pointer

[Dave Anderson]

----- Original Message -----
> On 02/15/12 06:36, Dave Anderson wrote:

> 
> I'm not too surprised.  In the world of back-end clustered storage systems,
> updating systems is a massive security/stability concern.  Consequently,
> new fangled stuff from less than a decade ago get incorporated slowly. :)
> 
> Analysis tools, however, can be (and are!!) updated.
> 
> > That being said, it's news to me that backtraces cannot be generated
> > for the active tasks from LKCD dumpfiles, unless it's some kind of
> > "live dump" or something?  Was there a panic or oops?  What's the
> > last thing shown by the "log" command?
> 
> Yes, it is a live dump, if that's what you mean by a crash dump.

OK, yes that's what I meant.  And that's unfortunate...

> Figuring out why ptlrpc_invalidate_import() is struggling is what I signed up for
> learning how to do.  Coercing crash into giving me stack traces for live/onproc
> processes is what I was hoping you would please be kind enough to help me figure out.
> My solution is the script (attached) that requires me to type four commands:
> 
>  > crash> ! bash live-bt.sh
>  > crash> < c-cmd
>  > crash> < c-cmd
>  > crash> < c-cmd

That's about the best you can do.  The task->stack pointer holds a
reference to the last time the task blocked in schedule(), but
the active tasks are either in user-space, or have re-entered the
kernel for another purpose.  If you can find something useful in
their stacks, then go for it -- and good luck!

Dave