Re: [BProc] Re: oops 3.2.6 w/sigbypass on 2.4.20

[Nicholas H. <he...@se...>]

On Wed, 2003-12-10 at 12:51, er...@he... wrote:
> 
> Hrm.  There's a lot of craziness in there.  Are all these oopses from
> the master node?  I'm going to assume yes for now.  Also, can I
> presume that you're not mixing master and slave nodes?  In other
> words, you're not running a bpslave on the same machine where you're
> running a bpmaster.

No strangeness in the setup, all are actuall hardware, and master is a
different node from slave.

> 
> >From what I've seen so far, I strongly suspect that there's a kernel
> stack overflow happening somewhere.  Some of the backtraces you're
> sending are very long which isn't a good sign.

I would put money on that, it makes sense -- especially from the oddness
we have been seeing lately in the bproc backtraces.

> 
> Some evidence that could support this theory is that the "ghost"
> pointer seems to have gotten set to 0x1 which is clearly an invalid
> pointer.  That led to the "g->last_response = jiffies;" line exploded.
> I don't think there's any plausible way of the pointer getting set
> like that except for some kind of random corruption.  Another clue is
> that the back traces are including calls to both ghost and masq stuff.
> ghost stuff is fine on the front end but masq stuff should *never* be
> called on the front end at all.  The only way that that would happen
> is if a process's masq pointer (in task_struct) got set to something
> non-zero.  Both of these live right at the end of task_struct so
> they'll be the first to get clobbered by a stack overflow.
> 
> Do you have CONFIG_DEBUG_STACKOVERFLOW turned on?  It might let us
> know if that's what's going on here.  If it is, it will give us a
> trace at the time of overflow - not some time later when BProc tries
> to use the corrupted data - and that would be very useful.

Darn -- well, I actually had turned that off, as it was oopsing all over
the place. I think I emailed you about that, or at least were talking
about reducing the size of the things on the kernel stack. See the
message on Sept17 Subject:2.4.20 oops. 

So, what can i do ? I can turn that option back on, and see if the
oopses are the same as in Sept.

Thanks for the help!
Nic
-- 
Nicholas Henke
Penguin Herder & Linux Cluster System Programmer
Liniac Project - Univ. of Pennsylvania