Re: [PATCH v4 2/5] x86, traps: Track entry into and exit from IST context

Paul E. McKenney
2015-01-28T20:18:54Z

On Wed, Jan 28, 2015 at 08:33:06AM -0800, Andy Lutomirski wrote:
> On Fri, Jan 23, 2015 at 5:25 PM, Andy Lutomirski <luto@amacapital.net> wrote:
> > On Fri, Jan 23, 2015 at 12:48 PM, Sasha Levin <sasha.levin@oracle.com> wrote:
> >> On 01/23/2015 01:34 PM, Andy Lutomirski wrote:
> >>> On Fri, Jan 23, 2015 at 10:04 AM, Borislav Petkov <bp@alien8.de> wrote:
> >>>> On Fri, Jan 23, 2015 at 09:58:01AM -0800, Andy Lutomirski wrote:
> >>>>>> [ 543.999079] Call Trace:
> >>>>>> [ 543.999079] dump_stack (lib/dump_stack.c:52)
> >>>>>> [ 543.999079] lockdep_rcu_suspicious (kernel/locking/lockdep.c:4259)
> >>>>>> [ 543.999079] atomic_notifier_call_chain (include/linux/rcupdate.h:892 kernel/notifier.c:182 kernel/notifier.c:193)
> >>>>>> [ 543.999079] ? atomic_notifier_call_chain (kernel/notifier.c:192)
> >>>>>> [ 543.999079] notify_die (kernel/notifier.c:538)
> >>>>>> [ 543.999079] ? atomic_notifier_call_chain (kernel/notifier.c:538)
> >>>>>> [ 543.999079] ? debug_smp_processor_id (lib/smp_processor_id.c:57)
> >>>>>> [ 543.999079] do_debug (arch/x86/kernel/traps.c:652)
> >>>>>> [ 543.999079] ? trace_hardirqs_on (kernel/locking/lockdep.c:2609)
> >>>>>> [ 543.999079] ? do_int3 (arch/x86/kernel/traps.c:610)
> >>>>>> [ 543.999079] ? trace_hardirqs_on_caller (kernel/locking/lockdep.c:2554 kernel/locking/lockdep.c:2601)
> >>>>>> [ 543.999079] debug (arch/x86/kernel/entry_64.S:1310)
> >>>>>
> >>>>> I don't know how to read this stack trace. Are we in do_int3,
> >>>>> do_debug, or both? I didn't change do_debug at all.
> >>>>
> >>>> It looks like we're in do_debug. do_int3 is only on the stack but not
> >>>> part of the current frame if I can trust the '?' ...
> >>>>
> >>>
> >>> It's possible that an int3 happened and I did something wrong on
> >>> return that caused a subsequent do_debug to screw up, but I don't see
> >>> how my patch would have caused that.
> >>>
> >>> Were there any earlier log messages?
> >>
> >> Nope, nothing odd before or after.
> >
> > Trinity just survived for a decent amount of time for me with my
> > patches, other than a bunch of apparently expected OOM kills. I have
> > no idea how to tell trinity how much memory to use.
>
> A longer trinity run on a larger VM survived (still with some OOM
> kills, but no taint) with these patches. I suspect that it's a
> regression somewhere else in the RCU changes. I have
> CONFIG_PROVE_RCU=y, so I should have seen the failure if it was there,
> I think.

If by "RCU changes" you mean my changes to the RCU infrastructure, I am
going to need more of a hint than I see in this thread thus far. ;-)

Thanx, Paul