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

Andy Lutomirski
2015-01-28T20:26:52Z

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.

--Andy