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

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Message-ID: <20150128174817.GQ19109@linux.vnet.ibm.com>
Date:	Wed, 28 Jan 2015 09:48:17 -0800
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	Sasha Levin <sasha.levin@...cle.com>,
	Borislav Petkov <bp@...en8.de>, X86 ML <x86@...nel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Tony Luck <tony.luck@...el.com>,
	Andi Kleen <andi@...stfloor.org>,
	Josh Triplett <josh@...htriplett.org>,
	Frédéric Weisbecker <fweisbec@...il.com>
Subject: Re: [PATCH v4 2/5] x86, traps: Track entry into and exit from IST
 context

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@...capital.net> wrote:
> > On Fri, Jan 23, 2015 at 12:48 PM, Sasha Levin <sasha.levin@...cle.com> wrote:
> >> On 01/23/2015 01:34 PM, Andy Lutomirski wrote:
> >>> On Fri, Jan 23, 2015 at 10:04 AM, Borislav Petkov <bp@...en8.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

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