linux-kernel - Re: [PATCH 0/3 v2] nmi perf fixes

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Message-ID: <20100910144634.GA1060@elte.hu>
Date:	Fri, 10 Sep 2010 16:46:34 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Don Zickus <dzickus@...hat.com>
Cc:	Peter Zijlstra <peterz@...radead.org>, robert.richter@....com,
	gorcunov@...il.com, fweisbec@...il.com,
	linux-kernel@...r.kernel.org, ying.huang@...el.com,
	ming.m.lin@...el.com, yinghai@...nel.org, andi@...stfloor.org,
	eranian@...gle.com
Subject: Re: [PATCH 0/3 v2] nmi perf fixes


* Don Zickus <dzickus@...hat.com> wrote:

> On Fri, Sep 10, 2010 at 01:41:40PM +0200, Peter Zijlstra wrote:
> > On Thu, 2010-09-02 at 15:07 -0400, Don Zickus wrote:
> > > Fixes to allow unknown nmis to pass through the perf nmi handler instead
> > > of being swallowed.  Contains patches that are already in Ingo's tree.  Added
> > > here for completeness.  Based on ingo/tip
> > > 
> > > Tested on intel/amd
> > > 
> > > v2: patch cleanups and consolidation, no code changes
> > > 
> > > Don Zickus (1):
> > >   perf, x86: Fix accidentally ack'ing a second event on intel perf
> > >     counter
> > > 
> > > Peter Zijlstra (1):
> > >   perf, x86: Fix handle_irq return values
> > > 
> > > Robert Richter (1):
> > >   perf, x86: Try to handle unknown nmis with an enabled PMU
> > > 
> > >  arch/x86/kernel/cpu/perf_event.c       |   59 +++++++++++++++++++++++++-------
> > >  arch/x86/kernel/cpu/perf_event_intel.c |   15 +++++---
> > >  arch/x86/kernel/cpu/perf_event_p4.c    |    2 +-
> > >  3 files changed, 56 insertions(+), 20 deletions(-)
> > 
> > Both Ingo and I are getting Dazed and confused on our AMD machines, it
> > started before yesterday (that is, after backing out all my recent
> > changes it still gets dazed), so I suspect this set.
> > 
> > I'll look at getting a trace of the thing, but if any of you has a
> > bright idea...
> 
> What are you running to create the problem?  I can try and duplicate 
> it here.

It happens easily here - just running something like:

   perf record -g ./hackbench 10

a couple of times triggers it. Note, unlike with the earlier bug, the 
NMIs are not permanently 'stuck' - and everything continues working. 
Obviously the messages are nasty looking so this is a regression we need 
to fix.

Thanks,

	Ingo
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