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

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Date:	Fri, 10 Sep 2010 18:37:27 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Robert Richter <robert.richter@....com>
Cc:	Don Zickus <dzickus@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	"gorcunov@...il.com" <gorcunov@...il.com>,
	"fweisbec@...il.com" <fweisbec@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"ying.huang@...el.com" <ying.huang@...el.com>,
	"ming.m.lin@...el.com" <ming.m.lin@...el.com>,
	"yinghai@...nel.org" <yinghai@...nel.org>,
	"andi@...stfloor.org" <andi@...stfloor.org>,
	"eranian@...gle.com" <eranian@...gle.com>
Subject: Re: [PATCH 0/3 v2] nmi perf fixes


* Robert Richter <robert.richter@....com> wrote:

> On 10.09.10 10:46:34, Ingo Molnar wrote:
> > 
> > * 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
> 
> I try to reproduce it, which systems are affected?

This is an older Barcelona box, will send you a dump of details off-list.

> > 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.
> 
> The patch below adds ratelimits.

This doesnt solve things though - even one unnecessary message will 
confuse users.

	Ingo
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