linux-kernel - Re: [PATCH -v3] perf, x86: try to handle unknown nmis with running perfctrs

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Message-ID: <20100825235229.GC5389@nowhere>
Date:	Thu, 26 Aug 2010 01:52:31 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Cyrill Gorcunov <gorcunov@...il.com>
Cc:	Don Zickus <dzickus@...hat.com>,
	Robert Richter <robert.richter@....com>,
	Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <peterz@...radead.org>,
	Lin Ming <ming.m.lin@...el.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Huang, Ying" <ying.huang@...el.com>,
	Yinghai Lu <yinghai@...nel.org>,
	Andi Kleen <andi@...stfloor.org>
Subject: Re: [PATCH -v3] perf, x86: try to handle unknown nmis with running
	perfctrs

On Wed, Aug 25, 2010 at 12:40:38AM +0400, Cyrill Gorcunov wrote:
> On Tue, Aug 24, 2010 at 04:27:18PM -0400, Don Zickus wrote:
> > On Tue, Aug 24, 2010 at 11:52:40PM +0400, Cyrill Gorcunov wrote:
> > > > I use 2.6.34 atm. Letme try 2.6.36 (which might require some time to recompile).
> > > > 
> > > > 	-- Cyrill
> > > 
> > > Don, for me it fails with somehow unrelated page handling fault - in
> > > reiserfs_evict_inode O_o Fails in __get_cpu_var I suspect might means
> > > a problem either in per-cpu allocator itself or we screw pointer somehow.
> > > Weird.
> > 
> > I just found out (with the help of the crash utility and Dave A.) that
> > Robert's percpu struct nmi clashes with the exception entry point .nmi.
> > I only see this problem in 2.6.36, so I am not sure what changed with
> > regards to compiler flags to confuse variables with text segments.
> > 
> 
> yeah, I suspect name clashes here but then I did grep over per-cpu variables
> in whole kernel and didn't find match so I thought the assumption was wrong,
> but eventually it happens to be true but via other way :) good to know, thanks!
> 
> > But renaming the percpu struct nmi to nmidon fixed the problem for me (I
> > am open to other suggestions :-) ).
> 
> nmi_don_zickus ;) well, I think nmi_pmu or something like that
> might be a bit modest ;)
> 
> > 
> > Regarding your reiserfs, what was the variable's name?
> > 
> 
> It seems to be different, it's pity that I had only 80x25 vga
> mode and was unable to snap the whole log. But actually I didn't
> even check precisely all .config options I had set since I was
> more interested in early stage where per-cpu access should already
> happen rather then real init'ed environmen. But I think I'll be
> moving completely to .36 this week so we will see how it goes.


There was a missing "return" in the end of reiserfs_evict_inode.

It has been fixed there:

http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=f4ae2faa40199b97b12f508234640bc565d166f8

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