linux-kernel - Re: [GIT PULL] perf fixes

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Date:	Tue, 1 Oct 2013 10:42:47 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Andi Kleen <ak@...ux.intel.com>
Cc:	Markus Trippelsdorf <markus@...ppelsdorf.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: Re: [GIT PULL] perf fixes


* Andi Kleen <ak@...ux.intel.com> wrote:

> > > Hmm, works for me. In fact I wrote it to fix a perf top issue.
> >
> > What 'issue' and why wasn't it described in the changelog more 
> > accurately?
> >
> > The blurb you wrote in the changelog:
> > 
> > | The libbfd C++ demangler doesn't seem to deal with cloned functions, 
> > | like symbol.clone.NUM.
> > |
> > | Just strip the dot part before demangling and add it back later.
> > 
> > Only alludes to a C++ symbol resolution annoyance and thus isn't very 
> > informative.
> 
> The issue was that I saw a long unreadable line noise string in 
> report/top, instead of a demangled function. After I stripped the 
> postfix I got the demangled symbol as expected.

We obviously don't want to trade output annoyances for crashes, nor does 
it justify the code uglies you introduced with the patch - which made the 
code obviously unrobust.

My guess would be that maybe it's the cast of a const pointer that 
possibly broke GCC's aliasing detection on Markus's system or so. But 
maybe there's a more direct bug in the code as well, the code you added is 
too ugly to be reviewed efficiently, please send a cleaned up version.

Thanks,

	Ingo
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