linux-kernel - Re: [PATCH] perf report: fix off-by-one for non-activation frames

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Date:   Tue, 16 May 2017 11:00:27 +0200
From:   Milian Wolff <milian.wolff@...b.com>
To:     Namhyung Kim <namhyung@...nel.org>
Cc:     Linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
        Arnaldo Carvalho de Melo <acme@...hat.com>,
        David Ahern <dsahern@...il.com>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Yao Jin <yao.jin@...ux.intel.com>, kernel-team@....com
Subject: Re: [PATCH] perf report: fix off-by-one for non-activation frames

On Dienstag, 16. Mai 2017 03:57:53 CEST Namhyung Kim wrote:
> On Mon, May 15, 2017 at 05:13:06PM +0200, Milian Wolff wrote:
> > On Monday, May 15, 2017 5:04:44 PM CEST Milian Wolff wrote:
> > > As the documentation for dwfl_frame_pc says, frames that
> > > are no activation frames need to have their program counter
> > > decremented by one to properly find the function of the caller.
> > 
> > Note that this leaves the perf build against libunwind in the current,
> > broken state. I do not know how to detect the activation property there.
> > Does anyone else? See elfutils source code for what it is doing:
> > 
> > https://sourceware.org/git/?p=elfutils.git;a=blob;f=libdwfl/
> > dwfl_frame_pc.c;h=296c815b9c73f42d79ac1778d2a0c420b89ee4eb;hb=HEAD
> 
> It seems that you can use unw_is_signal_frame().

Thank you! The v2 patch I just sent now uses that and it seems to work 
reliably in my quick test.

Cheers

-- 
Milian Wolff | milian.wolff@...b.com | Software Engineer
KDAB (Deutschland) GmbH&Co KG, a KDAB Group company
Tel: +49-30-521325470
KDAB - The Qt Experts
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