linux-kernel - Re: [PATCH v9 00/14] Add support for remote unwind

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Date:	Tue, 7 Jun 2016 12:12:15 -0300
From:	Arnaldo Carvalho de Melo <acme@...nel.org>
To:	Hekuang <hekuang@...wei.com>
Cc:	Jiri Olsa <jolsa@...hat.com>, peterz@...radead.org,
	mingo@...hat.com, alexander.shishkin@...ux.intel.com,
	wangnan0@...wei.com, jpoimboe@...hat.com, ak@...ux.intel.com,
	eranian@...gle.com, namhyung@...nel.org, adrian.hunter@...el.com,
	sukadev@...ux.vnet.ibm.com, masami.hiramatsu.pt@...achi.com,
	tumanova@...ux.vnet.ibm.com, kan.liang@...el.com,
	penberg@...nel.org, dsahern@...il.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v9 00/14] Add support for remote unwind

Em Sat, Jun 04, 2016 at 01:39:04PM +0800, Hekuang escreveu:
> 在 2016/6/4 5:09, Arnaldo Carvalho de Melo 写道:
> > Em Fri, Jun 03, 2016 at 06:06:02PM -0300, Arnaldo Carvalho de Melo escreveu:
> > > Anyway, please try your patchkit with 'perf top' and 'perf trace', as
> > > both don't use perf.data files, i.e. they work 'live', so probably
> > > things that you touch in normalize_arch() are not initialized and need
> > > to be setup.
> > Ah, no need to resend the whole patchkit, just find out what is the bug
> > and send me a patch and I'll insert it at the right point to avoid
> > introducing a bisect breaking point.

> > Your patchkit is in my perf/unwind branch at my tree, I already added
> > Jiri's Acked-by in all the patches.

> > git://git.kernel.org/pub/scm/linux/kernel/git/acme/linux.git

> I send the updated one after PATCH 10/14,  env->arch is null in live mode,
> comments are added and "perf top/trace" works now.

Ok, now it fails 'perf test unwind' and I bisected it to:


[acme@...et linux]$ git bisect good
e2b6ce1ca32cedeb2cef08f49aa812f0eadcc3c5 is the first bad commit
commit e2b6ce1ca32cedeb2cef08f49aa812f0eadcc3c5
Author: He Kuang <hekuang@...wei.com>
Date:   Fri Jun 3 03:33:19 2016 +0000

    perf unwind: Check the target platform before assigning unwind methods
    
    Currently, 'perf script' uses host unwind methods to parse perf.data
    callchain info without taking the target architecture into account, i.e.
    assuming the perf.data file was generated on the same machine where the
    analysis is being performed. So we get wrong result without any warnings
    when unwinding callchains of x86(32-bit) on x86(64-bit) machine.
    
    This patch adds an extra step that checks the target platform before
    assigning unwind methods. In later patches in this series, we can use
    this info to assign the right unwind methods for supported platforms.