linux-kernel - Re: [PATCH v7 13/14] perf callchain: Support x86 target platform

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Date:	Wed, 1 Jun 2016 10:40:27 +0200
From:	Jiri Olsa <jolsa@...hat.com>
To:	He Kuang <hekuang@...wei.com>
Cc:	peterz@...radead.org, mingo@...hat.com, acme@...nel.org,
	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 v7 13/14] perf callchain: Support x86 target platform

On Tue, May 31, 2016 at 11:19:11AM +0000, He Kuang wrote:

SNIP

> diff --git a/tools/perf/util/unwind-libunwind.c b/tools/perf/util/unwind-libunwind.c
> index e183390..5774317 100644
> --- a/tools/perf/util/unwind-libunwind.c
> +++ b/tools/perf/util/unwind-libunwind.c
> @@ -5,6 +5,7 @@
>  #include "arch/common.h"
>  
>  struct unwind_libunwind_ops __weak *local_unwind_libunwind_ops;
> +struct unwind_libunwind_ops __weak *x86_32_unwind_libunwind_ops;
>  
>  void unwind__register_ops(struct thread *thread,
>  			  struct unwind_libunwind_ops *ops)
> @@ -30,7 +31,13 @@ int unwind__prepare_access(struct thread *thread, struct map *map)
>  			 dso_type == DSO__TYPE_64BIT, map->dso->name);
>  
>  	arch = normalize_arch(thread->mg->machine->env->arch);
> -	pr_debug("unwind: target platform=%s\n", arch);
> +
> +	if (!strcmp(arch, "x86"))
> +		if (dso_type != DSO__TYPE_64BIT)
> +			ops = x86_32_unwind_libunwind_ops;
> +
> +	if (!ops)
> +		pr_err("unwind: target platform=%s is not supported\n", arch);

how could ops become NULL in here? it starts with local_unwind_libunwind_ops
I dont think this check is needed in here

jirka