linux-kernel - Re: [PATCH v7 10/14] perf tools: Check the target platform before assigning unwind methods

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Date:	Wed, 1 Jun 2016 10:40:01 +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 10/14] perf tools: Check the target platform before
 assigning unwind methods

On Tue, May 31, 2016 at 11:19:08AM +0000, He Kuang wrote:

SNIP

> -int unwind__prepare_access(struct thread *thread)
> +int unwind__prepare_access(struct thread *thread, struct map *map)
>  {
> -	unwind__register_ops(thread, local_unwind_libunwind_ops);
> +	const char *arch;
> +	enum dso_type dso_type;
> +	struct unwind_libunwind_ops *ops = local_unwind_libunwind_ops;
>  
> -	return thread->unwind_libunwind_ops->prepare_access(thread);
> +	if (!thread->mg->machine->env)
> +		return 0;
> +
> +	dso_type = dso__type(map->dso, thread->mg->machine);
> +	if (dso_type == DSO__TYPE_UNKNOWN)
> +		return 0;
> +
> +	if (thread->addr_space)
> +		pr_debug("unwind: thread map already set, 64bit is %d, dso=%s\n",
> +			 dso_type == DSO__TYPE_64BIT, map->dso->name);
> +
> +	arch = normalize_arch(thread->mg->machine->env->arch);
> +	pr_debug("unwind: target platform=%s\n", arch);
> +
> +	unwind__register_ops(thread, ops);
> +
> +	if (thread->unwind_libunwind_ops)
> +		return thread->unwind_libunwind_ops->prepare_access(thread);
> +	else
> +		return 0;

why do you need to check for thread->unwind_libunwind_ops != NULL?
it's all set at this point right?

jirka