Re: [PATCH v7 03/14] perf tools: Introducing struct unwind_libunwind_ops for local unwind

[Jiri Olsa <jolsa@redhat.com>]

On Tue, May 31, 2016 at 11:19:01AM +0000, He Kuang wrote:
> Currently, libunwind operations are fixed, and they are chosen
> according to the host architecture. This will lead a problem that if a
> thread is run as x86_32 on x86_64 machine, perf will use libunwind
> methods for x86_64 to parse the callchain and get wrong result.
> 
> This patch changes the fixed methods of libunwind operations to
> thread/map related, and each thread can have indivadual libunwind
> operations. Local libunwind methods are registered as default value.
> 
> Signed-off-by: He Kuang <hekuang@huawei.com>
> ---
>  tools/perf/util/thread.c           |  6 ++++
>  tools/perf/util/thread.h           |  4 ++-
>  tools/perf/util/unwind-libunwind.c | 58 +++++++++++++++++++++++++++++++++++---
>  tools/perf/util/unwind.h           | 19 +++++++++++++
>  4 files changed, 82 insertions(+), 5 deletions(-)
> 
> diff --git a/tools/perf/util/thread.c b/tools/perf/util/thread.c
> index 45fcb71..95ff1b8 100644
> --- a/tools/perf/util/thread.c
> +++ b/tools/perf/util/thread.c
> @@ -43,6 +43,12 @@ struct thread *thread__new(pid_t pid, pid_t tid)
>  		thread->cpu = -1;
>  		INIT_LIST_HEAD(&thread->comm_list);
>  
> +#ifdef HAVE_LIBUNWIND_SUPPORT
> +		unwind__register_ops(thread, local_unwind_libunwind_ops);
> +#else
> +		unwind__register_ops(thread, NULL);
> +#endif

is it needed to register NULL? it's there by init right?

jirka