Re: [PATCH 1/3] perf top: Fix freeze on --call-graph flat/folded

[Namhyung Kim <namhyung@kernel.org>]

Hi Jiri,

On Thu, Nov 26, 2015 at 09:38:53AM +0100, Jiri Olsa wrote:
> On Thu, Nov 26, 2015 at 04:08:18PM +0900, Namhyung Kim wrote:
> > The callchain rbtree is rebuilt periodically, so it needs to
> > reinitialize the root everytime.  Otherwise it can be stuck in the
> > rbtree insertion with stale pointers.
> > 
> > Signed-off-by: Namhyung Kim <namhyung@kernel.org>
> > ---
> >  tools/perf/util/callchain.c | 1 +
> >  1 file changed, 1 insertion(+)
> > 
> > diff --git a/tools/perf/util/callchain.c b/tools/perf/util/callchain.c
> > index fc3b1e0d09ee..564377d2bebf 100644
> > --- a/tools/perf/util/callchain.c
> > +++ b/tools/perf/util/callchain.c
> > @@ -290,6 +290,7 @@ static void
> >  sort_chain_flat(struct rb_root *rb_root, struct callchain_root *root,
> >  		u64 min_hit, struct callchain_param *param __maybe_unused)
> >  {
> > +	*rb_root = RB_ROOT;
> 
> it seems ok, but I did not find how this could be called twice?
> 
> the only sort I can see is done within:
>   __hists__insert_output_entry
> 
> do we allow resorting of the callchains?

No, but I think it's possible though.

It's called from perf top's display thread.

  display_thread()
  -> while (!done)
     -> perf_top__print_sym_table()
        -> hists__output_resort()
           -> __hists__insert_output_entry()

Thanks,
Namhyung