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

Jiri Olsa
2015-11-26T15:22:28Z

On Fri, Nov 27, 2015 at 12:10:31AM +0900, Namhyung Kim wrote:
> On Thu, Nov 26, 2015 at 03:00:34PM +0100, Jiri Olsa wrote:
> > On Thu, Nov 26, 2015 at 10:52:56PM +0900, Namhyung Kim wrote:
> > > 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.
> >
> > ah right.. top ;-) ok
> >
> > isn't there analogical issue with the other sorts?
> > graph_abs, graph_rel... I dont see that code doing this
>
> The sort_chain_graph_abs/rel() already do this. Unlike flat/folded
> callchains, they put child into each callchain_node's rbtree. So they
> reinitialize node->rb_root in __sort_chain_graph_abs/rel() and reset
> rb_root after finishing sort.

ook, thanks for explanation

Acked-by: Jiri Olsa <jolsa@kernel.org>

jirka