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

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Message-ID: <20151126140034.GA29453@krava.brq.redhat.com>
Date:	Thu, 26 Nov 2015 15:00:34 +0100
From:	Jiri Olsa <jolsa@...hat.com>
To:	Namhyung Kim <namhyung@...nel.org>
Cc:	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	LKML <linux-kernel@...r.kernel.org>,
	David Ahern <dsahern@...il.com>,
	Kan Liang <kan.liang@...el.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Andi Kleen <andi@...stfloor.org>,
	Wang Nan <wangnan0@...wei.com>
Subject: Re: [PATCH 1/3] perf top: Fix freeze on --call-graph flat/folded

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@...nel.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

thanks,
jirka

> 
>   display_thread()
>   -> while (!done)
>      -> perf_top__print_sym_table()
>         -> hists__output_resort()
>            -> __hists__insert_output_entry()
> 
> Thanks,
> Namhyung
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