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Date: Thu, 26 Nov 2015 15:00:34 +0100
From: Jiri Olsa <jolsa@redhat.com>
To: Namhyung Kim <namhyung@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>, Ingo Molnar <mingo@kernel.org>,
        Peter Zijlstra <a.p.zijlstra@chello.nl>,
        LKML <linux-kernel@vger.kernel.org>, David Ahern <dsahern@gmail.com>,
        Kan Liang <kan.liang@intel.com>,
        Frederic Weisbecker <fweisbec@gmail.com>,
        Andi Kleen <andi@firstfloor.org>, Wang Nan <wangnan0@huawei.com>
Subject: Re: [PATCH 1/3] perf top: Fix freeze on --call-graph flat/folded
Message-ID: <20151126140034.GA29453@krava.brq.redhat.com>
References: <1448521700-32062-1-git-send-email-namhyung@kernel.org>
 <20151126083853.GA8822@krava.brq.redhat.com>
 <20151126135256.GA18551@danjae.kornet>
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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

thanks,
jirka

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