linux-kernel - Re: [tip:perf/urgent] perf hists: Fix determination of a callchain node's childlessness

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Message-ID: <20160416194614.l6liupm35rmhg3ht@alap3.anarazel.de>
Date:	Sat, 16 Apr 2016 12:46:14 -0700
From:	Andres Freund <andres@...razel.de>
To:	tglx@...utronix.de, a.p.zijlstra@...llo.nl, namhyung@...nel.org,
	linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...nel.org,
	acme@...hat.com
Cc:	linux-tip-commits@...r.kernel.org
Subject: Re: [tip:perf/urgent] perf hists: Fix determination of a callchain
 node's childlessness

Hi,

Perhaps this should also go into stable? It'd be nice to fix that
regression for 4.4 and 4.5.

Regards,

Andres

On 2016-03-30 23:33:37 -0700, tip-bot for Andres Freund wrote:
> Commit-ID:  909890355507e92bdaf648e73870f6b5df606da8
> Gitweb:     http://git.kernel.org/tip/909890355507e92bdaf648e73870f6b5df606da8
> Author:     Andres Freund <andres@...razel.de>
> AuthorDate: Wed, 30 Mar 2016 21:02:45 +0200
> Committer:  Arnaldo Carvalho de Melo <acme@...hat.com>
> CommitDate: Wed, 30 Mar 2016 18:08:39 -0300
> 
> perf hists: Fix determination of a callchain node's childlessness
> 
> The 4b3a3212233a ("perf hists browser: Support flat callchains") commit
> over-aggressively tried to optimize callchain_node__init_have_children().
> 
> That lead to --tui mode not allowing to expand call chain elements if a
> call chain element had only one parent. That's why --inverted callgraphs
> looked halfway sane, but plain ones didn't.
> 
> Revert that individual optimization, it wasn't really related to the
> rest of the commit.
> 
> Signed-off-by: Andres Freund <andres@...razel.de>
> Acked-by: Namhyung Kim <namhyung@...nel.org>
> Tested-by: Arnaldo Carvalho de Melo <acme@...hat.com>
> Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
> Fixes: 4b3a3212233a ("perf hists browser: Support flat callchains")
> Link: http://lkml.kernel.org/r/20160330190245.GB13305@awork2.anarazel.de
> Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
> ---
>  tools/perf/ui/browsers/hists.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tools/perf/ui/browsers/hists.c b/tools/perf/ui/browsers/hists.c
> index 4b98165..2a83414 100644
> --- a/tools/perf/ui/browsers/hists.c
> +++ b/tools/perf/ui/browsers/hists.c
> @@ -337,7 +337,7 @@ static void callchain_node__init_have_children(struct callchain_node *node,
>  	chain = list_entry(node->val.next, struct callchain_list, list);
>  	chain->has_children = has_sibling;
>  
> -	if (node->val.next != node->val.prev) {
> +	if (!list_empty(&node->val)) {
>  		chain = list_entry(node->val.prev, struct callchain_list, list);
>  		chain->has_children = !RB_EMPTY_ROOT(&node->rb_root);
>  	}