linux-kernel - Re: [PATCH] perf hists browser: Fix segfault when showing callchain

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Message-ID: <20150108150824.GD15396@kernel.org>
Date:	Thu, 8 Jan 2015 12:08:24 -0300
From:	Arnaldo Carvalho de Melo <acme@...nel.org>
To:	Namhyung Kim <namhyung@...nel.org>
Cc:	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Jiri Olsa <jolsa@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Stephane Eranian <eranian@...gle.com>,
	Andi Kleen <andi@...stfloor.org>,
	Frederic Weisbecker <fweisbec@...il.com>
Subject: Re: [PATCH] perf hists browser: Fix segfault when showing callchain

Em Wed, Dec 24, 2014 at 03:04:36PM +0900, Namhyung Kim escreveu:
> When perf report on TUI shows callchain it checks first node has
> siblings to determine whether it needs to print percentage value.  But
> it missed a case that first node is NULL.  So sometimes it segfaults
> like below:

Thanks, applied.
 
>   $ perf top -g
>   perf: Segmentation fault
>   -------- backtrace --------
>   perf[0x4fcefb]
>   /usr/lib/libc.so.6(+0x33b20)[0x7f2a35839b20]
>   perf(rb_next+0x8)[0x47d3d8]
>   perf[0x4f6058]
>   perf[0x4f833b]
>   perf[0x4f8610]
>   perf[0x4f209e]
>   perf(ui_browser__run+0x3a)[0x4f2e6a]
>   perf[0x4f94ee]
>   perf(perf_evlist__tui_browse_hists+0x94)[0x4fbbf4]
>   perf[0x444d10]
>   /usr/lib/libpthread.so.0(+0x7314)[0x7f2a37070314]
>   /usr/lib/libc.so.6(clone+0x6d)[0x7f2a358ee5bd]
> 
>   $ addr2line -e `which perf` 0x4f6058
>   /home/namhyung/project/linux/tools/perf/ui/browsers/hists.c:553
> 
> I don't know why the backtrace didn't print some symbols..
> 
> Fixes: 4087d11cd945 ("perf hists browser: Print overhead percent value for first-level callchain")
> Signed-off-by: Namhyung Kim <namhyung@...nel.org>
> ---
>  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 e6bb04b5b09b..788506eef567 100644
> --- a/tools/perf/ui/browsers/hists.c
> +++ b/tools/perf/ui/browsers/hists.c
> @@ -550,7 +550,7 @@ static int hist_browser__show_callchain(struct hist_browser *browser,
>  	bool need_percent;
>  
>  	node = rb_first(root);
> -	need_percent = !!rb_next(node);
> +	need_percent = node && rb_next(node);
>  
>  	while (node) {
>  		struct callchain_node *child = rb_entry(node, struct callchain_node, rb_node);
> -- 
> 2.1.3
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