linux-kernel - [PATCH] perf c2c report: Properly check data presence in rb

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Date:   Fri, 21 Oct 2016 02:17:06 +0200
From:   Jiri Olsa <jolsa@...hat.com>
To:     Kim Phillips <kim.phillips@....com>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Ingo Molnar <mingo@...nel.org>, linux-kernel@...r.kernel.org,
        Linux Weekly News <lwn@....net>,
        Andi Kleen <andi@...stfloor.org>,
        David Ahern <dsahern@...il.com>,
        Don Zickus <dzickus@...hat.com>, Jiri Olsa <jolsa@...nel.org>,
        Joe Mario <jmario@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: [PATCH] perf c2c report: Properly check data presence in rb_tree loop

On Thu, Oct 20, 2016 at 06:02:24PM -0500, Kim Phillips wrote:

SNIP

> (gdb) bt
> #0  c2c_browser__update_nr_entries (hb=<optimized out>, hb=<optimized out>) at builtin-c2c.c:2142
> #1  perf_c2c__hists_browse (hists=0x8b2d90 <c2c+240>) at builtin-c2c.c:2287
> #2  perf_c2c_display (session=0x205b1a0) at builtin-c2c.c:2316
> #3  perf_c2c__report (argv=<optimized out>, argc=<optimized out>) at builtin-c2c.c:2621
> #4  cmd_c2c (argc=<optimized out>, argv=<optimized out>, prefix=<optimized out>) at builtin-c2c.c:2748
> #5  0x000000000048df61 in run_builtin (p=p@...ry=0x8be168 <commands+72>, argc=argc@...ry=2, argv=argv@...ry=0x7fffffffddb0)
>     at perf.c:358
> #6  0x00000000004249b6 in handle_internal_command (argv=0x7fffffffddb0, argc=2) at perf.c:420
> #7  run_argv (argv=0x7fffffffdb40, argcp=0x7fffffffdb4c) at perf.c:466
> #8  main (argc=2, argv=0x7fffffffddb0) at perf.c:610
> (gdb) 
> 
> All the above work fine when run under sudo.

ugh, stupid mistake.. attached patch fixes that for me

thanks,
jirka


---
Kim reported crash when there's no data stored. In this case
the TUI code crashes in c2c_browser__update_nr_entries, because
we dont check the initial rb_tree node for NULL.

Adding the missing check.

Reported-by: Kim Phillips <kim.phillips@....com>
Signed-off-by: Jiri Olsa <jolsa@...nel.org>
---
 tools/perf/builtin-c2c.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/perf/builtin-c2c.c b/tools/perf/builtin-c2c.c
index dc4f0636dfa1..c6d0dda594d9 100644
--- a/tools/perf/builtin-c2c.c
+++ b/tools/perf/builtin-c2c.c
@@ -2135,14 +2135,14 @@ static void c2c_browser__update_nr_entries(struct hist_browser *hb)
 	u64 nr_entries = 0;
 	struct rb_node *nd = rb_first(&hb->hists->entries);
 
-	do {
+	while (nd) {
 		struct hist_entry *he = rb_entry(nd, struct hist_entry, rb_node);
 
 		if (!he->filtered)
 			nr_entries++;
 
 		nd = rb_next(nd);
-	} while (nd);
+	}
 
 	hb->nr_non_filtered_entries = nr_entries;
 }
-- 
2.7.4