[PATCH 2/4] perf tools: callchain: Ignore empty callchains

[Frederic Weisbecker <fweisbec@gmail.com>]

When the callchain tree comes to insert an empty backtrace, it raises
a spurious warning about the fact we are inserting an empty.
This is spurious because the radix tree assumes it did something
wrong to reach this state. But it didn't, we just met an empty
callchain that has to be ignored.

Reported-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
---
 tools/perf/util/callchain.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/tools/perf/util/callchain.c b/tools/perf/util/callchain.c
index ce0c6d4..4c09b25 100644
--- a/tools/perf/util/callchain.c
+++ b/tools/perf/util/callchain.c
@@ -337,5 +337,7 @@ __append_chain(struct callchain_node *root, struct ip_callchain *chain,
 void append_chain(struct callchain_node *root, struct ip_callchain *chain,
 		  struct symbol **syms)
 {
+	if (!chain->nr)
+		return;
 	__append_chain_children(root, chain, syms, 0);
 }
-- 
1.6.2.3