perf: Resurrect flat callchains

commit 97aa1052739c6a06cb6b0467dbf410613d20bc97 upstream.

Initialize the callchain radix tree root correctly.

When we walk through the parents, we must stop after the root, but
since it wasn't well initialized, its parent pointer was random.

Also the number of hits was random because uninitialized, hence it
was part of the callchain while the root doesn't contain anything.

This fixes segfaults and percentages followed by empty callchains
while running:

	perf report -g flat

Reported-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/tools/perf/util/callchain.h b/tools/perf/util/callchain.h
index ad4626de4c2b9cfa8deb5c5b49b42c644a95a761..1b7a3897825db0d33c3b516930b7c72a70943e25 100644 (file)
--- a/tools/perf/util/callchain.h
+++ b/tools/perf/util/callchain.h
@@ -48,6 +48,9 @@ static inline void callchain_init(struct callchain_node *node)
        INIT_LIST_HEAD(&node->brothers);
        INIT_LIST_HEAD(&node->children);
        INIT_LIST_HEAD(&node->val);
+
+       node->parent = NULL;
+       node->hit = 0;
 }
 
 static inline u64 cumul_hits(struct callchain_node *node)