[PATCH] perf diff: Fix duplicated output column

[Namhyung Kim <namhyung@kernel.org>]

The commit b97511c5bc94 ("perf tools: Add overhead/overhead_children
keys defaults via string") moved initialization of column headers but it
missed to check the sort__mode.  As 'perf diff' doesn't call
perf_hpp__init(), the setup_overhead() also should not be called.

Before:

  # Baseline    Delta  Children  Overhead  Shared Object        Symbol
  # ........  .......  ........  ........  ...................  .......................
  #
      28.48%  -28.47%    28.48%    28.48%  [kernel.vmlinux ]    [k] intel_idle
      11.51%  -11.47%    11.51%    11.51%  libxul.so            [.] 0x0000000001a360f7
       3.49%   -3.49%     3.49%     3.49%  [kernel.vmlinux]     [k] generic_exec_single
       2.91%   -2.89%     2.91%     2.91%  libdbus-1.so.3.8.11  [.] 0x000000000000cdc2
       2.86%   -2.85%     2.86%     2.86%  libxcb.so.1.1.0      [.] 0x000000000000c890
       2.44%   -2.39%     2.44%     2.44%  [kernel.vmlinux]     [k] perf_event_aux_ctx

After:

  # Baseline    Delta  Shared Object        Symbol
  # ........  .......  ...................  .......................
  #
      28.48%  -28.47%  [kernel.vmlinux]     [k] intel_idle
      11.51%  -11.47%  libxul.so            [.] 0x0000000001a360f7
       3.49%   -3.49%  [kernel.vmlinux]     [k] generic_exec_single
       2.91%   -2.89%  libdbus-1.so.3.8.11  [.] 0x000000000000cdc2
       2.86%   -2.85%  libxcb.so.1.1.0      [.] 0x000000000000c890
       2.44%   -2.39%  [kernel.vmlinux]     [k] perf_event_aux_ctx

Cc: stable <stable@vger.kernel.org>  # 4.5
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
---
 tools/perf/util/sort.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/tools/perf/util/sort.c b/tools/perf/util/sort.c
index 772e2e461ec3..20e69edd5006 100644
--- a/tools/perf/util/sort.c
+++ b/tools/perf/util/sort.c
@@ -2438,6 +2438,9 @@ static char *prefix_if_not_in(const char *pre, char *str)
 
 static char *setup_overhead(char *keys)
 {
+	if (sort__mode == SORT_MODE__DIFF)
+		return keys;
+
 	keys = prefix_if_not_in("overhead", keys);
 
 	if (symbol_conf.cumulate_callchain)
-- 
2.8.2