perf tools: Prevent condition that all sort keys are elided

If given sort keys are all elided there'll be no output except for the
overhead column - actually the TUI shows a noisy output.  In this case
it'd be better to show up the sort keys rather than elide.

Before:

  $ perf report -s comm -c perf
  (...)
  # Overhead
  # ........
  #
     100.00%

After:

  $ perf report -s comm -c perf
  (...)
  # Overhead  Command
  # ........  .......
  #
     100.00%     perf
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Acked-by: Ingo Molnar <mingo@kernel.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1383900822-14609-1-git-send-email-namhyung@kernel.org
[ Us curly braces around multi-line statements, as requested by Ingo Molnar ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/sort.c

@@ -1137,6 +1137,8 @@ static void sort_entry__setup_elide(struct sort_entry *se,
 
 void sort__setup_elide(FILE *output)
 {
+	struct sort_entry *se;
+
 	sort_entry__setup_elide(&sort_dso, symbol_conf.dso_list,
 				"dso", output);
 	sort_entry__setup_elide(&sort_comm, symbol_conf.comm_list,
@@ -1172,4 +1174,15 @@ void sort__setup_elide(FILE *output)
 					"snoop", output);
 	}
 
+	/*
+	 * It makes no sense to elide all of sort entries.
+	 * Just revert them to show up again.
+	 */
+	list_for_each_entry(se, &hist_entry__sort_list, list) {
+		if (!se->elide)
+			return;
+	}
+
+	list_for_each_entry(se, &hist_entry__sort_list, list)
+		se->elide = false;
 }