perf lock contention: Fix debug stat if no contention

It should not divide if the total number is 0.  Otherwise it'd show
NaN in the bad rate output.  Also add a whitespace in the "output
for debug" message.

  $ sudo perf lock contention -abv true
  Looking at the vmlinux_path (8 entries long)
  symsrc__init: cannot get elf header.
  Using /proc/kcore for kernel data
  Using /proc/kallsyms for symbols
   contended   total wait     max wait     avg wait         type   caller

  === output for debug===

  bad: 0, total: 0
  bad rate: -nan %     <-------------------------  (here)
  histogram of events caused bad sequence
      acquire: 0
     acquired: 0
    contended: 0
      release: 0

Signed-off-by: Namhyung Kim <[email protected]>
Cc: Adrian Hunter <[email protected]>
Cc: Hao Luo <[email protected]>
Cc: Ian Rogers <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: [email protected]
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

1 files changed, 2 insertions, 2 deletions

diff --git a/tools/perf/builtin-lock.c b/tools/perf/builtin-lock.c
index 3c8a19ebc496..82dd2dfe5692 100644
--- a/tools/perf/builtin-lock.c
+++ b/tools/perf/builtin-lock.c
@@ -1323,10 +1323,10 @@ static void print_bad_events(int bad, int total)
 	for (i = 0; i < BROKEN_MAX; i++)
 		broken += bad_hist[i];
 
-	if (quiet || (broken == 0 && verbose <= 0))
+	if (quiet || total == 0 || (broken == 0 && verbose <= 0))
 		return;
 
-	pr_info("\n=== output for debug===\n\n");
+	pr_info("\n=== output for debug ===\n\n");
 	pr_info("bad: %d, total: %d\n", bad, total);
 	pr_info("bad rate: %.2f %%\n", (double)bad / (double)total * 100);
 	pr_info("histogram of events caused bad sequence\n");