linux-kernel - [PATCH v6 2/2] perf stat: Stop repeating when ref_perf

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Message-Id: <20240925132022.2650180-3-yeoreum.yun@arm.com>
Date: Wed, 25 Sep 2024 14:20:22 +0100
From: Levi Yun <yeoreum.yun@....com>
To: peterz@...radead.org,
	mingo@...hat.com,
	acme@...nel.org,
	namhyung@...nel.org,
	mark.rutland@....com,
	alexander.shishkin@...ux.intel.com,
	jolsa@...nel.org,
	irogers@...gle.com,
	adrian.hunter@...el.com,
	james.clark@...aro.org,
	howardchu95@...il.com
Cc: nd@....com,
	linux-perf-users@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Levi Yun <yeoreum.yun@....com>
Subject: [PATCH v6 2/2] perf stat: Stop repeating when ref_perf_stat() returns -1

Exit when run_perf_stat() returns an error to avoid continuously
repeating the same error message. It's not expected that COUNTER_FATAL
or internal errors are recoverable so there's no point in retrying.

This fixes the following flood of error messages for permission issues,
for example when perf_event_paranoid==3:
  perf stat -r 1044 -- false

  Error:
  Access to performance monitoring and observability operations is limited.
  ...
  Error:
  Access to performance monitoring and observability operations is limited.
  ...
  (repeating for 1044 times).

Signed-off-by: Levi Yun <yeoreum.yun@....com>
Reviewed-by: James Clark <james.clark@...aro.org>
---
 tools/perf/builtin-stat.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
index 2c46bdbd9914..6cad3435b198 100644
--- a/tools/perf/builtin-stat.c
+++ b/tools/perf/builtin-stat.c
@@ -968,6 +968,14 @@ static int __run_perf_stat(int argc, const char **argv, int run_idx)
 	return err;
 }

+/*
+ * Returns -1 for fatal errors which signifies to not continue
+ * when in repeat mode.
+ *
+ * Returns < -1 error codes when stat record is used. These
+ * result in the stat information being displayed, but writing
+ * to the file fails and is non fatal.
+ */
 static int run_perf_stat(int argc, const char **argv, int run_idx)
 {
 	int ret;
@@ -2899,7 +2907,10 @@ int cmd_stat(int argc, const char **argv)
 			evlist__reset_prev_raw_counts(evsel_list);

 		status = run_perf_stat(argc, argv, run_idx);
-		if (forever && status != -1 && !interval) {
+		if (status == -1)
+			break;
+
+		if (forever && !interval) {
 			print_counters(NULL, argc, argv);
 			perf_stat__reset_stats();
 		}
--
LEVI:{C3F47F37-75D8-414A-A8BA-3980EC8A46D7}