linux-kernel - [PATCH 1/4] perf bpf_counter: Add more error messages for bperf

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Date:   Tue,  3 Jan 2023 22:43:59 -0800
From:   Namhyung Kim <namhyung@...nel.org>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Jiri Olsa <jolsa@...nel.org>
Cc:     Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Ian Rogers <irogers@...gle.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        linux-perf-users@...r.kernel.org, Song Liu <songliubraving@...com>,
        bpf@...r.kernel.org
Subject: [PATCH 1/4] perf bpf_counter: Add more error messages for bperf

I found perf stat silently exits when it failed in bperf__load().
Let's add some error messages to notify users.

  $ sudo ./perf stat -a --bpf-counters -ddd sleep 1
  bpf_map_update_elem failed: err=-7

Signed-off-by: Namhyung Kim <namhyung@...nel.org>
---
 tools/perf/util/bpf_counter.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/bpf_counter.c b/tools/perf/util/bpf_counter.c
index eeee899fcf34..7f5cc1aa4903 100644
--- a/tools/perf/util/bpf_counter.c
+++ b/tools/perf/util/bpf_counter.c
@@ -471,8 +471,10 @@ static int bperf__load(struct evsel *evsel, struct target *target)
 
 	if (!all_cpu_map) {
 		all_cpu_map = perf_cpu_map__new(NULL);
-		if (!all_cpu_map)
+		if (!all_cpu_map) {
+			pr_err("failed to create all cpu map\n");
 			return -1;
+		}
 	}
 
 	evsel->bperf_leader_prog_fd = -1;
@@ -493,13 +495,16 @@ static int bperf__load(struct evsel *evsel, struct target *target)
 	err = bpf_map_lookup_elem(attr_map_fd, &evsel->core.attr, &entry);
 	if (err) {
 		err = bpf_map_update_elem(attr_map_fd, &evsel->core.attr, &entry, BPF_ANY);
-		if (err)
+		if (err) {
+			pr_err("updating perf_event_attr map failed: err=%d\n", err);
 			goto out;
+		}
 	}
 
 	evsel->bperf_leader_link_fd = bpf_link_get_fd_by_id(entry.link_id);
 	if (evsel->bperf_leader_link_fd < 0 &&
 	    bperf_reload_leader_program(evsel, attr_map_fd, &entry)) {
+		pr_err("reload leader program failed\n");
 		err = -1;
 		goto out;
 	}
-- 
2.39.0.314.g84b9a713c41-goog