linux-kernel - [PATCH 3/4] perf stat: Use evsel->core.cpus to iterate cpus in BPF cgroup counters

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Date:   Fri, 16 Sep 2022 11:41:31 -0700
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 3/4] perf stat: Use evsel->core.cpus to iterate cpus in BPF cgroup counters

If it mixes core and uncore events, each evsel would have different cpu map.
But it assumed they are same with evlist's all_cpus and accessed by the same
index.  This resulted in a crash like below.

  $ perf stat -a --bpf-counters --for-each_cgroup ^. -e cycles,imc/cas_count_read/ sleep 1
  Segmentation fault

While it's not recommended to use uncore events for cgroup aggregation, it
should not crash.

Signed-off-by: Namhyung Kim <namhyung@...nel.org>
---
 tools/perf/util/bpf_counter_cgroup.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/tools/perf/util/bpf_counter_cgroup.c b/tools/perf/util/bpf_counter_cgroup.c
index 97c69a249c6e..3c2df7522f6f 100644
--- a/tools/perf/util/bpf_counter_cgroup.c
+++ b/tools/perf/util/bpf_counter_cgroup.c
@@ -115,14 +115,14 @@ static int bperf_load_program(struct evlist *evlist)
 			evsel->cgrp = NULL;
 
 			/* open single copy of the events w/o cgroup */
-			err = evsel__open_per_cpu(evsel, evlist->core.all_cpus, -1);
+			err = evsel__open_per_cpu(evsel, evsel->core.cpus, -1);
 			if (err) {
 				pr_err("Failed to open first cgroup events\n");
 				goto out;
 			}
 
 			map_fd = bpf_map__fd(skel->maps.events);
-			perf_cpu_map__for_each_cpu(cpu, j, evlist->core.all_cpus) {
+			perf_cpu_map__for_each_cpu(cpu, j, evsel->core.cpus) {
 				int fd = FD(evsel, j);
 				__u32 idx = evsel->core.idx * total_cpus + cpu.cpu;
 
@@ -269,7 +269,7 @@ static int bperf_cgrp__read(struct evsel *evsel)
 			goto out;
 		}
 
-		perf_cpu_map__for_each_cpu(cpu, i, evlist->core.all_cpus) {
+		perf_cpu_map__for_each_cpu(cpu, i, evsel->core.cpus) {
 			counts = perf_counts(evsel->counts, i, 0);
 			counts->val = values[cpu.cpu].counter;
 			counts->ena = values[cpu.cpu].enabled;
-- 
2.37.3.968.ga6b4b080e4-goog