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Subject[PATCH 5.4 145/309] selftests/bpf: Fix perf_buffer test on systems w/ offline CPUs
Date
From: Andrii Nakryiko <andriin@fb.com>

commit 91cbdf740a476cf2c744169bf407de2e3ac1f3cf upstream.

Fix up perf_buffer.c selftest to take into account offline/missing CPUs.

Fixes: ee5cf82ce04a ("selftests/bpf: test perf buffer API")
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20191212013621.1691858-1-andriin@fb.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
tools/testing/selftests/bpf/prog_tests/perf_buffer.c | 29 +++++++++++++++----
1 file changed, 24 insertions(+), 5 deletions(-)

--- a/tools/testing/selftests/bpf/prog_tests/perf_buffer.c
+++ b/tools/testing/selftests/bpf/prog_tests/perf_buffer.c
@@ -4,6 +4,7 @@
#include <sched.h>
#include <sys/socket.h>
#include <test_progs.h>
+#include "libbpf_internal.h"

static void on_sample(void *ctx, int cpu, void *data, __u32 size)
{
@@ -19,7 +20,7 @@ static void on_sample(void *ctx, int cpu

void test_perf_buffer(void)
{
- int err, prog_fd, nr_cpus, i, duration = 0;
+ int err, prog_fd, on_len, nr_on_cpus = 0, nr_cpus, i, duration = 0;
const char *prog_name = "kprobe/sys_nanosleep";
const char *file = "./test_perf_buffer.o";
struct perf_buffer_opts pb_opts = {};
@@ -29,15 +30,27 @@ void test_perf_buffer(void)
struct bpf_object *obj;
struct perf_buffer *pb;
struct bpf_link *link;
+ bool *online;

nr_cpus = libbpf_num_possible_cpus();
if (CHECK(nr_cpus < 0, "nr_cpus", "err %d\n", nr_cpus))
return;

+ err = parse_cpu_mask_file("/sys/devices/system/cpu/online",
+ &online, &on_len);
+ if (CHECK(err, "nr_on_cpus", "err %d\n", err))
+ return;
+
+ for (i = 0; i < on_len; i++)
+ if (online[i])
+ nr_on_cpus++;
+
/* load program */
err = bpf_prog_load(file, BPF_PROG_TYPE_KPROBE, &obj, &prog_fd);
- if (CHECK(err, "obj_load", "err %d errno %d\n", err, errno))
- return;
+ if (CHECK(err, "obj_load", "err %d errno %d\n", err, errno)) {
+ obj = NULL;
+ goto out_close;
+ }

prog = bpf_object__find_program_by_title(obj, prog_name);
if (CHECK(!prog, "find_probe", "prog '%s' not found\n", prog_name))
@@ -64,6 +77,11 @@ void test_perf_buffer(void)
/* trigger kprobe on every CPU */
CPU_ZERO(&cpu_seen);
for (i = 0; i < nr_cpus; i++) {
+ if (i >= on_len || !online[i]) {
+ printf("skipping offline CPU #%d\n", i);
+ continue;
+ }
+
CPU_ZERO(&cpu_set);
CPU_SET(i, &cpu_set);

@@ -81,8 +99,8 @@ void test_perf_buffer(void)
if (CHECK(err < 0, "perf_buffer__poll", "err %d\n", err))
goto out_free_pb;

- if (CHECK(CPU_COUNT(&cpu_seen) != nr_cpus, "seen_cpu_cnt",
- "expect %d, seen %d\n", nr_cpus, CPU_COUNT(&cpu_seen)))
+ if (CHECK(CPU_COUNT(&cpu_seen) != nr_on_cpus, "seen_cpu_cnt",
+ "expect %d, seen %d\n", nr_on_cpus, CPU_COUNT(&cpu_seen)))
goto out_free_pb;

out_free_pb:
@@ -91,4 +109,5 @@ out_detach:
bpf_link__destroy(link);
out_close:
bpf_object__close(obj);
+ free(online);
}

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