CI occasionally reports failures in the percpu_alloc/cpu_flag_lru_percpu_hash selftest, for example:
First test_progs failure (test_progs_no_alu32-x86_64-llvm-21): #264/15 percpu_alloc/cpu_flag_lru_percpu_hash ... test_percpu_map_op_cpu_flag:FAIL:bpf_map_lookup_batch value on specified cpu unexpected bpf_map_lookup_batch value on specified cpu: actual 0 != expected 3735929054 The unexpected value indicates that an element was removed from the map. However, the test never calls delete_elem(), so the only possible cause is LRU eviction. This can happen when the current task migrates to another CPU: an update_elem() triggers eviction because there is no available LRU node on local freelist and global freelist. Harden the test against this behavior by provisioning sufficient spare elements. Set max_entries to 'nr_cpus * 2' and restrict the test to using the first nr_cpus entries, ensuring that updates do not spuriously trigger LRU eviction. Signed-off-by: Leon Hwang <[email protected]> --- .../testing/selftests/bpf/prog_tests/percpu_alloc.c | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-) diff --git a/tools/testing/selftests/bpf/prog_tests/percpu_alloc.c b/tools/testing/selftests/bpf/prog_tests/percpu_alloc.c index c1d0949f093f..a72ae0b29f6e 100644 --- a/tools/testing/selftests/bpf/prog_tests/percpu_alloc.c +++ b/tools/testing/selftests/bpf/prog_tests/percpu_alloc.c @@ -236,6 +236,8 @@ static void test_percpu_map_op_cpu_flag(struct bpf_map *map, void *keys, size_t err = bpf_map_update_batch(map_fd, keys, values, &count, &batch_opts); if (!ASSERT_OK(err, "bpf_map_update_batch all_cpus")) goto out; + if (!ASSERT_EQ(count, entries, "bpf_map_update_batch count")) + goto out; /* update values on specified CPU */ for (i = 0; i < entries; i++) @@ -246,6 +248,8 @@ static void test_percpu_map_op_cpu_flag(struct bpf_map *map, void *keys, size_t err = bpf_map_update_batch(map_fd, keys, values, &count, &batch_opts); if (!ASSERT_OK(err, "bpf_map_update_batch specified cpu")) goto out; + if (!ASSERT_EQ(count, entries, "bpf_map_update_batch count")) + goto out; /* lookup values on specified CPU */ batch = 0; @@ -254,6 +258,8 @@ static void test_percpu_map_op_cpu_flag(struct bpf_map *map, void *keys, size_t err = bpf_map_lookup_batch(map_fd, NULL, &batch, keys, values, &count, &batch_opts); if (!ASSERT_TRUE(!err || err == -ENOENT, "bpf_map_lookup_batch specified cpu")) goto out; + if (!ASSERT_EQ(count, entries, "bpf_map_lookup_batch count")) + goto out; for (i = 0; i < entries; i++) if (!ASSERT_EQ(values[i], value, @@ -269,6 +275,8 @@ static void test_percpu_map_op_cpu_flag(struct bpf_map *map, void *keys, size_t &batch_opts); if (!ASSERT_TRUE(!err || err == -ENOENT, "bpf_map_lookup_batch all_cpus")) goto out; + if (!ASSERT_EQ(count, entries, "bpf_map_lookup_batch count")) + goto out; for (i = 0; i < entries; i++) { values_row = (void *) values_percpu + @@ -287,7 +295,6 @@ static void test_percpu_map_op_cpu_flag(struct bpf_map *map, void *keys, size_t free(values); } - static void test_percpu_map_cpu_flag(enum bpf_map_type map_type) { struct percpu_alloc_array *skel; @@ -300,7 +307,7 @@ static void test_percpu_map_cpu_flag(enum bpf_map_type map_type) if (!ASSERT_GT(nr_cpus, 0, "libbpf_num_possible_cpus")) return; - max_entries = nr_cpus + 1; + max_entries = nr_cpus * 2; keys = calloc(max_entries, key_sz); if (!ASSERT_OK_PTR(keys, "calloc keys")) return; @@ -322,7 +329,7 @@ static void test_percpu_map_cpu_flag(enum bpf_map_type map_type) if (!ASSERT_OK(err, "test_percpu_alloc__load")) goto out; - test_percpu_map_op_cpu_flag(map, keys, key_sz, max_entries - 1, nr_cpus, true); + test_percpu_map_op_cpu_flag(map, keys, key_sz, nr_cpus, nr_cpus, true); out: percpu_alloc_array__destroy(skel); free(keys); -- 2.52.0
