Re: [PATCH bpf-next] selftests/bpf: fix some bugs in map_lookup_percpu_elem testcase

[Yonghong Song]

On 5/15/22 7:24 PM, Feng zhou wrote:
> From: Feng Zhou <zhoufeng.zf@xxxxxxxxxxxxx>
>
> comments from Andrii Nakryiko, details in here:
> https://lore.kernel.org/lkml/20220511093854.411-1-zhoufeng.zf@xxxxxxxxxxxxx/T/
>
> use /* */ instead of //
> use libbpf_num_possible_cpus() instead of sysconf(_SC_NPROCESSORS_ONLN)
> use 8 bytes for value size
> fix memory leak
> use ASSERT_EQ instead of ASSERT_OK
> add bpf_loop to fetch values on each possible CPU
>
> Fixes: ed7c13776e20c74486b0939a3c1de984c5efb6aa ("selftests/bpf: add test case for bpf_map_lookup_percpu_elem")
> Signed-off-by: Feng Zhou <zhoufeng.zf@xxxxxxxxxxxxx>

LGTM with a few nits below.
Acked-by: Yonghong Song <yhs@xxxxxx>

> ---
>   .../bpf/prog_tests/map_lookup_percpu_elem.c   | 49 +++++++++------
>   .../bpf/progs/test_map_lookup_percpu_elem.c   | 61 ++++++++++++-------
>   2 files changed, 70 insertions(+), 40 deletions(-)
>
> diff --git a/tools/testing/selftests/bpf/prog_tests/map_lookup_percpu_elem.c b/tools/testing/selftests/bpf/prog_tests/map_lookup_percpu_elem.c
> index 58b24c2112b0..89ca170f1c25 100644
> --- a/tools/testing/selftests/bpf/prog_tests/map_lookup_percpu_elem.c
> +++ b/tools/testing/selftests/bpf/prog_tests/map_lookup_percpu_elem.c
> @@ -1,30 +1,39 @@
> -// SPDX-License-Identifier: GPL-2.0
> -// Copyright (c) 2022 Bytedance
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/* Copyright (c) 2022 Bytedance */
>   
>   #include <test_progs.h>
>   

The above empty line is unnecessary.

>   #include "test_map_lookup_percpu_elem.skel.h"
>   
> -#define TEST_VALUE  1
> -
>   void test_map_lookup_percpu_elem(void)
>   {
>   	struct test_map_lookup_percpu_elem *skel;
> -	int key = 0, ret;
> -	int nr_cpus = sysconf(_SC_NPROCESSORS_ONLN);
> -	int *buf;
> +	__u64 key = 0, sum;
> +	int ret, i;
> +	int nr_cpus = libbpf_num_possible_cpus();
> +	__u64 *buf;
>   
> -	buf = (int *)malloc(nr_cpus*sizeof(int));
> +	buf = (__u64 *)malloc(nr_cpus*sizeof(__u64));
>   	if (!ASSERT_OK_PTR(buf, "malloc"))
>   		return;
> -	memset(buf, 0, nr_cpus*sizeof(int));
> -	buf[0] = TEST_VALUE;
>   
> -	skel = test_map_lookup_percpu_elem__open_and_load();
> -	if (!ASSERT_OK_PTR(skel, "test_map_lookup_percpu_elem__open_and_load"))
> -		return;
> +	for (i=0; i<nr_cpus; i++)
> +		buf[i] = i;
> +	sum = (nr_cpus-1)*nr_cpus/2;
> +
> +	skel = test_map_lookup_percpu_elem__open();
> +	if (!ASSERT_OK_PTR(skel, "test_map_lookup_percpu_elem__open"))
> +		goto exit;
> +
> +	skel->rodata->nr_cpus = nr_cpus;
> +
> +	ret = test_map_lookup_percpu_elem__load(skel);
> +	if (!ASSERT_OK(ret, "test_map_lookup_percpu_elem__load"))
> +		goto cleanup;
> +
>   	ret = test_map_lookup_percpu_elem__attach(skel);
> -	ASSERT_OK(ret, "test_map_lookup_percpu_elem__attach");
> +	if (!ASSERT_OK(ret, "test_map_lookup_percpu_elem__attach"))
> +		goto cleanup;
>   
>   	ret = bpf_map_update_elem(bpf_map__fd(skel->maps.percpu_array_map), &key, buf, 0);
>   	ASSERT_OK(ret, "percpu_array_map update");
> @@ -37,10 +46,14 @@ void test_map_lookup_percpu_elem(void)
>   
>   	syscall(__NR_getuid);
>   
> -	ret = skel->bss->percpu_array_elem_val == TEST_VALUE &&
> -	      skel->bss->percpu_hash_elem_val == TEST_VALUE &&
> -	      skel->bss->percpu_lru_hash_elem_val == TEST_VALUE;
> -	ASSERT_OK(!ret, "bpf_map_lookup_percpu_elem success");
> +	test_map_lookup_percpu_elem__detach(skel);
> +
> +	ASSERT_EQ(skel->bss->percpu_array_elem_sum, sum, "percpu_array lookup percpu elem");
> +	ASSERT_EQ(skel->bss->percpu_hash_elem_sum, sum, "percpu_hash lookup percpu elem");
> +	ASSERT_EQ(skel->bss->percpu_lru_hash_elem_sum, sum, "percpu_lru_hash lookup percpu elem");
>   
> +cleanup:
>   	test_map_lookup_percpu_elem__destroy(skel);
> +exit:
> +	free(buf);
>   }
[...]
> +struct read_percpu_elem_ctx {
> +	void *map;
> +	__u64 sum;
> +};
> +
> +static int read_percpu_elem_callback(__u32 index, struct read_percpu_elem_ctx *ctx)
> +{
> +	__u64 key = 0;
> +	__u64 *value;

Please add an empty line here.

> +	value = bpf_map_lookup_percpu_elem(ctx->map, &key, index);
> +	if (value)
> +		ctx->sum += *value;
> +	return 0;
> +}
> +
[...]