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

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在 2022/5/19 下午12:38, Andrii Nakryiko 写道:
On Wed, May 18, 2022 at 8:27 PM Feng Zhou <zhoufeng.zf@xxxxxxxxxxxxx> wrote:
在 2022/5/19 上午8:17, Andrii Nakryiko 写道:
On Sun, May 15, 2022 at 7:25 PM Feng zhou <zhoufeng.zf@xxxxxxxxxxxxx> 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>
---
   .../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 */
heh, so for SPDX license comment the rule is to use // in .c files :)
so keep SPDX as // and all others as /* */
will do. Thanks.

+/* Copyright (c) 2022 Bytedance */

   #include <test_progs.h>

   #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));
no need for casting
casting means no '(__u64 *)'?
just like this:
'buf = malloc(nr_cpus * sizeof(__u64));'

yes, in C you don't need to explicitly cast void * to other pointer types

Ok, Thanks.


          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++)
spaces between operators
will do. Thanks.

+               buf[i] = i;
+       sum = (nr_cpus-1)*nr_cpus/2;
same, please follow kernel code style
will do. Thanks.

+
+       skel = test_map_lookup_percpu_elem__open();
+       if (!ASSERT_OK_PTR(skel, "test_map_lookup_percpu_elem__open"))
+               goto exit;
+
nit: keep it simple, init skel to NULL and use single cleanup goto
label that will destroy skel unconditionally (it deals with NULL just
fine)
will do. Thanks.

+       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");
[...]





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