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

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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;
+}
+
[...]



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