linux-kernel - Re: [PATCH bpf v2 2/2] selftests/bpf: Add test for unpinning htab with internal timer struct

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Message-ID: <79ffb312-4aa4-425e-b05b-02aee21acfe6@linux.dev>
Date: Mon, 6 Oct 2025 21:04:26 -0700
From: Yonghong Song <yonghong.song@...ux.dev>
To: KaFai Wan <kafai.wan@...ux.dev>, ast@...nel.org, daniel@...earbox.net,
 andrii@...nel.org, martin.lau@...ux.dev, eddyz87@...il.com, song@...nel.org,
 john.fastabend@...il.com, kpsingh@...nel.org, sdf@...ichev.me,
 haoluo@...gle.com, jolsa@...nel.org, shuah@...nel.org, toke@...hat.com,
 linux-kernel@...r.kernel.org, bpf@...r.kernel.org,
 linux-kselftest@...r.kernel.org
Subject: Re: [PATCH bpf v2 2/2] selftests/bpf: Add test for unpinning htab
 with internal timer struct



On 10/6/25 6:22 PM, KaFai Wan wrote:
> Add test to verify that unpinning hash tables containing internal timer
> structures does not trigger context warnings.
>
> Each subtest (timer_prealloc and timer_no_prealloc) can trigger the
> context warning when unpinning, but the warning cannot be triggered
> twice within a short time interval (a HZ), which is expected behavior.
>
> Signed-off-by: KaFai Wan <kafai.wan@...ux.dev>

Ack with a nit below.

Acked-by: Yonghong Song <yonghong.song@...ux.dev>

> ---
>   .../selftests/bpf/prog_tests/pinning_htab.c   | 37 +++++++++++++++++++
>   .../selftests/bpf/progs/test_pinning_htab.c   | 25 +++++++++++++
>   2 files changed, 62 insertions(+)
>   create mode 100644 tools/testing/selftests/bpf/prog_tests/pinning_htab.c
>   create mode 100644 tools/testing/selftests/bpf/progs/test_pinning_htab.c
>
> diff --git a/tools/testing/selftests/bpf/prog_tests/pinning_htab.c b/tools/testing/selftests/bpf/prog_tests/pinning_htab.c
> new file mode 100644
> index 000000000000..fc804bb87b26
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/prog_tests/pinning_htab.c
> @@ -0,0 +1,37 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +#include <test_progs.h>
> +#include "test_pinning_htab.skel.h"
> +
> +static void unpin_map(const char *map_name, const char *pin_path)
> +{
> +	struct test_pinning_htab *skel;
> +	struct bpf_map *map;
> +	int err;
> +
> +	skel = test_pinning_htab__open_and_load();
> +	if (!ASSERT_OK_PTR(skel, "skel open_and_load"))
> +		return;
> +
> +	map = bpf_object__find_map_by_name(skel->obj, map_name);
> +	if (!ASSERT_OK_PTR(map, "bpf_object__find_map_by_name"))
> +		goto out;
> +
> +	err = bpf_map__pin(map, pin_path);
> +	if (!ASSERT_OK(err, "bpf_map__pin"))
> +		goto out;
> +
> +	err = bpf_map__unpin(map, pin_path);
> +	if (!ASSERT_OK(err, "bpf_map__unpin"))
> +		goto out;

No need to have 'goto out'. Just do
	ASSERT_OK(err, "bpf_map__unpin"

> +out:
> +	test_pinning_htab__destroy(skel);
> +}
> +
> +void test_pinning_htab(void)
> +{
> +	if (test__start_subtest("timer_prealloc"))
> +		unpin_map("timer_prealloc", "/sys/fs/bpf/timer_prealloc");
> +	if (test__start_subtest("timer_no_prealloc"))
> +		unpin_map("timer_no_prealloc", "/sys/fs/bpf/timer_no_prealloc");
> +}
> diff --git a/tools/testing/selftests/bpf/progs/test_pinning_htab.c b/tools/testing/selftests/bpf/progs/test_pinning_htab.c
> new file mode 100644
> index 000000000000..ae227930c73c
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/test_pinning_htab.c
> @@ -0,0 +1,25 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +#include "vmlinux.h"
> +#include <bpf/bpf_helpers.h>
> +
> +char _license[] SEC("license") = "GPL";
> +
> +struct timer_val {
> +	struct bpf_timer timer;
> +};
> +
> +struct {
> +	__uint(type, BPF_MAP_TYPE_HASH);
> +	__type(key, __u32);
> +	__type(value, struct timer_val);
> +	__uint(max_entries, 1);
> +} timer_prealloc SEC(".maps");
> +
> +struct {
> +	__uint(type, BPF_MAP_TYPE_HASH);
> +	__type(key, __u32);
> +	__type(value, struct timer_val);
> +	__uint(max_entries, 1);
> +	__uint(map_flags, BPF_F_NO_PREALLOC);
> +} timer_no_prealloc SEC(".maps");