linux-kernel - Re: [PATCH bpf-next v2 5/5] selftests/bpf: Fix arena_spin

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Message-ID: <46243c40-8e5e-47d3-97bd-71f29eeb0127@linux.ibm.com>
Date: Thu, 4 Sep 2025 13:39:31 +0530
From: Hari Bathini <hbathini@...ux.ibm.com>
To: Saket Kumar Bhaskar <skb99@...ux.ibm.com>, bpf@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, linux-kselftest@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc: sachinpb@...ux.ibm.com, venkat88@...ux.ibm.com, andrii@...nel.org,
        eddyz87@...il.com, mykolal@...com, ast@...nel.org,
        daniel@...earbox.net, martin.lau@...ux.dev, song@...nel.org,
        yonghong.song@...ux.dev, john.fastabend@...il.com, kpsingh@...nel.org,
        sdf@...ichev.me, haoluo@...gle.com, jolsa@...nel.org,
        christophe.leroy@...roup.eu, naveen@...nel.org, maddy@...ux.ibm.com,
        mpe@...erman.id.au, npiggin@...il.com, memxor@...il.com,
        iii@...ux.ibm.com, shuah@...nel.org
Subject: Re: [PATCH bpf-next v2 5/5] selftests/bpf: Fix arena_spin_lock
 selftest failure



On 29/08/25 10:21 pm, Saket Kumar Bhaskar wrote:
> For systems having CONFIG_NR_CPUS set to > 1024 in kernel config
> the selftest fails as arena_spin_lock_irqsave() returns EOPNOTSUPP.
> 
> The selftest is skipped incase bpf program returns EOPNOTSUPP,
> with a descriptive message logged.
> 
> Signed-off-by: Saket Kumar Bhaskar <skb99@...ux.ibm.com>
> ---
>   .../selftests/bpf/prog_tests/arena_spin_lock.c      | 13 +++++++++++++
>   tools/testing/selftests/bpf/progs/arena_spin_lock.c |  5 ++++-
>   2 files changed, 17 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/testing/selftests/bpf/prog_tests/arena_spin_lock.c b/tools/testing/selftests/bpf/prog_tests/arena_spin_lock.c
> index 0223fce4db2b..1ec1ca987893 100644
> --- a/tools/testing/selftests/bpf/prog_tests/arena_spin_lock.c
> +++ b/tools/testing/selftests/bpf/prog_tests/arena_spin_lock.c
> @@ -40,8 +40,13 @@ static void *spin_lock_thread(void *arg)
>   
>   	err = bpf_prog_test_run_opts(prog_fd, &topts);
>   	ASSERT_OK(err, "test_run err");
> +
> +	if (topts.retval == -EOPNOTSUPP)
> +		goto end;
> +
>   	ASSERT_EQ((int)topts.retval, 0, "test_run retval");
>   
> +end:
>   	pthread_exit(arg);
>   }
>   
> @@ -63,6 +68,7 @@ static void test_arena_spin_lock_size(int size)
>   	skel = arena_spin_lock__open_and_load();
>   	if (!ASSERT_OK_PTR(skel, "arena_spin_lock__open_and_load"))
>   		return;
> +
>   	if (skel->data->test_skip == 2) {
>   		test__skip();
>   		goto end;
> @@ -86,6 +92,13 @@ static void test_arena_spin_lock_size(int size)
>   			goto end_barrier;
>   	}
>   
> +	if (skel->data->test_skip == 2) {
> +		printf("%s:SKIP: %d CPUs exceed the maximum supported by arena spinlock\n",
> +		       __func__, get_nprocs());
> +		test__skip();
> +		goto end_barrier;
> +	}
> +
>   	ASSERT_EQ(skel->bss->counter, repeat * nthreads, "check counter value");
>   
>   end_barrier:
> diff --git a/tools/testing/selftests/bpf/progs/arena_spin_lock.c b/tools/testing/selftests/bpf/progs/arena_spin_lock.c
> index c4500c37f85e..a475b974438e 100644
> --- a/tools/testing/selftests/bpf/progs/arena_spin_lock.c
> +++ b/tools/testing/selftests/bpf/progs/arena_spin_lock.c
> @@ -37,8 +37,11 @@ int prog(void *ctx)
>   #if defined(ENABLE_ATOMICS_TESTS) && defined(__BPF_FEATURE_ADDR_SPACE_CAST)
>   	unsigned long flags;
>   
> -	if ((ret = arena_spin_lock_irqsave(&lock, flags)))
> +	if ((ret = arena_spin_lock_irqsave(&lock, flags))) {
> +		if (ret == -EOPNOTSUPP)
> +			test_skip = 2;
>   		return ret;

test_skip being set to `1` when the test runs seems counter intuitive.
How about setting test_skip to `0` when run conditions are met
and test_skip=1 if run conditions are not met and
test_skip=2 when operation is not supported?

- Hari