Re: [PATCH bpf-next 3/3] selftests/bpf: Add a runtime test for private stack and stack arguments

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] bpf: test flakiness due to parallel struct_ops attachment
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commit 30217e3723f8427977b857ce4b668a913d8e6da3
Author: Chen Pei <cp0613@linux.alibaba.com>
selftests/bpf: Add a runtime test for private stack and stack arguments

This commit adds a runtime test for combining private stacks with outgoing
stack arguments. It validates the structural layout via disassembly patterns
and checks runtime execution context across CPUs. It also includes a
struct_ops test to act as a kernel stack control case.

> diff --git a/tools/testing/selftests/bpf/prog_tests/private_stack_runtime.c b/tools/testing/selftests/bpf/prog_tests/private_stack_runtime.c
> new file mode 100644
> index 0000000000000..3af24ca8009f4
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/prog_tests/private_stack_runtime.c
> @@ -0,0 +1,83 @@
> +// SPDX-License-Identifier: GPL-2.0
> +#include <test_progs.h>
> +#include <network_helpers.h>
> +#include "private_stack_runtime.h"
> +#include "private_stack_runtime.skel.h"
> +
> +void test_private_stack_runtime(void)
> +{

[Severity: Medium]
Will this cause test flakiness in CI due to parallel execution?

The test function lacks the serial_ prefix, so it will run concurrently in
the test_progs worker threads rather than in isolation.

[ ... ]

> +	ASSERT_GT(tested, 0, "tested_cpus");
> +
> +	ops = bpf_map__attach_struct_ops(skel->maps.zero_stack_ops);
> +	if (!ASSERT_OK_PTR(ops, "attach_zero_stack"))
> +		goto out;

[Severity: Medium]
Since zero_stack_ops targets the singleton bpf_testmod_ops3 in bpf_testmod,
executing this concurrently with other non-serial tests that attach to the
same struct_ops (such as test_struct_ops_private_stack) can cause random
-EEXIST failures.

st_ops3_reg() in bpf_testmod.c enforces a single active attachment:

    if (st_ops3)
        ... err = -EEXIST

Could this function be renamed to serial_test_private_stack_runtime to avoid
resource conflicts with other tests?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261015021238.5657-1-cp0613@linux.alibaba.com?part=3