Re: [PATCH RFC bpf-next 2/2] selftests/bpf: Add LoongArch support for get_preempt_count()

[sashiko-bot@kernel.org]

Sashiko AI review found 1 potential issue(s):
- [High] BPF programs including `bpf_experimental.h` will fail to compile on LoongArch due to a non-existent `thread_info` field in `struct task_struct`.
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commit 82453686fe5eacd9f219e2a050dc016b297cfc79
Author: Tiezhu Yang <yangtiezhu@loongson.cn>

selftests/bpf: Add LoongArch support for get_preempt_count()

This commit adds LoongArch support for get_preempt_count() in the BPF
experimental helpers. It enables bpf_in_interrupt() and related macros to
work properly on LoongArch systems.

> diff --git a/tools/testing/selftests/bpf/bpf_experimental.h b/tools/testing/selftests/bpf/bpf_experimental.h
> index e5c039bc44cb4..5847bbf12d240 100644
> --- a/tools/testing/selftests/bpf/bpf_experimental.h
> +++ b/tools/testing/selftests/bpf/bpf_experimental.h
> @@ -507,6 +507,8 @@ static inline int get_preempt_count(void)
>  	return bpf_get_lowcore()->preempt_count;
>  #elif defined(bpf_target_riscv)
>  	return bpf_get_current_task_btf()->thread_info.preempt_count;
> +#elif defined(bpf_target_loongarch)
> +	return bpf_get_current_task_btf()->thread_info.preempt_count;

Will this compile successfully on LoongArch?

Since LoongArch does not select CONFIG_THREAD_INFO_IN_TASK, struct
thread_info is allocated on the kernel stack rather than being embedded
within struct task_struct. Because of this, the generated BTF and vmlinux.h
for LoongArch will not contain a thread_info field in task_struct.

Could this lead to a compiler error indicating that there is no member named
thread_info in struct task_struct when building BPF selftests?

>  #endif
>  	return 0;
>  }

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Sashiko AI review · https://sashiko.dev/#/patchset/20260420111516.19982-1-yangtiezhu@loongson.cn?part=2