Re: [PATCH bpf-next] selftests/bpf: Return -1 from get_preempt_count() for unsupported architecture

[Yonghong Song]

On 1/29/26 8:03 AM, Yonghong Song wrote:
> On 1/28/26 9:09 PM, Saket Kumar Bhaskar wrote:
> > Make get_preempt_count() to return -1 for unsupported
> > architectures instead of 0, so callers can distinguish not supported
> > from a valid preempt_count of 0.
> >
> > Signed-off-by: Saket Kumar Bhaskar <skb99@xxxxxxxxxxxxx>
>
> LGTM.
>
> Acked-by: Yonghong Song <yonghong.song@xxxxxxxxx>

Dig through further. My above Ack is invalid due the following usage
e.g.
static inline int bpf_in_nmi(void)
{
        return get_preempt_count() & NMI_MASK;
}
in bpf_experimental.h. In such cases, returning -1 for get_preempt_count()
may cause bpf_in_nmi() to be true, but this is incorrect.