Re: [PATCH v2 bpf-next 3/4] bpf: Allow using bpf_sk_storage in FENTRY/FEXIT/RAW_TP

[Martin KaFai Lau]

On Sat, Nov 14, 2020 at 05:17:20PM -0800, Jakub Kicinski wrote:
> On Thu, 12 Nov 2020 13:13:13 -0800 Martin KaFai Lau wrote:
> > This patch adds bpf_sk_storage_get_tracing_proto and
> > bpf_sk_storage_delete_tracing_proto.  They will check
> > in runtime that the helpers can only be called when serving
> > softirq or running in a task context.  That should enable
> > most common tracing use cases on sk.
> 
> > +   if (!in_serving_softirq() && !in_task())
> 
> This is a curious combination of checks. Would you mind indulging me
> with an explanation?
The current lock usage in bpf_local_storage.c is only expected to
run in either of these contexts.