Re: [PATCH bpf-next v3 3/6] bpf: Add KF_FORBID_SLEEP modifier for KF_ACQUIRE kfuncs

[Eduard Zingerman <eddyz87@gmail.com>]

On Tue, 2026-02-24 at 15:24 +0000, Puranjay Mohan wrote:

[...]

> > - remove the following check from do_check_insn():
> > 
> >   >   if (env->cur_state->active_locks) {
> >   >       if ((insn->src_reg == BPF_REG_0 &&
> >   >            insn->imm != BPF_FUNC_spin_unlock) ||
> >   >           (insn->src_reg == BPF_PSEUDO_KFUNC_CALL &&
> >   >            (insn->off != 0 || !kfunc_spin_allowed(insn->imm)))) {
> >   >           verbose(env,
> >   >               "function calls are not allowed while holding a lock\n");
> >   >           return -EINVAL;
> >   >       }
> >   >   }
> > 
> >   Relying instead on `sleepable && !in_sleepable_context()` checks in
> >   check_kfunc_call() and check_helper_call(). (As one more refactoring patch).
> 
> But removing the above hunk has other effects, this check is not just
> about sleepable but all function calls under bpf_spin_lock. Do we want
> to relax this now?

Discussed this off-list.
The side-effect of this change is that calls to any non-sleepable
helpers / kfuncs would be allowed while holding a spin lock.
This should be fine, but probably belongs to a separate series.