On Wed, May 20, 2020 at 5:35 AM Thomas Gleixner <t...@linutronix.de> wrote: > > Andy Lutomirski <l...@kernel.org> writes: > > On Mon, May 18, 2020 at 4:53 PM Thomas Gleixner <t...@linutronix.de> wrote: > >> > >> Andy Lutomirski <l...@kernel.org> writes: > >> > Actually, I revoke my ack. Can you make one of two changes: > >> > > >> > Option A: Add an assertion to run_on_irqstack to verify that irq_count > >> > was -1 at the beginning? I suppose this also means you could just > >> > explicitly write 0 instead of adding and subtracting. > >> > > >> > Option B: Make run_on_irqstack() just call the function on the current > >> > stack if we're already on the irq stack. > >> > > >> > Right now, it's too easy to mess up and not verify the right > >> > precondition before calling run_on_irqstack(). > >> > > >> > If you choose A, perhaps add a helper to do the if(irq_needs_irqstack) > >> > dance so that users can just do: > >> > > >> > run_on_irqstack_if_needed(...); > >> > > >> > instead of checking everything themselves. > >> > >> I'll have a look tomorrow morning with brain awake. > > > > Also, reading more of the series, I suspect that asm_call_on_stack is > > logically in the wrong section or that the noinstr stuff is otherwise > > not quite right. I think that objtool should not accept > > run_on_irqstack() from noinstr code. See followups on patch 10. > > It's in entry.text which is non-instrumentable as well.
Hmm. I suppose we can chalk this up to the noinstr checking not being entirely perfect.
