On Thu, Nov 29, 2018 at 9:02 AM Andy Lutomirski <l...@amacapital.net> wrote:
> >
> > - just restart the instruction (with the suggested "ptregs->rip --")
> >
> > - to avoid any "oh, we're not making progress" issues, just fix the
> > instruction yourself to be the right call, by looking it up in the
> > "what needs to be fixed" tables.
>
> I thought that too. I think it deadlocks. CPU A does text_poke_bp(). CPU B
> is waiting for a spinlock with IRQs off. CPU C holds the spinlock and hits
> the int3. The int3 never goes away because CPU A is waiting for CPU B to
> handle the sync_core IPI.
>
> Or do you think we can avoid the IPI while the int3 is there?
I'm handwaving and thinking that CPU C that hits the int3 can just fix
up the instruction directly in its own caches, and return.
Yes, it does what he "text_poke" *will* do (so now the instruction
gets rewritten _twice_), but who cares? It's idempotent.
And no, I don't have code, just "maybe some handwaving like this"
Linus
