On Sat, Aug 25, 2018 at 09:21:22PM -0700, Andy Lutomirski wrote: > I just re-read text_poke(). It's, um, horrible. Not only is the > implementation overcomplicated and probably buggy, but it's SLOOOOOW. > It's totally the wrong API -- poking one instruction at a time > basically can't be efficient on x86. The API should either poke lots > of instructions at once or should be text_poke_begin(); ...; > text_poke_end();. I don't think anybody ever cared about performance here. Only correctness. That whole text_poke_bp() thing is entirely tricky. FWIW, before text_poke_bp(), text_poke() would only be used from stop_machine, so all the other CPUs would be stuck busy-waiting with IRQs disabled. These days, yeah, that's lots more dodgy, but yes text_mutex should be serializing all that. And on that, I so hate comments like: "must be called under foo_mutex", we have lockdep_assert_held() for that.
