On Mon, 2 Sept 2024 at 08:43, Peter Zijlstra [off-list ref] wrote:

and Linus took objection to similar patterns. But perhaps my naming
wasn't right.

Well, more of a "this stuff is new, let's start very limited and very clear".

I'm not loving the inactive guard, but I did try to think of a better
model for it, and I can't.  I absolutely hate the *example*, though:

  void func(bool a)
  {
        DEFINE_INACTIVE_GUARD(preempt_notrace, myguard);

        [...]
        if (a) {
                might_sleep();
                activate_guard(preempt_notrace, myguard)();
        }
        [ protected code ]
  }

because that "protected code" obviously is *NOT* protected code. It's
conditionally protected only in one situation.

Honestly, I still think the guard macros are new enough that we should
strive to avoid them in complicated cases like this. And this *is*
complicated. It *looks* simple, but when even the example that was
given was pure and utter garbage, it's clearly not *actually* simple.

Once some code is sometimes protected, and sometimes isn't, and you
have magic compiler stuff that *hides* it, I'm not sure we should use
the magic compiler stuff.

                Linus