Re: [PATCH 3/6] dax: add tracepoint infrastructure, PMD tracing

From: Linus Torvalds
Date: Sun Nov 27 2016 - 19:58:56 EST

On Sun, Nov 27, 2016 at 2:42 PM, Dave Chinner <david@xxxxxxxxxxxxx> wrote:
> And that's exactly why we need a method of marking tracepoints as
> stable. How else are we going to know whether a specific tracepoint
> is stable if the kernel code doesn't document that it's stable?

You are living in some unrealistic dream-world where you think you can
get the right tracepoint on the first try.

So there is no way in hell I would ever mark any tracepoint "stable"
until it has had a fair amount of use, and there are useful tools that
actually make use of it, and it has shown itself to be the right

And once that actually happens, what's the advantage of marking it
stable? None. It's a catch-22. Before it has uses and has been tested
and found to be good, it's not stable. And after, it's pointless.

So at no point does such a "stable" tracepoint marking make sense. At
most, you end up adding a comment saying "this tracepoint is used by
tools such-and-such".