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

[Linus Torvalds]

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
trace-point.

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".

                   Linus