Re: perf: definition of a "regression"

From: Ingo Molnar
Date: Thu Jun 02 2011 - 03:45:56 EST



* Vince Weaver <vweaver1@xxxxxxxxxxxx> wrote:

> On Sat, 28 May 2011, Peter Zijlstra wrote:
>
> > On Fri, 2011-05-27 at 23:38 -0400, Vince Weaver wrote:
> > > on that note (and while trying to document exactly what the ioctls do) it
> > > seems that a PERF_EVENT_IOC_REFRESH with an argument of anything higher
> > > than one does not work on kernels 2.6.36 and newer. The behavior acts
> > > as if 1 was passed, even if you pass in, say, 3.
> >
> > Urgh, no that should definitely work. Thanks for the test-case, I'll
> > work on that (probably not until Monday though, but who knows).
>
> So wait, the two regressions I found in 2.6.37 are WONTFIX because
> they are too old, even though they break existing userspace code?
>
> And this older regression in 2.6.36 is going to be fixed, even
> though perf, PAPI, and libpfm4 don't trigger the buggy
> functionality at all?

Btw., these considerations are flexible and we can reconsider and
change the WONTFIX if there's a patch available and doesn't look
horrible to backport. We can also mark fixes that havent been marked
-stable originally as -stable later on, etc.

So please don't feel needlessly bitter about past decisions: when
there's some good technical solution to a problem (or we were plain
out wrong about a decision) we try hard not to stand in the way.

Thanks,

Ingo
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