Re: [PATCH] x86/debug: Remove perpetually broken, unmaintainable dwarf annotations

From: Andy Lutomirski <luto@amacapital.net>
To: Ingo Molnar <mingo@kernel.org>
Cc: "Jan Beulich" <JBeulich@suse.com>,
	"Borislav Petkov" <bp@alien8.de>,
	"Peter Zijlstra" <a.p.zijlstra@chello.nl>,
	"Ingo Molnar" <mingo@elte.hu>, "Brian Gerst" <brgerst@gmail.com>,
	"Frédéric Weisbecker" <fweisbec@gmail.com>,
	"Thomas Gleixner" <tglx@linutronix.de>,
	"Linus Torvalds" <torvalds@linux-foundation.org>,
	"Denys Vlasenko" <dvlasenk@redhat.com>,
	"Josh Poimboeuf" <jpoimboe@redhat.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"H. Peter Anvin" <hpa@zytor.com>
Subject: Re: [PATCH] x86/debug: Remove perpetually broken, unmaintainable dwarf annotations
Date: Fri, 29 May 2015 10:47:31 -0700	[thread overview]
Message-ID: <CALCETrWw0hogKsf3wO5aYeuJB0j5-wE5Hzm4==X5bJsbZNiY3g@mail.gmail.com> (raw)
In-Reply-To: <20150528131743.GA9496@gmail.com>

On Thu, May 28, 2015 at 6:17 AM, Ingo Molnar <mingo@kernel.org> wrote:
>
> * Jan Beulich <JBeulich@suse.com> wrote:
>
>> > and meanwhile you can keep a revert of this patch ported to SUSE kernels in
>> > whatever fashion you prefer.
>>
>> Funny suggestion - I don't think that's reasonable for us to do. Or if we were
>> to, we could as well invest in doing the re-work you're asking for; I don't
>> think anyone will have the time to do either.
>
> That's fair enough: if there's not enough resources to keep a feature maintainable
> upstream then it should not be upstream in that form.
>
> This isn't just some driver we can let bit-rot in peace until it finds a
> maintainer (or not), without affecting anyone but users of that driver.
>
> This is hundreds of usage sites of ugly code intermixed with critical pieces of
> assembly code that negatively affects the hackability of everything.
>
> Also, with the feature missing completely, maybe someone finds a method to
> introduce it in a maintainable fashion, while with the feature included upstream
> there's very little pressure to do that. As a bonus we'd also win a workable dwarf
> unwinder.

Before doing something drastic like this, I think we should get Josh's
opinion, since I think he's working on a new (?) unwinder.

FWIW, musl is considering some kind of automatic annotation scheme:

http://www.openwall.com/lists/musl/2015/05/13/5

--Andy