From: Andy Lutomirski <luto@kernel.org>
To: Al Viro <viro@zeniv.linux.org.uk>
Cc: ksummit-discuss@lists.linuxfoundation.org
Subject: Re: [Ksummit-discuss] [topic proposal] tracepoints and ABI stability warranties
Date: Tue, 6 Sep 2016 22:30:32 -0700 [thread overview]
Message-ID: <CALCETrVRFVkpk5bbH1jYxhh3nWYoJtXMFaMo2yR25sntGOrnDw@mail.gmail.com> (raw)
In-Reply-To: <20160907051039.GG2356@ZenIV.linux.org.uk>
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On Sep 6, 2016 10:10 PM, "Al Viro" <viro@zeniv.linux.org.uk> wrote:
>
> On Wed, Sep 07, 2016 at 01:41:00AM +0300, Alexey Dobriyan wrote:
>
> > Gentlemen's agreement then:
> > * kernel developers don't break tracepoints on purpose and maintain
> > compatibility in simple cases (long => int, deleted field, etc),
> > * real, justified tracepoint breakage doesn't count.
>
> No go. Scenario:
>
> 1) piss-poor API is added in form of tracehook. It exports some
information
> that can be used to derive something genuinely interesting. Most of the
> time. Corner cases are unsolvable, even though it might be possible to
> provide the interesting part sanely. Just not in that form. Moreover,
> faking the bits used to derive that information so that existing userland
> logics would yield the right result is bloody hard and restricts what we
> can do kernel-side, even though the real thing userland wants would not
have
> such problems.
>
Agreed.
I wouldn't mind a policy that tracepoints are simply never stable. Maybe
we should even deliberately change them periodically to drive the point
home.
The kernel should be able to have a debug API that is genuinely for
*debugging* and doesn't freeze the underlying implementation.
Windows, AFAICT, works like this. If you write a production program that
invokes WinDbg or similar, it's going to break down the road.
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next prev parent reply other threads:[~2016-09-07 5:30 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-06 18:51 Al Viro
2016-09-06 19:22 ` Steven Rostedt
2016-09-06 21:36 ` Alexey Dobriyan
2016-09-06 21:53 ` Steven Rostedt
2016-09-06 22:41 ` Alexey Dobriyan
2016-09-06 23:12 ` Steven Rostedt
2016-09-08 11:43 ` Alexey Dobriyan
2016-09-07 5:10 ` Al Viro
2016-09-07 5:30 ` Andy Lutomirski [this message]
2016-09-07 6:41 ` Vlastimil Babka
2016-09-19 12:51 ` Michal Hocko
2016-09-07 13:15 ` Christian Borntraeger
2016-09-07 15:30 ` Shuah Khan
2016-09-07 16:10 ` Rik van Riel
2016-09-08 3:24 ` Masami Hiramatsu
2016-09-15 19:23 ` Mark Brown
2016-09-06 22:02 ` Alexey Dobriyan
2016-09-06 22:15 ` Steven Rostedt
2016-09-06 21:05 ` Shuah Khan
2016-09-08 3:13 ` Masami Hiramatsu
2016-09-07 23:17 ` Masami Hiramatsu
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