linux-kernel - Re: [Intel-gfx] The i915 stable patch marking is totally broken

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Message-ID: <87a88pfogs.fsf@intel.com>
Date:   Mon, 13 Mar 2017 12:41:39 +0200
From:   Jani Nikula <jani.nikula@...ux.intel.com>
To:     Daniel Vetter <daniel@...ll.ch>,
        Greg KH <gregkh@...uxfoundation.org>
Cc:     Daniel Vetter <daniel.vetter@...el.com>,
        intel-gfx <intel-gfx@...ts.freedesktop.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        stable <stable@...r.kernel.org>
Subject: Re: [Intel-gfx] The i915 stable patch marking is totally broken

On Mon, 13 Mar 2017, Daniel Vetter <daniel@...ll.ch> wrote:
> Our cherry-pick sha1 work exactly like yours: They don't make sense
> when you only look at the tree a patch has been cherry-picked _to_,
> since they're the sha1 from the tree they've been cherry-picked
> _from_. When you clone a fresh copy of your stable tree then the
> cherry-pick numbers also point nowhere. Only once you've pulled the
> future tree they're from (Linus' git in your case) do they make sense.
>
> Same for our cherry-picks, except the future tree isn't Linus' git
> (we'd have managed to make sha1 collisions cheaply otherwise ...) but
> the future Linus' git tree. Which is maintained by Stephen Rothwell in
> linux-next. As soon as you make sure you have the latest
> linux-next.git they will all resolve to something meaningful.

Indeed, if there's a cherry-pick reference to a commit that's *not* in
linux-next, we deserve to be yelled at. The branches that feed to
linux-next that we cherry-pick from are non-rebasing, so the commit ids
should not change when they eventually hit Linus' tree.

>> So if a commit says "cherry-pick", I guess I can always assume it's safe
>> to add, right?  If not, _then_ I have to run the "search backwards"
>> logic, right?
>>
>> Ok, let me think about this a bit to see if that's possible to script...

Most of our cherry-picking is scripted, so if there's further annotation
that you'd like, just let us know. (Too bad it's virtually impossible to
modify the commit being cherry-picked. Unless someone(tm) comes up with
a way to share git-notes in a sensible, distributed way.)

BR,
Jani.


-- 
Jani Nikula, Intel Open Source Technology Center