Re: [patch 2/2] Documentation/process: Add tip tree handbook

From: Greg KH <gregkh@linuxfoundation.org>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: "Paul E. McKenney" <paulmck@linux.ibm.com>,
	Dan Williams <dan.j.williams@intel.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	X86 ML <x86@kernel.org>, John Stultz <john.stultz@linaro.org>,
	acme@redhat.com, frederic@kernel.org,
	Jonathan Corbet <corbet@lwn.net>,
	Andy Lutomirski <luto@kernel.org>,
	Marc Zyngier <marc.zyngier@arm.com>,
	Daniel Lezcano <daniel.lezcano@linaro.org>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Ard Biesheuvel <ard.biesheuvel@linaro.org>,
	Will Deacon <will.deacon@arm.com>,
	Mark Brown <broonie@kernel.org>
Subject: Re: [patch 2/2] Documentation/process: Add tip tree handbook
Date: Thu, 8 Nov 2018 13:06:15 -0800	[thread overview]
Message-ID: <20181108210615.GC22691@kroah.com> (raw)
In-Reply-To: <alpine.DEB.2.21.1811082042001.1640@nanos.tec.linutronix.de>

On Thu, Nov 08, 2018 at 08:58:32PM +0100, Thomas Gleixner wrote:
> On Thu, 8 Nov 2018, Paul E. McKenney wrote:
> > On Thu, Nov 08, 2018 at 09:19:33AM -0800, Dan Williams wrote:
> > > On Thu, Nov 8, 2018 at 1:13 AM Peter Zijlstra <peterz@infradead.org> wrote:
> > > >
> > > > On Thu, Nov 08, 2018 at 08:40:12AM +0100, Ingo Molnar wrote:
> > > > > > + - Cc: ``cc-ed-person <person@mail>``
> > > > > > +
> > > > > > +   If the patch should be backported to stable, then please add a '``Cc:
> > > > > > +   stable@vger.kernel.org``' tag, but do not Cc stable when sending your
> > > > > > +   mail.
> > > > >
> > > > > Can I suggest a more canonical form:
> > > > >
> > > > >       Cc: <stable@vger.kernel.org> # v4.18 and later kernels
> > > > >
> > > > > It would be nice if people adding Cc: stable lines would actually try to
> > > > > figure out which exact kernel versions are affected.
> > > 
> > > I know at least StGit mail does not grok that "#"notation. I've
> > > stopped using it in favor of a "Fixes:" tag. I would think "Fixes:" is
> > > preferred over "# <KVER>" if only because it can be used to track
> > > fixes to commits that have been backported to stable. Is there any
> > > reason for "# <KVER>" to continue in a world where we have "Fixes:"?
> > 
> > I sometimes have fixes that need to be different for different past
> > releases.  And there have been cases where RCU patches would apply and
> > build cleanly against releases for which it was not appropriate, but
> > would have some low-probability failure.  Which meant that it could be
> > expected to pass light testing.  :-/
> > 
> > So I sometimes need a way of saying which versions a given patch applies
> > to, independent of the version into which the bug was introduced.
> 
> I can understand that you want to limit the scope of automatic backports.
> 
> But we really should try to always use of the Fixes: tag. In most cases the
> SHA1 of the commit in the fixes tag defines the backport scope. 
> 
> For the rare cases where the buggy commit is really old, but you want to
> limit the backport scope for a reason then I really like to avoid to
> overload the Cc stable tag and have a dedicated tag instead. Something
> like:
> 
>     Fixes: 1234567890AB ("subsys/comp: Short summary")
>     Backport-to: 4.14

Ick, no.  Just stick to the "Fixes:" tag.  My scripts can now track when
a patch is backported to a stable tree so that I know to apply it to
older ones despite the original patch showing up in a newer release.

And yes, those scripts are new, as Sasha is about to point out all of
the places where I missed this in the past :)

thanks,

greg k-h