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Date:   Wed, 7 Feb 2018 06:37:06 -0800
From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     Guenter Roeck <linux@roeck-us.net>
Cc:     Harsh Shandilya <msfjarvis@gmail.com>, akpm@linux-foundation.org,
        ben.hutchings@codethink.co.uk, linux-kernel@vger.kernel.org,
        lkft-triage@lists.linaro.org, patches@kernelci.org,
        shuahkh@osg.samsung.com, stable@vger.kernel.org,
        torvalds@linux-foundation.org
Subject: Re: [PATCH 3.18 00/36] 3.18.94-stable review
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On Tue, Feb 06, 2018 at 06:48:17AM -0800, Guenter Roeck wrote:
> On 02/06/2018 05:14 AM, Greg Kroah-Hartman wrote:
> > Thanks for letting me know, that's great to hear as I just had a
> > question from some companies who are worried that taking stable patches
> > will cause tons of merge issues.  It hasn't in my experience, and seeing
> > reports of this from others is great news.
> > 
> 
> From merging v4.4 and v4.14 into the respective ChromeOS branches, I would conclude
> that merging is for the most part easy. Major source of conflicts, if they happen,
> is that we may already have picked up additional commits from upstream.
> 
> This is only true, though, if merges are done on a release-by-release basis
> and if the merge happens shortly after a stable release is available. Otherwise,
> as time goes by, merges become more and more difficult (almost exponentially
> over time). Wait for more than 2-3 months between merges and it becomes almost
> impossible.
> 
> For reference, the top of tree for both branches is
> 	v4.14.16-3823-g597d36f1d331
> 	v4.4.114-12977-ga207b53fe939

Ugh, 12k patches is not trivial, gotta love those graphic drivers :(

> meaning there are _lots_ of patches on top of the mainline stable releases.
> 
> Also, overall, the rate of regressions is quite low (if I recall correctly,
> somewhere between 3 and 5 in chromeos-4.4, and one so far in chromeos-4.14,
> ie below 0.1%).

Thanks a lot for the feedback, this helps out a lot when talking to
companies that are "afraid" of doing merges with stable.

Based on this, one phone vendor just forward merged their 4.4.y based
tree to the latest release in a few hours with no reported problems at
all, so it has already helped out with tangable results.

thanks,

greg k-h