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Kernel development cycle

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Hi, please help me understand some general practices involved in kernel development. 
Specifically, I'm interested in how patches are included or reverted in different kernel 
versions.

Let's consider a practical example, the history of patch "drm/i915/execlists: Reset RING 
registers upon resume" [1]. This patch was committed 641 commits after version 4.8-rc2:

$ git describe bafb2f7d4755bf1571bd5e9a03b97f3fc4fe69ae
v4.8-rc2-641-gbafb2f7d4755

So I would expect to find it in version 4.8, which is the stable, final release of v4.8, following 
all the release canditates.

However, if I search for the tag that follows (and hence contains) that commit, I do not find 
version 4.8, nor version 4.9, but 4.10:

$ git describe --contains bafb2f7d4755bf1571bd5e9a03b97f3fc4fe69ae
v4.10-rc1~154^2~44^2~178

Why? Why not v4.8-rc3? This means that the patch has been included neither in v4.8 nor in 
v4.9, but only in version 4.10-rc1, right? Why so much time was needed, considering it was 
the 621st commit on top ov v4.8-rc2?

Another thing that confuses me is the following. In fact that patch ended up in v4.9.9 [2]. If 
my reasoning above is correct, it was backported from v4.10, right?

Then some problems were reported, and it was reverted in v4.9.23 with commit 
0ee72d8f9b8e17b8e4ccfebc7a25cbc2d395cd6a [3]. (What led to the decision of reverting it 
is explained in  [4] and [5]).

So my question now is--what version contains this patch? Is it true that I find it in v4.10? 

Stretch currently provides kernel version 4.9.30:

$ uname -v
#1 SMP Debian 4.9.30-2+deb9u2 (2017-06-26)

Since v4.9.30 follows v4.9.23, the patch is not be included in Stretch's kernel, so this 
explains why I'm experiencing the bug addressed by this patch. 

Thanks for your help.

[1] https://patchwork.freedesktop.org/patch/111587/
[2] https://www.kernel.org/pub/linux/kernel/v4.x/ChangeLog-4.9.9	
[3] https://www.kernel.org/pub/linux/kernel/v4.x/ChangeLog-4.9.23
[4] https://bugs.freedesktop.org/show_bug.cgi?id=100221#c10
[5] http://mid.mail-archive.com/1489443835.5568.7.camel@mailbox.org
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Kernel development cycle solitone <solitone@mail.com> - 2017-08-01 14:20 +0200
  Re: Kernel development cycle solitone <solitone@mail.com> - 2017-08-10 07:40 +0200

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