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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@xxxxxxxxxxx

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