question about one of your ubuntu patch

[David Lee]

Hi,

Thanks for your reply. Very helpful to me.

There is no upstream Linux 4.15 stable branch.

There is no upstream linux 4.15 long term support branch. But there is a
Linux stable branch
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/log/?h=linux-4.15.y
.

Ubuntu's bionic is based on Linux 4.15. But there is also linux 4.15-linux
4.15.18 branch in ubuntu-bionic. And commits in Linux 4.15-4.15.18 in
ubuntu git is the same as it in Linux git except some ubuntu sauce patches.

Besides, how does ubuntu know if there is a new patch added in upstream?
And how do ubuntu determine if a patch is necessary for ubuntu?
Thanks

On Tue, Aug 11, 2020 at 4:32 AM Thadeu Lima de Souza Cascardo <
cascardo at canonical.com> wrote:

> On Tue, Aug 11, 2020 at 12:33:17AM -0700, David Lee wrote:
> > Hi,
> >
> > I saw your email in the patch "serdev: Fix serdev_uevent failure on ACPI
> > enumerated serdev-controllers 586ca5b1a90b66eb0a2805c9419683e33d1d418b"
> in
> > ubuntu's git repository.
> > I am surprised to find that this patch in ubuntu git is committed on Apr
> 12
> > 10:06:37 2018. But this patch is committed to linux 4.15 stable branch
> > on Apr 12 12:31:11 2018.
> > In ubuntu git repository, this patch is also in Linux 4.15 stable branch.
> > Why a patch is committed before it's added in Linux 4.15 stable branch?
> >
> > Thanks
>
> Hi, David.
>
> There is no upstream Linux 4.15 stable branch. Upstream kernel.org git
> trees
> closest to 4.15 are 4.14 and 4.19. Kamal Mostafa, from the Ubuntu Kernel
> team
> picks up commits from those trees in order to apply them to Ubuntu bionic
> kernel tree, which is based on 4.15. As upstream has stopped publishing
> updates
> to 4.15 and Ubuntu picked up 4.15 for its Bionic release, we have Kamal do
> the
> great job of tracking commits to 4.14 and 4.19 and make pull requests so
> those
> can be included in Ubuntu's kernel.
>
> But patches are also submitted to Ubuntu's kernel through other ways and
> for
> other reasons, like when they fix specific bugs tracked at launchpad. It
> may
> happen that such patches match upstream commits that have both landed on
> Kamal's tree and directly on Ubuntu's tree.
>
> And by git's distributed nature, the same patch may be applied on different
> dates, or it may happen that they are rebased or reapplied, causing them to
> have different commit ids, and even different commit dates or commit
> authors,
> or have had their messages changed because of sign-offs.
>
> I didn't investigate the specific case you pointed out, but it may be that
> with
> the explanations above, you may find other differences between those two
> commits that might explain what might have happened.
>
> Regards.
> Thadeu Cascardo.
>
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