question about one of your ubuntu patch

[Kamal Mostafa]

Hi David-

On Tue, Sep 8, 2020 at 5:11 AM David Lee <saynice111 at gmail.com> wrote:

> I think if commits are chosen, porting them should be easy. Can you give
> me more details on why
> it's time consuming?
>

Because each of the upstream stable trees gain patches at a rate > 5000 per
year.  The majority of those patches are indeed relatively easy to port,
but a significant fraction do not apply easily, and require analysis,
porting, and testing effort.   We do this porting process continuously for
multiple supported Ubuntu kernel versions.


> > I just found a patch in
>> > https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1857158, "rtc:
>> disable
>> > uie before setting time and enable after"--7e7c005b4b1f1f169bcc. It's
>> > in v4.19.89. But it's not patched in Ubuntu-4.15.0-76.86,which is
>> issued at
>> > Jan 17 2020.
>> > Ubuntu-4.15.0-76.86 contains the commit in the "Fixes:"
>> > in 7e7c005b4b1f1f169bcc, which means that ubuntu introduces the bug.
>> It's
>> > necessary to be patched. And the patch is also in the list of
>> > https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1857158. I
>> thought all
>> > the patches
>> > in that website are to be added in ubuntu. Why is not it added in
>> ubuntu?
>>
>
As Jeurg noted, that patch was indeed ported to Ubuntu Bionic and released
as indicated in the bug you linked.

It has a different SHA in the bionic repo (which will always be true for
stable patches) than the upstream SHA.  In general, when you're looking for
an upstream commit in an Ubuntu kernel repo, your best bet is to search by
title.  Here's your example, and another one where the patch title doesn't
exactly match upstream (because we merged it before upstream did):

$ git log --oneline --grep="rtc: disable uie"
be2063280b82 rtc: disable uie before setting time and enable after

$ git log --oneline --grep="s390/mm: fix page table"
b77f29531a23 UBUNTU: SAUCE: s390/mm: fix page table upgrade vs 2ndary
address mode accesses


> Is there any other rules?
>>
>
For Bionic's 4.15 kernel (where we port upstream stable patch sets from
4.14-stable and 4.19-stable) the general rule is that almost every patch
from 4.14-stable will get applied or ported (rarely, we determine that a
4.14-stable patch is just unsuitable for 4.15) -- but for the 4.19-stable
patch sets, only those that can be reasonably ported to 4.15 are accepted
(a large portion of them aren't suitable).

As Thadeu described, the upstream patch sets I'm referring to above are the
"stable" and "longterm" series, here: https://www.kernel.org/

Hope that helps answer your questions.

 -Kamal Mostafa (Canonical Kernel Team)
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