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docs: reporting-issues.rst: improved process esp. for stable regressions

Browse source 
Provide a shorter and easier process for users that deal with
regressions in stable and longterm kernels, as those should be reported
quickly.

To realize this in the least-confusing way and without having steps
multiple times in different places, split the 'search for existing
reports' into two. That has the additinal benefit that users will search
for them quickly when going through the step by step guide and thus will
save them trouble if the find reports.

Signed-off-by: Thorsten Leemhuis <linux@leemhuis.info>
CC: Randy Dunlap <rdunlap@infradead.org>
Link: https://lore.kernel.org/r/d934c15e536bceeff5c40a126930ddf803548e08.1616181657.git.linux@leemhuis.info
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
This commit is contained in:
Thorsten Leemhuis 2021-03-19 20:27:49 +01:00 committed by Jonathan Corbet
parent 9bc4430db5
commit 4b9d49d1ec
1 changed files with 194 additions and 293 deletions
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487
Documentation/admin-guide/reporting-issues.rst
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@ -100,6 +100,11 @@ process won't feel wasted in the end:
willing to install the latest Linux version yourself. Be aware the latter
will often be needed anyway to hunt down and fix issues.
* Perform a rough search for existing reports with your favorite internet
search engine; additionally, check the archives of the Linux Kernel Mailing
List (LKML). If you find matching reports, join the discussion instead of
sending a new one.
* See if the issue you are dealing with qualifies as regression, security
issue, or a really severe problem: those are 'issues of high priority' that
need special handling in some steps that are about to follow.
@ -122,16 +127,18 @@ process won't feel wasted in the end:
needs to get reported to the kernel developers separately, unless they are
strongly entangled.
* If you are facing a regression within a stable or longterm version line
(say something broke when updating from 5.10.4 to 5.10.5), scroll down to
'Dealing with regressions within a stable and longterm kernel line'.
* Locate the driver or kernel subsystem that seems to be causing the issue.
Find out how and where its developers expect reports. Note: most of the
time this won't be bugzilla.kernel.org, as issues typically need to be sent
by mail to a maintainer and a public mailing list.
* Search the archives of the bug tracker or mailing list in question
thoroughly for reports that might match your issue. Also check if you find
something with your favorite internet search engine or in the Linux Kernel
Mailing List (LKML) archives. If you find anything, join the discussion
instead of sending a new report.
thoroughly for reports that might match your issue. If you find anything,
join the discussion instead of sending a new report.
After these preparations you'll now enter the main part:
@ -187,17 +194,15 @@ After these preparations you'll now enter the main part:
help yourself, if you don't get any help or if it's unsatisfying.
Reporting issues only occurring in older kernel version lines
-------------------------------------------------------------
Reporting regressions within a stable and longterm kernel line
--------------------------------------------------------------
This section is for you, if you tried the latest mainline kernel as outlined
above, but failed to reproduce your issue there; at the same time you want to
see the issue fixed in older version lines or a vendor kernel that's regularly
rebased on new stable or longterm releases. If that case follow these steps:
* Prepare yourself for the possibility that going through the next few steps
might not get the issue solved in older releases: the fix might be too big
or risky to get backported there.
This subsection is for you, if you followed above process and got sent here at
the point about regression within a stable or longterm kernel version line. You
face one of those if something breaks when updating from 5.10.4 to 5.10.5 (a
switch from 5.9.15 to 5.10.5 does not qualify). The developers want to fix such
regressions as quickly as possible, hence there is a streamlined process to
report them:
* Check if the kernel developers still maintain the Linux kernel version
line you care about: go to the front page of kernel.org and make sure it
@ -210,6 +215,30 @@ rebased on new stable or longterm releases. If that case follow these steps:
kernel. Ensure this kernel is not tainted and still shows the problem, as
the issue might have already been fixed there.
* Send a short problem report by mail to the people and mailing lists the
:ref:`MAINTAINERS <maintainers>` file specifies in the section 'STABLE
BRANCH'. Roughly describe the issue and ideally explain how to reproduce
it. Mention the first version that shows the problem and the last version
that's working fine. Then wait for further instructions.
The reference section below explains each of these steps in more detail.
Reporting issues only occurring in older kernel version lines
-------------------------------------------------------------
This subsection is for you, if you tried the latest mainline kernel as outlined
above, but failed to reproduce your issue there; at the same time you want to
see the issue fixed in older version lines or a vendor kernel that's regularly
rebased on new stable or longterm releases. If that case follow these steps:
* Prepare yourself for the possibility that going through the next few steps
might not get the issue solved in older releases: the fix might be too big
or risky to get backported there.
* Perform the first three steps in the section "Dealing with regressions
within a stable and longterm kernel line" above.
* Search the Linux kernel version control system for the change that fixed
the issue in mainline, as its commit message might tell you if the fix is
scheduled for backporting already. If you don't find anything that way,
@ -218,22 +247,13 @@ rebased on new stable or longterm releases. If that case follow these steps:
deemed unsuitable for backporting. If backporting was not considered at
all, join the newest discussion, asking if it's in the cards.
* Check if you're dealing with a regression that was never present in
mainline by installing the first release of the version line you care
about. If the issue doesn't show up with it, you basically need to report
the issue with this version like you would report a problem with mainline
(see above). This ideally includes a bisection followed by a search for
existing reports on the net; with the help of the subject and the two
relevant commit-ids. If that doesn't turn up anything, write the report; CC
or forward the report to the stable maintainers, the stable mailing list,
and those who authored the change. Include the shortened commit-id if you
found the change that causes it.
* One of the former steps should lead to a solution. If that doesn't work
out, ask the maintainers for the subsystem that seems to be causing the
issue for advice; CC the mailing list for the particular subsystem as well
as the stable mailing list.
The reference section below explains each of these steps in more detail.
Reference section: Reporting issues to the kernel maintainers
=============================================================
@ -329,44 +349,25 @@ better than not reporting the issue at all: sometimes such reports directly or
indirectly will help to get the issue fixed over time.
Search for existing reports
---------------------------
Search for existing reports, first run
--------------------------------------
*Search the archives of the bug tracker or mailing list in question
thoroughly for reports that might match your issue. Also check if you find
something with your favorite internet search engine or in the Linux Kernel
Mailing List (LKML) archives. If you find anything, join the discussion
instead of sending a new report.*
*Perform a rough search for existing reports with your favorite internet
search engine; additionally, check the archives of the Linux Kernel Mailing
List (LKML). If you find matching reports, join the discussion instead of
sending a new one.*
Reporting an issue that someone else already brought forward is often a waste
of time for everyone involved, especially you as the reporter. So it's in your
own interest to thoroughly check if somebody reported the issue already. Thus
do not hurry with this step of the reporting process. Spending 30 to 60 minutes
or even more time can save you and others quite a lot of time and trouble.
Reporting an issue that someone else already brought forward is often a waste of
time for everyone involved, especially you as the reporter. So it's in your own
interest to thoroughly check if somebody reported the issue already. At this
step of the process it's okay to just perform a rough search: a later step will
tell you to perform a more detailed search once you know where your issue needs
to be reported to. Nevertheless, do not hurry with this step of the reporting
process, it can save you time and trouble.
The best place to search is the bug tracker or the mailing list where your
report needs to be filed. You'll find quite a few of those lists on
`lore.kernel.org <https://lore.kernel.org/>`_, but some are hosted in
different places. That for example is the case for the ath10k WiFi driver used
as example in the previous step. But you'll often find the archives for these
lists easily on the net. Searching for 'archive ath10k@lists.infradead.org' for
example will quickly lead you to the `Info page for the ath10k mailing list
<https://lists.infradead.org/mailman/listinfo/ath10k>`_, which at the top links
to its `list archives <https://lists.infradead.org/pipermail/ath10k/>`_.
Sadly this and quite a few other lists miss a way to search the archives. In
those cases use a regular internet search engine and add something like
'site:lists.infradead.org/pipermail/ath10k/' to your search terms, which limits
the results to the archives at that URL.
Additionally, search the internet and the `Linux Kernel Mailing List (LKML)
archives <https://lore.kernel.org/lkml/>`_, as maybe the real culprit might be
in some other subsystem. Searching in `bugzilla.kernel.org
<https://bugzilla.kernel.org/>`_ might also be a good idea, but if you find
anything there keep in mind: most subsystems expect reports in different
places, hence those you find there might have not even reached the people
responsible for the subsystem in question. Nevertheless, the data there might
provide valuable insights.
Simply search the internet with your favorite search engine first. Afterwards,
search the `Linux Kernel Mailing List (LKML) archives
<https://lore.kernel.org/lkml/>`_.
If you get flooded with results consider telling your search engine to limit
search timeframe to the past month or year. And wherever you search, make sure
@ -387,6 +388,15 @@ developers might look for people that can provide additional information or
test a proposed fix. Jump to the section 'Duties after the report went out' for
details on how to get properly involved.
Note, searching `bugzilla.kernel.org <https://bugzilla.kernel.org/>`_ might also
be a good idea, as that might provide valuable insights or turn up matching
reports. If you find the latter, just keep in mind: most subsystems expect
reports in different places, as described below in the section "Check where you
need to report your issue". The developers that should take care of the issue
thus might not even be aware of the bugzilla ticket. Hence, check the ticket if
the issue already got reported as outlined in this document and if not consider
doing so.
Issue of high priority?
-----------------------
@ -591,9 +601,25 @@ due to faulty hardware apart from a kernel issue that rarely happens and thus
is hard to reproduce.
Locate kernel area that causes the issue
Regression in stable or longterm kernel?
----------------------------------------
*If you are facing a regression within a stable or longterm version line
(say something broke when updating from 5.10.4 to 5.10.5), scroll down to
'Dealing with regressions within a stable and longterm kernel line'.*
Regression within a stable and longterm kernel version line are something the
Linux developers want to fix badly, as such issues are even more unwanted than
regression in the main development branch, as they can quickly affect a lot of
people. The developers thus want to learn about such issues as quickly as
possible, hence there is a streamlined process to report them. Note,
regressions with newer kernel version line (say something broke when switching
from 5.9.15 to 5.10.5) do not qualify.
Check where you need to report your issue
-----------------------------------------
*Locate the driver or kernel subsystem that seems to be causing the issue.
Find out how and where its developers expect reports. Note: most of the
time this won't be bugzilla.kernel.org, as issues typically need to be sent
@ -769,63 +795,39 @@ modified during tree-wide cleanups by developers that do not care about the
particular driver at all.
Search for existing reports
---------------------------
Search for existing reports, second run
---------------------------------------
*Search the archives of the bug tracker or mailing list in question
thoroughly for reports that might match your issue. Also check if you find
something with your favorite internet search engine or in the Linux Kernel
Mailing List (LKML) archives. If you find anything, join the discussion
instead of sending a new report.*
thoroughly for reports that might match your issue. If you find anything,
join the discussion instead of sending a new report.*
Reporting an issue that someone else already brought forward is often a waste
of time for everyone involved, especially you as the reporter. So it's in your
own interest to thoroughly check if somebody reported the issue already. Thus
do not hurry with this step of the reporting process. Spending 30 to 60 minutes
or even more time can save you and others quite a lot of time and trouble.
As mentioned earlier already: reporting an issue that someone else already
brought forward is often a waste of time for everyone involved, especially you
as the reporter. That's why you should search for existing report again, now
that you know where they need to be reported to. If it's mailing list, you will
often find its archives on `lore.kernel.org <https://lore.kernel.org/>`_.
The best place to search is the bug tracker or the mailing list where your
report needs to be filed. You'll find quite a few of those lists on
`lore.kernel.org <https://lore.kernel.org/>`_, but some are hosted in
different places. That for example is the case for the ath10k WiFi driver used
as example in the previous step. But you'll often find the archives for these
lists easily on the net. Searching for 'archive ath10k@lists.infradead.org' for
example will quickly lead you to the `Info page for the ath10k mailing list
<https://lists.infradead.org/mailman/listinfo/ath10k>`_, which at the top links
to its `list archives <https://lists.infradead.org/pipermail/ath10k/>`_.
Sadly this and quite a few other lists miss a way to search the archives. In
those cases use a regular internet search engine and add something like
But some list are hosted in different places. That for example is the case for
the ath10k WiFi driver used as example in the previous step. But you'll often
find the archives for these lists easily on the net. Searching for 'archive
ath10k@lists.infradead.org' for example will lead you to the `Info page for the
ath10k mailing list <https://lists.infradead.org/mailman/listinfo/ath10k>`_,
which at the top links to its
`list archives <https://lists.infradead.org/pipermail/ath10k/>`_. Sadly this and
quite a few other lists miss a way to search the archives. In those cases use a
regular internet search engine and add something like
'site:lists.infradead.org/pipermail/ath10k/' to your search terms, which limits
the results to the archives at that URL.
Additionally, search the internet and the `Linux Kernel Mailing List (LKML)
archives <https://lore.kernel.org/lkml/>`_, as maybe the real culprit might be
in some other subsystem. Searching in `bugzilla.kernel.org
<https://bugzilla.kernel.org/>`_ might also be a good idea, but if you find
anything there keep in mind: most subsystems expect reports in different
places, hence those you find there might have not even reached the people
responsible for the subsystem in question. Nevertheless, the data there might
provide valuable insights.
It's also wise to check the internet, LKML and maybe bugzilla.kernel.org again
at this point.
If you get flooded with results consider telling your search engine to limit
search timeframe to the past month or year. And wherever you search, make sure
to use good search terms; vary them a few times, too. While doing so try to
look at the issue from the perspective of someone else: that will help you to
come up with other words to use as search terms. Also make sure not to use too
many search terms at once. Remember to search with and without information like
the name of the kernel driver or the name of the affected hardware component.
But its exact brand name (say 'ASUS Red Devil Radeon RX 5700 XT Gaming OC')
often is not much helpful, as it is too specific. Instead try search terms like
the model line (Radeon 5700 or Radeon 5000) and the code name of the main chip
('Navi' or 'Navi10') with and without its manufacturer ('AMD').
For details how to search and what to do if you find matching reports see
"Search for existing reports, first run" above.
In case you find an existing report about your issue, join the discussion, as
you might be able to provide valuable additional information. That can be
important even when a fix is prepared or in its final stages already, as
developers might look for people that can provide additional information or
test a proposed fix. Jump to the section 'Duties after the report went out' for
details on how to get properly involved.
Do not hurry with this step of the reporting process: spending 30 to 60 minutes
or even more time can save you and others quite a lot of time and trouble.
Install a fresh kernel for testing
@ -1512,32 +1514,11 @@ easier. And with a bit of luck there might be someone in the team that knows a
bit about programming and might be able to write a fix.
Details about reporting issues only occurring in older kernel version lines
---------------------------------------------------------------------------
Reference for "Reporting issues only occurring in older kernel version lines"
-----------------------------------------------------------------------------
This subsection provides details for steps you need to take if you could not
reproduce your issue with a mainline kernel, but want to see it fixed in older
version lines (aka stable and longterm kernels).
Some fixes are too complex
~~~~~~~~~~~~~~~~~~~~~~~~~~
*Prepare yourself for the possibility that going through the next few steps
might not get the issue solved in older releases: the fix might be too big
or risky to get backported there.*
Even small and seemingly obvious code-changes sometimes introduce new and
totally unexpected problems. The maintainers of the stable and longterm kernels
are very aware of that and thus only apply changes to these kernels that are
within rules outlined in 'Documentation/process/stable-kernel-rules.rst'.
Complex or risky changes for example do not qualify and thus only get applied
to mainline. Other fixes are easy to get backported to the newest stable and
longterm kernels, but too risky to integrate into older ones. So be aware the
fix you are hoping for might be one of those that won't be backported to the
version line your care about. In that case you'll have no other choice then to
live with the issue or switch to a newer Linux version, unless you want to
patch the fix into your kernels yourself.
This subsection provides details for step you need to perform if you face a
regression within a stable and longterm kernel line.
Make sure the particular version line still gets support
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
@ -1581,7 +1562,85 @@ Reproduce issue with the newest release
Before investing any more time in this process you want to check if the issue
was already fixed in the latest release of version line you're interested in.
This kernel needs to be vanilla and shouldn't be tainted before the issue
happens, as detailed outlined already above in the process of testing mainline.
happens, as detailed outlined already above in the section "Install a fresh
kernel for testing".
Report the regression
~~~~~~~~~~~~~~~~~~~~~
*Send a short problem report by mail to the people and mailing lists the
:ref:`MAINTAINERS <maintainers>` file specifies in the section 'STABLE
BRANCH'. Roughly describe the issue and ideally explain how to reproduce
it. Mention the first version that shows the problem and the last version
that's working fine. Then wait for further instructions.*
When reporting a regression that happens within a stable or longterm kernel
line (say when updating from 5.10.4 to 5.10.5) a brief report is enough for
the start to get the issue reported quickly. Hence a rough description is all
it takes.
But note, it helps developers a great deal if you can specify the exact version
that introduced the problem. Hence if possible within a reasonable time frame,
try to find that version using vanilla kernels. Lets assume something broke when
your distributor released a update from Linux kernel 5.10.5 to 5.10.8. Then as
instructed above go and check the latest kernel from that version line, say
5.10.9. If it shows the problem, try a vanilla 5.10.5 to ensure that no patches
the distributor applied interfere. If the issue doesn't manifest itself there,
try 5.10.7 and then (depending on the outcome) 5.10.8 or 5.10.6 to find the
first version where things broke. Mention it in the report and state that 5.10.9
is still broken.
What the previous paragraph outlines is basically a rough manual 'bisection'.
Once your report is out your might get asked to do a proper one, as it allows to
pinpoint the exact change that causes the issue (which then can easily get
reverted to fix the issue quickly). Hence consider to do a proper bisection
right away if time permits. See the section 'Special care for regressions' and
the document 'Documentation/admin-guide/bug-bisect.rst' for details how to
perform one.
Reference for "Reporting regressions within a stable and longterm kernel line"
------------------------------------------------------------------------------
This section provides details for steps you need to take if you could not
reproduce your issue with a mainline kernel, but want to see it fixed in older
version lines (aka stable and longterm kernels).
Some fixes are too complex
~~~~~~~~~~~~~~~~~~~~~~~~~~
*Prepare yourself for the possibility that going through the next few steps
might not get the issue solved in older releases: the fix might be too big
or risky to get backported there.*
Even small and seemingly obvious code-changes sometimes introduce new and
totally unexpected problems. The maintainers of the stable and longterm kernels
are very aware of that and thus only apply changes to these kernels that are
within rules outlined in 'Documentation/process/stable-kernel-rules.rst'.
Complex or risky changes for example do not qualify and thus only get applied
to mainline. Other fixes are easy to get backported to the newest stable and
longterm kernels, but too risky to integrate into older ones. So be aware the
fix you are hoping for might be one of those that won't be backported to the
version line your care about. In that case you'll have no other choice then to
live with the issue or switch to a newer Linux version, unless you want to
patch the fix into your kernels yourself.
Common preparations
~~~~~~~~~~~~~~~~~~~
*Perform the first three steps in the section "Reporting issues only
occurring in older kernel version lines" above.*
You need to carry out a few steps already described in another section of this
guide. Those steps will let you:
* Check if the kernel developers still maintain the Linux kernel version line
you care about.
* Search the Linux stable mailing list for exiting reports.
* Check with the latest release.
Check code history and search for existing discussions
@ -1636,164 +1695,6 @@ discussions abound it.
join the discussion: mention the version where you face the issue and that
you would like to see it fixed, if suitable.
Details about reporting issues only occurring in older kernel version lines
---------------------------------------------------------------------------
This subsection provides details for steps you need to take if you could not
reproduce your issue with a mainline kernel, but want to see it fixed in older
version lines (aka stable and longterm kernels).
Some fixes are too complex
~~~~~~~~~~~~~~~~~~~~~~~~~~
*Prepare yourself for the possibility that going through the next few steps
might not get the issue solved in older releases: the fix might be too big
or risky to get backported there.*
Even small and seemingly obvious code-changes sometimes introduce new and
totally unexpected problems. The maintainers of the stable and longterm kernels
are very aware of that and thus only apply changes to these kernels that are
within rules outlined in 'Documentation/process/stable-kernel-rules.rst'.
Complex or risky changes for example do not qualify and thus only get applied
to mainline. Other fixes are easy to get backported to the newest stable and
longterm kernels, but too risky to integrate into older ones. So be aware the
fix you are hoping for might be one of those that won't be backported to the
version line your care about. In that case you'll have no other choice then to
live with the issue or switch to a newer Linux version, unless you want to
patch the fix into your kernels yourself.
Make sure the particular version line still gets support
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
*Check if the kernel developers still maintain the Linux kernel version
line you care about: go to the front page of kernel.org and make sure it
mentions the latest release of the particular version line without an
'[EOL]' tag.*
Most kernel version lines only get supported for about three months, as
maintaining them longer is quite a lot of work. Hence, only one per year is
chosen and gets supported for at least two years (often six). That's why you
need to check if the kernel developers still support the version line you care
for.
Note, if kernel.org lists two 'stable' version lines on the front page, you
should consider switching to the newer one and forget about the older one:
support for it is likely to be abandoned soon. Then it will get a "end-of-life"
(EOL) stamp. Version lines that reached that point still get mentioned on the
kernel.org front page for a week or two, but are unsuitable for testing and
reporting.
Search stable mailing list
~~~~~~~~~~~~~~~~~~~~~~~~~~
*Check the archives of the Linux stable mailing list for existing reports.*
Maybe the issue you face is already known and was fixed or is about to. Hence,
`search the archives of the Linux stable mailing list
<https://lore.kernel.org/stable/>`_ for reports about an issue like yours. If
you find any matches, consider joining the discussion, unless the fix is
already finished and scheduled to get applied soon.
Reproduce issue with the newest release
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
*Install the latest release from the particular version line as a vanilla
kernel. Ensure this kernel is not tainted and still shows the problem, as
the issue might have already been fixed there.*
Before investing any more time in this process you want to check if the issue
was already fixed in the latest release of version line you're interested in.
This kernel needs to be vanilla and shouldn't be tainted before the issue
happens, as detailed outlined already above in the process of testing mainline.
Check code history and search for existing discussions
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
*Search the Linux kernel version control system for the change that fixed
the issue in mainline, as its commit message might tell you if the fix is
scheduled for backporting already. If you don't find anything that way,
search the appropriate mailing lists for posts that discuss such an issue
or peer-review possible fixes; then check the discussions if the fix was
deemed unsuitable for backporting. If backporting was not considered at
all, join the newest discussion, asking if it's in the cards.*
In a lot of cases the issue you deal with will have happened with mainline, but
got fixed there. The commit that fixed it would need to get backported as well
to get the issue solved. That's why you want to search for it or any
discussions abound it.
* First try to find the fix in the Git repository that holds the Linux kernel
sources. You can do this with the web interfaces `on kernel.org
<https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/>`_
or its mirror `on GitHub <https://github.com/torvalds/linux>`_; if you have
a local clone you alternatively can search on the command line with ``git
log --grep=<pattern>``.
If you find the fix, look if the commit message near the end contains a
'stable tag' that looks like this:
Cc: <stable@vger.kernel.org> # 5.4+
If that's case the developer marked the fix safe for backporting to version
line 5.4 and later. Most of the time it's getting applied there within two
weeks, but sometimes it takes a bit longer.
* If the commit doesn't tell you anything or if you can't find the fix, look
again for discussions about the issue. Search the net with your favorite
internet search engine as well as the archives for the `Linux kernel
developers mailing list <https://lore.kernel.org/lkml/>`_. Also read the
section `Locate kernel area that causes the issue` above and follow the
instructions to find the subsystem in question: its bug tracker or mailing
list archive might have the answer you are looking for.
* If you see a proposed fix, search for it in the version control system as
outlined above, as the commit might tell you if a backport can be expected.
* Check the discussions for any indicators the fix might be too risky to get
backported to the version line you care about. If that's the case you have
to live with the issue or switch to the kernel version line where the fix
got applied.
* If the fix doesn't contain a stable tag and backporting was not discussed,
join the discussion: mention the version where you face the issue and that
you would like to see it fixed, if suitable.
Check if it's a regression specific to stable or longterm kernels
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
*Check if you're dealing with a regression that was never present in
mainline by installing the first release of the version line you care
about. If the issue doesn't show up with it, you basically need to report
the issue with this version like you would report a problem with mainline
(see above). This ideally includes a bisection followed by a search for
existing reports on the net; with the help of the subject and the two
relevant commit-ids. If that doesn't turn up anything, write the report; CC
or forward the report to the stable maintainers, the stable mailing list,
and those who authored the change. Include the shortened commit-id if you
found the change that causes it.*
Sometimes you won't find anything in the previous step: the issue you face
might have never occurred in mainline, as it is caused by some change that is
incomplete or not correctly applied. To check this, install the first release
from version line you care about, e.g., if you care about 5.4.x, install 5.4.
If the issue doesn't show itself there, it's a regression specific to the
particular version line. In that case you need to report it like an issue
happening in mainline, like the last few steps in the main section in the above
outline.
One of them suggests doing a bisection, which you are strongly advised to do in
this case. After finding the culprit, search the net for existing reports
again: not only search for the exact subject and the commit-id (proper and
shortened to twelve characters) of the change, but also for the commit-id
(proper and shortened) mentioned as 'Upstream commit' in the commit message.
Write the report; just keep a few specialties in mind: CC or forward the report
to the stable maintainers, the stable mailing list, which the :ref:`MAINTAINERS
<maintainers>` file mentions in the section "STABLE BRANCH". If you performed a
successful bisection, CC the author of the change and include its subject and
the shortened commit-id.
Ask for advice
~~~~~~~~~~~~~~