Adding upstream version 6.1.76.upstream/6.1.76

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

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+.. SPDX-License-Identifier: (GPL-2.0+ OR CC-BY-4.0)
+.. [see the bottom of this file for redistribution information]
+
+Reporting regressions
++++++++++++++++++++++
+
+"*We don't cause regressions*" is the first rule of Linux kernel development;
+Linux founder and lead developer Linus Torvalds established it himself and
+ensures it's obeyed.
+
+This document describes what the rule means for users and how the Linux kernel's
+development model ensures to address all reported regressions; aspects relevant
+for kernel developers are left to Documentation/process/handling-regressions.rst.
+
+
+The important bits (aka "TL;DR")
+================================
+
+#. It's a regression if something running fine with one Linux kernel works worse
+   or not at all with a newer version. Note, the newer kernel has to be compiled
+   using a similar configuration; the detailed explanations below describes this
+   and other fine print in more detail.
+
+#. Report your issue as outlined in Documentation/admin-guide/reporting-issues.rst,
+   it already covers all aspects important for regressions and repeated
+   below for convenience. Two of them are important: start your report's subject
+   with "[REGRESSION]" and CC or forward it to `the regression mailing list
+   <https://lore.kernel.org/regressions/>`_ (regressions@lists.linux.dev).
+
+#. Optional, but recommended: when sending or forwarding your report, make the
+   Linux kernel regression tracking bot "regzbot" track the issue by specifying
+   when the regression started like this::
+
+       #regzbot introduced v5.13..v5.14-rc1
+
+
+All the details on Linux kernel regressions relevant for users
+==============================================================
+
+
+The important basics
+--------------------
+
+
+What is a "regression" and what is the "no regressions rule"?
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+It's a regression if some application or practical use case running fine with
+one Linux kernel works worse or not at all with a newer version compiled using a
+similar configuration. The "no regressions rule" forbids this to take place; if
+it happens by accident, developers that caused it are expected to quickly fix
+the issue.
+
+It thus is a regression when a WiFi driver from Linux 5.13 works fine, but with
+5.14 doesn't work at all, works significantly slower, or misbehaves somehow.
+It's also a regression if a perfectly working application suddenly shows erratic
+behavior with a newer kernel version; such issues can be caused by changes in
+procfs, sysfs, or one of the many other interfaces Linux provides to userland
+software. But keep in mind, as mentioned earlier: 5.14 in this example needs to
+be built from a configuration similar to the one from 5.13. This can be achieved
+using ``make olddefconfig``, as explained in more detail below.
+
+Note the "practical use case" in the first sentence of this section: developers
+despite the "no regressions" rule are free to change any aspect of the kernel
+and even APIs or ABIs to userland, as long as no existing application or use
+case breaks.
+
+Also be aware the "no regressions" rule covers only interfaces the kernel
+provides to the userland. It thus does not apply to kernel-internal interfaces
+like the module API, which some externally developed drivers use to hook into
+the kernel.
+
+How do I report a regression?
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Just report the issue as outlined in
+Documentation/admin-guide/reporting-issues.rst, it already describes the
+important points. The following aspects outlined there are especially relevant
+for regressions:
+
+ * When checking for existing reports to join, also search the `archives of the
+   Linux regressions mailing list <https://lore.kernel.org/regressions/>`_ and
+   `regzbot's web-interface <https://linux-regtracking.leemhuis.info/regzbot/>`_.
+
+ * Start your report's subject with "[REGRESSION]".
+
+ * In your report, clearly mention the last kernel version that worked fine and
+   the first broken one. Ideally try to find the exact change causing the
+   regression using a bisection, as explained below in more detail.
+
+ * Remember to let the Linux regressions mailing list
+   (regressions@lists.linux.dev) know about your report:
+
+   * If you report the regression by mail, CC the regressions list.
+
+   * If you report your regression to some bug tracker, forward the submitted
+     report by mail to the regressions list while CCing the maintainer and the
+     mailing list for the subsystem in question.
+
+   If it's a regression within a stable or longterm series (e.g.
+   v5.15.3..v5.15.5), remember to CC the `Linux stable mailing list
+   <https://lore.kernel.org/stable/>`_ (stable@vger.kernel.org).
+
+  In case you performed a successful bisection, add everyone to the CC the
+  culprit's commit message mentions in lines starting with "Signed-off-by:".
+
+When CCing for forwarding your report to the list, consider directly telling the
+aforementioned Linux kernel regression tracking bot about your report. To do
+that, include a paragraph like this in your mail::
+
+       #regzbot introduced: v5.13..v5.14-rc1
+
+Regzbot will then consider your mail a report for a regression introduced in the
+specified version range. In above case Linux v5.13 still worked fine and Linux
+v5.14-rc1 was the first version where you encountered the issue. If you
+performed a bisection to find the commit that caused the regression, specify the
+culprit's commit-id instead::
+
+       #regzbot introduced: 1f2e3d4c5d
+
+Placing such a "regzbot command" is in your interest, as it will ensure the
+report won't fall through the cracks unnoticed. If you omit this, the Linux
+kernel's regressions tracker will take care of telling regzbot about your
+regression, as long as you send a copy to the regressions mailing lists. But the
+regression tracker is just one human which sometimes has to rest or occasionally
+might even enjoy some time away from computers (as crazy as that might sound).
+Relying on this person thus will result in an unnecessary delay before the
+regressions becomes mentioned `on the list of tracked and unresolved Linux
+kernel regressions <https://linux-regtracking.leemhuis.info/regzbot/>`_ and the
+weekly regression reports sent by regzbot. Such delays can result in Linus
+Torvalds being unaware of important regressions when deciding between "continue
+development or call this finished and release the final?".
+
+Are really all regressions fixed?
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Nearly all of them are, as long as the change causing the regression (the
+"culprit commit") is reliably identified. Some regressions can be fixed without
+this, but often it's required.
+
+Who needs to find the root cause of a regression?
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Developers of the affected code area should try to locate the culprit on their
+own. But for them that's often impossible to do with reasonable effort, as quite
+a lot of issues only occur in a particular environment outside the developer's
+reach -- for example, a specific hardware platform, firmware, Linux distro,
+system's configuration, or application. That's why in the end it's often up to
+the reporter to locate the culprit commit; sometimes users might even need to
+run additional tests afterwards to pinpoint the exact root cause. Developers
+should offer advice and reasonably help where they can, to make this process
+relatively easy and achievable for typical users.
+
+How can I find the culprit?
+~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Perform a bisection, as roughly outlined in
+Documentation/admin-guide/reporting-issues.rst and described in more detail by
+Documentation/admin-guide/bug-bisect.rst. It might sound like a lot of work, but
+in many cases finds the culprit relatively quickly. If it's hard or
+time-consuming to reliably reproduce the issue, consider teaming up with other
+affected users to narrow down the search range together.
+
+Who can I ask for advice when it comes to regressions?
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Send a mail to the regressions mailing list (regressions@lists.linux.dev) while
+CCing the Linux kernel's regression tracker (regressions@leemhuis.info); if the
+issue might better be dealt with in private, feel free to omit the list.
+
+
+Additional details about regressions
+------------------------------------
+
+
+What is the goal of the "no regressions rule"?
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Users should feel safe when updating kernel versions and not have to worry
+something might break. This is in the interest of the kernel developers to make
+updating attractive: they don't want users to stay on stable or longterm Linux
+series that are either abandoned or more than one and a half years old. That's
+in everybody's interest, as `those series might have known bugs, security
+issues, or other problematic aspects already fixed in later versions
+<http://www.kroah.com/log/blog/2018/08/24/what-stable-kernel-should-i-use/>`_.
+Additionally, the kernel developers want to make it simple and appealing for
+users to test the latest pre-release or regular release. That's also in
+everybody's interest, as it's a lot easier to track down and fix problems, if
+they are reported shortly after being introduced.
+
+Is the "no regressions" rule really adhered in practice?
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+It's taken really seriously, as can be seen by many mailing list posts from
+Linux creator and lead developer Linus Torvalds, some of which are quoted in
+Documentation/process/handling-regressions.rst.
+
+Exceptions to this rule are extremely rare; in the past developers almost always
+turned out to be wrong when they assumed a particular situation was warranting
+an exception.
+
+Who ensures the "no regressions" is actually followed?
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The subsystem maintainers should take care of that, which are watched and
+supported by the tree maintainers -- e.g. Linus Torvalds for mainline and
+Greg Kroah-Hartman et al. for various stable/longterm series.
+
+All of them are helped by people trying to ensure no regression report falls
+through the cracks. One of them is Thorsten Leemhuis, who's currently acting as
+the Linux kernel's "regressions tracker"; to facilitate this work he relies on
+regzbot, the Linux kernel regression tracking bot. That's why you want to bring
+your report on the radar of these people by CCing or forwarding each report to
+the regressions mailing list, ideally with a "regzbot command" in your mail to
+get it tracked immediately.
+
+How quickly are regressions normally fixed?
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Developers should fix any reported regression as quickly as possible, to provide
+affected users with a solution in a timely manner and prevent more users from
+running into the issue; nevertheless developers need to take enough time and
+care to ensure regression fixes do not cause additional damage.
+
+The answer thus depends on various factors like the impact of a regression, its
+age, or the Linux series in which it occurs. In the end though, most regressions
+should be fixed within two weeks.
+
+Is it a regression, if the issue can be avoided by updating some software?
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Almost always: yes. If a developer tells you otherwise, ask the regression
+tracker for advice as outlined above.
+
+Is it a regression, if a newer kernel works slower or consumes more energy?
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Yes, but the difference has to be significant. A five percent slow-down in a
+micro-benchmark thus is unlikely to qualify as regression, unless it also
+influences the results of a broad benchmark by more than one percent. If in
+doubt, ask for advice.
+
+Is it a regression, if an external kernel module breaks when updating Linux?
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+No, as the "no regression" rule is about interfaces and services the Linux
+kernel provides to the userland. It thus does not cover building or running
+externally developed kernel modules, as they run in kernel-space and hook into
+the kernel using internal interfaces occasionally changed.
+
+How are regressions handled that are caused by security fixes?
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+In extremely rare situations security issues can't be fixed without causing
+regressions; those fixes are given way, as they are the lesser evil in the end.
+Luckily this middling almost always can be avoided, as key developers for the
+affected area and often Linus Torvalds himself try very hard to fix security
+issues without causing regressions.
+
+If you nevertheless face such a case, check the mailing list archives if people
+tried their best to avoid the regression. If not, report it; if in doubt, ask
+for advice as outlined above.
+
+What happens if fixing a regression is impossible without causing another?
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Sadly these things happen, but luckily not very often; if they occur, expert
+developers of the affected code area should look into the issue to find a fix
+that avoids regressions or at least their impact. If you run into such a
+situation, do what was outlined already for regressions caused by security
+fixes: check earlier discussions if people already tried their best and ask for
+advice if in doubt.
+
+A quick note while at it: these situations could be avoided, if people would
+regularly give mainline pre-releases (say v5.15-rc1 or -rc3) from each
+development cycle a test run. This is best explained by imagining a change
+integrated between Linux v5.14 and v5.15-rc1 which causes a regression, but at
+the same time is a hard requirement for some other improvement applied for
+5.15-rc1. All these changes often can simply be reverted and the regression thus
+solved, if someone finds and reports it before 5.15 is released. A few days or
+weeks later this solution can become impossible, as some software might have
+started to rely on aspects introduced by one of the follow-up changes: reverting
+all changes would then cause a regression for users of said software and thus is
+out of the question.
+
+Is it a regression, if some feature I relied on was removed months ago?
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+It is, but often it's hard to fix such regressions due to the aspects outlined
+in the previous section. It hence needs to be dealt with on a case-by-case
+basis. This is another reason why it's in everybody's interest to regularly test
+mainline pre-releases.
+
+Does the "no regression" rule apply if I seem to be the only affected person?
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+It does, but only for practical usage: the Linux developers want to be free to
+remove support for hardware only to be found in attics and museums anymore.
+
+Note, sometimes regressions can't be avoided to make progress -- and the latter
+is needed to prevent Linux from stagnation. Hence, if only very few users seem
+to be affected by a regression, it for the greater good might be in their and
+everyone else's interest to lettings things pass. Especially if there is an
+easy way to circumvent the regression somehow, for example by updating some
+software or using a kernel parameter created just for this purpose.
+
+Does the regression rule apply for code in the staging tree as well?
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Not according to the `help text for the configuration option covering all
+staging code <https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/staging/Kconfig>`_,
+which since its early days states::
+
+       Please note that these drivers are under heavy development, may or
+       may not work, and may contain userspace interfaces that most likely
+       will be changed in the near future.
+
+The staging developers nevertheless often adhere to the "no regressions" rule,
+but sometimes bend it to make progress. That's for example why some users had to
+deal with (often negligible) regressions when a WiFi driver from the staging
+tree was replaced by a totally different one written from scratch.
+
+Why do later versions have to be "compiled with a similar configuration"?
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Because the Linux kernel developers sometimes integrate changes known to cause
+regressions, but make them optional and disable them in the kernel's default
+configuration. This trick allows progress, as the "no regressions" rule
+otherwise would lead to stagnation.
+
+Consider for example a new security feature blocking access to some kernel
+interfaces often abused by malware, which at the same time are required to run a
+few rarely used applications. The outlined approach makes both camps happy:
+people using these applications can leave the new security feature off, while
+everyone else can enable it without running into trouble.
+
+How to create a configuration similar to the one of an older kernel?
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Start your machine with a known-good kernel and configure the newer Linux
+version with ``make olddefconfig``. This makes the kernel's build scripts pick
+up the configuration file (the ".config" file) from the running kernel as base
+for the new one you are about to compile; afterwards they set all new
+configuration options to their default value, which should disable new features
+that might cause regressions.
+
+Can I report a regression I found with pre-compiled vanilla kernels?
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+You need to ensure the newer kernel was compiled with a similar configuration
+file as the older one (see above), as those that built them might have enabled
+some known-to-be incompatible feature for the newer kernel. If in doubt, report
+the matter to the kernel's provider and ask for advice.
+
+
+More about regression tracking with "regzbot"
+---------------------------------------------
+
+What is regression tracking and why should I care about it?
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Rules like "no regressions" need someone to ensure they are followed, otherwise
+they are broken either accidentally or on purpose. History has shown this to be
+true for Linux kernel development as well. That's why Thorsten Leemhuis, the
+Linux Kernel's regression tracker, and some people try to ensure all regression
+are fixed by keeping an eye on them until they are resolved. Neither of them are
+paid for this, that's why the work is done on a best effort basis.
+
+Why and how are Linux kernel regressions tracked using a bot?
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Tracking regressions completely manually has proven to be quite hard due to the
+distributed and loosely structured nature of Linux kernel development process.
+That's why the Linux kernel's regression tracker developed regzbot to facilitate
+the work, with the long term goal to automate regression tracking as much as
+possible for everyone involved.
+
+Regzbot works by watching for replies to reports of tracked regressions.
+Additionally, it's looking out for posted or committed patches referencing such
+reports with "Link:" tags; replies to such patch postings are tracked as well.
+Combined this data provides good insights into the current state of the fixing
+process.
+
+How to see which regressions regzbot tracks currently?
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Check out `regzbot's web-interface <https://linux-regtracking.leemhuis.info/regzbot/>`_.
+
+What kind of issues are supposed to be tracked by regzbot?
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The bot is meant to track regressions, hence please don't involve regzbot for
+regular issues. But it's okay for the Linux kernel's regression tracker if you
+involve regzbot to track severe issues, like reports about hangs, corrupted
+data, or internal errors (Panic, Oops, BUG(), warning, ...).
+
+How to change aspects of a tracked regression?
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+By using a 'regzbot command' in a direct or indirect reply to the mail with the
+report. The easiest way to do that: find the report in your "Sent" folder or the
+mailing list archive and reply to it using your mailer's "Reply-all" function.
+In that mail, use one of the following commands in a stand-alone paragraph (IOW:
+use blank lines to separate one or multiple of these commands from the rest of
+the mail's text).
+
+ * Update when the regression started to happen, for example after performing a
+   bisection::
+
+       #regzbot introduced: 1f2e3d4c5d
+
+ * Set or update the title::
+
+       #regzbot title: foo
+
+ * Monitor a discussion or bugzilla.kernel.org ticket where additions aspects of
+   the issue or a fix are discussed:::
+
+       #regzbot monitor: https://lore.kernel.org/r/30th.anniversary.repost@klaava.Helsinki.FI/
+       #regzbot monitor: https://bugzilla.kernel.org/show_bug.cgi?id=123456789
+
+ * Point to a place with further details of interest, like a mailing list post
+   or a ticket in a bug tracker that are slightly related, but about a different
+   topic::
+
+       #regzbot link: https://bugzilla.kernel.org/show_bug.cgi?id=123456789
+
+ * Mark a regression as invalid::
+
+       #regzbot invalid: wasn't a regression, problem has always existed
+
+Regzbot supports a few other commands primarily used by developers or people
+tracking regressions. They and more details about the aforementioned regzbot
+commands can be found in the `getting started guide
+<https://gitlab.com/knurd42/regzbot/-/blob/main/docs/getting_started.md>`_ and
+the `reference documentation <https://gitlab.com/knurd42/regzbot/-/blob/main/docs/reference.md>`_
+for regzbot.
+
+..
+   end-of-content
+..
+   This text is available under GPL-2.0+ or CC-BY-4.0, as stated at the top
+   of the file. If you want to distribute this text under CC-BY-4.0 only,
+   please use "The Linux kernel developers" for author attribution and link
+   this as source:
+   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/plain/Documentation/admin-guide/reporting-regressions.rst
+..
+   Note: Only the content of this RST file as found in the Linux kernel sources
+   is available under CC-BY-4.0, as versions of this text that were processed
+   (for example by the kernel's build system) might contain content taken from
+   files which use a more restrictive license.