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 Reporting issues
 ++++++++++++++++
 
 
 The short guide (aka TL;DR)
 ===========================
 
 Are you facing a regression with vanilla kernels from the same stable or
 longterm series? One still supported? Then search the `LKML
 <https://lore.kernel.org/lkml/>`_ and the `Linux stable mailing list
 <https://lore.kernel.org/stable/>`_ archives for matching reports to join. If
 you don't find any, install `the latest release from that series
 <https://kernel.org/>`_. If it still shows the issue, report it to the stable
 mailing list (stable@vger.kernel.org) and CC the regressions list
 (regressions@lists.linux.dev); ideally also CC the maintainer and the mailing
 list for the subsystem in question.
 
 In all other cases try your best guess which kernel part might be causing the
 issue. Check the :ref:`MAINTAINERS <maintainers>` file for how its developers
 expect to be told about problems, which most of the time will be by email with a
 mailing list in CC. Check the destination's archives for matching reports;
 search the `LKML <https://lore.kernel.org/lkml/>`_ and the web, too. If you
 don't find any to join, install `the latest mainline kernel
 <https://kernel.org/>`_. If the issue is present there, send a report.
 
 The issue was fixed there, but you would like to see it resolved in a still
 supported stable or longterm series as well? Then install its latest release.
 If it shows the problem, search for the change that fixed it in mainline and
 check if backporting is in the works or was discarded; if it's neither, ask
 those who handled the change for it.
 
 **General remarks**: When installing and testing a kernel as outlined above,
 ensure it's vanilla (IOW: not patched and not using add-on modules). Also make
 sure it's built and running in a healthy environment and not already tainted
 before the issue occurs.
 
 If you are facing multiple issues with the Linux kernel at once, report each
 separately. While writing your report, include all information relevant to the
 issue, like the kernel and the distro used. In case of a regression, CC the
 regressions mailing list (regressions@lists.linux.dev) to your report. Also try
 to pin-point the culprit with a bisection; if you succeed, include its
 commit-id and CC everyone in the sign-off-by chain.
 
 Once the report is out, answer any questions that come up and help where you
 can. That includes keeping the ball rolling by occasionally retesting with newer
 releases and sending a status update afterwards.
 
 Step-by-step guide how to report issues to the kernel maintainers
 =================================================================
 
 The above TL;DR outlines roughly how to report issues to the Linux kernel
 developers. It might be all that's needed for people already familiar with
 reporting issues to Free/Libre & Open Source Software (FLOSS) projects. For
 everyone else there is this section. It is more detailed and uses a
 step-by-step approach. It still tries to be brief for readability and leaves
 out a lot of details; those are described below the step-by-step guide in a
 reference section, which explains each of the steps in more detail.
 
 Note: this section covers a few more aspects than the TL;DR and does things in
 a slightly different order. That's in your interest, to make sure you notice
 early if an issue that looks like a Linux kernel problem is actually caused by
 something else. These steps thus help to ensure the time you invest in this
 process won't feel wasted in the end:
 
  * Are you facing an issue with a Linux kernel a hardware or software vendor
    provided? Then in almost all cases you are better off to stop reading this
    document and reporting the issue to your vendor instead, unless you are
    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) <https://lore.kernel.org/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.
 
  * Make sure it's not the kernel's surroundings that are causing the issue
    you face.
 
  * Create a fresh backup and put system repair and restore tools at hand.
 
  * Ensure your system does not enhance its kernels by building additional
    kernel modules on-the-fly, which solutions like DKMS might be doing locally
    without your knowledge.
 
  * Check if your kernel was 'tainted' when the issue occurred, as the event
    that made the kernel set this flag might be causing the issue you face.
 
  * Write down coarsely how to reproduce the issue. If you deal with multiple
    issues at once, create separate notes for each of them and make sure they
    work independently on a freshly booted system. That's needed, as each issue
    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. If you find anything,
    join the discussion instead of sending a new report.
 
 After these preparations you'll now enter the main part:
 
  * Unless you are already running the latest 'mainline' Linux kernel, better
    go and install it for the reporting process. Testing and reporting with
    the latest 'stable' Linux can be an acceptable alternative in some
    situations; during the merge window that actually might be even the best
    approach, but in that development phase it can be an even better idea to
    suspend your efforts for a few days anyway. Whatever version you choose,
    ideally use a 'vanilla' build. Ignoring these advices will dramatically
    increase the risk your report will be rejected or ignored.
 
  * Ensure the kernel you just installed does not 'taint' itself when
    running.
 
  * Reproduce the issue with the kernel you just installed. If it doesn't show
    up there, scroll down to the instructions for issues only happening with
    stable and longterm kernels.
 
  * Optimize your notes: try to find and write the most straightforward way to
    reproduce your issue. Make sure the end result has all the important
    details, and at the same time is easy to read and understand for others
    that hear about it for the first time. And if you learned something in this
    process, consider searching again for existing reports about the issue.
 
  * If your failure involves a 'panic', 'Oops', 'warning', or 'BUG', consider
    decoding the kernel log to find the line of code that triggered the error.
 
  * If your problem is a regression, try to narrow down when the issue was
    introduced as much as possible.
 
  * Start to compile the report by writing a detailed description about the
    issue. Always mention a few things: the latest kernel version you installed
    for reproducing, the Linux Distribution used, and your notes on how to
    reproduce the issue. Ideally, make the kernel's build configuration
    (.config) and the output from ``dmesg`` available somewhere on the net and
    link to it. Include or upload all other information that might be relevant,
    like the output/screenshot of an Oops or the output from ``lspci``. Once
    you wrote this main part, insert a normal length paragraph on top of it
    outlining the issue and the impact quickly. On top of this add one sentence
    that briefly describes the problem and gets people to read on. Now give the
    thing a descriptive title or subject that yet again is shorter. Then you're
    ready to send or file the report like the MAINTAINERS file told you, unless
    you are dealing with one of those 'issues of high priority': they need
    special care which is explained in 'Special handling for high priority
    issues' below.
 
  * Wait for reactions and keep the thing rolling until you can accept the
    outcome in one way or the other. Thus react publicly and in a timely manner
    to any inquiries. Test proposed fixes. Do proactive testing: retest with at
    least every first release candidate (RC) of a new mainline version and
    report your results. Send friendly reminders if things stall. And try to
    help yourself, if you don't get any help or if it's unsatisfying.
 
 
 Reporting regressions within a stable and longterm kernel line
 --------------------------------------------------------------
 
 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
    <https://kernel.org/>`_ and make sure it mentions
    the latest release of the particular version line without an '[EOL]' tag.
 
  * Check the archives of the `Linux stable mailing list
    <https://lore.kernel.org/stable/>`_ for existing reports.
 
  * 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. If you first noticed the
    problem with a vendor kernel, check a vanilla build of the last version
    known to work performs fine as well.
 
  * Send a short problem report to the Linux stable mailing list
    (stable@vger.kernel.org) and CC the Linux regressions mailing list
    (regressions@lists.linux.dev); if you suspect the cause in a particular
    subsystem, CC its maintainer and its mailing list. 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 a still supported stable or longterm series or vendor
 kernels regularly rebased on those. If that the 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,
    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.
 
  * 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
 =============================================================
 
 The detailed guides above outline all the major steps in brief fashion, which
 should be enough for most people. But sometimes there are situations where even
 experienced users might wonder how to actually do one of those steps. That's
 what this section is for, as it will provide a lot more details on each of the
 above steps. Consider this as reference documentation: it's possible to read it
 from top to bottom. But it's mainly meant to skim over and a place to look up
 details how to actually perform those steps.
 
 A few words of general advice before digging into the details:
 
  * The Linux kernel developers are well aware this process is complicated and
    demands more than other FLOSS projects. We'd love to make it simpler. But
    that would require work in various places as well as some infrastructure,
    which would need constant maintenance; nobody has stepped up to do that
    work, so that's just how things are for now.
 
  * A warranty or support contract with some vendor doesn't entitle you to
    request fixes from developers in the upstream Linux kernel community: such
    contracts are completely outside the scope of the Linux kernel, its
    development community, and this document. That's why you can't demand
    anything such a contract guarantees in this context, not even if the
    developer handling the issue works for the vendor in question. If you want
    to claim your rights, use the vendor's support channel instead. When doing
    so, you might want to mention you'd like to see the issue fixed in the
    upstream Linux kernel; motivate them by saying it's the only way to ensure
    the fix in the end will get incorporated in all Linux distributions.
 
  * If you never reported an issue to a FLOSS project before you should consider
    reading `How to Report Bugs Effectively
    <https://www.chiark.greenend.org.uk/~sgtatham/bugs.html>`_, `How To Ask
    Questions The Smart Way
    <http://www.catb.org/esr/faqs/smart-questions.html>`_, and `How to ask good
    questions <https://jvns.ca/blog/good-questions/>`_.
 
 With that off the table, find below the details on how to properly report
 issues to the Linux kernel developers.
 
 
 Make sure you're using the upstream Linux kernel
 ------------------------------------------------
 
    *Are you facing an issue with a Linux kernel a hardware or software vendor
    provided? Then in almost all cases you are better off to stop reading this
    document and reporting the issue to your vendor instead, unless you are
    willing to install the latest Linux version yourself. Be aware the latter
    will often be needed anyway to hunt down and fix issues.*
 
 Like most programmers, Linux kernel developers don't like to spend time dealing
 with reports for issues that don't even happen with their current code. It's
 just a waste everybody's time, especially yours. Unfortunately such situations
 easily happen when it comes to the kernel and often leads to frustration on both
 sides. That's because almost all Linux-based kernels pre-installed on devices
 (Computers, Laptops, Smartphones, Routers, …) and most shipped by Linux
 distributors are quite distant from the official Linux kernel as distributed by
 kernel.org: these kernels from these vendors are often ancient from the point of
 Linux development or heavily modified, often both.
 
 Most of these vendor kernels are quite unsuitable for reporting issues to the
 Linux kernel developers: an issue you face with one of them might have been
 fixed by the Linux kernel developers months or years ago already; additionally,
 the modifications and enhancements by the vendor might be causing the issue you
 face, even if they look small or totally unrelated. That's why you should report
 issues with these kernels to the vendor. Its developers should look into the
 report and, in case it turns out to be an upstream issue, fix it directly
 upstream or forward the report there. In practice that often does not work out
 or might not what you want. You thus might want to consider circumventing the
 vendor by installing the very latest Linux kernel core yourself. If that's an
 option for you move ahead in this process, as a later step in this guide will
 explain how to do that once it rules out other potential causes for your issue.
 
 Note, the previous paragraph is starting with the word 'most', as sometimes
 developers in fact are willing to handle reports about issues occurring with
 vendor kernels. If they do in the end highly depends on the developers and the
 issue in question. Your chances are quite good if the distributor applied only
 small modifications to a kernel based on a recent Linux version; that for
 example often holds true for the mainline kernels shipped by Debian GNU/Linux
 Sid or Fedora Rawhide. Some developers will also accept reports about issues
 with kernels from distributions shipping the latest stable kernel, as long as
 its only slightly modified; that for example is often the case for Arch Linux,
 regular Fedora releases, and openSUSE Tumbleweed. But keep in mind, you better
 want to use a mainline Linux and avoid using a stable kernel for this
 process, as outlined in the section 'Install a fresh kernel for testing' in more
 detail.
 
 Obviously you are free to ignore all this advice and report problems with an old
 or heavily modified vendor kernel to the upstream Linux developers. But note,
 those often get rejected or ignored, so consider yourself warned. But it's still
 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, first run
 --------------------------------------
 
    *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. 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.
 
 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
 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').
 
 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.
 
 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?
 -----------------------
 
     *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.*
 
 Linus Torvalds and the leading Linux kernel developers want to see some issues
 fixed as soon as possible, hence there are 'issues of high priority' that get
 handled slightly differently in the reporting process. Three type of cases
 qualify: regressions, security issues, and really severe problems.
 
 You deal with 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 document
 Documentation/admin-guide/reporting-regressions.rst explains this in more
 detail. It also provides a good deal of other information about regressions you
 might want to be aware of; it for example explains how to add your issue to the
 list of tracked regressions, to ensure it won't fall through the cracks.
 
 What qualifies as security issue is left to your judgment. Consider reading
 Documentation/admin-guide/security-bugs.rst before proceeding, as it
 provides additional details how to best handle security issues.
 
 An issue is a 'really severe problem' when something totally unacceptably bad
 happens. That's for example the case when a Linux kernel corrupts the data it's
 handling or damages hardware it's running on. You're also dealing with a severe
 issue when the kernel suddenly stops working with an error message ('kernel
 panic') or without any farewell note at all. Note: do not confuse a 'panic' (a
 fatal error where the kernel stop itself) with a 'Oops' (a recoverable error),
 as the kernel remains running after the latter.
 
 
 Ensure a healthy environment
 ----------------------------
 
     *Make sure it's not the kernel's surroundings that are causing the issue
     you face.*
 
 Problems that look a lot like a kernel issue are sometimes caused by build or
 runtime environment. It's hard to rule out that problem completely, but you
 should minimize it:
 
  * Use proven tools when building your kernel, as bugs in the compiler or the
    binutils can cause the resulting kernel to misbehave.
 
  * Ensure your computer components run within their design specifications;
    that's especially important for the main processor, the main memory, and the
    motherboard. Therefore, stop undervolting or overclocking when facing a
    potential kernel issue.
 
  * Try to make sure it's not faulty hardware that is causing your issue. Bad
    main memory for example can result in a multitude of issues that will
    manifest itself in problems looking like kernel issues.
 
  * If you're dealing with a filesystem issue, you might want to check the file
    system in question with ``fsck``, as it might be damaged in a way that leads
    to unexpected kernel behavior.
 
  * When dealing with a regression, make sure it's not something else that
    changed in parallel to updating the kernel. The problem for example might be
    caused by other software that was updated at the same time. It can also
    happen that a hardware component coincidentally just broke when you rebooted
    into a new kernel for the first time. Updating the systems BIOS or changing
    something in the BIOS Setup can also lead to problems that on look a lot
    like a kernel regression.
 
 
 Prepare for emergencies
 -----------------------
 
     *Create a fresh backup and put system repair and restore tools at hand.*
 
 Reminder, you are dealing with computers, which sometimes do unexpected things,
 especially if you fiddle with crucial parts like the kernel of its operating
 system. That's what you are about to do in this process. Thus, make sure to
 create a fresh backup; also ensure you have all tools at hand to repair or
 reinstall the operating system as well as everything you need to restore the
 backup.
 
 
 Make sure your kernel doesn't get enhanced
 ------------------------------------------
 
     *Ensure your system does not enhance its kernels by building additional
     kernel modules on-the-fly, which solutions like DKMS might be doing locally
     without your knowledge.*
 
 The risk your issue report gets ignored or rejected dramatically increases if
 your kernel gets enhanced in any way. That's why you should remove or disable
 mechanisms like akmods and DKMS: those build add-on kernel modules
 automatically, for example when you install a new Linux kernel or boot it for
 the first time. Also remove any modules they might have installed. Then reboot
 before proceeding.
 
 Note, you might not be aware that your system is using one of these solutions:
 they often get set up silently when you install Nvidia's proprietary graphics
 driver, VirtualBox, or other software that requires a some support from a
 module not part of the Linux kernel. That why your might need to uninstall the
 packages with such software to get rid of any 3rd party kernel module.
 
 
 Check 'taint' flag
 ------------------
 
     *Check if your kernel was 'tainted' when the issue occurred, as the event
     that made the kernel set this flag might be causing the issue you face.*
 
 The kernel marks itself with a 'taint' flag when something happens that might
 lead to follow-up errors that look totally unrelated. The issue you face might
 be such an error if your kernel is tainted. That's why it's in your interest to
 rule this out early before investing more time into this process. This is the
 only reason why this step is here, as this process later will tell you to
 install the latest mainline kernel; you will need to check the taint flag again
 then, as that's when it matters because it's the kernel the report will focus
 on.
 
 On a running system is easy to check if the kernel tainted itself: if ``cat
 /proc/sys/kernel/tainted`` returns '0' then the kernel is not tainted and
 everything is fine. Checking that file is impossible in some situations; that's
 why the kernel also mentions the taint status when it reports an internal
 problem (a 'kernel bug'), a recoverable error (a 'kernel Oops') or a
 non-recoverable error before halting operation (a 'kernel panic'). Look near
 the top of the error messages printed when one of these occurs and search for a
 line starting with 'CPU:'. It should end with 'Not tainted' if the kernel was
 not tainted when it noticed the problem; it was tainted if you see 'Tainted:'
 followed by a few spaces and some letters.
 
 If your kernel is tainted, study Documentation/admin-guide/tainted-kernels.rst
 to find out why. Try to eliminate the reason. Often it's caused by one these
 three things:
 
  1. A recoverable error (a 'kernel Oops') occurred and the kernel tainted
     itself, as the kernel knows it might misbehave in strange ways after that
     point. In that case check your kernel or system log and look for a section
     that starts with this::
 
        Oops: 0000 [#1] SMP
 
     That's the first Oops since boot-up, as the '#1' between the brackets shows.
     Every Oops and any other problem that happens after that point might be a
     follow-up problem to that first Oops, even if both look totally unrelated.
     Rule this out by getting rid of the cause for the first Oops and reproducing
     the issue afterwards. Sometimes simply restarting will be enough, sometimes
     a change to the configuration followed by a reboot can eliminate the Oops.
     But don't invest too much time into this at this point of the process, as
     the cause for the Oops might already be fixed in the newer Linux kernel
     version you are going to install later in this process.
 
  2. Your system uses a software that installs its own kernel modules, for
     example Nvidia's proprietary graphics driver or VirtualBox. The kernel
     taints itself when it loads such module from external sources (even if
     they are Open Source): they sometimes cause errors in unrelated kernel
     areas and thus might be causing the issue you face. You therefore have to
     prevent those modules from loading when you want to report an issue to the
     Linux kernel developers. Most of the time the easiest way to do that is:
     temporarily uninstall such software including any modules they might have
     installed. Afterwards reboot.
 
  3. The kernel also taints itself when it's loading a module that resides in
     the staging tree of the Linux kernel source. That's a special area for
     code (mostly drivers) that does not yet fulfill the normal Linux kernel
     quality standards. When you report an issue with such a module it's
     obviously okay if the kernel is tainted; just make sure the module in
     question is the only reason for the taint. If the issue happens in an
     unrelated area reboot and temporarily block the module from being loaded
     by specifying ``foo.blacklist=1`` as kernel parameter (replace 'foo' with
     the name of the module in question).
 
 
 Document how to reproduce issue
 -------------------------------
 
     *Write down coarsely how to reproduce the issue. If you deal with multiple
     issues at once, create separate notes for each of them and make sure they
     work independently on a freshly booted system. That's needed, as each issue
     needs to get reported to the kernel developers separately, unless they are
     strongly entangled.*
 
 If you deal with multiple issues at once, you'll have to report each of them
 separately, as they might be handled by different developers. Describing
 various issues in one report also makes it quite difficult for others to tear
 it apart. Hence, only combine issues in one report if they are very strongly
 entangled.
 
 Additionally, during the reporting process you will have to test if the issue
 happens with other kernel versions. Therefore, it will make your work easier if
 you know exactly how to reproduce an issue quickly on a freshly booted system.
 
 Note: it's often fruitless to report issues that only happened once, as they
 might be caused by a bit flip due to cosmic radiation. That's why you should
 try to rule that out by reproducing the issue before going further. Feel free
 to ignore this advice if you are experienced enough to tell a one-time error
 due to faulty hardware apart from a kernel issue that rarely happens and thus
 is hard to reproduce.
 
 
 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
     by mail to a maintainer and a public mailing list.*
 
 It's crucial to send your report to the right people, as the Linux kernel is a
 big project and most of its developers are only familiar with a small subset of
 it. Quite a few programmers for example only care for just one driver, for
 example one for a WiFi chip; its developer likely will only have small or no
 knowledge about the internals of remote or unrelated "subsystems", like the TCP
 stack, the PCIe/PCI subsystem, memory management or file systems.
 
 Problem is: the Linux kernel lacks a central bug tracker where you can simply
 file your issue and make it reach the developers that need to know about it.
 That's why you have to find the right place and way to report issues yourself.
 You can do that with the help of a script (see below), but it mainly targets
 kernel developers and experts. For everybody else the MAINTAINERS file is the
 better place.
 
 How to read the MAINTAINERS file
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 To illustrate how to use the :ref:`MAINTAINERS <maintainers>` file, lets assume
 the WiFi in your Laptop suddenly misbehaves after updating the kernel. In that
 case it's likely an issue in the WiFi driver. Obviously it could also be some
 code it builds upon, but unless you suspect something like that stick to the
 driver. If it's really something else, the driver's developers will get the
 right people involved.
 
 Sadly, there is no way to check which code is driving a particular hardware
 component that is both universal and easy.
 
 In case of a problem with the WiFi driver you for example might want to look at
 the output of ``lspci -k``, as it lists devices on the PCI/PCIe bus and the
 kernel module driving it::
 
        [user@something ~]$ lspci -k
        [...]
        3a:00.0 Network controller: Qualcomm Atheros QCA6174 802.11ac Wireless Network Adapter (rev 32)
          Subsystem: Bigfoot Networks, Inc. Device 1535
          Kernel driver in use: ath10k_pci
          Kernel modules: ath10k_pci
        [...]
 
 But this approach won't work if your WiFi chip is connected over USB or some
 other internal bus. In those cases you might want to check your WiFi manager or
 the output of ``ip link``. Look for the name of the problematic network
 interface, which might be something like 'wlp58s0'. This name can be used like
 this to find the module driving it::
 
        [user@something ~]$ realpath --relative-to=/sys/module/ /sys/class/net/wlp58s0/device/driver/module
        ath10k_pci
 
 In case tricks like these don't bring you any further, try to search the
 internet on how to narrow down the driver or subsystem in question. And if you
 are unsure which it is: just try your best guess, somebody will help you if you
 guessed poorly.
 
 Once you know the driver or subsystem, you want to search for it in the
 MAINTAINERS file. In the case of 'ath10k_pci' you won't find anything, as the
 name is too specific. Sometimes you will need to search on the net for help;
 but before doing so, try a somewhat shorted or modified name when searching the
 MAINTAINERS file, as then you might find something like this::
 
        QUALCOMM ATHEROS ATH10K WIRELESS DRIVER
        Mail:          A. Some Human <shuman@example.com>
        Mailing list:  ath10k@lists.infradead.org
        Status:        Supported
        Web-page:      https://wireless.wiki.kernel.org/en/users/Drivers/ath10k
        SCM:           git git://git.kernel.org/pub/scm/linux/kernel/git/kvalo/ath.git
        Files:         drivers/net/wireless/ath/ath10k/
 
 Note: the line description will be abbreviations, if you read the plain
 MAINTAINERS file found in the root of the Linux source tree. 'Mail:' for
 example will be 'M:', 'Mailing list:' will be 'L', and 'Status:' will be 'S:'.
 A section near the top of the file explains these and other abbreviations.
 
 First look at the line 'Status'. Ideally it should be 'Supported' or
 'Maintained'. If it states 'Obsolete' then you are using some outdated approach
 that was replaced by a newer solution you need to switch to. Sometimes the code
 only has someone who provides 'Odd Fixes' when feeling motivated. And with
 'Orphan' you are totally out of luck, as nobody takes care of the code anymore.
 That only leaves these options: arrange yourself to live with the issue, fix it
 yourself, or find a programmer somewhere willing to fix it.
 
 After checking the status, look for a line starting with 'bugs:': it will tell
 you where to find a subsystem specific bug tracker to file your issue. The
 example above does not have such a line. That is the case for most sections, as
 Linux kernel development is completely driven by mail. Very few subsystems use
 a bug tracker, and only some of those rely on bugzilla.kernel.org.
 
 In this and many other cases you thus have to look for lines starting with
 'Mail:' instead. Those mention the name and the email addresses for the
 maintainers of the particular code. Also look for a line starting with 'Mailing
 list:', which tells you the public mailing list where the code is developed.
 Your report later needs to go by mail to those addresses. Additionally, for all
 issue reports sent by email, make sure to add the Linux Kernel Mailing List
 (LKML) <linux-kernel@vger.kernel.org> to CC. Don't omit either of the mailing
 lists when sending your issue report by mail later! Maintainers are busy people
 and might leave some work for other developers on the subsystem specific list;
 and LKML is important to have one place where all issue reports can be found.
 
 
 Finding the maintainers with the help of a script
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 For people that have the Linux sources at hand there is a second option to find
 the proper place to report: the script 'scripts/get_maintainer.pl' which tries
 to find all people to contact. It queries the MAINTAINERS file and needs to be
 called with a path to the source code in question. For drivers compiled as
 module if often can be found with a command like this::
 
        $ modinfo ath10k_pci | grep filename | sed 's!/lib/modules/.*/kernel/!!; s!filename:!!; s!\.ko\(\|\.xz\)!!'
        drivers/net/wireless/ath/ath10k/ath10k_pci.ko
 
 Pass parts of this to the script::
 
        $ ./scripts/get_maintainer.pl -f drivers/net/wireless/ath/ath10k*
        Some Human <shuman@example.com> (supporter:QUALCOMM ATHEROS ATH10K WIRELESS DRIVER)
        Another S. Human <asomehuman@example.com> (maintainer:NETWORKING DRIVERS)
        ath10k@lists.infradead.org (open list:QUALCOMM ATHEROS ATH10K WIRELESS DRIVER)
        linux-wireless@vger.kernel.org (open list:NETWORKING DRIVERS (WIRELESS))
        netdev@vger.kernel.org (open list:NETWORKING DRIVERS)
        linux-kernel@vger.kernel.org (open list)
 
 Don't sent your report to all of them. Send it to the maintainers, which the
 script calls "supporter:"; additionally CC the most specific mailing list for
 the code as well as the Linux Kernel Mailing List (LKML). In this case you thus
 would need to send the report to 'Some Human <shuman@example.com>' with
 'ath10k@lists.infradead.org' and 'linux-kernel@vger.kernel.org' in CC.
 
 Note: in case you cloned the Linux sources with git you might want to call
 ``get_maintainer.pl`` a second time with ``--git``. The script then will look
 at the commit history to find which people recently worked on the code in
 question, as they might be able to help. But use these results with care, as it
 can easily send you in a wrong direction. That for example happens quickly in
 areas rarely changed (like old or unmaintained drivers): sometimes such code is
 modified during tree-wide cleanups by developers that do not care about the
 particular driver at all.
 
 
 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. If you find anything,
     join the discussion instead of sending a new report.*
 
 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/>`_.
 
 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.
 
 It's also wise to check the internet, LKML and maybe bugzilla.kernel.org again
 at this point. If your report needs to be filed in a bug tracker, you may want
 to check the mailing list archives for the subsystem as well, as someone might
 have reported it only there.
 
 For details how to search and what to do if you find matching reports see
 "Search for existing reports, first run" above.
 
 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
 ----------------------------------
 
     *Unless you are already running the latest 'mainline' Linux kernel, better
     go and install it for the reporting process. Testing and reporting with
     the latest 'stable' Linux can be an acceptable alternative in some
     situations; during the merge window that actually might be even the best
     approach, but in that development phase it can be an even better idea to
     suspend your efforts for a few days anyway. Whatever version you choose,
     ideally use a 'vanilla' built. Ignoring these advices will dramatically
     increase the risk your report will be rejected or ignored.*
 
 As mentioned in the detailed explanation for the first step already: Like most
 programmers, Linux kernel developers don't like to spend time dealing with
 reports for issues that don't even happen with the current code. It's just a
 waste everybody's time, especially yours. That's why it's in everybody's
 interest that you confirm the issue still exists with the latest upstream code
 before reporting it. You are free to ignore this advice, but as outlined
 earlier: doing so dramatically increases the risk that your issue report might
 get rejected or simply ignored.
 
 In the scope of the kernel "latest upstream" normally means:
 
  * Install a mainline kernel; the latest stable kernel can be an option, but
    most of the time is better avoided. Longterm kernels (sometimes called 'LTS
    kernels') are unsuitable at this point of the process. The next subsection
    explains all of this in more detail.
 
  * The over next subsection describes way to obtain and install such a kernel.
    It also outlines that using a pre-compiled kernel are fine, but better are
    vanilla, which means: it was built using Linux sources taken straight `from
    kernel.org <https://kernel.org/>`_ and not modified or enhanced in any way.
 
 Choosing the right version for testing
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 Head over to `kernel.org <https://kernel.org/>`_ to find out which version you
 want to use for testing. Ignore the big yellow button that says 'Latest release'
 and look a little lower at the table. At its top you'll see a line starting with
 mainline, which most of the time will point to a pre-release with a version
 number like '5.8-rc2'. If that's the case, you'll want to use this mainline
 kernel for testing, as that where all fixes have to be applied first. Do not let
 that 'rc' scare you, these 'development kernels' are pretty reliable — and you
 made a backup, as you were instructed above, didn't you?
 
 In about two out of every nine to ten weeks, mainline might point you to a
 proper release with a version number like '5.7'. If that happens, consider
 suspending the reporting process until the first pre-release of the next
 version (5.8-rc1) shows up on kernel.org. That's because the Linux development
 cycle then is in its two-week long 'merge window'. The bulk of the changes and
 all intrusive ones get merged for the next release during this time. It's a bit
 more risky to use mainline during this period. Kernel developers are also often
 quite busy then and might have no spare time to deal with issue reports. It's
 also quite possible that one of the many changes applied during the merge
 window fixes the issue you face; that's why you soon would have to retest with
 a newer kernel version anyway, as outlined below in the section 'Duties after
 the report went out'.
 
 That's why it might make sense to wait till the merge window is over. But don't
 to that if you're dealing with something that shouldn't wait. In that case
 consider obtaining the latest mainline kernel via git (see below) or use the
 latest stable version offered on kernel.org. Using that is also acceptable in
 case mainline for some reason does currently not work for you. An in general:
 using it for reproducing the issue is also better than not reporting it issue
 at all.
 
 Better avoid using the latest stable kernel outside merge windows, as all fixes
 must be applied to mainline first. That's why checking the latest mainline
 kernel is so important: any issue you want to see fixed in older version lines
 needs to be fixed in mainline first before it can get backported, which can
 take a few days or weeks. Another reason: the fix you hope for might be too
 hard or risky for backporting; reporting the issue again hence is unlikely to
 change anything.
 
 These aspects are also why longterm kernels (sometimes called "LTS kernels")
 are unsuitable for this part of the reporting process: they are to distant from
 the current code. Hence go and test mainline first and follow the process
 further: if the issue doesn't occur with mainline it will guide you how to get
 it fixed in older version lines, if that's in the cards for the fix in question.
 
 How to obtain a fresh Linux kernel
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 **Using a pre-compiled kernel**: This is often the quickest, easiest, and safest
 way for testing — especially is you are unfamiliar with the Linux kernel. The
 problem: most of those shipped by distributors or add-on repositories are build
 from modified Linux sources. They are thus not vanilla and therefore often
 unsuitable for testing and issue reporting: the changes might cause the issue
 you face or influence it somehow.
 
 But you are in luck if you are using a popular Linux distribution: for quite a
 few of them you'll find repositories on the net that contain packages with the
 latest mainline or stable Linux built as vanilla kernel. It's totally okay to
 use these, just make sure from the repository's description they are vanilla or
 at least close to it. Additionally ensure the packages contain the latest
 versions as offered on kernel.org. The packages are likely unsuitable if they
 are older than a week, as new mainline and stable kernels typically get released
 at least once a week.
 
 Please note that you might need to build your own kernel manually later: that's
 sometimes needed for debugging or testing fixes, as described later in this
 document. Also be aware that pre-compiled kernels might lack debug symbols that
 are needed to decode messages the kernel prints when a panic, Oops, warning, or
 BUG occurs; if you plan to decode those, you might be better off compiling a
 kernel yourself (see the end of this subsection and the section titled 'Decode
 failure messages' for details).
 
 **Using git**: Developers and experienced Linux users familiar with git are
 often best served by obtaining the latest Linux kernel sources straight from the
 `official development repository on kernel.org
 <https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/>`_.
 Those are likely a bit ahead of the latest mainline pre-release. Don't worry
 about it: they are as reliable as a proper pre-release, unless the kernel's
 development cycle is currently in the middle of a merge window. But even then
 they are quite reliable.
 
 **Conventional**: People unfamiliar with git are often best served by
 downloading the sources as tarball from `kernel.org <https://kernel.org/>`_.
 
 How to actually build a kernel is not described here, as many websites explain
 the necessary steps already. If you are new to it, consider following one of
 those how-to's that suggest to use ``make localmodconfig``, as that tries to
 pick up the configuration of your current kernel and then tries to adjust it
 somewhat for your system. That does not make the resulting kernel any better,
 but quicker to compile.
 
 Note: If you are dealing with a panic, Oops, warning, or BUG from the kernel,
 please try to enable CONFIG_KALLSYMS when configuring your kernel.
 Additionally, enable CONFIG_DEBUG_KERNEL and CONFIG_DEBUG_INFO, too; the
 latter is the relevant one of those two, but can only be reached if you enable
 the former. Be aware CONFIG_DEBUG_INFO increases the storage space required to
 build a kernel by quite a bit. But that's worth it, as these options will allow
 you later to pinpoint the exact line of code that triggers your issue. The
 section 'Decode failure messages' below explains this in more detail.
 
 But keep in mind: Always keep a record of the issue encountered in case it is
 hard to reproduce. Sending an undecoded report is better than not reporting
 the issue at all.
 
 
 Check 'taint' flag
 ------------------
 
     *Ensure the kernel you just installed does not 'taint' itself when
     running.*
 
 As outlined above in more detail already: the kernel sets a 'taint' flag when
 something happens that can lead to follow-up errors that look totally
 unrelated. That's why you need to check if the kernel you just installed does
 not set this flag. And if it does, you in almost all the cases needs to
 eliminate the reason for it before you reporting issues that occur with it. See
 the section above for details how to do that.
 
 
 Reproduce issue with the fresh kernel
 -------------------------------------
 
     *Reproduce the issue with the kernel you just installed. If it doesn't show
     up there, scroll down to the instructions for issues only happening with
     stable and longterm kernels.*
 
 Check if the issue occurs with the fresh Linux kernel version you just
 installed. If it was fixed there already, consider sticking with this version
 line and abandoning your plan to report the issue. But keep in mind that other
 users might still be plagued by it, as long as it's not fixed in either stable
 and longterm version from kernel.org (and thus vendor kernels derived from
 those). If you prefer to use one of those or just want to help their users,
 head over to the section "Details about reporting issues only occurring in
 older kernel version lines" below.
 
 
 Optimize description to reproduce issue
 ---------------------------------------
 
     *Optimize your notes: try to find and write the most straightforward way to
     reproduce your issue. Make sure the end result has all the important
     details, and at the same time is easy to read and understand for others
     that hear about it for the first time. And if you learned something in this
     process, consider searching again for existing reports about the issue.*
 
 An unnecessarily complex report will make it hard for others to understand your
 report. Thus try to find a reproducer that's straight forward to describe and
 thus easy to understand in written form. Include all important details, but at
 the same time try to keep it as short as possible.
 
 In this in the previous steps you likely have learned a thing or two about the
 issue you face. Use this knowledge and search again for existing reports
 instead you can join.
 
 
 Decode failure messages
 -----------------------
 
     *If your failure involves a 'panic', 'Oops', 'warning', or 'BUG', consider
     decoding the kernel log to find the line of code that triggered the error.*
 
 When the kernel detects an internal problem, it will log some information about
 the executed code. This makes it possible to pinpoint the exact line in the
 source code that triggered the issue and shows how it was called. But that only
 works if you enabled CONFIG_DEBUG_INFO and CONFIG_KALLSYMS when configuring
 your kernel. If you did so, consider to decode the information from the
 kernel's log. That will make it a lot easier to understand what lead to the
 'panic', 'Oops', 'warning', or 'BUG', which increases the chances that someone
 can provide a fix.
 
 Decoding can be done with a script you find in the Linux source tree. If you
 are running a kernel you compiled yourself earlier, call it like this::
 
        [user@something ~]$ sudo dmesg | ./linux-5.10.5/scripts/decode_stacktrace.sh ./linux-5.10.5/vmlinux
 
 If you are running a packaged vanilla kernel, you will likely have to install
 the corresponding packages with debug symbols. Then call the script (which you
 might need to get from the Linux sources if your distro does not package it)
 like this::
 
        [user@something ~]$ sudo dmesg | ./linux-5.10.5/scripts/decode_stacktrace.sh \
         /usr/lib/debug/lib/modules/5.10.10-4.1.x86_64/vmlinux /usr/src/kernels/5.10.10-4.1.x86_64/
 
 The script will work on log lines like the following, which show the address of
 the code the kernel was executing when the error occurred::
 
        [   68.387301] RIP: 0010:test_module_init+0x5/0xffa [test_module]
 
 Once decoded, these lines will look like this::
 
        [   68.387301] RIP: 0010:test_module_init (/home/username/linux-5.10.5/test-module/test-module.c:16) test_module
 
 In this case the executed code was built from the file
 '~/linux-5.10.5/test-module/test-module.c' and the error occurred by the
 instructions found in line '16'.
 
 The script will similarly decode the addresses mentioned in the section
 starting with 'Call trace', which show the path to the function where the
 problem occurred. Additionally, the script will show the assembler output for
 the code section the kernel was executing.
 
 Note, if you can't get this to work, simply skip this step and mention the
 reason for it in the report. If you're lucky, it might not be needed. And if it
 is, someone might help you to get things going. Also be aware this is just one
 of several ways to decode kernel stack traces. Sometimes different steps will
 be required to retrieve the relevant details. Don't worry about that, if that's
 needed in your case, developers will tell you what to do.
 
 
 Special care for regressions
 ----------------------------
 
     *If your problem is a regression, try to narrow down when the issue was
     introduced as much as possible.*
 
 Linux lead developer Linus Torvalds insists that the Linux kernel never
 worsens, that's why he deems regressions as unacceptable and wants to see them
 fixed quickly. That's why changes that introduced a regression are often
 promptly reverted if the issue they cause can't get solved quickly any other
 way. Reporting a regression is thus a bit like playing a kind of trump card to
 get something quickly fixed. But for that to happen the change that's causing
 the regression needs to be known. Normally it's up to the reporter to track
 down the culprit, as maintainers often won't have the time or setup at hand to
 reproduce it themselves.
 
 To find the change there is a process called 'bisection' which the document
 Documentation/admin-guide/bug-bisect.rst describes in detail. That process
 will often require you to build about ten to twenty kernel images, trying to
 reproduce the issue with each of them before building the next. Yes, that takes
 some time, but don't worry, it works a lot quicker than most people assume.
 Thanks to a 'binary search' this will lead you to the one commit in the source
 code management system that's causing the regression. Once you find it, search
 the net for the subject of the change, its commit id and the shortened commit id
 (the first 12 characters of the commit id). This will lead you to existing
 reports about it, if there are any.
 
 Note, a bisection needs a bit of know-how, which not everyone has, and quite a
 bit of effort, which not everyone is willing to invest. Nevertheless, it's
 highly recommended performing a bisection yourself. If you really can't or
 don't want to go down that route at least find out which mainline kernel
 introduced the regression. If something for example breaks when switching from
 5.5.15 to 5.8.4, then try at least all the mainline releases in that area (5.6,
 5.7 and 5.8) to check when it first showed up. Unless you're trying to find a
 regression in a stable or longterm kernel, avoid testing versions which number
 has three sections (5.6.12, 5.7.8), as that makes the outcome hard to
 interpret, which might render your testing useless. Once you found the major
 version which introduced the regression, feel free to move on in the reporting
 process. But keep in mind: it depends on the issue at hand if the developers
 will be able to help without knowing the culprit. Sometimes they might
 recognize from the report want went wrong and can fix it; other times they will
 be unable to help unless you perform a bisection.
 
 When dealing with regressions make sure the issue you face is really caused by
 the kernel and not by something else, as outlined above already.
 
 In the whole process keep in mind: an issue only qualifies as regression if the
 older and the newer kernel got built with a similar configuration. This can be
 achieved by using ``make olddefconfig``, as explained in more detail by
 Documentation/admin-guide/reporting-regressions.rst; that document also
 provides a good deal of other information about regressions you might want to be
 aware of.
 
 
 Write and send the report
 -------------------------
 
     *Start to compile the report by writing a detailed description about the
     issue. Always mention a few things: the latest kernel version you installed
     for reproducing, the Linux Distribution used, and your notes on how to
     reproduce the issue. Ideally, make the kernel's build configuration
     (.config) and the output from ``dmesg`` available somewhere on the net and
     link to it. Include or upload all other information that might be relevant,
     like the output/screenshot of an Oops or the output from ``lspci``. Once
     you wrote this main part, insert a normal length paragraph on top of it
     outlining the issue and the impact quickly. On top of this add one sentence
     that briefly describes the problem and gets people to read on. Now give the
     thing a descriptive title or subject that yet again is shorter. Then you're
     ready to send or file the report like the MAINTAINERS file told you, unless
     you are dealing with one of those 'issues of high priority': they need
     special care which is explained in 'Special handling for high priority
     issues' below.*
 
 Now that you have prepared everything it's time to write your report. How to do
 that is partly explained by the three documents linked to in the preface above.
 That's why this text will only mention a few of the essentials as well as
 things specific to the Linux kernel.
 
 There is one thing that fits both categories: the most crucial parts of your
 report are the title/subject, the first sentence, and the first paragraph.
 Developers often get quite a lot of mail. They thus often just take a few
 seconds to skim a mail before deciding to move on or look closer. Thus: the
 better the top section of your report, the higher are the chances that someone
 will look into it and help you. And that is why you should ignore them for now
 and write the detailed report first. ;-)
 
 Things each report should mention
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 Describe in detail how your issue happens with the fresh vanilla kernel you
 installed. Try to include the step-by-step instructions you wrote and optimized
 earlier that outline how you and ideally others can reproduce the issue; in
 those rare cases where that's impossible try to describe what you did to
 trigger it.
 
 Also include all the relevant information others might need to understand the
 issue and its environment. What's actually needed depends a lot on the issue,
 but there are some things you should include always:
 
  * the output from ``cat /proc/version``, which contains the Linux kernel
    version number and the compiler it was built with.
 
  * the Linux distribution the machine is running (``hostnamectl | grep
    "Operating System"``)
 
  * the architecture of the CPU and the operating system (``uname -mi``)
 
  * if you are dealing with a regression and performed a bisection, mention the
    subject and the commit-id of the change that is causing it.
 
 In a lot of cases it's also wise to make two more things available to those
 that read your report:
 
  * the configuration used for building your Linux kernel (the '.config' file)
 
  * the kernel's messages that you get from ``dmesg`` written to a file. Make
    sure that it starts with a line like 'Linux version 5.8-1
    (foobar@example.com) (gcc (GCC) 10.2.1, GNU ld version 2.34) #1 SMP Mon Aug
    3 14:54:37 UTC 2020' If it's missing, then important messages from the first
    boot phase already got discarded. In this case instead consider using
    ``journalctl -b 0 -k``; alternatively you can also reboot, reproduce the
    issue and call ``dmesg`` right afterwards.
 
 These two files are big, that's why it's a bad idea to put them directly into
 your report. If you are filing the issue in a bug tracker then attach them to
 the ticket. If you report the issue by mail do not attach them, as that makes
 the mail too large; instead do one of these things:
 
  * Upload the files somewhere public (your website, a public file paste
    service, a ticket created just for this purpose on `bugzilla.kernel.org
    <https://bugzilla.kernel.org/>`_, ...) and include a link to them in your
    report. Ideally use something where the files stay available for years, as
    they could be useful to someone many years from now; this for example can
    happen if five or ten years from now a developer works on some code that was
    changed just to fix your issue.
 
  * Put the files aside and mention you will send them later in individual
    replies to your own mail. Just remember to actually do that once the report
    went out. ;-)
 
 Things that might be wise to provide
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 Depending on the issue you might need to add more background data. Here are a
 few suggestions what often is good to provide:
 
  * If you are dealing with a 'warning', an 'OOPS' or a 'panic' from the kernel,
    include it. If you can't copy'n'paste it, try to capture a netconsole trace
    or at least take a picture of the screen.
 
  * If the issue might be related to your computer hardware, mention what kind
    of system you use. If you for example have problems with your graphics card,
    mention its manufacturer, the card's model, and what chip is uses. If it's a
    laptop mention its name, but try to make sure it's meaningful. 'Dell XPS 13'
    for example is not, because it might be the one from 2012; that one looks
    not that different from the one sold today, but apart from that the two have
    nothing in common. Hence, in such cases add the exact model number, which
    for example are '9380' or '7390' for XPS 13 models introduced during 2019.
    Names like 'Lenovo Thinkpad T590' are also somewhat ambiguous: there are
    variants of this laptop with and without a dedicated graphics chip, so try
    to find the exact model name or specify the main components.
 
  * Mention the relevant software in use. If you have problems with loading
    modules, you want to mention the versions of kmod, systemd, and udev in use.
    If one of the DRM drivers misbehaves, you want to state the versions of
    libdrm and Mesa; also specify your Wayland compositor or the X-Server and
    its driver. If you have a filesystem issue, mention the version of
    corresponding filesystem utilities (e2fsprogs, btrfs-progs, xfsprogs, ...).
 
  * Gather additional information from the kernel that might be of interest. The
    output from ``lspci -nn`` will for example help others to identify what
    hardware you use. If you have a problem with hardware you even might want to
    make the output from ``sudo lspci -vvv`` available, as that provides
    insights how the components were configured. For some issues it might be
    good to include the contents of files like ``/proc/cpuinfo``,
    ``/proc/ioports``, ``/proc/iomem``, ``/proc/modules``, or
    ``/proc/scsi/scsi``. Some subsystem also offer tools to collect relevant
    information. One such tool is ``alsa-info.sh`` `which the audio/sound
    subsystem developers provide <https://www.alsa-project.org/wiki/AlsaInfo>`_.
 
 Those examples should give your some ideas of what data might be wise to
 attach, but you have to think yourself what will be helpful for others to know.
 Don't worry too much about forgetting something, as developers will ask for
 additional details they need. But making everything important available from
 the start increases the chance someone will take a closer look.
 
 
 The important part: the head of your report
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 Now that you have the detailed part of the report prepared let's get to the
 most important section: the first few sentences. Thus go to the top, add
 something like 'The detailed description:' before the part you just wrote and
 insert two newlines at the top. Now write one normal length paragraph that
 describes the issue roughly. Leave out all boring details and focus on the
 crucial parts readers need to know to understand what this is all about; if you
 think this bug affects a lot of users, mention this to get people interested.
 
 Once you did that insert two more lines at the top and write a one sentence
 summary that explains quickly what the report is about. After that you have to
 get even more abstract and write an even shorter subject/title for the report.
 
 Now that you have written this part take some time to optimize it, as it is the
 most important parts of your report: a lot of people will only read this before
 they decide if reading the rest is time well spent.
 
 Now send or file the report like the :ref:`MAINTAINERS <maintainers>` file told
 you, unless it's one of those 'issues of high priority' outlined earlier: in
 that case please read the next subsection first before sending the report on
 its way.
 
 Special handling for high priority issues
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 Reports for high priority issues need special handling.
 
 **Severe issues**: make sure the subject or ticket title as well as the first
 paragraph makes the severeness obvious.
 
 **Regressions**: make the report's subject start with '[REGRESSION]'.
 
 In case you performed a successful bisection, use the title of the change that
 introduced the regression as the second part of your subject. Make the report
 also mention the commit id of the culprit. In case of an unsuccessful bisection,
 make your report mention the latest tested version that's working fine (say 5.7)
 and the oldest where the issue occurs (say 5.8-rc1).
 
 When sending the report by mail, CC the Linux regressions mailing list
 (regressions@lists.linux.dev). In case the report needs to be filed to some web
 tracker, proceed to do so. Once filed, forward the report by mail to the
 regressions list; CC the maintainer and the mailing list for the subsystem in
 question. Make sure to inline the forwarded report, hence do not attach it.
 Also add a short note at the top where you mention the URL to the ticket.
 
 When mailing or forwarding the report, in case of a successful bisection add the
 author of the culprit to the recipients; also CC everyone in the signed-off-by
 chain, which you find at the end of its commit message.
 
 **Security issues**: for these issues your will have to evaluate if a
 short-term risk to other users would arise if details were publicly disclosed.
 If that's not the case simply proceed with reporting the issue as described.
 For issues that bear such a risk you will need to adjust the reporting process
 slightly:
 
  * If the MAINTAINERS file instructed you to report the issue by mail, do not
    CC any public mailing lists.
 
  * If you were supposed to file the issue in a bug tracker make sure to mark
    the ticket as 'private' or 'security issue'. If the bug tracker does not
    offer a way to keep reports private, forget about it and send your report as
    a private mail to the maintainers instead.
 
 In both cases make sure to also mail your report to the addresses the
 MAINTAINERS file lists in the section 'security contact'. Ideally directly CC
 them when sending the report by mail. If you filed it in a bug tracker, forward
 the report's text to these addresses; but on top of it put a small note where
 you mention that you filed it with a link to the ticket.
 
 See Documentation/admin-guide/security-bugs.rst for more information.
 
 
 Duties after the report went out
 --------------------------------
 
     *Wait for reactions and keep the thing rolling until you can accept the
     outcome in one way or the other. Thus react publicly and in a timely manner
     to any inquiries. Test proposed fixes. Do proactive testing: retest with at
     least every first release candidate (RC) of a new mainline version and
     report your results. Send friendly reminders if things stall. And try to
     help yourself, if you don't get any help or if it's unsatisfying.*
 
 If your report was good and you are really lucky then one of the developers
 might immediately spot what's causing the issue; they then might write a patch
 to fix it, test it, and send it straight for integration in mainline while
 tagging it for later backport to stable and longterm kernels that need it. Then
 all you need to do is reply with a 'Thank you very much' and switch to a version
 with the fix once it gets released.
 
 But this ideal scenario rarely happens. That's why the job is only starting
 once you got the report out. What you'll have to do depends on the situations,
 but often it will be the things listed below. But before digging into the
 details, here are a few important things you need to keep in mind for this part
 of the process.
 
 
 General advice for further interactions
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 **Always reply in public**: When you filed the issue in a bug tracker, always
 reply there and do not contact any of the developers privately about it. For
 mailed reports always use the 'Reply-all' function when replying to any mails
 you receive. That includes mails with any additional data you might want to add
 to your report: go to your mail applications 'Sent' folder and use 'reply-all'
 on your mail with the report. This approach will make sure the public mailing
 list(s) and everyone else that gets involved over time stays in the loop; it
 also keeps the mail thread intact, which among others is really important for
 mailing lists to group all related mails together.
 
 There are just two situations where a comment in a bug tracker or a 'Reply-all'
 is unsuitable:
 
  * Someone tells you to send something privately.
 
  * You were told to send something, but noticed it contains sensitive
    information that needs to be kept private. In that case it's okay to send it
    in private to the developer that asked for it. But note in the ticket or a
    mail that you did that, so everyone else knows you honored the request.
 
 **Do research before asking for clarifications or help**: In this part of the
 process someone might tell you to do something that requires a skill you might
 not have mastered yet. For example, you might be asked to use some test tools
 you never have heard of yet; or you might be asked to apply a patch to the
 Linux kernel sources to test if it helps. In some cases it will be fine sending
 a reply asking for instructions how to do that. But before going that route try
 to find the answer own your own by searching the internet; alternatively
 consider asking in other places for advice. For example ask a friend or post
 about it to a chatroom or forum you normally hang out.
 
 **Be patient**: If you are really lucky you might get a reply to your report
 within a few hours. But most of the time it will take longer, as maintainers
 are scattered around the globe and thus might be in a different time zone – one
 where they already enjoy their night away from keyboard.
 
 In general, kernel developers will take one to five business days to respond to
 reports. Sometimes it will take longer, as they might be busy with the merge
 windows, other work, visiting developer conferences, or simply enjoying a long
 summer holiday.
 
 The 'issues of high priority' (see above for an explanation) are an exception
 here: maintainers should address them as soon as possible; that's why you
 should wait a week at maximum (or just two days if it's something urgent)
 before sending a friendly reminder.
 
 Sometimes the maintainer might not be responding in a timely manner; other
 times there might be disagreements, for example if an issue qualifies as
 regression or not. In such cases raise your concerns on the mailing list and
 ask others for public or private replies how to move on. If that fails, it
 might be appropriate to get a higher authority involved. In case of a WiFi
 driver that would be the wireless maintainers; if there are no higher level
 maintainers or all else fails, it might be one of those rare situations where
 it's okay to get Linus Torvalds involved.
 
 **Proactive testing**: Every time the first pre-release (the 'rc1') of a new
 mainline kernel version gets released, go and check if the issue is fixed there
 or if anything of importance changed. Mention the outcome in the ticket or in a
 mail you sent as reply to your report (make sure it has all those in the CC
 that up to that point participated in the discussion). This will show your
 commitment and that you are willing to help. It also tells developers if the
 issue persists and makes sure they do not forget about it. A few other
 occasional retests (for example with rc3, rc5 and the final) are also a good
 idea, but only report your results if something relevant changed or if you are
 writing something anyway.
 
 With all these general things off the table let's get into the details of how
 to help to get issues resolved once they were reported.
 
 Inquires and testing request
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 Here are your duties in case you got replies to your report:
 
 **Check who you deal with**: Most of the time it will be the maintainer or a
 developer of the particular code area that will respond to your report. But as
 issues are normally reported in public it could be anyone that's replying —
 including people that want to help, but in the end might guide you totally off
 track with their questions or requests. That rarely happens, but it's one of
 many reasons why it's wise to quickly run an internet search to see who you're
 interacting with. By doing this you also get aware if your report was heard by
 the right people, as a reminder to the maintainer (see below) might be in order
 later if discussion fades out without leading to a satisfying solution for the
 issue.
 
 **Inquiries for data**: Often you will be asked to test something or provide
 additional details. Try to provide the requested information soon, as you have
 the attention of someone that might help and risk losing it the longer you
 wait; that outcome is even likely if you do not provide the information within
 a few business days.
 
 **Requests for testing**: When you are asked to test a diagnostic patch or a
 possible fix, try to test it in timely manner, too. But do it properly and make
 sure to not rush it: mixing things up can happen easily and can lead to a lot
 of confusion for everyone involved. A common mistake for example is thinking a
 proposed patch with a fix was applied, but in fact wasn't. Things like that
 happen even to experienced testers occasionally, but they most of the time will
 notice when the kernel with the fix behaves just as one without it.
 
 What to do when nothing of substance happens
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 Some reports will not get any reaction from the responsible Linux kernel
 developers; or a discussion around the issue evolved, but faded out with
 nothing of substance coming out of it.
 
 In these cases wait two (better: three) weeks before sending a friendly
 reminder: maybe the maintainer was just away from keyboard for a while when
 your report arrived or had something more important to take care of. When
 writing the reminder, kindly ask if anything else from your side is needed to
 get the ball running somehow. If the report got out by mail, do that in the
 first lines of a mail that is a reply to your initial mail (see above) which
 includes a full quote of the original report below: that's on of those few
 situations where such a 'TOFU' (Text Over, Fullquote Under) is the right
 approach, as then all the recipients will have the details at hand immediately
 in the proper order.
 
 After the reminder wait three more weeks for replies. If you still don't get a
 proper reaction, you first should reconsider your approach. Did you maybe try
 to reach out to the wrong people? Was the report maybe offensive or so
 confusing that people decided to completely stay away from it? The best way to
 rule out such factors: show the report to one or two people familiar with FLOSS
 issue reporting and ask for their opinion. Also ask them for their advice how
 to move forward. That might mean: prepare a better report and make those people
 review it before you send it out. Such an approach is totally fine; just
 mention that this is the second and improved report on the issue and include a
 link to the first report.
 
 If the report was proper you can send a second reminder; in it ask for advice
 why the report did not get any replies. A good moment for this second reminder
 mail is shortly after the first pre-release (the 'rc1') of a new Linux kernel
 version got published, as you should retest and provide a status update at that
 point anyway (see above).
 
 If the second reminder again results in no reaction within a week, try to
 contact a higher-level maintainer asking for advice: even busy maintainers by
 then should at least have sent some kind of acknowledgment.
 
 Remember to prepare yourself for a disappointment: maintainers ideally should
 react somehow to every issue report, but they are only obliged to fix those
 'issues of high priority' outlined earlier. So don't be too devastating if you
 get a reply along the lines of 'thanks for the report, I have more important
 issues to deal with currently and won't have time to look into this for the
 foreseeable future'.
 
 It's also possible that after some discussion in the bug tracker or on a list
 nothing happens anymore and reminders don't help to motivate anyone to work out
 a fix. Such situations can be devastating, but is within the cards when it
 comes to Linux kernel development. This and several other reasons for not
 getting help are explained in 'Why some issues won't get any reaction or remain
 unfixed after being reported' near the end of this document.
 
 Don't get devastated if you don't find any help or if the issue in the end does
 not get solved: the Linux kernel is FLOSS and thus you can still help yourself.
 You for example could try to find others that are affected and team up with
 them to get the issue resolved. Such a team could prepare a fresh report
 together that mentions how many you are and why this is something that in your
 option should get fixed. Maybe together you can also narrow down the root cause
 or the change that introduced a regression, which often makes developing a fix
 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.
 
 
 Reference for "Reporting regressions within a stable and longterm kernel line"
 ------------------------------------------------------------------------------
 
 This subsection provides details for the steps 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
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
     *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. If you first noticed the
     problem with a vendor kernel, check a vanilla build of the last version
     known to work performs fine as well.*
 
 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 section "Install a fresh
 kernel for testing".
 
 Did you first notice the regression with a vendor kernel? Then changes the
 vendor applied might be interfering. You need to rule that out by performing
 a recheck. Say something broke when you updated from 5.10.4-vendor.42 to
 5.10.5-vendor.43. Then after testing the latest 5.10 release as outlined in
 the previous paragraph check if a vanilla build of Linux 5.10.4 works fine as
 well. If things are broken there, the issue does not qualify as upstream
 regression and you need switch back to the main step-by-step guide to report
 the issue.
 
 Report the regression
 ~~~~~~~~~~~~~~~~~~~~~
 
     *Send a short problem report to the Linux stable mailing list
     (stable@vger.kernel.org) and CC the Linux regressions mailing list
     (regressions@lists.linux.dev); if you suspect the cause in a particular
     subsystem, CC its maintainer and its mailing list. 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 to the
 stable and regressions mailing list is all it takes; but in case you suspect
 the cause in a particular subsystem, CC its maintainers and its mailing list
 as well, because that will speed things up.
 
 And 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. In case of a successful bisection add the author of the culprit to
 the recipients; also CC everyone in the signed-off-by chain, which you find at
 the end of its commit message.
 
 
 Reference for "Reporting issues only occurring in older kernel version lines"
 -----------------------------------------------------------------------------
 
 This section provides details for the 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
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
     *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.
 
 
 Ask for advice
 ~~~~~~~~~~~~~~
 
     *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.*
 
 If the previous three steps didn't get you closer to a solution there is only
 one option left: ask for advice. Do that in a mail you sent to the maintainers
 for the subsystem where the issue seems to have its roots; CC the mailing list
 for the subsystem as well as the stable mailing list (stable@vger.kernel.org).
 
 
 Why some issues won't get any reaction or remain unfixed after being reported
 =============================================================================
 
 When reporting a problem to the Linux developers, be aware only 'issues of high
 priority' (regressions, security issues, severe problems) are definitely going
 to get resolved. The maintainers or if all else fails Linus Torvalds himself
 will make sure of that. They and the other kernel developers will fix a lot of
 other issues as well. But be aware that sometimes they can't or won't help; and
 sometimes there isn't even anyone to send a report to.
 
 This is best explained with kernel developers that contribute to the Linux
 kernel in their spare time. Quite a few of the drivers in the kernel were
 written by such programmers, often because they simply wanted to make their
 hardware usable on their favorite operating system.
 
 These programmers most of the time will happily fix problems other people
 report. But nobody can force them to do, as they are contributing voluntarily.
 
 Then there are situations where such developers really want to fix an issue,
 but can't: sometimes they lack hardware programming documentation to do so.
 This often happens when the publicly available docs are superficial or the
 driver was written with the help of reverse engineering.
 
 Sooner or later spare time developers will also stop caring for the driver.
 Maybe their test hardware broke, got replaced by something more fancy, or is so
 old that it's something you don't find much outside of computer museums
 anymore. Sometimes developer stops caring for their code and Linux at all, as
 something different in their life became way more important. In some cases
 nobody is willing to take over the job as maintainer – and nobody can be forced
 to, as contributing to the Linux kernel is done on a voluntary basis. Abandoned
 drivers nevertheless remain in the kernel: they are still useful for people and
 removing would be a regression.
 
 The situation is not that different with developers that are paid for their
 work on the Linux kernel. Those contribute most changes these days. But their
 employers sooner or later also stop caring for their code or make its
 programmer focus on other things. Hardware vendors for example earn their money
 mainly by selling new hardware; quite a few of them hence are not investing
 much time and energy in maintaining a Linux kernel driver for something they
 stopped selling years ago. Enterprise Linux distributors often care for a
 longer time period, but in new versions often leave support for old and rare
 hardware aside to limit the scope. Often spare time contributors take over once
 a company orphans some code, but as mentioned above: sooner or later they will
 leave the code behind, too.
 
 Priorities are another reason why some issues are not fixed, as maintainers
 quite often are forced to set those, as time to work on Linux is limited.
 That's true for spare time or the time employers grant their developers to
 spend on maintenance work on the upstream kernel. Sometimes maintainers also
 get overwhelmed with reports, even if a driver is working nearly perfectly. To
 not get completely stuck, the programmer thus might have no other choice than
 to prioritize issue reports and reject some of them.
 
 But don't worry too much about all of this, a lot of drivers have active
 maintainers who are quite interested in fixing as many issues as possible.
 
 
 Closing words
 =============
 
 Compared with other Free/Libre & Open Source Software it's hard to report
 issues to the Linux kernel developers: the length and complexity of this
 document and the implications between the lines illustrate that. But that's how
 it is for now. The main author of this text hopes documenting the state of the
 art will lay some groundwork to improve the situation over time.
 
 
 ..
    end-of-content
 ..
    This document is maintained by Thorsten Leemhuis <linux@leemhuis.info>. If
    you spot a typo or small mistake, feel free to let him know directly and
    he'll fix it. You are free to do the same in a mostly informal way if you
    want to contribute changes to the text, but for copyright reasons please CC
    linux-doc@vger.kernel.org and "sign-off" your contribution as
    Documentation/process/submitting-patches.rst outlines in the section "Sign
    your work - the Developer's Certificate of Origin".
 ..
    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-issues.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.

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