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diff --git a/Documentation/admin-guide/reporting-issues.rst b/Documentation/admin-guide/reporting-issues.rst new file mode 100644 index 000000000000..ec62151fe672 --- /dev/null +++ b/Documentation/admin-guide/reporting-issues.rst @@ -0,0 +1,1764 @@ +.. SPDX-License-Identifier: (GPL-2.0+ OR CC-BY-4.0) +.. See the bottom of this file for additional redistribution information. + +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. |