| Background |
| ========== |
| |
| The upstream Linux kernel maintainers only fix bugs for specific kernel |
| versions. Those versions include the current "release candidate" (or -rc) |
| kernel, any "stable" kernel versions, and any "long term" kernels. |
| |
| Please see https://www.kernel.org/ for a list of supported kernels. Any |
| kernel marked with [EOL] is "end of life" and will not have any fixes |
| backported to it. |
| |
| If you've found a bug on a kernel version isn't listed on kernel.org, |
| contact your Linux distribution or embedded vendor for support. |
| Alternatively, you can attempt to run one of the supported stable or -rc |
| kernels, and see if you can reproduce the bug on that. It's preferable |
| to reproduce the bug on the latest -rc kernel. |
| |
| |
| How to report Linux kernel bugs |
| =============================== |
| |
| |
| Identify the problematic subsystem |
| ---------------------------------- |
| |
| Identifying which part of the Linux kernel might be causing your issue |
| increases your chances of getting your bug fixed. Simply posting to the |
| generic linux-kernel mailing list (LKML) may cause your bug report to be |
| lost in the noise of a mailing list that gets 1000+ emails a day. |
| |
| Instead, try to figure out which kernel subsystem is causing the issue, |
| and email that subsystem's maintainer and mailing list. If the subsystem |
| maintainer doesn't answer, then expand your scope to mailing lists like |
| LKML. |
| |
| |
| Identify who to notify |
| ---------------------- |
| |
| Once you know the subsystem that is causing the issue, you should send a |
| bug report. Some maintainers prefer bugs to be reported via bugzilla |
| (https://bugzilla.kernel.org), while others prefer that bugs be reported |
| via the subsystem mailing list. |
| |
| To find out where to send an emailed bug report, find your subsystem or |
| device driver in the MAINTAINERS file. Search in the file for relevant |
| entries, and send your bug report to the person(s) listed in the "M:" |
| lines, making sure to Cc the mailing list(s) in the "L:" lines. When the |
| maintainer replies to you, make sure to 'Reply-all' in order to keep the |
| public mailing list(s) in the email thread. |
| |
| If you know which driver is causing issues, you can pass one of the driver |
| files to the get_maintainer.pl script: |
| perl scripts/get_maintainer.pl -f <filename> |
| |
| If it is a security bug, please copy the Security Contact listed in the |
| MAINTAINERS file. They can help coordinate bugfix and disclosure. See |
| Documentation/SecurityBugs for more information. |
| |
| If you can't figure out which subsystem caused the issue, you should file |
| a bug in kernel.org bugzilla and send email to |
| linux-kernel@vger.kernel.org, referencing the bugzilla URL. (For more |
| information on the linux-kernel mailing list see |
| http://www.tux.org/lkml/). |
| |
| |
| Tips for reporting bugs |
| ----------------------- |
| |
| If you haven't reported a bug before, please read: |
| |
| http://www.chiark.greenend.org.uk/~sgtatham/bugs.html |
| http://www.catb.org/esr/faqs/smart-questions.html |
| |
| It's REALLY important to report bugs that seem unrelated as separate email |
| threads or separate bugzilla entries. If you report several unrelated |
| bugs at once, it's difficult for maintainers to tease apart the relevant |
| data. |
| |
| |
| Gather information |
| ------------------ |
| |
| The most important information in a bug report is how to reproduce the |
| bug. This includes system information, and (most importantly) |
| step-by-step instructions for how a user can trigger the bug. |
| |
| If the failure includes an "OOPS:", take a picture of the screen, capture |
| a netconsole trace, or type the message from your screen into the bug |
| report. Please read "Documentation/oops-tracing.txt" before posting your |
| bug report. This explains what you should do with the "Oops" information |
| to make it useful to the recipient. |
| |
| This is a suggested format for a bug report sent via email or bugzilla. |
| Having a standardized bug report form makes it easier for you not to |
| overlook things, and easier for the developers to find the pieces of |
| information they're really interested in. If some information is not |
| relevant to your bug, feel free to exclude it. |
| |
| First run the ver_linux script included as scripts/ver_linux, which |
| reports the version of some important subsystems. Run this script with |
| the command "sh scripts/ver_linux". |
| |
| Use that information to fill in all fields of the bug report form, and |
| post it to the mailing list with a subject of "PROBLEM: <one line |
| summary from [1.]>" for easy identification by the developers. |
| |
| [1.] One line summary of the problem: |
| [2.] Full description of the problem/report: |
| [3.] Keywords (i.e., modules, networking, kernel): |
| [4.] Kernel information |
| [4.1.] Kernel version (from /proc/version): |
| [4.2.] Kernel .config file: |
| [5.] Most recent kernel version which did not have the bug: |
| [6.] Output of Oops.. message (if applicable) with symbolic information |
| resolved (see Documentation/oops-tracing.txt) |
| [7.] A small shell script or example program which triggers the |
| problem (if possible) |
| [8.] Environment |
| [8.1.] Software (add the output of the ver_linux script here) |
| [8.2.] Processor information (from /proc/cpuinfo): |
| [8.3.] Module information (from /proc/modules): |
| [8.4.] Loaded driver and hardware information (/proc/ioports, /proc/iomem) |
| [8.5.] PCI information ('lspci -vvv' as root) |
| [8.6.] SCSI information (from /proc/scsi/scsi) |
| [8.7.] Other information that might be relevant to the problem |
| (please look in /proc and include all information that you |
| think to be relevant): |
| [X.] Other notes, patches, fixes, workarounds: |
| |
| |
| Follow up |
| ========= |
| |
| Expectations for bug reporters |
| ------------------------------ |
| |
| Linux kernel maintainers expect bug reporters to be able to follow up on |
| bug reports. That may include running new tests, applying patches, |
| recompiling your kernel, and/or re-triggering your bug. The most |
| frustrating thing for maintainers is for someone to report a bug, and then |
| never follow up on a request to try out a fix. |
| |
| That said, it's still useful for a kernel maintainer to know a bug exists |
| on a supported kernel, even if you can't follow up with retests. Follow |
| up reports, such as replying to the email thread with "I tried the latest |
| kernel and I can't reproduce my bug anymore" are also helpful, because |
| maintainers have to assume silence means things are still broken. |
| |
| Expectations for kernel maintainers |
| ----------------------------------- |
| |
| Linux kernel maintainers are busy, overworked human beings. Some times |
| they may not be able to address your bug in a day, a week, or two weeks. |
| If they don't answer your email, they may be on vacation, or at a Linux |
| conference. Check the conference schedule at LWN.net for more info: |
| https://lwn.net/Calendar/ |
| |
| In general, kernel maintainers take 1 to 5 business days to respond to |
| bugs. The majority of kernel maintainers are employed to work on the |
| kernel, and they may not work on the weekends. Maintainers are scattered |
| around the world, and they may not work in your time zone. Unless you |
| have a high priority bug, please wait at least a week after the first bug |
| report before sending the maintainer a reminder email. |
| |
| The exceptions to this rule are regressions, kernel crashes, security holes, |
| or userspace breakage caused by new kernel behavior. Those bugs should be |
| addressed by the maintainers ASAP. If you suspect a maintainer is not |
| responding to these types of bugs in a timely manner (especially during a |
| merge window), escalate the bug to LKML and Linus Torvalds. |
| |
| Thank you! |
| |
| [Some of this is taken from Frohwalt Egerer's original linux-kernel FAQ] |
