linux/REPORTING-BUGS
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Prefs
   1Background
   2==========
   3
   4The upstream Linux kernel maintainers only fix bugs for specific kernel
   5versions.  Those versions include the current "release candidate" (or -rc)
   6kernel, any "stable" kernel versions, and any "long term" kernels.
   7
   8Please see https://www.kernel.org/ for a list of supported kernels.  Any
   9kernel marked with [EOL] is "end of life" and will not have any fixes
  10backported to it.
  11
  12If you've found a bug on a kernel version isn't listed on kernel.org,
  13contact your Linux distribution or embedded vendor for support.
  14Alternatively, you can attempt to run one of the supported stable or -rc
  15kernels, and see if you can reproduce the bug on that.  It's preferable
  16to reproduce the bug on the latest -rc kernel.
  17
  18
  19How to report Linux kernel bugs
  20===============================
  21
  22
  23Identify the problematic subsystem
  24----------------------------------
  25
  26Identifying which part of the Linux kernel might be causing your issue
  27increases your chances of getting your bug fixed. Simply posting to the
  28generic linux-kernel mailing list (LKML) may cause your bug report to be
  29lost in the noise of a mailing list that gets 1000+ emails a day.
  30
  31Instead, try to figure out which kernel subsystem is causing the issue,
  32and email that subsystem's maintainer and mailing list.  If the subsystem
  33maintainer doesn't answer, then expand your scope to mailing lists like
  34LKML.
  35
  36
  37Identify who to notify
  38----------------------
  39
  40Once you know the subsystem that is causing the issue, you should send a
  41bug report.  Some maintainers prefer bugs to be reported via bugzilla
  42(https://bugzilla.kernel.org), while others prefer that bugs be reported
  43via the subsystem mailing list.
  44
  45To find out where to send an emailed bug report, find your subsystem or
  46device driver in the MAINTAINERS file.  Search in the file for relevant
  47entries, and send your bug report to the person(s) listed in the "M:"
  48lines, making sure to Cc the mailing list(s) in the "L:" lines.  When the
  49maintainer replies to you, make sure to 'Reply-all' in order to keep the
  50public mailing list(s) in the email thread.
  51
  52If you know which driver is causing issues, you can pass one of the driver
  53files to the get_maintainer.pl script:
  54     perl scripts/get_maintainer.pl -f <filename>
  55
  56If it is a security bug, please copy the Security Contact listed in the
  57MAINTAINERS file.  They can help coordinate bugfix and disclosure.  See
  58Documentation/SecurityBugs for more information.
  59
  60If you can't figure out which subsystem caused the issue, you should file
  61a bug in kernel.org bugzilla and send email to
  62linux-kernel@vger.kernel.org, referencing the bugzilla URL.  (For more
  63information on the linux-kernel mailing list see
  64http://www.tux.org/lkml/).
  65
  66
  67Tips for reporting bugs
  68-----------------------
  69
  70If you haven't reported a bug before, please read:
  71
  72http://www.chiark.greenend.org.uk/~sgtatham/bugs.html
  73http://www.catb.org/esr/faqs/smart-questions.html
  74
  75It's REALLY important to report bugs that seem unrelated as separate email
  76threads or separate bugzilla entries.  If you report several unrelated
  77bugs at once, it's difficult for maintainers to tease apart the relevant
  78data.
  79
  80
  81Gather information
  82------------------
  83
  84The most important information in a bug report is how to reproduce the
  85bug.  This includes system information, and (most importantly)
  86step-by-step instructions for how a user can trigger the bug.
  87
  88If the failure includes an "OOPS:", take a picture of the screen, capture
  89a netconsole trace, or type the message from your screen into the bug
  90report.  Please read "Documentation/oops-tracing.txt" before posting your
  91bug report. This explains what you should do with the "Oops" information
  92to make it useful to the recipient.
  93
  94This is a suggested format for a bug report sent via email or bugzilla.
  95Having a standardized bug report form makes it easier for you not to
  96overlook things, and easier for the developers to find the pieces of
  97information they're really interested in.  If some information is not
  98relevant to your bug, feel free to exclude it.
  99
 100First run the ver_linux script included as scripts/ver_linux, which
 101reports the version of some important subsystems.  Run this script with
 102the command "sh scripts/ver_linux".
 103
 104Use that information to fill in all fields of the bug report form, and
 105post it to the mailing list with a subject of "PROBLEM: <one line
 106summary from [1.]>" for easy identification by the developers.
 107
 108[1.] One line summary of the problem:
 109[2.] Full description of the problem/report:
 110[3.] Keywords (i.e., modules, networking, kernel):
 111[4.] Kernel information
 112[4.1.] Kernel version (from /proc/version):
 113[4.2.] Kernel .config file:
 114[5.] Most recent kernel version which did not have the bug:
 115[6.] Output of Oops.. message (if applicable) with symbolic information
 116     resolved (see Documentation/oops-tracing.txt)
 117[7.] A small shell script or example program which triggers the
 118     problem (if possible)
 119[8.] Environment
 120[8.1.] Software (add the output of the ver_linux script here)
 121[8.2.] Processor information (from /proc/cpuinfo):
 122[8.3.] Module information (from /proc/modules):
 123[8.4.] Loaded driver and hardware information (/proc/ioports, /proc/iomem)
 124[8.5.] PCI information ('lspci -vvv' as root)
 125[8.6.] SCSI information (from /proc/scsi/scsi)
 126[8.7.] Other information that might be relevant to the problem
 127       (please look in /proc and include all information that you
 128       think to be relevant):
 129[X.] Other notes, patches, fixes, workarounds:
 130
 131
 132Follow up
 133=========
 134
 135Expectations for bug reporters
 136------------------------------
 137
 138Linux kernel maintainers expect bug reporters to be able to follow up on
 139bug reports.  That may include running new tests, applying patches,
 140recompiling your kernel, and/or re-triggering your bug.  The most
 141frustrating thing for maintainers is for someone to report a bug, and then
 142never follow up on a request to try out a fix.
 143
 144That said, it's still useful for a kernel maintainer to know a bug exists
 145on a supported kernel, even if you can't follow up with retests.  Follow
 146up reports, such as replying to the email thread with "I tried the latest
 147kernel and I can't reproduce my bug anymore" are also helpful, because
 148maintainers have to assume silence means things are still broken.
 149
 150Expectations for kernel maintainers
 151-----------------------------------
 152
 153Linux kernel maintainers are busy, overworked human beings.  Some times
 154they may not be able to address your bug in a day, a week, or two weeks.
 155If they don't answer your email, they may be on vacation, or at a Linux
 156conference.  Check the conference schedule at LWN.net for more info:
 157        https://lwn.net/Calendar/
 158
 159In general, kernel maintainers take 1 to 5 business days to respond to
 160bugs.  The majority of kernel maintainers are employed to work on the
 161kernel, and they may not work on the weekends.  Maintainers are scattered
 162around the world, and they may not work in your time zone.  Unless you
 163have a high priority bug, please wait at least a week after the first bug
 164report before sending the maintainer a reminder email.
 165
 166The exceptions to this rule are regressions, kernel crashes, security holes,
 167or userspace breakage caused by new kernel behavior.  Those bugs should be
 168addressed by the maintainers ASAP.  If you suspect a maintainer is not
 169responding to these types of bugs in a timely manner (especially during a
 170merge window), escalate the bug to LKML and Linus Torvalds.
 171
 172Thank you!
 173
 174[Some of this is taken from Frohwalt Egerer's original linux-kernel FAQ]
 175
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