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Based on kernel version 4.16.1. Page generated on 2018-04-09 11:52 EST.

1	.. _reportingbugs:
2	
3	Reporting bugs
4	++++++++++++++
5	
6	Background
7	==========
8	
9	The upstream Linux kernel maintainers only fix bugs for specific kernel
10	versions.  Those versions include the current "release candidate" (or -rc)
11	kernel, any "stable" kernel versions, and any "long term" kernels.
12	
13	Please see https://www.kernel.org/ for a list of supported kernels.  Any
14	kernel marked with [EOL] is "end of life" and will not have any fixes
15	backported to it.
16	
17	If you've found a bug on a kernel version that isn't listed on kernel.org,
18	contact your Linux distribution or embedded vendor for support.
19	Alternatively, you can attempt to run one of the supported stable or -rc
20	kernels, and see if you can reproduce the bug on that.  It's preferable
21	to reproduce the bug on the latest -rc kernel.
22	
23	
24	How to report Linux kernel bugs
25	===============================
26	
27	
28	Identify the problematic subsystem
29	----------------------------------
30	
31	Identifying which part of the Linux kernel might be causing your issue
32	increases your chances of getting your bug fixed. Simply posting to the
33	generic linux-kernel mailing list (LKML) may cause your bug report to be
34	lost in the noise of a mailing list that gets 1000+ emails a day.
35	
36	Instead, try to figure out which kernel subsystem is causing the issue,
37	and email that subsystem's maintainer and mailing list.  If the subsystem
38	maintainer doesn't answer, then expand your scope to mailing lists like
39	LKML.
40	
41	
42	Identify who to notify
43	----------------------
44	
45	Once you know the subsystem that is causing the issue, you should send a
46	bug report.  Some maintainers prefer bugs to be reported via bugzilla
47	(https://bugzilla.kernel.org), while others prefer that bugs be reported
48	via the subsystem mailing list.
49	
50	To find out where to send an emailed bug report, find your subsystem or
51	device driver in the MAINTAINERS file.  Search in the file for relevant
52	entries, and send your bug report to the person(s) listed in the "M:"
53	lines, making sure to Cc the mailing list(s) in the "L:" lines.  When the
54	maintainer replies to you, make sure to 'Reply-all' in order to keep the
55	public mailing list(s) in the email thread.
56	
57	If you know which driver is causing issues, you can pass one of the driver
58	files to the get_maintainer.pl script::
59	
60	     perl scripts/get_maintainer.pl -f <filename>
61	
62	If it is a security bug, please copy the Security Contact listed in the
63	MAINTAINERS file.  They can help coordinate bugfix and disclosure.  See
64	:ref:`Documentation/admin-guide/security-bugs.rst <securitybugs>` for more information.
65	
66	If you can't figure out which subsystem caused the issue, you should file
67	a bug in kernel.org bugzilla and send email to
68	linux-kernel@vger.kernel.org, referencing the bugzilla URL.  (For more
69	information on the linux-kernel mailing list see
70	http://www.tux.org/lkml/).
71	
72	
73	Tips for reporting bugs
74	-----------------------
75	
76	If you haven't reported a bug before, please read:
77	
78		http://www.chiark.greenend.org.uk/~sgtatham/bugs.html
79	
80		http://www.catb.org/esr/faqs/smart-questions.html
81	
82	It's REALLY important to report bugs that seem unrelated as separate email
83	threads or separate bugzilla entries.  If you report several unrelated
84	bugs at once, it's difficult for maintainers to tease apart the relevant
85	data.
86	
87	
88	Gather information
89	------------------
90	
91	The most important information in a bug report is how to reproduce the
92	bug.  This includes system information, and (most importantly)
93	step-by-step instructions for how a user can trigger the bug.
94	
95	If the failure includes an "OOPS:", take a picture of the screen, capture
96	a netconsole trace, or type the message from your screen into the bug
97	report.  Please read "Documentation/admin-guide/bug-hunting.rst" before posting your
98	bug report. This explains what you should do with the "Oops" information
99	to make it useful to the recipient.
100	
101	This is a suggested format for a bug report sent via email or bugzilla.
102	Having a standardized bug report form makes it easier for you not to
103	overlook things, and easier for the developers to find the pieces of
104	information they're really interested in.  If some information is not
105	relevant to your bug, feel free to exclude it.
106	
107	First run the ver_linux script included as scripts/ver_linux, which
108	reports the version of some important subsystems.  Run this script with
109	the command ``awk -f scripts/ver_linux``.
110	
111	Use that information to fill in all fields of the bug report form, and
112	post it to the mailing list with a subject of "PROBLEM: <one line
113	summary from [1.]>" for easy identification by the developers::
114	
115	  [1.] One line summary of the problem:
116	  [2.] Full description of the problem/report:
117	  [3.] Keywords (i.e., modules, networking, kernel):
118	  [4.] Kernel information
119	  [4.1.] Kernel version (from /proc/version):
120	  [4.2.] Kernel .config file:
121	  [5.] Most recent kernel version which did not have the bug:
122	  [6.] Output of Oops.. message (if applicable) with symbolic information
123	       resolved (see Documentation/admin-guide/bug-hunting.rst)
124	  [7.] A small shell script or example program which triggers the
125	       problem (if possible)
126	  [8.] Environment
127	  [8.1.] Software (add the output of the ver_linux script here)
128	  [8.2.] Processor information (from /proc/cpuinfo):
129	  [8.3.] Module information (from /proc/modules):
130	  [8.4.] Loaded driver and hardware information (/proc/ioports, /proc/iomem)
131	  [8.5.] PCI information ('lspci -vvv' as root)
132	  [8.6.] SCSI information (from /proc/scsi/scsi)
133	  [8.7.] Other information that might be relevant to the problem
134	         (please look in /proc and include all information that you
135	         think to be relevant):
136	  [X.] Other notes, patches, fixes, workarounds:
137	
138	
139	Follow up
140	=========
141	
142	Expectations for bug reporters
143	------------------------------
144	
145	Linux kernel maintainers expect bug reporters to be able to follow up on
146	bug reports.  That may include running new tests, applying patches,
147	recompiling your kernel, and/or re-triggering your bug.  The most
148	frustrating thing for maintainers is for someone to report a bug, and then
149	never follow up on a request to try out a fix.
150	
151	That said, it's still useful for a kernel maintainer to know a bug exists
152	on a supported kernel, even if you can't follow up with retests.  Follow
153	up reports, such as replying to the email thread with "I tried the latest
154	kernel and I can't reproduce my bug anymore" are also helpful, because
155	maintainers have to assume silence means things are still broken.
156	
157	Expectations for kernel maintainers
158	-----------------------------------
159	
160	Linux kernel maintainers are busy, overworked human beings.  Some times
161	they may not be able to address your bug in a day, a week, or two weeks.
162	If they don't answer your email, they may be on vacation, or at a Linux
163	conference.  Check the conference schedule at https://LWN.net for more info:
164	
165		https://lwn.net/Calendar/
166	
167	In general, kernel maintainers take 1 to 5 business days to respond to
168	bugs.  The majority of kernel maintainers are employed to work on the
169	kernel, and they may not work on the weekends.  Maintainers are scattered
170	around the world, and they may not work in your time zone.  Unless you
171	have a high priority bug, please wait at least a week after the first bug
172	report before sending the maintainer a reminder email.
173	
174	The exceptions to this rule are regressions, kernel crashes, security holes,
175	or userspace breakage caused by new kernel behavior.  Those bugs should be
176	addressed by the maintainers ASAP.  If you suspect a maintainer is not
177	responding to these types of bugs in a timely manner (especially during a
178	merge window), escalate the bug to LKML and Linus Torvalds.
179	
180	Thank you!
181	
182	[Some of this is taken from Frohwalt Egerer's original linux-kernel FAQ]
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