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hh _documenthsourceNlineNubhcomment)}(h0SPDX-License-Identifier: (GPL-2.0+ OR CC-BY-4.0)h]h0SPDX-License-Identifier: (GPL-2.0+ OR CC-BY-4.0)}hhsbah}(h]h ]h"]h$]h&] xml:spacepreserveuh1hhhhhhO/var/lib/git/docbuild/linux/Documentation/admin-guide/reporting-regressions.rsthKubh)}(h<[see the bottom of this file for redistribution information]h]h<[see the bottom of this file for redistribution information]}hhsbah}(h]h ]h"]h$]h&]hhuh1hhhhhhhhKubhsection)}(hhh](htitle)}(hReporting regressionsh]hReporting regressions}(hhhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhhhhhKubh paragraph)}(h"*We don't cause regressions*" is the first rule of Linux kernel development;
Linux founder and lead developer Linus Torvalds established it himself and
ensures it's obeyed.h](h“}(hhhhhNhNubhemphasis)}(h*We don't cause regressions*h]hWe don’t cause regressions}(hhhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhubh” is the first rule of Linux kernel development;
Linux founder and lead developer Linus Torvalds established it himself and
ensures it’s obeyed.}(hhhhhNhNubeh}(h]h ]h"]h$]h&]uh1hhhhKhhhhubh)}(hThis document describes what the rule means for users and how the Linux kernel's
development model ensures to address all reported regressions; aspects relevant
for kernel developers are left to Documentation/process/handling-regressions.rst.h]hThis document describes what the rule means for users and how the Linux kernel’s
development model ensures to address all reported regressions; aspects relevant
for kernel developers are left to Documentation/process/handling-regressions.rst.}(hhhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhhhhubh)}(hhh](h)}(h The important bits (aka "TL;DR")h]h$The important bits (aka “TL;DR”)}(hj hhhNhNubah}(h]h ]h"]h$]h&]uh1hhj hhhhhKubhenumerated_list)}(hhh](h list_item)}(hX It's a regression if something running fine with one Linux kernel works worse
or not at all with a newer version. Note, the newer kernel has to be compiled
using a similar configuration; the detailed explanations below describes this
and other fine print in more detail.
h]h)}(hX It's a regression if something running fine with one Linux kernel works worse
or not at all with a newer version. Note, the newer kernel has to be compiled
using a similar configuration; the detailed explanations below describes this
and other fine print in more detail.h]hX It’s a regression if something running fine with one Linux kernel works worse
or not at all with a newer version. Note, the newer kernel has to be compiled
using a similar configuration; the detailed explanations below describes this
and other fine print in more detail.}(hj% hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhj! ubah}(h]h ]h"]h$]h&]uh1j hj hhhhhNubj )}(hXu Report your issue as outlined in Documentation/admin-guide/reporting-issues.rst,
it already covers all aspects important for regressions and repeated
below for convenience. Two of them are important: start your report's subject
with "[REGRESSION]" and CC or forward it to `the regression mailing list
`_ (regressions@lists.linux.dev).
h]h)}(hXt Report your issue as outlined in Documentation/admin-guide/reporting-issues.rst,
it already covers all aspects important for regressions and repeated
below for convenience. Two of them are important: start your report's subject
with "[REGRESSION]" and CC or forward it to `the regression mailing list
`_ (regressions@lists.linux.dev).h](hX Report your issue as outlined in Documentation/admin-guide/reporting-issues.rst,
it already covers all aspects important for regressions and repeated
below for convenience. Two of them are important: start your report’s subject
with “[REGRESSION]” and CC or forward it to }(hj= hhhNhNubh reference)}(hE`the regression mailing list
`_h]hthe regression mailing list}(hjG hhhNhNubah}(h]h ]h"]h$]h&]namethe regression mailing listrefuri$https://lore.kernel.org/regressions/uh1jE hj= ubhtarget)}(h'
h]h}(h]the-regression-mailing-listah ]h"]the regression mailing listah$]h&]refurijX uh1jY
referencedKhj= ubh (}(hj= hhhNhNubjF )}(hregressions@lists.linux.devh]hregressions@lists.linux.dev}(hjm hhhNhNubah}(h]h ]h"]h$]h&]refuri"mailto:regressions@lists.linux.devuh1jE hj= ubh).}(hj= hhhNhNubeh}(h]h ]h"]h$]h&]uh1hhhhKhj9 ubah}(h]h ]h"]h$]h&]uh1j hj hhhhhNubj )}(hOptional, but recommended: when sending or forwarding your report, make the
Linux kernel regression tracking bot "regzbot" track the issue by specifying
when the regression started like this::
#regzbot introduced: v5.13..v5.14-rc1
h](h)}(hOptional, but recommended: when sending or forwarding your report, make the
Linux kernel regression tracking bot "regzbot" track the issue by specifying
when the regression started like this::h]hOptional, but recommended: when sending or forwarding your report, make the
Linux kernel regression tracking bot “regzbot” track the issue by specifying
when the regression started like this:}(hj hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhj ubh
literal_block)}(h%#regzbot introduced: v5.13..v5.14-rc1h]h%#regzbot introduced: v5.13..v5.14-rc1}hj sbah}(h]h ]h"]h$]h&]hhuh1j hhhK"hj ubeh}(h]h ]h"]h$]h&]uh1j hj hhhhhNubeh}(h]h ]h"]h$]h&]enumtypearabicprefixhsuffix.uh1j hj hhhhhKubeh}(h]the-important-bits-aka-tl-drah ]h"] the important bits (aka "tl;dr")ah$]h&]uh1hhhhhhhhKubh)}(hhh](h)}(h>All the details on Linux kernel regressions relevant for usersh]h>All the details on Linux kernel regressions relevant for users}(hj hhhNhNubah}(h]h ]h"]h$]h&]uh1hhj hhhhhK&ubh)}(hhh](h)}(hThe important basicsh]hThe important basics}(hj hhhNhNubah}(h]h ]h"]h$]h&]uh1hhj hhhhhK*ubh)}(hhh](h)}(h=What is a "regression" and what is the "no regressions" rule?h]hEWhat is a “regression” and what is the “no regressions” rule?}(hj hhhNhNubah}(h]h ]h"]h$]h&]uh1hhj hhhhhK.ubh)}(hXG It's 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 "no regressions" rule forbids this to take place; if
it happens by accident, developers that caused it are expected to quickly fix
the issue.h]hXM It’s 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 “no regressions” rule forbids this to take place; if
it happens by accident, developers that caused it are expected to quickly fix
the issue.}(hj hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhK0hj hhubh)}(hXj It thus is a regression when a WiFi driver from Linux 5.13 works fine, but with
5.14 doesn't work at all, works significantly slower, or misbehaves somehow.
It's also a regression if a perfectly working application suddenly shows erratic
behavior with a newer kernel version; such issues can be caused by changes in
procfs, sysfs, or one of the many other interfaces Linux provides to userland
software. But keep in mind, as mentioned earlier: 5.14 in this example needs to
be built from a configuration similar to the one from 5.13. This can be achieved
using ``make olddefconfig``, as explained in more detail below.h](hX5 It thus is a regression when a WiFi driver from Linux 5.13 works fine, but with
5.14 doesn’t work at all, works significantly slower, or misbehaves somehow.
It’s also a regression if a perfectly working application suddenly shows erratic
behavior with a newer kernel version; such issues can be caused by changes in
procfs, sysfs, or one of the many other interfaces Linux provides to userland
software. But keep in mind, as mentioned earlier: 5.14 in this example needs to
be built from a configuration similar to the one from 5.13. This can be achieved
using }(hj hhhNhNubhliteral)}(h``make olddefconfig``h]hmake olddefconfig}(hj hhhNhNubah}(h]h ]h"]h$]h&]uh1j hj ubh$, as explained in more detail below.}(hj hhhNhNubeh}(h]h ]h"]h$]h&]uh1hhhhK6hj hhubh)}(hNote the "practical use case" in the first sentence of this section: developers
despite the "no regressions" rule are free to change any aspect of the kernel
and even APIs or ABIs to userland, as long as no existing application or use
case breaks.h]hNote the “practical use case” in the first sentence of this section: developers
despite the “no regressions” rule are free to change any aspect of the kernel
and even APIs or ABIs to userland, as long as no existing application or use
case breaks.}(hj+ hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhK?hj hhubh)}(hAlso be aware the "no regressions" rule covers only interfaces the kernel
provides to the userland. It thus does not apply to kernel-internal interfaces
like the module API, which some externally developed drivers use to hook into
the kernel.h]hAlso be aware the “no regressions” rule covers only interfaces the kernel
provides to the userland. It thus does not apply to kernel-internal interfaces
like the module API, which some externally developed drivers use to hook into
the kernel.}(hj9 hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKDhj hhubeh}(h]8what-is-a-regression-and-what-is-the-no-regressions-ruleah ]h"]=what is a "regression" and what is the "no regressions" rule?ah$]h&]uh1hhj hhhhhK.ubh)}(hhh](h)}(hHow do I report a regression?h]hHow do I report a regression?}(hjR hhhNhNubah}(h]h ]h"]h$]h&]uh1hhjO hhhhhKJubh)}(hJust report the issue as outlined in
Documentation/admin-guide/reporting-issues.rst, it already describes the
important points. The following aspects outlined there are especially relevant
for regressions:h]hJust report the issue as outlined in
Documentation/admin-guide/reporting-issues.rst, it already describes the
important points. The following aspects outlined there are especially relevant
for regressions:}(hj` hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKLhjO hhubhblock_quote)}(hX * When checking for existing reports to join, also search the `archives of the
Linux regressions mailing list `_ and
`regzbot's web-interface `_.
* Start your report's subject with "[REGRESSION]".
* In your report, clearly mention the last kernel version that worked fine and
the first broken one. Ideally try to find the exact change causing the
regression using a bisection, as explained below in more detail.
* Remember to let the Linux regressions mailing list
(regressions@lists.linux.dev) know about your report:
* If you report the regression by mail, CC the regressions list.
* If you report your regression to some bug tracker, forward the submitted
report by mail to the regressions list while CCing the maintainer and the
mailing list for the subsystem in question.
If it's a regression within a stable or longterm series (e.g.
v5.15.3..v5.15.5), remember to CC the `Linux stable mailing list
`_ (stable@vger.kernel.org).
In case you performed a successful bisection, add everyone to the CC the
culprit's commit message mentions in lines starting with "Signed-off-by:".
h](hbullet_list)}(hhh](j )}(hWhen checking for existing reports to join, also search the `archives of the
Linux regressions mailing list `_ and
`regzbot's web-interface `_.
h]h)}(hWhen checking for existing reports to join, also search the `archives of the
Linux regressions mailing list `_ and
`regzbot's web-interface `_.h](h