Adding upstream version 4.19.249.upstream/4.19.249upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 76 insertions, 0 deletions

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+Bisecting a bug
++++++++++++++++
+
+Last updated: 28 October 2016
+
+Introduction
+============
+
+Always try the latest kernel from kernel.org and build from source. If you are
+not confident in doing that please report the bug to your distribution vendor
+instead of to a kernel developer.
+
+Finding bugs is not always easy. Have a go though. If you can't find it don't
+give up. Report as much as you have found to the relevant maintainer. See
+MAINTAINERS for who that is for the subsystem you have worked on.
+
+Before you submit a bug report read
+:ref:`Documentation/admin-guide/reporting-bugs.rst <reportingbugs>`.
+
+Devices not appearing
+=====================
+
+Often this is caused by udev/systemd. Check that first before blaming it
+on the kernel.
+
+Finding patch that caused a bug
+===============================
+
+Using the provided tools with ``git`` makes finding bugs easy provided the bug
+is reproducible.
+
+Steps to do it:
+
+- build the Kernel from its git source
+- start bisect with [#f1]_::
+
+	$ git bisect start
+
+- mark the broken changeset with::
+
+	$ git bisect bad [commit]
+
+- mark a changeset where the code is known to work with::
+
+	$ git bisect good [commit]
+
+- rebuild the Kernel and test
+- interact with git bisect by using either::
+
+	$ git bisect good
+
+  or::
+
+	$ git bisect bad
+
+  depending if the bug happened on the changeset you're testing
+- After some interactions, git bisect will give you the changeset that
+  likely caused the bug.
+
+- For example, if you know that the current version is bad, and version
+  4.8 is good, you could do::
+
+           $ git bisect start
+           $ git bisect bad                 # Current version is bad
+           $ git bisect good v4.8
+
+
+.. [#f1] You can, optionally, provide both good and bad arguments at git
+	 start with ``git bisect start [BAD] [GOOD]``
+
+For further references, please read:
+
+- The man page for ``git-bisect``
+- `Fighting regressions with git bisect <https://www.kernel.org/pub/software/scm/git/docs/git-bisect-lk2009.html>`_
+- `Fully automated bisecting with "git bisect run" <https://lwn.net/Articles/317154>`_
+- `Using Git bisect to figure out when brokenness was introduced <http://webchick.net/node/99>`_