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Embedded Linux Experts

.. _submitchecklist:

Linux Kernel patch submission checklist
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Here are some basic things that developers should do if they want to see their
kernel patch submissions accepted more quickly.

These are all above and beyond the documentation that is provided in
:ref:`Documentation/process/submitting-patches.rst <submittingpatches>`
and elsewhere regarding submitting Linux kernel patches.


1) If you use a facility then #include the file that defines/declares
   that facility.  Don't depend on other header files pulling in ones
   that you use.

2) Builds cleanly:

  a) with applicable or modified ``CONFIG`` options ``=y``, ``=m``, and
     ``=n``.  No ``gcc`` warnings/errors, no linker warnings/errors.

  b) Passes ``allnoconfig``, ``allmodconfig``

  c) Builds successfully when using ``O=builddir``

3) Builds on multiple CPU architectures by using local cross-compile tools
   or some other build farm.

4) ppc64 is a good architecture for cross-compilation checking because it
   tends to use ``unsigned long`` for 64-bit quantities.

5) Check your patch for general style as detailed in
   :ref:`Documentation/process/coding-style.rst <codingstyle>`.
   Check for trivial violations with the patch style checker prior to
   submission (``scripts/checkpatch.pl``).
   You should be able to justify all violations that remain in
   your patch.

6) Any new or modified ``CONFIG`` options don't muck up the config menu.

7) All new ``Kconfig`` options have help text.

8) Has been carefully reviewed with respect to relevant ``Kconfig``
   combinations.  This is very hard to get right with testing -- brainpower
   pays off here.

9) Check cleanly with sparse.

10) Use ``make checkstack`` and ``make namespacecheck`` and fix any problems
    that they find.

    .. note::

       ``checkstack`` does not point out problems explicitly,
       but any one function that uses more than 512 bytes on the stack is a
       candidate for change.

11) Include :ref:`kernel-doc <kernel_doc>` to document global  kernel APIs.
    (Not required for static functions, but OK there also.) Use
    ``make htmldocs`` or ``make pdfdocs`` to check the
    :ref:`kernel-doc <kernel_doc>` and fix any issues.

12) Has been tested with ``CONFIG_PREEMPT``, ``CONFIG_DEBUG_PREEMPT``,
    ``CONFIG_DEBUG_SLAB``, ``CONFIG_DEBUG_PAGEALLOC``, ``CONFIG_DEBUG_MUTEXES``,
    ``CONFIG_DEBUG_SPINLOCK``, ``CONFIG_DEBUG_ATOMIC_SLEEP``,
    ``CONFIG_PROVE_RCU`` and ``CONFIG_DEBUG_OBJECTS_RCU_HEAD`` all
    simultaneously enabled.

13) Has been build- and runtime tested with and without ``CONFIG_SMP`` and
    ``CONFIG_PREEMPT.``

14) If the patch affects IO/Disk, etc: has been tested with and without
    ``CONFIG_LBDAF.``

15) All codepaths have been exercised with all lockdep features enabled.

16) All new ``/proc`` entries are documented under ``Documentation/``

17) All new kernel boot parameters are documented in
    ``Documentation/admin-guide/kernel-parameters.rst``.

18) All new module parameters are documented with ``MODULE_PARM_DESC()``

19) All new userspace interfaces are documented in ``Documentation/ABI/``.
    See ``Documentation/ABI/README`` for more information.
    Patches that change userspace interfaces should be CCed to
    linux-api@vger.kernel.org.

20) Check that it all passes ``make headers_check``.

21) Has been checked with injection of at least slab and page-allocation
    failures.  See ``Documentation/fault-injection/``.

    If the new code is substantial, addition of subsystem-specific fault
    injection might be appropriate.

22) Newly-added code has been compiled with ``gcc -W`` (use
    ``make EXTRA_CFLAGS=-W``).  This will generate lots of noise, but is good
    for finding bugs like "warning: comparison between signed and unsigned".

23) Tested after it has been merged into the -mm patchset to make sure
    that it still works with all of the other queued patches and various
    changes in the VM, VFS, and other subsystems.

24) All memory barriers {e.g., ``barrier()``, ``rmb()``, ``wmb()``} need a
    comment in the source code that explains the logic of what they are doing
    and why.

25) If any ioctl's are added by the patch, then also update
    ``Documentation/ioctl/ioctl-number.txt``.

26) If your modified source code depends on or uses any of the kernel
    APIs or features that are related to the following ``Kconfig`` symbols,
    then test multiple builds with the related ``Kconfig`` symbols disabled
    and/or ``=m`` (if that option is available) [not all of these at the
    same time, just various/random combinations of them]:

    ``CONFIG_SMP``, ``CONFIG_SYSFS``, ``CONFIG_PROC_FS``, ``CONFIG_INPUT``, ``CONFIG_PCI``, ``CONFIG_BLOCK``, ``CONFIG_PM``, ``CONFIG_MAGIC_SYSRQ``,
    ``CONFIG_NET``, ``CONFIG_INET=n`` (but latter with ``CONFIG_NET=y``).