Documentation/process/stable-kernel-rules.rst - linux - Git at Google

 .. _stable_kernel_rules:

 Everything you ever wanted to know about Linux -stable releases
 ===============================================================

 Rules on what kind of patches are accepted, and which ones are not, into the
 "-stable" tree:

  - It or an equivalent fix must already exist in Linus' tree (upstream).
  - It must be obviously correct and tested.
  - It cannot be bigger than 100 lines, with context.
  - It must follow the
    :ref:`Documentation/process/submitting-patches.rst <submittingpatches>`
    rules.
  - It must either fix a real bug that bothers people or just add a device ID.
    To elaborate on the former:

    - It fixes a problem like an oops, a hang, data corruption, a real security
      issue, a hardware quirk, a build error (but not for things marked
      CONFIG_BROKEN), or some "oh, that's not good" issue.
    - Serious issues as reported by a user of a distribution kernel may also
      be considered if they fix a notable performance or interactivity issue.
      As these fixes are not as obvious and have a higher risk of a subtle
      regression they should only be submitted by a distribution kernel
      maintainer and include an addendum linking to a bugzilla entry if it
      exists and additional information on the user-visible impact.
    - No "This could be a problem..." type of things like a "theoretical race
      condition", unless an explanation of how the bug can be exploited is also
      provided.
    - No "trivial" fixes without benefit for users (spelling changes, whitespace
      cleanups, etc).


 Procedure for submitting patches to the -stable tree
 ----------------------------------------------------

 .. note::

    Security patches should not be handled (solely) by the -stable review
    process but should follow the procedures in
    :ref:`Documentation/process/security-bugs.rst <securitybugs>`.

 There are three options to submit a change to -stable trees:

  1. Add a 'stable tag' to the description of a patch you then submit for
     mainline inclusion.
  2. Ask the stable team to pick up a patch already mainlined.
  3. Submit a patch to the stable team that is equivalent to a change already
     mainlined.

 The sections below describe each of the options in more detail.

 :ref:`option_1` is **strongly** preferred, it is the easiest and most common.
 :ref:`option_2` is mainly meant for changes where backporting was not considered
 at the time of submission. :ref:`option_3` is an alternative to the two earlier
 options for cases where a mainlined patch needs adjustments to apply in older
 series (for example due to API changes).

 When using option 2 or 3 you can ask for your change to be included in specific
 stable series. When doing so, ensure the fix or an equivalent is applicable,
 submitted, or already present in all newer stable trees still supported. This is
 meant to prevent regressions that users might later encounter on updating, if
 e.g. a fix merged for 5.19-rc1 would be backported to 5.10.y, but not to 5.15.y.

 .. _option_1:

 Option 1
 ********

 To have a patch you submit for mainline inclusion later automatically picked up
 for stable trees, add the tag

 .. code-block:: none

      Cc: stable@vger.kernel.org

 in the sign-off area. Once the patch is mainlined it will be applied to the
 stable tree without anything else needing to be done by the author or
 subsystem maintainer.

 To sent additional instructions to the stable team, use a shell-style inline
 comment:

  * To specify any additional patch prerequisites for cherry picking use the
    following format in the sign-off area:

    .. code-block:: none

      Cc: <stable@vger.kernel.org> # 3.3.x: a1f84a3: sched: Check for idle
      Cc: <stable@vger.kernel.org> # 3.3.x: 1b9508f: sched: Rate-limit newidle
      Cc: <stable@vger.kernel.org> # 3.3.x: fd21073: sched: Fix affinity logic
      Cc: <stable@vger.kernel.org> # 3.3.x
      Signed-off-by: Ingo Molnar <mingo@elte.hu>

    The tag sequence has the meaning of:

    .. code-block:: none

      git cherry-pick a1f84a3
      git cherry-pick 1b9508f
      git cherry-pick fd21073
      git cherry-pick <this commit>

    Note that for a patch series, you do not have to list as prerequisites the
    patches present in the series itself. For example, if you have the following
    patch series:

    .. code-block:: none

      patch1
      patch2

    where patch2 depends on patch1, you do not have to list patch1 as
    prerequisite of patch2 if you have already marked patch1 for stable
    inclusion.

  * For patches that may have kernel version prerequisites specify them using
    the following format in the sign-off area:

    .. code-block:: none

      Cc: <stable@vger.kernel.org> # 3.3.x

    The tag has the meaning of:

    .. code-block:: none

      git cherry-pick <this commit>

    For each "-stable" tree starting with the specified version.

    Note, such tagging is unnecessary if the stable team can derive the
    appropriate versions from Fixes: tags.

  * To delay pick up of patches, use the following format:

    .. code-block:: none

      Cc: <stable@vger.kernel.org> # after 4 weeks in mainline

  * For any other requests, just add a note to the stable tag. This for example
    can be used to point out known problems:

    .. code-block:: none

      Cc: <stable@vger.kernel.org> # see patch description, needs adjustments for <= 6.3

 .. _option_2:

 Option 2
 ********

 If the patch already has been merged to mainline, send an email to
 stable@vger.kernel.org containing the subject of the patch, the commit ID,
 why you think it should be applied, and what kernel versions you wish it to
 be applied to.

 .. _option_3:

 Option 3
 ********

 Send the patch, after verifying that it follows the above rules, to
 stable@vger.kernel.org and mention the kernel versions you wish it to be applied
 to. When doing so, you must note the upstream commit ID in the changelog of your
 submission with a separate line above the commit text, like this:

 .. code-block:: none

     commit <sha1> upstream.

 or alternatively:

 .. code-block:: none

     [ Upstream commit <sha1> ]

 If the submitted patch deviates from the original upstream patch (for example
 because it had to be adjusted for the older API), this must be very clearly
 documented and justified in the patch description.


 Following the submission
 ------------------------

 The sender will receive an ACK when the patch has been accepted into the
 queue, or a NAK if the patch is rejected.  This response might take a few
 days, according to the schedules of the stable team members.

 If accepted, the patch will be added to the -stable queue, for review by other
 developers and by the relevant subsystem maintainer.


 Review cycle
 ------------

  - When the -stable maintainers decide for a review cycle, the patches will be
    sent to the review committee, and the maintainer of the affected area of
    the patch (unless the submitter is the maintainer of the area) and CC: to
    the linux-kernel mailing list.
  - The review committee has 48 hours in which to ACK or NAK the patch.
  - If the patch is rejected by a member of the committee, or linux-kernel
    members object to the patch, bringing up issues that the maintainers and
    members did not realize, the patch will be dropped from the queue.
  - The ACKed patches will be posted again as part of release candidate (-rc)
    to be tested by developers and testers.
  - Usually only one -rc release is made, however if there are any outstanding
    issues, some patches may be modified or dropped or additional patches may
    be queued. Additional -rc releases are then released and tested until no
    issues are found.
  - Responding to the -rc releases can be done on the mailing list by sending
    a "Tested-by:" email with any testing information desired. The "Tested-by:"
    tags will be collected and added to the release commit.
  - At the end of the review cycle, the new -stable release will be released
    containing all the queued and tested patches.
  - Security patches will be accepted into the -stable tree directly from the
    security kernel team, and not go through the normal review cycle.
    Contact the kernel security team for more details on this procedure.


 Trees
 -----

  - The queues of patches, for both completed versions and in progress
    versions can be found at:

 	https://git.kernel.org/pub/scm/linux/kernel/git/stable/stable-queue.git

  - The finalized and tagged releases of all stable kernels can be found
    in separate branches per version at:

 	https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git

  - The release candidate of all stable kernel versions can be found at:

         https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable-rc.git/

    .. warning::
       The -stable-rc tree is a snapshot in time of the stable-queue tree and
       will change frequently, hence will be rebased often. It should only be
       used for testing purposes (e.g. to be consumed by CI systems).


 Review committee
 ----------------

  - This is made up of a number of kernel developers who have volunteered for
    this task, and a few that haven't.
	.. _stable_kernel_rules:

	Everything you ever wanted to know about Linux -stable releases
	===============================================================

	Rules on what kind of patches are accepted, and which ones are not, into the
	"-stable" tree:

	- It or an equivalent fix must already exist in Linus' tree (upstream).
	- It must be obviously correct and tested.
	- It cannot be bigger than 100 lines, with context.
	- It must follow the
	:ref:`Documentation/process/submitting-patches.rst <submittingpatches>`
	rules.
	- It must either fix a real bug that bothers people or just add a device ID.
	To elaborate on the former:

	- It fixes a problem like an oops, a hang, data corruption, a real security
	issue, a hardware quirk, a build error (but not for things marked
	CONFIG_BROKEN), or some "oh, that's not good" issue.
	- Serious issues as reported by a user of a distribution kernel may also
	be considered if they fix a notable performance or interactivity issue.
	As these fixes are not as obvious and have a higher risk of a subtle
	regression they should only be submitted by a distribution kernel
	maintainer and include an addendum linking to a bugzilla entry if it
	exists and additional information on the user-visible impact.
	- No "This could be a problem..." type of things like a "theoretical race
	condition", unless an explanation of how the bug can be exploited is also
	provided.
	- No "trivial" fixes without benefit for users (spelling changes, whitespace
	cleanups, etc).


	Procedure for submitting patches to the -stable tree
	----------------------------------------------------

	.. note::

	Security patches should not be handled (solely) by the -stable review
	process but should follow the procedures in
	:ref:`Documentation/process/security-bugs.rst <securitybugs>`.

	There are three options to submit a change to -stable trees:

	1. Add a 'stable tag' to the description of a patch you then submit for
	mainline inclusion.
	2. Ask the stable team to pick up a patch already mainlined.
	3. Submit a patch to the stable team that is equivalent to a change already
	mainlined.

	The sections below describe each of the options in more detail.

	:ref:`option_1` is strongly preferred, it is the easiest and most common.
	:ref:`option_2` is mainly meant for changes where backporting was not considered
	at the time of submission. :ref:`option_3` is an alternative to the two earlier
	options for cases where a mainlined patch needs adjustments to apply in older
	series (for example due to API changes).

	When using option 2 or 3 you can ask for your change to be included in specific
	stable series. When doing so, ensure the fix or an equivalent is applicable,
	submitted, or already present in all newer stable trees still supported. This is
	meant to prevent regressions that users might later encounter on updating, if
	e.g. a fix merged for 5.19-rc1 would be backported to 5.10.y, but not to 5.15.y.

	.. _option_1:

	Option 1
	********

	To have a patch you submit for mainline inclusion later automatically picked up
	for stable trees, add the tag

	.. code-block:: none

	Cc: stable@vger.kernel.org

	in the sign-off area. Once the patch is mainlined it will be applied to the
	stable tree without anything else needing to be done by the author or
	subsystem maintainer.

	To sent additional instructions to the stable team, use a shell-style inline
	comment:

	* To specify any additional patch prerequisites for cherry picking use the
	following format in the sign-off area:

	.. code-block:: none

	Cc: <stable@vger.kernel.org> # 3.3.x: a1f84a3: sched: Check for idle
	Cc: <stable@vger.kernel.org> # 3.3.x: 1b9508f: sched: Rate-limit newidle
	Cc: <stable@vger.kernel.org> # 3.3.x: fd21073: sched: Fix affinity logic
	Cc: <stable@vger.kernel.org> # 3.3.x
	Signed-off-by: Ingo Molnar <mingo@elte.hu>

	The tag sequence has the meaning of:

	.. code-block:: none

	git cherry-pick a1f84a3
	git cherry-pick 1b9508f
	git cherry-pick fd21073
	git cherry-pick <this commit>

	Note that for a patch series, you do not have to list as prerequisites the
	patches present in the series itself. For example, if you have the following
	patch series:

	.. code-block:: none

	patch1
	patch2

	where patch2 depends on patch1, you do not have to list patch1 as
	prerequisite of patch2 if you have already marked patch1 for stable
	inclusion.

	* For patches that may have kernel version prerequisites specify them using
	the following format in the sign-off area:

	.. code-block:: none

	Cc: <stable@vger.kernel.org> # 3.3.x

	The tag has the meaning of:

	.. code-block:: none

	git cherry-pick <this commit>

	For each "-stable" tree starting with the specified version.

	Note, such tagging is unnecessary if the stable team can derive the
	appropriate versions from Fixes: tags.

	* To delay pick up of patches, use the following format:

	.. code-block:: none

	Cc: <stable@vger.kernel.org> # after 4 weeks in mainline

	* For any other requests, just add a note to the stable tag. This for example
	can be used to point out known problems:

	.. code-block:: none

	Cc: <stable@vger.kernel.org> # see patch description, needs adjustments for <= 6.3

	.. _option_2:

	Option 2
	********

	If the patch already has been merged to mainline, send an email to
	stable@vger.kernel.org containing the subject of the patch, the commit ID,
	why you think it should be applied, and what kernel versions you wish it to
	be applied to.

	.. _option_3:

	Option 3
	********

	Send the patch, after verifying that it follows the above rules, to
	stable@vger.kernel.org and mention the kernel versions you wish it to be applied
	to. When doing so, you must note the upstream commit ID in the changelog of your
	submission with a separate line above the commit text, like this:

	.. code-block:: none

	commit <sha1> upstream.

	or alternatively:

	.. code-block:: none

	[ Upstream commit <sha1> ]

	If the submitted patch deviates from the original upstream patch (for example
	because it had to be adjusted for the older API), this must be very clearly
	documented and justified in the patch description.


	Following the submission
	------------------------

	The sender will receive an ACK when the patch has been accepted into the
	queue, or a NAK if the patch is rejected. This response might take a few
	days, according to the schedules of the stable team members.

	If accepted, the patch will be added to the -stable queue, for review by other
	developers and by the relevant subsystem maintainer.


	Review cycle
	------------

	- When the -stable maintainers decide for a review cycle, the patches will be
	sent to the review committee, and the maintainer of the affected area of
	the patch (unless the submitter is the maintainer of the area) and CC: to
	the linux-kernel mailing list.
	- The review committee has 48 hours in which to ACK or NAK the patch.
	- If the patch is rejected by a member of the committee, or linux-kernel
	members object to the patch, bringing up issues that the maintainers and
	members did not realize, the patch will be dropped from the queue.
	- The ACKed patches will be posted again as part of release candidate (-rc)
	to be tested by developers and testers.
	- Usually only one -rc release is made, however if there are any outstanding
	issues, some patches may be modified or dropped or additional patches may
	be queued. Additional -rc releases are then released and tested until no
	issues are found.
	- Responding to the -rc releases can be done on the mailing list by sending
	a "Tested-by:" email with any testing information desired. The "Tested-by:"
	tags will be collected and added to the release commit.
	- At the end of the review cycle, the new -stable release will be released
	containing all the queued and tested patches.
	- Security patches will be accepted into the -stable tree directly from the
	security kernel team, and not go through the normal review cycle.
	Contact the kernel security team for more details on this procedure.


	Trees
	-----

	- The queues of patches, for both completed versions and in progress
	versions can be found at:

	https://git.kernel.org/pub/scm/linux/kernel/git/stable/stable-queue.git

	- The finalized and tagged releases of all stable kernels can be found
	in separate branches per version at:

	https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git

	- The release candidate of all stable kernel versions can be found at:

	https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable-rc.git/

	.. warning::
	The -stable-rc tree is a snapshot in time of the stable-queue tree and
	will change frequently, hence will be rebased often. It should only be
	used for testing purposes (e.g. to be consumed by CI systems).


	Review committee
	----------------

	- This is made up of a number of kernel developers who have volunteered for
	this task, and a few that haven't.