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 must be obviously correct and tested.
  • It cannot be bigger than 100 lines, with context.
  • It must fix only one thing.
  • It must fix a real bug that bothers people (not a, “This could be aproblem…” type thing).
  • It must fix a problem that causes a build error (but not for thingsmarked CONFIG_BROKEN), an oops, a hang, data corruption, a realsecurity issue, or some “oh, that’s not good” issue. In short, somethingcritical.
  • Serious issues as reported by a user of a distribution kernel may alsobe considered if they fix a notable performance or interactivity issue.As these fixes are not as obvious and have a higher risk of a subtleregression they should only be submitted by a distribution kernelmaintainer and include an addendum linking to a bugzilla entry if itexists and additional information on the user-visible impact.
  • New device IDs and quirks are also accepted.
  • No “theoretical race condition” issues, unless an explanation of how therace can be exploited is also provided.
  • It cannot contain any “trivial” fixes in it (spelling changes,whitespace cleanups, etc).
  • It must follow theDocumentation/process/submitting-patches.rstrules.
  • It or an equivalent fix must already exist in Linus’ tree (upstream).

Procedure for submitting patches to the -stable tree

For all other submissions, choose one of the following procedures

Option 1

To have the patch automatically included in the stable tree, add the tag

Cc: stable@vger.kernel.org

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

Option 2

After the patch has been merged to Linus’ tree, send an email tostable@vger.kernel.org containing the subject of the patch, the commit ID,why you think it should be applied, and what kernel version you wish it tobe applied to.

Option 3

Send the patch, after verifying that it follows the above rules, tostable@vger.kernel.org. You must note the upstream commit ID in thechangelog of your submission, as well as the kernel version you wishit to be applied to.

Option 1 isstrongly preferred, is the easiest and most common.Option 2 andOption 3 are more useful if the patch isn’t deemedworthy at the time it is applied to a public git tree (for instance, becauseit deserves more regression testing first).Option 3 is especiallyuseful if the patch needs some special handling to apply to an older kernel(e.g., if API’s have changed in the meantime).

Note that forOption 3, if the patch deviates from the originalupstream patch (for example because it had to be backported) this must be veryclearly documented and justified in the patch description.

The upstream commit ID must be specified with a separate line above the committext, like this:

commit <sha1> upstream.

Additionally, some patches submitted viaOption 1 may have additionalpatch prerequisites which can be cherry-picked. This can be specified in thefollowing format in the sign-off area:

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

The tag sequence has the meaning of:

git cherry-pick a1f84a3git cherry-pick 1b9508fgit cherry-pick fd21073git cherry-pick <this commit>

Also, some patches may have kernel version prerequisites. This can bespecified in the following format in the sign-off area:

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

The tag has the meaning of:

git cherry-pick <this commit>

For each “-stable” tree starting with the specified version.

Following the submission:

  • The sender will receive an ACK when the patch has been accepted into thequeue, or a NAK if the patch is rejected. This response might take a fewdays, according to the developer’s schedules.
  • If accepted, the patch will be added to the -stable queue, for review byother developers and by the relevant subsystem maintainer.

Review cycle

  • When the -stable maintainers decide for a review cycle, the patches will besent to the review committee, and the maintainer of the affected area ofthe patch (unless the submitter is the maintainer of the area) and CC: tothe 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-kernelmembers object to the patch, bringing up issues that the maintainers andmembers did not realize, the patch will be dropped from the queue.
  • At the end of the review cycle, the ACKed patches will be added to thelatest -stable release, and a new -stable release will happen.
  • Security patches will be accepted into the -stable tree directly from thesecurity kernel team, and not go through the normal review cycle.Contact the kernel security team for more details on this procedure.

Trees

Review committee

  • This is made up of a number of kernel developers who have volunteered forthis task, and a few that haven’t.