1.. _stable_kernel_rules: 2 3Everything you ever wanted to know about Linux -stable releases 4=============================================================== 5 6Rules on what kind of patches are accepted, and which ones are not, into the 7"-stable" tree: 8 9- It or an equivalent fix must already exist in Linux mainline (upstream). 10- It must be obviously correct and tested. 11- It cannot be bigger than 100 lines, with context. 12- It must follow the 13 :ref:`Documentation/process/submitting-patches.rst <submittingpatches>` 14 rules. 15- It must either fix a real bug that bothers people or just add a device ID. 16 To elaborate on the former: 17 18 - It fixes a problem like an oops, a hang, data corruption, a real security 19 issue, a hardware quirk, a build error (but not for things marked 20 CONFIG_BROKEN), or some "oh, that's not good" issue. 21 - Serious issues as reported by a user of a distribution kernel may also 22 be considered if they fix a notable performance or interactivity issue. 23 As these fixes are not as obvious and have a higher risk of a subtle 24 regression they should only be submitted by a distribution kernel 25 maintainer and include an addendum linking to a bugzilla entry if it 26 exists and additional information on the user-visible impact. 27 - No "This could be a problem..." type of things like a "theoretical race 28 condition", unless an explanation of how the bug can be exploited is also 29 provided. 30 - No "trivial" fixes without benefit for users (spelling changes, whitespace 31 cleanups, etc). 32 33 34Procedure for submitting patches to the -stable tree 35---------------------------------------------------- 36 37.. note:: 38 39 Security patches should not be handled (solely) by the -stable review 40 process but should follow the procedures in 41 :ref:`Documentation/process/security-bugs.rst <securitybugs>`. 42 43There are three options to submit a change to -stable trees: 44 451. Add a 'stable tag' to the description of a patch you then submit for 46 mainline inclusion. 472. Ask the stable team to pick up a patch already mainlined. 483. Submit a patch to the stable team that is equivalent to a change already 49 mainlined. 50 51The sections below describe each of the options in more detail. 52 53:ref:`option_1` is **strongly** preferred, it is the easiest and most common. 54:ref:`option_2` is mainly meant for changes where backporting was not considered 55at the time of submission. :ref:`option_3` is an alternative to the two earlier 56options for cases where a mainlined patch needs adjustments to apply in older 57series (for example due to API changes). 58 59When using option 2 or 3 you can ask for your change to be included in specific 60stable series. When doing so, ensure the fix or an equivalent is applicable, 61submitted, or already present in all newer stable trees still supported. This is 62meant to prevent regressions that users might later encounter on updating, if 63e.g. a fix merged for 5.19-rc1 would be backported to 5.10.y, but not to 5.15.y. 64 65.. _option_1: 66 67Option 1 68******** 69 70To have a patch you submit for mainline inclusion later automatically picked up 71for stable trees, add this tag in the sign-off area:: 72 73 Cc: stable@vger.kernel.org 74 75Once the patch is mainlined it will be applied to the stable tree without 76anything else needing to be done by the author or subsystem maintainer. 77 78To sent additional instructions to the stable team, use a shell-style inline 79comment to pass arbitrary or predefined notes: 80 81* Specify any additional patch prerequisites for cherry picking:: 82 83 Cc: <stable@vger.kernel.org> # 3.3.x: a1f84a3: sched: Check for idle 84 Cc: <stable@vger.kernel.org> # 3.3.x: 1b9508f: sched: Rate-limit newidle 85 Cc: <stable@vger.kernel.org> # 3.3.x: fd21073: sched: Fix affinity logic 86 Cc: <stable@vger.kernel.org> # 3.3.x 87 Signed-off-by: Ingo Molnar <mingo@elte.hu> 88 89 The tag sequence has the meaning of:: 90 91 git cherry-pick a1f84a3 92 git cherry-pick 1b9508f 93 git cherry-pick fd21073 94 git cherry-pick <this commit> 95 96 Note that for a patch series, you do not have to list as prerequisites the 97 patches present in the series itself. For example, if you have the following 98 patch series:: 99 100 patch1 101 patch2 102 103 where patch2 depends on patch1, you do not have to list patch1 as 104 prerequisite of patch2 if you have already marked patch1 for stable 105 inclusion. 106 107* Point out kernel version prerequisites:: 108 109 Cc: <stable@vger.kernel.org> # 3.3.x 110 111 The tag has the meaning of:: 112 113 git cherry-pick <this commit> 114 115 For each "-stable" tree starting with the specified version. 116 117 Note, such tagging is unnecessary if the stable team can derive the 118 appropriate versions from Fixes: tags. 119 120* Delay pick up of patches:: 121 122 Cc: <stable@vger.kernel.org> # after -rc3 123 124* Point out known problems:: 125 126 Cc: <stable@vger.kernel.org> # see patch description, needs adjustments for <= 6.3 127 128.. _option_2: 129 130Option 2 131******** 132 133If the patch already has been merged to mainline, send an email to 134stable@vger.kernel.org containing the subject of the patch, the commit ID, 135why you think it should be applied, and what kernel versions you wish it to 136be applied to. 137 138.. _option_3: 139 140Option 3 141******** 142 143Send the patch, after verifying that it follows the above rules, to 144stable@vger.kernel.org and mention the kernel versions you wish it to be applied 145to. When doing so, you must note the upstream commit ID in the changelog of your 146submission with a separate line above the commit text, like this:: 147 148 commit <sha1> upstream. 149 150Or alternatively:: 151 152 [ Upstream commit <sha1> ] 153 154If the submitted patch deviates from the original upstream patch (for example 155because it had to be adjusted for the older API), this must be very clearly 156documented and justified in the patch description. 157 158 159Following the submission 160------------------------ 161 162The sender will receive an ACK when the patch has been accepted into the 163queue, or a NAK if the patch is rejected. This response might take a few 164days, according to the schedules of the stable team members. 165 166If accepted, the patch will be added to the -stable queue, for review by other 167developers and by the relevant subsystem maintainer. 168 169 170Review cycle 171------------ 172 173- When the -stable maintainers decide for a review cycle, the patches will be 174 sent to the review committee, and the maintainer of the affected area of 175 the patch (unless the submitter is the maintainer of the area) and CC: to 176 the linux-kernel mailing list. 177- The review committee has 48 hours in which to ACK or NAK the patch. 178- If the patch is rejected by a member of the committee, or linux-kernel 179 members object to the patch, bringing up issues that the maintainers and 180 members did not realize, the patch will be dropped from the queue. 181- The ACKed patches will be posted again as part of release candidate (-rc) 182 to be tested by developers and testers. 183- Usually only one -rc release is made, however if there are any outstanding 184 issues, some patches may be modified or dropped or additional patches may 185 be queued. Additional -rc releases are then released and tested until no 186 issues are found. 187- Responding to the -rc releases can be done on the mailing list by sending 188 a "Tested-by:" email with any testing information desired. The "Tested-by:" 189 tags will be collected and added to the release commit. 190- At the end of the review cycle, the new -stable release will be released 191 containing all the queued and tested patches. 192- Security patches will be accepted into the -stable tree directly from the 193 security kernel team, and not go through the normal review cycle. 194 Contact the kernel security team for more details on this procedure. 195 196 197Trees 198----- 199 200- The queues of patches, for both completed versions and in progress 201 versions can be found at: 202 203 https://git.kernel.org/pub/scm/linux/kernel/git/stable/stable-queue.git 204 205- The finalized and tagged releases of all stable kernels can be found 206 in separate branches per version at: 207 208 https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git 209 210- The release candidate of all stable kernel versions can be found at: 211 212 https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable-rc.git/ 213 214 .. warning:: 215 The -stable-rc tree is a snapshot in time of the stable-queue tree and 216 will change frequently, hence will be rebased often. It should only be 217 used for testing purposes (e.g. to be consumed by CI systems). 218 219 220Review committee 221---------------- 222 223- This is made up of a number of kernel developers who have volunteered for 224 this task, and a few that haven't. 225