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 Linus' tree (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 45 1. Add a 'stable tag' to the description of a patch you then submit for 46 mainline inclusion. 47 2. Ask the stable team to pick up a patch already mainlined. 48 3. 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 the tag 72 73.. code-block:: none 74 75 Cc: stable@vger.kernel.org 76 77in the sign-off area. Once the patch is mainlined it will be applied to the 78stable tree without anything else needing to be done by the author or 79subsystem maintainer. 80 81To sent additional instructions to the stable team, use a shell-style inline 82comment: 83 84 * To specify any additional patch prerequisites for cherry picking use the 85 following format in the sign-off area: 86 87 .. code-block:: none 88 89 Cc: <stable@vger.kernel.org> # 3.3.x: a1f84a3: sched: Check for idle 90 Cc: <stable@vger.kernel.org> # 3.3.x: 1b9508f: sched: Rate-limit newidle 91 Cc: <stable@vger.kernel.org> # 3.3.x: fd21073: sched: Fix affinity logic 92 Cc: <stable@vger.kernel.org> # 3.3.x 93 Signed-off-by: Ingo Molnar <mingo@elte.hu> 94 95 The tag sequence has the meaning of: 96 97 .. code-block:: none 98 99 git cherry-pick a1f84a3 100 git cherry-pick 1b9508f 101 git cherry-pick fd21073 102 git cherry-pick <this commit> 103 104 Note that for a patch series, you do not have to list as prerequisites the 105 patches present in the series itself. For example, if you have the following 106 patch series: 107 108 .. code-block:: none 109 110 patch1 111 patch2 112 113 where patch2 depends on patch1, you do not have to list patch1 as 114 prerequisite of patch2 if you have already marked patch1 for stable 115 inclusion. 116 117 * For patches that may have kernel version prerequisites specify them using 118 the following format in the sign-off area: 119 120 .. code-block:: none 121 122 Cc: <stable@vger.kernel.org> # 3.3.x 123 124 The tag has the meaning of: 125 126 .. code-block:: none 127 128 git cherry-pick <this commit> 129 130 For each "-stable" tree starting with the specified version. 131 132 Note, such tagging is unnecessary if the stable team can derive the 133 appropriate versions from Fixes: tags. 134 135 * To delay pick up of patches, use the following format: 136 137 .. code-block:: none 138 139 Cc: <stable@vger.kernel.org> # after 4 weeks in mainline 140 141 * For any other requests, just add a note to the stable tag. This for example 142 can be used to point out known problems: 143 144 .. code-block:: none 145 146 Cc: <stable@vger.kernel.org> # see patch description, needs adjustments for <= 6.3 147 148.. _option_2: 149 150Option 2 151******** 152 153If the patch already has been merged to mainline, send an email to 154stable@vger.kernel.org containing the subject of the patch, the commit ID, 155why you think it should be applied, and what kernel versions you wish it to 156be applied to. 157 158.. _option_3: 159 160Option 3 161******** 162 163Send the patch, after verifying that it follows the above rules, to 164stable@vger.kernel.org and mention the kernel versions you wish it to be applied 165to. When doing so, you must note the upstream commit ID in the changelog of your 166submission with a separate line above the commit text, like this: 167 168.. code-block:: none 169 170 commit <sha1> upstream. 171 172or alternatively: 173 174.. code-block:: none 175 176 [ Upstream commit <sha1> ] 177 178If the submitted patch deviates from the original upstream patch (for example 179because it had to be adjusted for the older API), this must be very clearly 180documented and justified in the patch description. 181 182 183Following the submission 184------------------------ 185 186The sender will receive an ACK when the patch has been accepted into the 187queue, or a NAK if the patch is rejected. This response might take a few 188days, according to the schedules of the stable team members. 189 190If accepted, the patch will be added to the -stable queue, for review by other 191developers and by the relevant subsystem maintainer. 192 193 194Review cycle 195------------ 196 197 - When the -stable maintainers decide for a review cycle, the patches will be 198 sent to the review committee, and the maintainer of the affected area of 199 the patch (unless the submitter is the maintainer of the area) and CC: to 200 the linux-kernel mailing list. 201 - The review committee has 48 hours in which to ACK or NAK the patch. 202 - If the patch is rejected by a member of the committee, or linux-kernel 203 members object to the patch, bringing up issues that the maintainers and 204 members did not realize, the patch will be dropped from the queue. 205 - The ACKed patches will be posted again as part of release candidate (-rc) 206 to be tested by developers and testers. 207 - Usually only one -rc release is made, however if there are any outstanding 208 issues, some patches may be modified or dropped or additional patches may 209 be queued. Additional -rc releases are then released and tested until no 210 issues are found. 211 - Responding to the -rc releases can be done on the mailing list by sending 212 a "Tested-by:" email with any testing information desired. The "Tested-by:" 213 tags will be collected and added to the release commit. 214 - At the end of the review cycle, the new -stable release will be released 215 containing all the queued and tested patches. 216 - Security patches will be accepted into the -stable tree directly from the 217 security kernel team, and not go through the normal review cycle. 218 Contact the kernel security team for more details on this procedure. 219 220 221Trees 222----- 223 224 - The queues of patches, for both completed versions and in progress 225 versions can be found at: 226 227 https://git.kernel.org/pub/scm/linux/kernel/git/stable/stable-queue.git 228 229 - The finalized and tagged releases of all stable kernels can be found 230 in separate branches per version at: 231 232 https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git 233 234 - The release candidate of all stable kernel versions can be found at: 235 236 https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable-rc.git/ 237 238 .. warning:: 239 The -stable-rc tree is a snapshot in time of the stable-queue tree and 240 will change frequently, hence will be rebased often. It should only be 241 used for testing purposes (e.g. to be consumed by CI systems). 242 243 244Review committee 245---------------- 246 247 - This is made up of a number of kernel developers who have volunteered for 248 this task, and a few that haven't. 249