00-readme.txt: add lkml/rt-list post text
diff --git a/00-readme.txt b/00-readme.txt
new file mode 100644
index 0000000..958da96
--- /dev/null
+++ b/00-readme.txt
@@ -0,0 +1,271 @@
+From: Paul Gortmaker <paul.gortmaker@windriver.com>
+Date: Wed Dec 28 21:53:20 EST 2016
+Subject: 4.9-rt: uprev notes, incremental uprev, adding bisection ability
+
+TL;DR: incremental -rt patch uprev from 4.8-rt to the new 4.9-rt
+covering 175 touch down points on mainline merges & tags by Linus;
+useful for rt developers and bugfixers to research and bisect with.
+
+If you just want the bisect points generated on your machine, then:
+
+ mkdir rt-test
+ cd rt-test
+ # clone mainline or clone from a local copy with >=4.9 tags in it.
+ git clone /path/to/my/existing/mainline/linux linux-rt-bisect
+ git clone git://git.kernel.org/pub/scm/linux/kernel/git/paulg/4.9-rt-patches.git
+
+ cd linux-rt-bisect
+ ../4.9-rt-patches/scripts/create-branches.sh
+
+ ------ end TL;DR ------ 8< -------- end TL;DR ------
+
+Now that 4.9-rt1 is out there, we can do what was done[1] for 4.8-rt
+and create an incremental uprev to get an idea of what mainline
+merges impacted the patches in the preempt-rt series to bring more
+clarity into what conflicts arose:
+
+https://git.kernel.org/cgit/linux/kernel/git/paulg/4.9-rt-patches.git
+
+The usual suspects have impact to rt: scheduler changes in tip, x86
+changes in tip, CPU hotplug (this time) in tip, large "patch bombs"
+from akpm, and even somewhat net-next content from davem.
+
+
+Points of interest:
+-------------------
+
+lglocks: -removed from mainline, so we get to drop the -rt
+ extensions to that support. However -rt specific users need
+ to be converted to something else; e.g. see the new /* XXX */
+ in cpu_stopper_thread, where an lglock used to be used.
+
+thread_info: -x86 dabbled with THREAD_INFO_IN_TASK then disabled it
+ again before rc2. With the benefit of hindsight, we can
+ take the disable commit and temporarily backport it so that
+ we essentially never have it in task, which means saving a
+ whole lot of mess in the preempt_lazy patches for nothing.
+ (see Add / Delete patch marked with "*" at end of this post)
+
+new/removed patches: -there were six new patches added and 16
+ patches removed. A couple of the "removed" patches were not
+ really removed, but instead squished as fixups into another
+ related patch.
+
+Further details can be found at the end of this post, where the merges
+and the patches they impacted are listed. A majority of the changes
+are just basic context refresh -- updating the patch to match the
+changes in the surrounding code without changing what the patch
+really is doing.
+
+One can also inspect the commit logs in the above git repo since the
+baseline v4.8.15-rt10 commit.
+
+Sanity boot testing was done on RT_FULL for x86-64 along the way on
+selected "high risk" merges, like those listed above. The final
+result is that the patches at the end of the incremental uprev here
+match the patches of v4.9-rt1 just recently released.
+
+
+Bisecting to find new issues in 4.9-rt:
+---------------------------------------
+
+The other benefit of this is that it allows one to quasi-bisect the
+preempt-rt (treated as a whole) across the some 15,000 patches that
+make up the new 4.9 content. This allowed me to solve several bugs
+in 4.8-rt that I would have had an extrememly hard time to solve in
+any other way. I won't repeat every detail of how this process
+makes sense, since I've documented that in the past[2].
+
+The 15,000 odd commits of 4.9 made it to mainline via ~165 merges
+from Linus between 4.8 and v4.9-rc1 (the merge window) where we can
+apply the -rt patches and see which feature merges cause disruption
+to the -rt patches.
+
+Not every feature/maintainer-merge causes issues with the -rt patch
+queue: I had to create just over 50 commits to the v4.8.15-rt10
+baseline in order to have about 30 possible series of patches to
+cover all those 165 merges from 4.8 to mainline 4.9-rc1.
+
+Since Linux development has a lot less commits in rc2, rc3, ...
+rc8, and final 4.9 -- those tags represent the remaining bisection
+points that can be created and used from this repo. I didn't do
+per-merge patch application testng post-rc1 (just as was done for
+the 4.8-rt incremental uprev earlier) since it would be pointless.
+
+ ---
+
+Quick recap on how to use this repo to do merge level bisect:
+
+1) Full list of feature merges in mainline repo you can test on:
+ git log --oneline --merges --author=Torvalds \
+ --reverse ^v4.8 v4.9-rc1
+
+2) Tags in this 4.9-rt patch repo look like:
+ rt-v4.8-101-g7af8a0f80888
+ rt-v4.8-304-g4b978934a440
+ rt-v4.8-373-g00bcf5cdd6c0
+ rt-v4.8-558-ge606d81d2d95
+ rt-v4.8-627-gaf79ad2b1f33
+ [...]
+ rt-v4.8-12632-ga379f71a30dd
+ rt-v4.8-14088-g6b25e21fa6f2
+ rt-v4.8-15054-g9ffc66941df2
+ rt-v4.9-rc1
+ rt-v4.9-rc2
+ [...]
+ rt-v4.9-rc8
+ rt-v4.9
+
+3) Say you want to test -rt on this merge from #1:
+ "af79ad2b1f33 Merge branch 'sched-core-for-linus' ..."
+ You run "git describe af79ad2b1f33" and get:
+ v4.8-627-gaf79ad2b1f33
+ No problem, you check out the patches tagged in #2 with the
+ matching name. These will apply to that merge as a baseline.
+
+4) Or, you did as in #3 but you have a merge that doesn't have a
+ matching tag in the patch repo released here, like:
+ v4.8-346-gde956b8f45b3
+ The patches you want to use are on tag "rt-v4.8-304-g4b978934a440"
+ since "304" is the highest mainline commit count to your "346"
+ commit count without going over (think "Price is Right".) The
+ "304" will cover Linus merges 304-->372 inclusive. You don't use
+ "373" since that is only for 373-->557 inclusive.
+
+5) Check out your merge commit on mainline repo from #1. Check out
+ your patch tag from #3/#4 in the -rt patch repo. Apply the
+ patches in the series file of the patch repo to mainline just
+ as you would any other series of patches.
+
+Or you can use the script in the repo to automatically generate all
+of the rt bisect points (can take 4h on a reasonably fast machine).
+
+
+Links:
+------
+[1] https://lkml.kernel.org/r/20160906182508.GB9950@windriver.com
+
+[2] https://lwn.net/Articles/431364/
+
+
+Summary of merges that impacted the -rt patch set:
+--------------------------------------------------
+
+[commits since v4.8] A=add M=modify D=delete
+
+[101] 7af8a0f8 Merge tag 'arm64-upstream' of arm64/linux
+ M arch-arm64-Add-lazy-preempt-support.patch
+ M localversion.patch (reset to "rt0")
+
+[304] 4b978934 Merge branch 'core-rcu-for-linus' of tip/tip
+ M patch-to-introduce-rcu-bh-qs-where-safe-from-softirq.patch
+ M rcu-merge-rcu-bh-into-rcu-preempt-for-rt.patch
+
+[373] 00bcf5cd Merge branch 'locking-core-for-linus' of tip/tip
+ D lglocks-rt.patch
+ D lockinglglocks_Use_preempt_enabledisable_nort.patch
+ D stomp-machine-create-lg_global_trylock_relax-primiti.patch
+ D stomp-machine-use-lg_global_trylock_relax-to-dead-wi.patch
+ M stop-machine-raw-lock.patch
+
+[558] e606d81d Merge branch 'ras-core-for-linus' of tip/tip
+ M x86-mce-timer-hrtimer.patch
+ M x86-mce-use-swait-queue-for-mce-wakeups.patch
+
+[627] af79ad2b Merge branch 'sched-core-for-linus' of tip/tip
+ M cpu-rt-rework-cpu-down.patch
+ M workqueue-distangle-from-rq-lock.patch
+ M introduce_migrate_disable_cpu_light.patch
+
+[728] 1a4a2bc4 Merge branch 'x86-asm-for-linus' of tip/tip
+ M x86-preempt-lazy.patch
+* A sched-core-x86-Make-struct-thread_info-arch-specific.patch
+ D dump-stack-don-t-disable-preemption-during-trace.patch
+ M sched-rt-mutex-wakeup.patch
+ M introduce_migrate_disable_cpu_light.patch
+
+[759] a6c4e4cd Merge branch 'x86-platform-for-linus' of tip/tip
+ M x86-UV-raw_spinlock-conversion.patch
+
+[773] 8e4ef638 Merge branch 'x86-vdso-for-linus' of tip/tip
+ M oleg-signal-rt-fix.patch
+
+[869] 999dcbe2 Merge branch 'irq-core-for-linus' of tip/tip
+ M softirq-split-locks.patch
+
+[918] 597f03f9 Merge branch 'smp-hotplug-for-linus' of tip/tip
+ M md-raid5-percpu-handling-rt-aware.patch
+ M softirq-split-timer-softirqs-out-of-ksoftirqd.patch
+ M softirq-split-timer-softirqs-out-of-ksoftirqd.patch
+ M softirq-preempt-fix-3-re.patch
+
+[4177] 687ee0ad Merge davem/net-next
+ M net-fix-iptable-xt-write-recseq-begin-rt-fallout.patch
+ M net-Qdisc-use-a-seqlock-instead-seqcount.patch
+ D skbufhead-raw-lock-free-skbs.patch
+ M skbufhead-raw-lock.patch
+ M mm-workingset-do-not-protect-workingset_shadow_nodes.patch
+
+[8856] 14986a34 Merge branch 'for-linus' of ebiederm/user-namespace
+ D lockdep-Quiet-gcc-about-dangerous-__builtin_return_a.patch
+
+[9031] 95107b30 Merge tag 'trace-v4.9' of rostedt/linux-trace
+ M latency-hist.patch
+
+[10067] 513a4bef Merge branch 'for-4.9/block' of git://git.kernel.dk/linux-block
+ M workqueue-use-locallock.patch
+ D workqueue-use-rcu_readlock-in-put_pwq_unlocked.patch
+ M block-mq-don-t-complete-requests-via-IPI.patch
+ M block-mq-drop-preempt-disable.patch
+
+[11288] b66484cd Merge branch 'akpm' (patches from Andrew)
+ M sched-mmdrop-delayed.patch
+
+[11412] 12e3d3cd Merge branch 'for-4.9/block-irq' of git://git.kernel.dk/linux-block
+ M block-mq-don-t-complete-requests-via-IPI.patch
+
+[11417] 24532f76 Merge branch 'for-4.9/block-smp' of git://git.kernel.dk/linux-block
+ D blk-mq-revert-raw-locks-post-pone-notifier-to-POST_D.patchto-POST_D.patch
+
+[12632] a379f71a Merge branch 'akpm' (patches from Andrew)
+ M dm-make-rt-aware.patch
+ D relay-fix-timer-madness.patch
+ D ipc-msg-Implement-lockless-pipelined-wakeups.patch
+
+[14088] 6b25e21f Merge tag 'drm-for-v4.9' of git://people.freedesktop.org/~airlied/linux
+ M drmi915_Use_local_lockunlock_irq()_in_intel_pipe_update_startend().patch
+
+[15054] 9ffc6694 Merge tag 'gcc-plugins-v4.9-rc1' of kees/linux
+ D mm-page-alloc-use-local-lock-on-target-cpu.patch
+ M rcu-Eliminate-softirq-processing-from-rcutree.patch
+ M random-make-it-work-on-rt.patch
+ M tasklet-rt-prevent-tasklets-from-going-into-infinite-spin-in-rt.patch
+
+[v4.9-rc1] tag v4.9-rc1
+ A arm-include-definition-for-cpumask_t.patch
+ A btrfs-drop-trace_btrfs_all_work_done-from-normal_wor.patch
+ A btrfs-swap-free-and-trace-point-in-run_ordered_work.patch
+ A kernel-sched-move-stack-kprobe-clean-up-to-__put_tas.patch
+ A locking-percpu-rwsem-use-swait-for-the-wating-writer.patch
+ A mm-page-alloc-use-local-lock-on-target-cpu.patch
+ D hwlat-detector-Don-t-ignore-threshold-module-paramet.patch
+ D hwlat-detector-Update-hwlat_detector-to-add-outer-lo.patch
+ D hwlat-detector-Use-thread-instead-of-stop-machine.patch
+ D hwlat-detector-Use-trace_clock_local-if-available.patch
+ D hwlatdetect.patch
+
+[v4.9-rc2] tag v4.9-rc2
+ M cpu-rt-make-hotplug-lock-a-sleeping-spinlock-on-rt.patch
+ M cpu-rt-rework-cpu-down.patch
+ A peterz-percpu-rwsem-rt.patch
+* D sched-core-x86-Make-struct-thread_info-arch-specific.patch
+
+[v4.9-rc3] tag v4.9-rc3
+ M softirq-split-timer-softirqs-out-of-ksoftirqd.patch
+
+[v4.9-rc8] tag v4.9-rc8
+ M mm-workingset-do-not-protect-workingset_shadow_nodes.patch
+
+[v4.9] tag v4.9
+ M localversion.patch (set to "rt1")
+ M rtmutex-futex-prepare-rt.patch
