[GIT PULL] RCU changes for v6.9

[Boqun Feng <boqun.feng@gmail.com>]

Hi Linus,

Please pull this for the RCU changes of v6.9:

The following changes since commit 41bccc98fb7931d63d03f326a746ac4d429c1dd3:

  Linux 6.8-rc2 (2024-01-28 17:01:12 -0800)

are available in the Git repository at:

  git://git.kernel.org/pub/scm/linux/kernel/git/boqun/linux.git tags/rcu.next.v6.9

for you to fetch changes up to 3add00be5fe5810d7aa5ec3af8b6a245ef33144b:

  Merge branches 'rcu-doc.2024.02.14a', 'rcu-nocb.2024.02.14a', 'rcu-exp.2024.02.14a', 'rcu-tasks.2024.02.26a' and 'rcu-misc.2024.02.14a' into rcu.2024.02.26a (2024-02-26 17:37:25 -0800)


Two merge conflicts were detected by linux-next:

* https://lore.kernel.org/lkml/20240226135745.12ac854d@canb.auug.org.au/
* https://lore.kernel.org/lkml/20240227125522.2bdbe6be@canb.auug.org.au/

These conflict resolutions from linux-next look good to me, plus I made
my own resolutions at branch merge/rcu.2024.02.27a for your reference.


Some highlights of the changes:

* Eliminates deadlocks involving do_exit() and RCU tasks, by Paul:
  Instead of SRCU read side critical sections, now a percpu list is used
  in do_exit() for scaning yet-to-exit tasks.

* Fixes a deadlock due to the dependency between workqueue and RCU
  expedited grace period, reported by Anna-Maria Behnsen and Thomas
  Gleixner and fixed by Frederic: Now RCU expedited always uses its own
  kthread worker instead of a workqueue.


Regards,
Boqun


----------------------------------------------------------------
RCU pull request for v6.9

This pull request contains the following branches:

rcu-doc.2024.02.14a: Documentation updates.

rcu-nocb.2024.02.14a: RCU NOCB updates, code cleanups, unnecessary
        barrier removals and minor bug fixes.

rcu-exp.2024.02.14a: RCU exp, fixing a circular dependency between
        workqueue and RCU expedited callback handling.

rcu-tasks.2024.02.26a: RCU tasks, avoiding deadlocks in do_exit() when
        calling synchronize_rcu_task() with a mutex hold, maintaining
	real-time response in rcu_tasks_postscan() and a minor
        fix for tasks trace quiescence check.

rcu-misc.2024.02.14a: Misc updates, comments and readibility
	improvement, boot time parameter for lazy RCU and rcutorture
	improvement.

----------------------------------------------------------------
Boqun Feng (1):
      Merge branches 'rcu-doc.2024.02.14a', 'rcu-nocb.2024.02.14a', 'rcu-exp.2024.02.14a', 'rcu-tasks.2024.02.26a' and 'rcu-misc.2024.02.14a' into rcu.2024.02.26a

Frederic Weisbecker (13):
      rcu/nocb: Remove needless LOAD-ACQUIRE
      rcu/nocb: Remove needless full barrier after callback advancing
      rcu/nocb: Make IRQs disablement symmetric
      rcu/nocb: Re-arrange call_rcu() NOCB specific code
      rcu/exp: Remove full barrier upon main thread wakeup
      rcu/exp: Fix RCU expedited parallel grace period kworker allocation failure recovery
      rcu/exp: Handle RCU expedited grace period kworker allocation failure
      rcu: s/boost_kthread_mutex/kthread_mutex
      rcu/exp: Move expedited kthread worker creation functions above rcutree_prepare_cpu()
      rcu/exp: Make parallel exp gp kworker per rcu node
      rcu/exp: Handle parallel exp gp kworkers affinity
      rcu/exp: Remove rcu_par_gp_wq
      rcu: Rename jiffies_till_flush to jiffies_lazy_flush

Joel Fernandes (Google) (1):
      srcu: Improve comments about acceleration leak

Onkarnath (1):
      rcu/sync: remove un-used rcu_sync_enter_start function

Paul E. McKenney (16):
      doc: Spinlocks are implied RCU readers
      doc: Make whatisRCU.rst note that spinlocks are RCU readers
      doc: Make checklist.rst note that spinlocks are implied RCU readers
      doc: Add CONFIG_RCU_STRICT_GRACE_PERIOD to checklist.rst
      doc: Add EARLY flag to early-parsed kernel boot parameters
      context_tracking: Fix kerneldoc headers for __ct_user_{enter,exit}()
      doc: Clarify use of slab constructors and SLAB_TYPESAFE_BY_RCU
      doc: Update checklist.rst discussion of callback execution
      rcutorture: Suppress rtort_pipe_count warnings until after stalls
      rcu-tasks: Repair RCU Tasks Trace quiescence check
      rcu-tasks: Add data to eliminate RCU-tasks/do_exit() deadlocks
      rcu-tasks: Initialize callback lists at rcu_init() time
      rcu-tasks: Initialize data to eliminate RCU-tasks/do_exit() deadlocks
      rcu-tasks: Maintain lists to eliminate RCU-tasks/do_exit() deadlocks
      rcu-tasks: Eliminate deadlocks involving do_exit() and RCU tasks
      rcu-tasks: Maintain real-time response in rcu_tasks_postscan()

Qais Yousef (1):
      rcu: Provide a boot time parameter to control lazy RCU

Zqiang (2):
      rcu/nocb: Fix WARN_ON_ONCE() in the rcu_nocb_bypass_lock()
      rcu/nocb: Check rdp_gp->nocb_timer in __call_rcu_nocb_wake()

 Documentation/RCU/checklist.rst                 |  32 +-
 Documentation/RCU/rcu_dereference.rst           |   5 +-
 Documentation/RCU/whatisRCU.rst                 |  19 +-
 Documentation/admin-guide/kernel-parameters.rst |   1 +
 Documentation/admin-guide/kernel-parameters.txt | 489 ++++++++++++------------
 include/linux/rcu_sync.h                        |   1 -
 include/linux/rcupdate.h                        |   4 +-
 include/linux/sched.h                           |   2 +
 init/init_task.c                                |   1 +
 kernel/context_tracking.c                       |   4 +
 kernel/fork.c                                   |   1 +
 kernel/rcu/Kconfig                              |  13 +
 kernel/rcu/rcu.h                                |  19 +-
 kernel/rcu/rcuscale.c                           |   6 +-
 kernel/rcu/rcutorture.c                         |  13 +-
 kernel/rcu/srcutree.c                           |  24 +-
 kernel/rcu/sync.c                               |  16 -
 kernel/rcu/tasks.h                              | 135 +++++--
 kernel/rcu/tiny.c                               |   1 +
 kernel/rcu/tree.c                               | 237 ++++++++----
 kernel/rcu/tree.h                               |  20 +-
 kernel/rcu/tree_exp.h                           |  83 +---
 kernel/rcu/tree_nocb.h                          |  69 ++--
 kernel/rcu/tree_plugin.h                        |  52 +--
 24 files changed, 687 insertions(+), 560 deletions(-)