RCU changes for v6.4

Hello, Linus,

The following changes since commit fe15c26ee26efa11741a7b632e9f23b01aca4cc6:

Linux 6.3-rc1 (2023-03-05 14:52:03 -0800)

are available in the Git repository at:

git://git.kernel.org/pub/scm/linux/kernel/git/jfern/linux.git tags/rcu.6.4.april5.2023.3

for you to fetch changes up to 8ae99857748bece993962dd8d04e096f9e76731f:

Merge branches 'rcu/staging-core', 'rcu/staging-docs' and 'rcu/staging-kfree', remote-tracking branches 'paul/srcu-cf.2023.04.04a', 'fbq/rcu/lockdep.2023.03.27a' and 'fbq/rcu/rcutorture.2023.03.20a' into rcu/staging (2023-04-05 13:50:37 +0000)

Highlights of RCU changes for 6.4 include:

1. Updates and additions to MAINTAINERS files, with Boqun being added to the RCU entry and Zqiang being added as an RCU reviewer. I have also transitioned from reviewer to maintainer; however, Paul will be taking over sending RCU pull-requests for the next merge window.

2. Resolution of hotplug warning in nohz code, achieved by fixing cpu_is_hotpluggable() through interaction with the nohz subsystem. Tick dependency modifications by Zqiang, focusing on fixing usage of the TICK_DEP_BIT_RCU_EXP bitmask.

3. Avoid needless calls to the rcu-lazy shrinker for CONFIG_RCU_LAZY=n kernels, fixed by Zqiang.

4. Improvements to rcu-tasks stall reporting by Neeraj.

5. Initial renaming of k[v]free_rcu() to k[v]free_rcu_mightsleep() for increased robustness, affecting several components like mac802154, drbd, vmw_vmci, tracing, and more. A report [1] by Eric Dumazet showed that the API could be unknowingly used in an atomic context, so we'd rather make sure they know what they're asking for by being explicit:
[1] https://lore.kernel.org/all/[email protected]/

6. Documentation updates, including corrections to spelling, clarifications in comments, and improvements to the srcu_size_state comments.

7. Better srcu_struct cache locality for readers, by adjusting the size of srcu_struct in support of SRCU usage by Christoph Hellwig.

8. Teach lockdep to detect deadlocks between srcu_read_lock() vs synchronize_srcu() contributed by Boqun. Previously lockdep could not detect such deadlocks, now it can.

9. Integration of rcutorture and rcu-related tools, targeted for v6.4 from Boqun's tree, featuring new SRCU deadlock scenarios, test_nmis module parameter, and more.

10. Miscellaneous changes, various code cleanups and comment improvements.

Thank you for considering these RCU updates for the 6.4 release.

----------------------------------------------------------------
Bhaskar Chowdhury (1):
tools: rcu: Add usage function and check for argument

Boqun Feng (5):
locking/lockdep: Introduce lock_sync()
rcu: Annotate SRCU's update-side lockdep dependencies
locking: Reduce the number of locks in ww_mutex stress tests locking/lockdep: Improve the deadlock scenario print for sync and read lock
MAINTAINERS: Add Boqun to RCU entry

Frederic Weisbecker (1):
rcu: Further comment and explain the state space of GP sequences

Joel Fernandes (Google) (7):
srcu: Clarify comments on memory barrier "E"
MAINTAINERS: Change Joel Fernandes from R: to M:
MAINTAINERS: Add Zqiang as a RCU reviewer
tick/nohz: Fix cpu_is_hotpluggable() by checking with nohz subsystem
mac802154: Rename kfree_rcu() to kvfree_rcu_mightsleep()
checkpatch: Error out if deprecated RCU API used
Merge branches 'rcu/staging-core', 'rcu/staging-docs' and 'rcu/staging-kfree', remote-tracking branches 'paul/srcu-cf.2023.04.04a', 'fbq/rcu/lockdep.2023.03.27a' and 'fbq/rcu/rcutorture.2023.03.20a' into rcu/staging

Neeraj Upadhyay (1):
rcu-tasks: Report stalls during synchronize_srcu() in rcu_tasks_postscan()

Paul E. McKenney (35):
rcutorture: Add test_nmis module parameter
rcutorture: Set CONFIG_BOOTPARAM_HOTPLUG_CPU0 to offline CPU 0
rcutorture: Make scenario TREE04 enable lazy call_rcu()
torture: Permit kvm-again.sh --duration to default to previous run
torture: Enable clocksource watchdog with "tsc=watchdog"
rcuscale: Move shutdown from wait_event() to wait_event_idle()
refscale: Move shutdown from wait_event() to wait_event_idle()
rcutorture: Add SRCU deadlock scenarios
rcutorture: Add RCU Tasks Trace and SRCU deadlock scenarios
rcutorture: Add srcu_lockdep.sh
rcu-tasks: Fix warning for unused tasks_rcu_exit_srcu
srcu: Add whitespace to __SRCU_STRUCT_INIT() & __DEFINE_SRCU()
srcu: Use static init for statically allocated in-module srcu_struct
srcu: Begin offloading srcu_struct fields to srcu_update
srcu: Move ->level from srcu_struct to srcu_usage
srcu: Move ->srcu_size_state from srcu_struct to srcu_usage
srcu: Move ->srcu_cb_mutex from srcu_struct to srcu_usage
srcu: Move ->lock initialization after srcu_usage allocation
srcu: Move ->lock from srcu_struct to srcu_usage
srcu: Move ->srcu_gp_mutex from srcu_struct to srcu_usage
srcu: Move grace-period fields from srcu_struct to srcu_usage
srcu: Move heuristics fields from srcu_struct to srcu_usage
srcu: Move ->sda_is_static from srcu_struct to srcu_usage
srcu: Move srcu_barrier() fields from srcu_struct to srcu_usage
srcu: Move work-scheduling fields from srcu_struct to srcu_usage
srcu: Check for readers at module-exit time
srcu: Fix long lines in srcu_get_delay()
srcu: Fix long lines in cleanup_srcu_struct()
srcu: Fix long lines in srcu_gp_end()
srcu: Fix long lines in srcu_funnel_gp_start()
rcu: Add comment to rcu_do_batch() identifying rcuoc code path
rcu: Remove CONFIG_SRCU
mm: Remove "select SRCU"
kvm: Remove "select SRCU"
arch/x86: Remove "select SRCU"

Pingfan Liu (1):
srcu: Add comments for srcu_size_state

Qiuxu Zhuo (1):
Documentation/RCU: s/not/note/ in checklist.rst

Randy Dunlap (1):
Documentation: RCU: Correct spelling

Uladzislau Rezki (Sony) (9):
doc: Update whatisRCU.rst
drbd: Rename kvfree_rcu() to kvfree_rcu_mightsleep()
misc: vmw_vmci: Rename kvfree_rcu() to kvfree_rcu_mightsleep()
tracing: Rename kvfree_rcu() to kvfree_rcu_mightsleep() lib/test_vmalloc.c: Rename kvfree_rcu() to kvfree_rcu_mightsleep() net/sysctl: Rename kvfree_rcu() to kvfree_rcu_mightsleep() net/mlx5: Rename kfree_rcu() to kfree_rcu_mightsleep() ext4/super: Rename kfree_rcu() to kfree_rcu_mightsleep()
rcuscale: Rename kfree_rcu() to kfree_rcu_mightsleep()

Xu Panda (1):
rcu/trace: use strscpy() to instead of strncpy()

Yue Hu (1):
rcutorture: Eliminate variable n_rcu_torture_boost_rterror

Zheng Yejian (1):
rcu: Avoid stack overflow due to __rcu_irq_enter_check_tick() being kprobe-ed

Zqiang (7):
rcutorture: Create nocb kthreads only when testing rcu in CONFIG_RCU_NOCB_CPU=y kernels
rcu: Fix set/clear TICK_DEP_BIT_RCU_EXP bitmask race
rcu: Fix missing TICK_DEP_MASK_RCU_EXP dependency check
rcu: Register rcu-lazy shrinker only for CONFIG_RCU_LAZY=y kernels
rcu: Remove never-set needwake assignment from rcu_report_qs_rdp()
rcu: Permit start_poll_synchronize_rcu_expedited() to be invoked early
rcu: Protect rcu_print_task_exp_stall() ->exp_tasks access

 .../Expedited-Grace-Periods.rst                    |   6 +-
 .../Memory-Ordering/Tree-RCU-Memory-Ordering.rst   |   2 +-
 Documentation/RCU/RTFP.txt                         |  10 +-
 Documentation/RCU/UP.rst                           |   4 +-
 Documentation/RCU/checklist.rst                    |   2 +-
 Documentation/RCU/lockdep.rst                      |   2 +-
 Documentation/RCU/torture.rst                      |   4 +-
 Documentation/RCU/whatisRCU.rst                    |   6 +-
 MAINTAINERS                                        |   4 +-
 arch/arm64/kvm/Kconfig                             |   1 -
 arch/mips/kvm/Kconfig                              |   1 -
 arch/powerpc/kvm/Kconfig                           |   1 -
 arch/riscv/kvm/Kconfig                             |   1 -
 arch/s390/kvm/Kconfig                              |   1 -
 arch/x86/Kconfig                                   |   2 -
 arch/x86/kvm/Kconfig                               |   1 -
 drivers/base/cpu.c                                 |   3 +-
 drivers/block/drbd/drbd_nl.c                       |   6 +-
 drivers/block/drbd/drbd_receiver.c                 |   4 +-
 drivers/block/drbd/drbd_state.c                    |   2 +-
 drivers/misc/vmw_vmci/vmci_context.c               |   2 +-
 drivers/misc/vmw_vmci/vmci_event.c                 |   2 +-
 .../ethernet/mellanox/mlx5/core/en/tc/int_port.c   |   2 +-
 .../ethernet/mellanox/mlx5/core/en_accel/macsec.c  |   4 +-
 fs/ext4/super.c                                    |   2 +-
 include/linux/lockdep.h                            |   8 +-
 include/linux/notifier.h                           |   5 +-
 include/linux/srcu.h                               |  34 +-
 include/linux/srcutiny.h                           |   6 +-
 include/linux/srcutree.h                           |  94 +++--
 include/linux/tick.h                               |   2 +
 include/trace/events/rcu.h                         |   4 +-
 include/trace/events/timer.h                       |   3 +-
 kernel/locking/lockdep.c                           |  64 ++-
 kernel/locking/test-ww_mutex.c                     |   2 +-
 kernel/rcu/Kconfig                                 |   3 -
 kernel/rcu/rcu.h                                   |  43 +-
 kernel/rcu/rcuscale.c                              |   9 +-
 kernel/rcu/rcutorture.c                            | 234 ++++++++++-
 kernel/rcu/refscale.c                              |   2 +-
 kernel/rcu/srcutiny.c                              |   2 +
 kernel/rcu/srcutree.c                              | 438 ++++++++++++---------
 kernel/rcu/tasks.h                                 |  33 ++
 kernel/rcu/tree.c                                  |  18 +-
 kernel/rcu/tree_exp.h                              |  16 +-
 kernel/rcu/tree_nocb.h                             |   4 +
 kernel/time/tick-sched.c                           |  16 +-
 kernel/trace/trace_osnoise.c                       |   2 +-
 kernel/trace/trace_probe.c                         |   2 +-
 lib/test_vmalloc.c                                 |   2 +-
 mm/Kconfig                                         |   1 -
 net/core/sysctl_net_core.c                         |   4 +-
 net/mac802154/scan.c                               |   4 +-
 scripts/checkpatch.pl                              |   9 +
 tools/rcu/extract-stall.sh                         |  26 +-
 .../testing/selftests/rcutorture/bin/kvm-again.sh  |   2 +-
 .../selftests/rcutorture/bin/srcu_lockdep.sh       |  78 ++++
 tools/testing/selftests/rcutorture/bin/torture.sh  |   6 +-
 .../selftests/rcutorture/configs/rcu/TREE01        |   1 +
 .../selftests/rcutorture/configs/rcu/TREE04        |   1 +
 .../selftests/rcutorture/doc/TREE_RCU-kconfig.txt  |   4 -
 61 files changed, 915 insertions(+), 342 deletions(-)
 mode change 100644 => 100755 tools/rcu/extract-stall.sh
 create mode 100755 tools/testing/selftests/rcutorture/bin/srcu_lockdep.sh