Re: [GIT PULL rcu/next] RCU commits for 4.19

[Ingo Molnar <mingo@kernel.org>]

* Paul E. McKenney <paulmck@linux.vnet.ibm.com> wrote:

> Hello, Ingo!
> 
> This pull request contains the following changes:
> 
> 1.	An optimization and a fix for RCU expedited grace periods, with
> 	the fix being from Boqun Feng.
> 
> 	http://lkml.kernel.org/r/20180625224308.GA10064@linux.vnet.ibm.com
> 
> 2.	Miscellaneous fixes, including a lockdep-annotation fix from
> 	Boqun Feng.
> 
> 	http://lkml.kernel.org/r/20180625230410.GA13250@linux.vnet.ibm.com
> 
> 3.	SRCU updates.
> 
> 	http://lkml.kernel.org/r/20180625224734.GA10860@linux.vnet.ibm.com
> 
> 4.	Updates to rcutorture and associated scripting.
> 
> 	http://lkml.kernel.org/r/20180625225735.GA11793@linux.vnet.ibm.com
> 
> 5.	Introduce grace-period sequence numbers to the RCU-bh, RCU-preempt,
> 	and RCU-sched flavors, replacing the old ->gpnum and ->completed
> 	pair of fields.  This change allows lockless code to obtain the
> 	complete grace-period state with a single READ_ONCE(), which is
> 	needed to maintain tolerable lock contention during the upcoming
> 	consolidation of the three RCU flavors.  Note that grace-period
> 	sequence numbers are already used by rcu_barrier(), expedited
> 	RCU grace periods, and SRCU, and are thus already heavily used
> 	and well-tested.  Joel Fernandes contributed a number of excellent
> 	fixes and improvements.
> 
> 	http://lkml.kernel.org/r/20180626000841.GA15696@linux.vnet.ibm.com
> 
> 6.	Clean up some grace-period-reporting loose ends, including
> 	improving the handling of quiescent states from offline CPUs
> 	and fixing some false-positive WARN_ON_ONCE() invocations.
> 	(Strictly speaking, the WARN_ON_ONCE() invocations were quite
> 	correct, but their invariants were (harmlessly) violated by the
> 	earlier sloppy handling of quiescent states from offline CPUs.)
> 	In addition, improve grace-period forward-progress guarantees so
> 	as to allow removal of fail-safe checks that required otherwise
> 	needless lock acquisitions.  Finally, add more diagnostics to
> 	help debug the upcoming consolidation of the RCU-bh, RCU-preempt,
> 	and RCU-sched flavors.
> 
> 	http://lkml.kernel.org/r/20180626002052.GA24146@linux.vnet.ibm.com
> 
> 7.	Additional miscellaneous fixes, including those contributed by
> 	Byungchul Park, Mauro Carvalho Chehab, Joe Perches, Joel Fernandes,
> 	Steven Rostedt, Andrea Parri, and Neil Brown.
> 
> 	http://lkml.kernel.org/r/20180626003448.GA26209@linux.vnet.ibm.com
> 
> 8.	Additional torture-test changes, including several contributed by
> 	Arnd Bergmann and Joel Fernandes.
> 
> 	http://lkml.kernel.org/r/20180626005205.GA28179@linux.vnet.ibm.com
> 
> The layout of this pull request is unusual due to the large footprint
> of the commits in #5 and #6.  Therefore #1-#4 are branches on top of
> v4.18-rc1, #5 and #6 are stacked on top of each other based off of the
> merge point for #1-#4, and #7 and #8 are branches on top of #6.
> 
> Although I merged this series with v4.18-rc4 without conflicts and tested
> the results, Stephen Rothwell has reported a couple of conflicts with
> this series in the course of his -next integration-testing efforts and
> has provided the following resolutions:
> 
> http://lkml.kernel.org/r/20180514134636.61831bcc@canb.auug.org.au
> http://lkml.kernel.org/r/20180622122717.5f475829@canb.auug.org.au
> 
> Both of these resolutions look good to me.
> 
> This pull request increases the size of RCU by not quite 500 lines.
> Of this, about 200 is due to adding test code to rcutorture in
> order to adequately test the consolidated RCU-bh, RCU-preempt, and
> RCU-sched flavors.  The purpose of adding this test code early is to
> test it against RCU-sched, which happens to already support compound RCU
> read-side critical sections via rcu_read_lock_sched(), preempt_disable(),
> local_bh_disable(), and local_irq_save().  The remainder are primarily
> due to the addition of diagnostics and the fixing of quiescent-state and
> grace-period reporting.  This size increase is temporary: The overall
> effect of this set of cleanups, the consolidation of the three RCU
> flavors, and additional cleanups will be to -decrease- RCU's line count
> by a couple of hundred lines.
> 
> All of these changes have been subjected to 0day Test Robot and -next
> testing, and are available in the git repository at:
> 
>   git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git for-mingo
> 
> for you to fetch changes up to 18952651dae8efcc6d565c97f8fe5629b399cb3e:
> 
>   Merge branches 'fixes1.2018.07.12b' and 'torture1.2018.07.12b' into HEAD (2018-07-12 15:42:41 -0700)
> 
> ----------------------------------------------------------------
> Andrea Parri (1):
>       doc: Update synchronize_rcu() definition in whatisRCU.txt
> 
> Arnd Bergmann (1):
>       rcutorture: Use monotonic timestamp for stall detection
> 
> Boqun Feng (2):
>       rcu: Use the proper lockdep annotation in dump_blkd_tasks()
>       rcu: Make expedited GPs handle CPU 0 being offline
> 
> Byungchul Park (2):
>       rcu: Improve rcu_note_voluntary_context_switch() reporting
>       rcu: Check the range of jiffies_till_{first,next}_fqs when setting them
> 
> Joe Perches (1):
>       rcu: Use pr_fmt to prefix "rcu: " to logging output
> 
> Joel Fernandes (1):
>       rcu: Rename the grace-period-request variables and parameters
> 
> Joel Fernandes (Google) (10):
>       rcu: Produce last "CleanupMore" trace only if late-breaking request
>       rcu: Fix cpustart tracepoint gp_seq number
>       rcu: Use better variable names in funnel locking loop
>       rcu: Identify grace period is in progress as we advance up the tree
>       rcu: Add comment documenting how rcu_seq_snap works
>       rcu: Assign higher prio to RCU threads if rcutorture is built-in
>       rcutorture: Disable RT throttling for boost tests
>       rcutorture: Make boost test more robust
>       rcutorture: Add support to detect if boost kthread prio is too low
>       rcutorture: Fix rcu_barrier successes counter
> 
> Mauro Carvalho Chehab (1):
>       rcu: rcupdate.h: Get rid of Sphinx warnings at rcu_pointer_handoff()
> 
> NeilBrown (1):
>       rculist: Improve documentation for list_for_each_entry_from_rcu()
> 
> Paul E. McKenney (98):
>       rcu: Make expedited grace period use direct call on last leaf
>       srcu: Fix typos in __call_srcu() header comment
>       srcu: Document that srcu_funnel_gp_start() implies srcu_funnel_exp_start()
>       srcu: Add address of first callback to rcutorture output
>       srcu: Introduce srcu_read_{un,}lock_notrace()
>       torture: Use a single build directory for torture scenarios
>       rcutorture: Remove obsolete TREE08-T.boot file
>       rcutorture: Make kvm-find-errors.sh find close calls
>       torture: Make online/offline messages appear only for verbose=2
>       torture: Keep old-school dmesg format
>       rcu: Add debugging info to assertion
>       rcu: Exclude near-simultaneous RCU CPU stall warnings
>       rcu: Diagnostics for grace-period startup hangs
>       rcu: Make rcu_gp_cleanup() write only once to ->gp_flags
>       Merge branches 'expedited.2018.07.12a', 'fixes.2018.07.12a', 'srcu.2018.06.25b' and 'torture.2018.06.25b' into HEAD
>       rcu: Introduce grace-period sequence numbers
>       rcu: Move rcu_gp_slow() to ->gp_seq
>       rcu: Make rcutorture's batches-completed API use ->gp_seq
>       rcu: Convert rcu_check_gp_kthread_starvation() to GP sequence number
>       rcu: Make quiescent-state reporting use ->gp_seq
>       rcu: Convert conditional grace-period primitives to ->gp_seq
>       rcu: Move RCU's grace-period-change code to ->gp_seq
>       rcu: Convert rcu_gpnum_ovf() to ->gp_seq
>       rcu: Move rcu_implicit_dynticks_qs() to ->gp_seq
>       rcu: Move rcu_try_advance_all_cbs() to ->gp_seq
>       rcu: Move rcu_nocb_gp_get() to ->gp_seq
>       rcu: Move rcu_gp_in_progress() to ->gp_seq
>       rcu: Convert ->rcu_iw_gpnum to ->gp_seq
>       rcu: Convert ->completedqs to ->gp_seq
>       rcu: Convert grace-period requests to ->gp_seq
>       rcu: Make RCU CPU stall warnings use ->gp_seq
>       rcutorture: Convert rcutorture_get_gp_data() to ->gp_seq
>       rcu: Move from ->need_future_gp[] to ->gp_seq_needed
>       rcu: Make rcu_nocb_wait_gp() check if GP already requested
>       rcu: Convert rcu_grace_period tracepoint to gp_seq
>       rcu: Convert rcu_future_grace_period tracepoint to gp_seq
>       rcu: Convert rcu_grace_period_init tracepoint to gp_seq
>       rcu: Convert rcu_preempt_task tracepoint to ->gp_seq
>       rcu: Convert rcu_unlock_preempted_task tracepoint to ->gp_seq
>       rcu: Convert rcu_quiescent_state_report tracepoint to ->gp_seq
>       rcu: Convert rcu_fqs tracepoint to ->gp_seq
>       rcu: Remove ->gpnum and ->completed
>       rcu: Make simple callback acceleration refer to rdp->gp_seq_needed
>       doc: Update data-structure documentation for ->gp_seq
>       doc: Update memory-ordering documentation for ->gp-seq
>       doc: Update RCU CPU stall-warning documentation
>       rcu: Don't funnel-lock above leaf node if GP in progress
>       rcu: Make rcu_start_this_gp() check for grace period already started
>       rcutorture: Correctly handle grace-period sequence wrap
>       rcu: Regularize resetting of rcu_data wrap indicator
>       rcu: Clean up handling of tasks blocked across full-rcu_node offline
>       rcu: Fix an obsolete ->qsmaskinit comment
>       rcu: Make rcu_init_new_rnp() stop upon already-set bit
>       rcu: Make rcu_report_unblock_qs_rnp() warn on violated preconditions
>       rcu: Fix typo and add additional debug
>       rcu: Replace smp_wmb() with smp_store_release() for stall check
>       rcu: Prevent useless FQS scan after all CPUs have checked in
>       rcu: Suppress false-positive offline-CPU lockdep-RCU splat
>       rcu: Suppress false-positive preempted-task splats
>       rcu: Suppress more involved false-positive preempted-task splats
>       rcu: Suppress false-positive splats from mid-init task resume
>       rcu: Fix grace-period hangs from mid-init task resume
>       rcu: Fix grace-period hangs due to race with CPU offline
>       rcu: Add RCU-preempt check for waiting on newly onlined CPU
>       rcu: Move grace-period pre-init delay after pre-init
>       rcu: Remove failsafe check for lost quiescent state
>       rcu: Remove CPU-hotplug failsafe from force-quiescent-state code path
>       rcu: Add up-tree information to dump_blkd_tasks() diagnostics
>       rcu: Add CPU online/offline state to dump_blkd_tasks()
>       rcu: Record ->gp_state for both phases of grace-period initialization
>       rcu: Add diagnostics for offline CPUs failing to report QS
>       rcu: Make rcu_read_unlock_special() static
>       rcu: Improve RCU-tasks naming and comments
>       rcu: Mark task as .need_qs less aggressively
>       rcu: Inline rcu_dynticks_momentary_idle() into its sole caller
>       rcu: Clarify and correct the rcu_preempt_qs() header comment
>       rcu: Remove unused rcu_kick_nohz_cpu() function
>       rcu: Remove unused local variable "cpu"
>       rcu: Remove "inline" from panic_on_rcu_stall() and rcu_blocking_is_gp()
>       rcu: Remove "inline" from rcu_torture_print_module_parms()
>       rcu: Remove "inline" from rcu_perf_print_module_parms()
>       rcu: Remove __maybe_unused from rcu_cpu_has_callbacks()
>       rcu: Use RCU CPU stall timeout for rcu_check_gp_start_stall()
>       rcu: Add diagnostics for rcutorture writer stall warning
>       rcu: Make rcu_seq_diff() more exact
>       MAINTAINERS: Update RCU, SRCU, and TORTURE-TEST entries
>       rcu: Print stall-warning NMI dyntick state in hexadecimal
>       srcu: Add grace-period number to rcutorture statistics printout
>       rcutorture: Change units of onoff_interval to jiffies
>       rcu: Remove rcutorture test version and sequence number
>       rcuperf: Remove unused torturing_tasks() function
>       rcutorture: Extract common code from rcu_torture_reader()
>       rcutorture: Use atomic increment for n_rcu_torture_timers
>       rcutorture: Use per-CPU random state for rcu_torture_timer()
>       rcutorture: Make rcu_torture_timer() use rcu_torture_one_read()
>       rcutorture: Handle extended read-side critical sections
>       rcutorture: Emphasize testing of single reader protection type
>       Merge branches 'fixes1.2018.07.12b' and 'torture1.2018.07.12b' into HEAD
> 
> Steven Rostedt (VMware) (2):
>       rcu: Speed up calling of RCU tasks callbacks
>       rcu: Add comment to the last sleep in the rcu tasks loop
> 
>  .../Design/Data-Structures/Data-Structures.html    |  118 +--
>  .../Memory-Ordering/Tree-RCU-Memory-Ordering.html  |   22 +-
>  .../Design/Memory-Ordering/TreeRCU-gp-cleanup.svg  |  123 +--
>  .../Design/Memory-Ordering/TreeRCU-gp-init-1.svg   |   16 +-
>  .../Design/Memory-Ordering/TreeRCU-gp-init-3.svg   |   56 +-
>  .../RCU/Design/Memory-Ordering/TreeRCU-gp.svg      |  237 ++---
>  .../RCU/Design/Memory-Ordering/TreeRCU-qs.svg      |   12 +-
>  Documentation/RCU/stallwarn.txt                    |   24 +-
>  Documentation/RCU/whatisRCU.txt                    |   18 +-
>  Documentation/admin-guide/kernel-parameters.txt    |    4 +-
>  MAINTAINERS                                        |    9 +-
>  include/linux/rculist.h                            |   19 +-
>  include/linux/rcupdate.h                           |   20 +-
>  include/linux/rcutiny.h                            |    2 +-
>  include/linux/srcu.h                               |   17 +
>  include/linux/torture.h                            |    4 +-
>  include/trace/events/rcu.h                         |  112 ++-
>  kernel/locking/locktorture.c                       |    5 +-
>  kernel/rcu/rcu.h                                   |  104 +-
>  kernel/rcu/rcuperf.c                               |   57 +-
>  kernel/rcu/rcutorture.c                            |  462 ++++++---
>  kernel/rcu/srcutree.c                              |   39 +-
>  kernel/rcu/tiny.c                                  |    4 +-
>  kernel/rcu/tree.c                                  | 1019 +++++++++++---------
>  kernel/rcu/tree.h                                  |   71 +-
>  kernel/rcu/tree_exp.h                              |   14 +-
>  kernel/rcu/tree_plugin.h                           |  176 ++--
>  kernel/rcu/update.c                                |   45 +-
>  kernel/torture.c                                   |   15 +-
>  .../testing/selftests/rcutorture/bin/configinit.sh |   26 +-
>  .../testing/selftests/rcutorture/bin/kvm-build.sh  |   11 +-
>  .../selftests/rcutorture/bin/kvm-recheck-rcu.sh    |    1 +
>  .../selftests/rcutorture/bin/kvm-recheck.sh        |    1 +
>  .../selftests/rcutorture/bin/kvm-test-1-run.sh     |    5 +-
>  tools/testing/selftests/rcutorture/bin/kvm.sh      |    2 +-
>  .../selftests/rcutorture/bin/parse-console.sh      |    7 +
>  .../selftests/rcutorture/configs/rcu/TREE03.boot   |    4 +-
>  .../selftests/rcutorture/configs/rcu/TREE08-T.boot |    1 -
>  .../rcutorture/configs/rcu/ver_functions.sh        |    2 +-
>  39 files changed, 1675 insertions(+), 1209 deletions(-)
>  delete mode 100644 tools/testing/selftests/rcutorture/configs/rcu/TREE08-T.boot

Pulled into tip:core/rcu, thanks a lot Paul!

	Ingo