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Message-Id: <20181002100356.GX4222@linux.ibm.com>
Date: Tue, 2 Oct 2018 03:03:56 -0700
From: "Paul E. McKenney" <paulmck@...ux.ibm.com>
To: Ingo Molnar <mingo@...nel.org>
Cc: linux-kernel@...r.kernel.org, josh@...htriplett.org,
rostedt@...dmis.org, mathieu.desnoyers@...icios.com,
jiangshanlai@...il.com, efault@....de, byungchul.park@....com,
joel@...lfernandes.org, mhillenb@...zon.de, dwmw2@...radead.org,
peterz@...radead.org
Subject: Re: [GIT PULL rcu/next] RCU commits for 4.20/5.0
On Tue, Oct 02, 2018 at 10:24:29AM +0200, Ingo Molnar wrote:
>
> * Paul E. McKenney <paulmck@...ux.ibm.com> wrote:
>
> > Hello, Ingo,
> >
> > This pull request contains the following changes:
> >
> > 1. Documentation updates, including some good-eye catches from
> > Joel Fernandes.
> >
> > http://lkml.kernel.org/r/20180829211637.GA20980@linux.vnet.ibm.com
> >
> > 2. SRCU updates, most notably changes enabling call_srcu() to be
> > invoked very early in the boot sequence.
> >
> > http://lkml.kernel.org/r/20180829212036.GA22033@linux.vnet.ibm.com
> >
> > 3. Torture-test updates, including some preliminary work towards
> > making rcutorture better able to find problems that result in
> > insufficient grace-period forward progress.
> >
> > http://lkml.kernel.org/r/20180829214722.GA23411@linux.vnet.ibm.com
> >
> > 4. Consolidate the RCU-bh, RCU-preempt, and RCU-sched flavors into
> > a single flavor similar to RCU-sched in !PREEMPT kernels and
> > into a single flavor similar to RCU-preempt (but also waiting
> > on preempt-disabled sequences of code) in PREEMPT kernels. This
> > branch also includes a refactoring of rcu_{nmi,irq}_{enter,exit}()
> > from Byungchul Park.
> >
> > http://lkml.kernel.org/r/20180829222021.GA29944@linux.vnet.ibm.com
> >
> > 5. Now that there is only one RCU flavor in any given running kernel,
> > the many "rsp" pointers are no longer required, and this cleanup
> > series removes them.
> >
> > http://lkml.kernel.org/r/20180829223830.GA1800@linux.vnet.ibm.com
> >
> > 6. This branch carries out additional cleanups made possible by
> > the RCU flavor consolidation, including inlining how-trivial
> > functions, updating comments and definitions, and removing
> > now-unneeded rcutorture scenarios.
> >
> > http://lkml.kernel.org/r/20180829225340.GA7019@linux.vnet.ibm.com
> >
> > 7. Initial changes to RCU to better promote forward progress of
> > grace periods, including fixing a bug found by Marius Hillenbrand
> > and David Woodhouse, with the fix suggested by Peter Zijlstra.
> >
> > http://lkml.kernel.org/r/20180829230035.GA7751@linux.vnet.ibm.com
> >
> > 8. Now that there is only one flavor of RCU in any running kernel,
> > there is also only on rcu_data structure per CPU. This means
> > that the rcu_dynticks structure can be merged into the rcu_data
> > structure, a task taken on by this branch. This branch also
> > contains a -rt-related fix from Mike Galbraith.
> >
> > http://lkml.kernel.org/r/20180829230715.GA9431@linux.vnet.ibm.com
> >
> > Once again, the layout of this pull request is unusual due to the large
> > footprint of the commits in #4-#8 above. These five branches are therefore
> > stacked on top of each other instead of my usual practice of laying them
> > out in parallel.
> >
> > This pull request decreases the size of RCU by more than 450 lines,
> > offsetting the increase of the v4.19 merge window. I expect a further
> > decrease due to additional outside-of-RCU cleanups, though this will be
> > offset by additional forward-progress testing and fixes in response to
> > Marius's and David's location of a forward-progress bug that escaped to
> > the field -- rcutorture should have located that bug, after all.
> >
> > 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 b56ada120921fbb0a4fb2a5bee163717182e7e9e:
> >
> > Merge branches 'doc.2018.08.30a', 'dynticks.2018.08.30b', 'srcu.2018.08.30b' and 'torture.2018.08.29a' into HEAD (2018-08-30 16:12:53 -0700)
> >
> > ----------------------------------------------------------------
> > Byungchul Park (1):
> > rcu: Refactor rcu_{nmi,irq}_{enter,exit}()
> >
> > Joel Fernandes (Google) (2):
> > doc: Fix broken RCU-requirements link to LKML archive
> > doc: Improve rcu_dynticks::dynticks documentation
> >
> > Mike Galbraith (1):
> > rcu: Convert rcu_state.ofl_lock to raw_spinlock_t
> >
> > Paul E. McKenney (137):
> > doc: Add design documentation on interruption of NMI handlers
> > torture: Stop overwriting Make.out file with obsolete version
> > rcutorture: Force occasional reader waits
> > rcutorture: Warn on bad torture type for built-in tests
> > rcuperf: Warn on bad perf type for built-in tests
> > rcutorture: Remove TREE06 and TREE08 from the default test list
> > rcutorture: Add forward-progress tests for RCU grace periods
> > rcutorture: Also use GP sequence to judge forward progress
> > rcutorture: Avoid no-test complaint if too few forward-progress tries
> > rcutorture: Vary forward-progress test interval
> > rcutorture: Add self-propagating callback to forward-progress testing
> > rcutorture: Increase rcu_read_delay() longdelay_ms
> > rcutorture: Limit reader duration if irq or bh disabled
> > rcutorture: Reduce priority of forward-progress testing
> > rcutorture: Adjust number of reader kthreads per CPU-hotplug operations
> > rcutorture: Print forward-progress test interval on error
> > rcutorture: Check GP completion at stutter end
> > rcutorture: Maintain self-propagating CB only during forward-progress test
> > doc: Update removal of RCU-bh/sched update machinery
> > doc: Fix broken HTML directive
> > rcu: Defer reporting RCU-preempt quiescent states when disabled
> > rcutorture: Test extended "rcu" read-side critical sections
> > rcu: Allow processing deferred QSes for exiting RCU-preempt readers
> > rcu: Remove now-unused ->b.exp_need_qs field from the rcu_special union
> > rcu: Add warning to detect half-interrupts
> > rcu: Apply RCU-bh QSes to RCU-sched and RCU-preempt when safe
> > rcu: Report expedited grace periods at context-switch time
> > rcu: Define RCU-bh update API in terms of RCU
> > rcu: Update comments and help text for no more RCU-bh updaters
> > rcu: Drop "wake" parameter from rcu_report_exp_rdp()
> > rcu: Fix typo in rcu_get_gp_kthreads_prio() header comment
> > rcu: Define RCU-sched API in terms of RCU for Tree RCU PREEMPT builds
> > rcu: Express Tiny RCU updates in terms of RCU rather than RCU-sched
> > rcu: Remove RCU_STATE_INITIALIZER()
> > rcu: Eliminate rcu_state structure's ->call field
> > rcu: Remove rcu_state structure's ->rda field
> > rcu: Remove rcu_state_p pointer to default rcu_state structure
> > rcu: Remove rcu_data_p pointer to default rcu_data structure
> > rcu: Remove rsp parameter from rcu_report_qs_rnp()
> > rcu: Remove rsp parameter from rcu_report_qs_rsp()
> > rcu: Remove rsp parameter from rcu_report_unblock_qs_rnp()
> > rcu: Remove rsp parameter from rcu_report_qs_rdp()
> > rcu: Remove rsp parameter from rcu_gp_in_progress()
> > rcu: Remove rsp parameter from rcu_get_root()
> > rcu: Remove rsp parameter from record_gp_stall_check_time()
> > rcu: Remove rsp parameter from rcu_check_gp_kthread_starvation()
> > rcu: Remove rsp parameter from rcu_dump_cpu_stacks()
> > rcu: Remove rsp parameter from rcu_stall_kick_kthreads()
> > rcu: Remove rsp parameter from print_other_cpu_stall()
> > rcu: Remove rsp parameter from print_cpu_stall()
> > rcu: Remove rsp parameter from check_cpu_stall()
> > rcu: Remove rsp parameter from rcu_future_gp_cleanup()
> > rcu: Remove rsp parameter from rcu_gp_kthread_wake()
> > rcu: Remove rsp parameter from rcu_accelerate_cbs()
> > rcu: Remove rsp parameter from rcu_accelerate_cbs_unlocked()
> > rcu: Remove rsp parameter from rcu_advance_cbs()
> > rcu: Remove rsp parameter from __note_gp_changes()
> > rcu: Remove rsp parameter from note_gp_changes()
> > rcu: Remove rsp parameter from rcu_gp_slow()
> > rcu: Remove rsp parameter from rcu_gp_kthread() and friends
> > rcu: Remove rsp parameter from rcu_check_quiescent_state()
> > rcu: Remove rsp parameter from CPU hotplug functions
> > rcu: Remove rsp parameter from rcu_do_batch()
> > rcu: Remove rsp parameter from force-quiescent-state functions
> > rcu: Remove rsp parameter from rcu_check_gp_start_stall()
> > rcu: Remove rsp parameter from __rcu_process_callbacks()
> > rcu: Remove rsp parameter from __call_rcu() and friend
> > rcu: Remove rsp parameter from __rcu_pending()
> > rcu: Remove rsp parameter from _rcu_barrier() and friends
> > rcu: Remove rsp parameter from rcu_boot_init_percpu_data() and friends
> > rcu: Remove rsp parameter from rcu_init_one() and friends
> > rcu: Remove rsp parameter from rcu_print_detail_task_stall()
> > rcu: Remove rsp parameter from dump_blkd_tasks() and friend
> > rcu: Remove rsp parameter from rcu_spawn_one_boost_kthread()
> > rcu: Remove rsp parameter from print_cpu_stall_info()
> > rcu: Remove rsp parameter from no-CBs CPU functions
> > rcu: Remove rsp parameter from expedited grace-period functions
> > rcu: Remove rsp parameter from rcu_node tree accessor macros
> > rcu: Remove rcu_data structure's ->rsp field
> > rcu: Remove last non-flavor-traversal rsp local variable from tree_plugin.h
> > rcu: Remove for_each_rcu_flavor() flavor-traversal macro
> > rcu: Simplify rcutorture_get_gp_data()
> > rcu: Restructure rcu_check_gp_kthread_starvation()
> > rcu: Eliminate stall-warning use of rsp
> > rcu: Eliminate grace-period management code use of rsp
> > rcu: Eliminate callback-invocation/invocation use of rsp
> > rcu: Eliminate quiescent-state and grace-period-nonstart use of rsp
> > rcu: Eliminate RCU-barrier use of rsp
> > rcu: Eliminate initialization-time use of rsp
> > rcu: Fix typo in force_qs_rnp()'s parameter's parameter
> > rcu: Inline increment_cpu_stall_ticks() into its sole caller
> > rcu: Pull rcu_gp_kthread() FQS loop into separate function
> > rcu: Consolidate RCU-bh update-side function definitions
> > rcu: Consolidate RCU-sched update-side function definitions
> > rcutorture: Add RCU-bh and RCU-sched support for extended readers
> > rcu: Stop testing RCU-bh and RCU-sched
> > rcutorture: Remove the "rcu_bh" and "sched" torture types
> > rcuperf: Remove the "rcu_bh" and "sched" torture types
> > rcu: Remove now-unused rcutorture APIs
> > rcu: Clean up flavor-related definitions and comments in rcupdate.h
> > rcu: Clean up flavor-related definitions and comments in rculist.h
> > rcu: Clean up flavor-related definitions and comments in rcupdate_wait.h
> > rcu: Clean up flavor-related definitions and comments in Kconfig
> > rcu: Clean up flavor-related definitions and comments in rcu.h
> > rcu: Clean up flavor-related definitions and comments in rcutorture.c
> > rcu: Clean up flavor-related definitions and comments in srcutree.h
> > rcu: Clean up flavor-related definitions and comments in tiny.c
> > rcu: Clean up flavor-related definitions and comments in tree.c
> > rcu: Clean up flavor-related definitions and comments in tree_exp.h
> > rcu: Clean up flavor-related definitions and comments in tree_plugin.h
> > rcu: Clean up flavor-related definitions and comments in update.c
> > rcu: Remove !PREEMPT code from rcu_note_voluntary_context_switch()
> > rcu: Define rcu_all_qs() only in !PREEMPT builds
> > rcu: Inline _rcu_barrier() into its sole remaining caller
> > rcu: Make need_resched() respond to urgent RCU-QS needs
> > rcu: Provide improved interrupt-from-idle check in rcu_check_callbacks()
> > rcutorture: Dump reader protection sequence if failures or close calls
> > rcu: Motivate Tiny RCU forward progress
> > rcu: Eliminate ->rcu_qs_ctr from the rcu_dynticks structure
> > rcu: Provide functions for determining if call_rcu() has been invoked
> > rcu: Compute jiffies_till_sched_qs from other kernel parameters
> > rcu: More aggressively enlist scheduler aid for nohz_full CPUs
> > rcu: Avoid resched_cpu() when rescheduling the current CPU
> > rcu: Convert "1UL << x" to "BIT(x)"
> > rcu: Remove unused rcu_dynticks_snap() from Tiny RCU
> > rcu: Merge rcu_dynticks structure into rcu_data structure
> > rcu: Switch ->tick_nohz_enabled_snap to rcu_data structure
> > rcu: Switch last accelerate/advance to rcu_data structure
> > rcu: Switch lazy counts to rcu_data structure
> > rcu: Switch urgent quiescent-state requests to rcu_data structure
> > rcu: Switch dyntick nesting counters to rcu_data structure
> > rcu: Switch ->dynticks to rcu_data structure, remove rcu_dynticks
> > rcu: Remove obsolete ->dynticks_fqs and ->cond_resched_completed
> > srcu: Make call_srcu() available during very early boot
> > rcutorture: Test early boot call_srcu()
> > srcu: Make early-boot call_srcu() reuse workqueue lists
> > Merge branches 'doc.2018.08.30a', 'dynticks.2018.08.30b', 'srcu.2018.08.30b' and 'torture.2018.08.29a' into HEAD
> >
> > .../Design/Data-Structures/Data-Structures.html | 31 +-
> > .../Expedited-Grace-Periods.html | 9 +-
> > .../RCU/Design/Requirements/Requirements.html | 214 +-
> > Documentation/RCU/stallwarn.txt | 13 +-
> > Documentation/RCU/whatisRCU.txt | 3 +-
> > Documentation/admin-guide/kernel-parameters.txt | 31 +-
> > Documentation/kernel-per-CPU-kthreads.txt | 2 +-
> > include/linux/rculist.h | 32 +-
> > include/linux/rcupdate.h | 154 +-
> > include/linux/rcupdate_wait.h | 14 +-
> > include/linux/rcutiny.h | 53 +-
> > include/linux/rcutree.h | 31 +-
> > include/linux/sched.h | 6 +-
> > include/linux/srcutree.h | 13 +-
> > include/linux/torture.h | 2 +-
> > include/trace/events/rcu.h | 25 +-
> > kernel/rcu/Kconfig | 14 +-
> > kernel/rcu/rcu.h | 67 +-
> > kernel/rcu/rcuperf.c | 66 +-
> > kernel/rcu/rcutorture.c | 397 ++--
> > kernel/rcu/srcutiny.c | 29 +-
> > kernel/rcu/srcutree.c | 31 +-
> > kernel/rcu/tiny.c | 154 +-
> > kernel/rcu/tree.c | 2213 ++++++++------------
> > kernel/rcu/tree.h | 132 +-
> > kernel/rcu/tree_exp.h | 426 ++--
> > kernel/rcu/tree_plugin.h | 790 +++----
> > kernel/rcu/update.c | 70 +-
> > kernel/softirq.c | 3 +-
> > kernel/torture.c | 3 +-
> > .../selftests/rcutorture/bin/kvm-test-1-run.sh | 1 -
> > .../selftests/rcutorture/configs/rcu/CFLIST | 2 -
> > .../selftests/rcutorture/configs/rcu/SRCU-P.boot | 1 +
> > .../selftests/rcutorture/configs/rcu/SRCU-u.boot | 1 +
> > .../selftests/rcutorture/configs/rcu/TINY02.boot | 2 -
> > .../selftests/rcutorture/configs/rcu/TREE01.boot | 2 +-
> > .../selftests/rcutorture/configs/rcu/TREE04.boot | 2 +-
> > .../selftests/rcutorture/configs/rcu/TREE05.boot | 3 +-
> > .../selftests/rcutorture/configs/rcu/TREE06.boot | 2 -
> > .../selftests/rcutorture/configs/rcu/TREE08.boot | 2 -
> > 40 files changed, 2294 insertions(+), 2752 deletions(-)
>
> Pulled into tip:core/rcu, thanks a lot Paul!
>
> The code and complexity reduction from the consolidation of the RCU models is pretty
> impressive IMO! :-)
Glad you like it! ;-)
Which reminds me...
If you are running rcutorture in -tip on NO_HZ_FULL kernel with RCU
callback offloading enabled, you are not extremely excited about
getting splats from rcutorture's new forward-progress testing,
I reccommend that you add "rcutorture.fwd_progress=0" to your kernel
boot parameters. I added forward-progress testing because of people
finding a forward-progress issue in real-life testing. (The fix to that
specific issue is included and called out in #7 above.)
Thanx, Paul
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