On Wed, Aug 29, 2018 at 03:20:21PM -0700, Paul E. McKenney wrote:
> Hello!
>
> This series contains the RCU flavor consolidation, along with some initial
> cleanup work enabled by that consolidation (and some that became apparent
> while cleaning up):
>
> 1. Refactor rcu_{nmi,irq}_{enter,exit}(), saving a branch on the
> idle entry/exit hotpaths, courtesy of Byungchul Park,
>
> 2. Defer reporting RCU-preempt quiescent states when disabled.
> This is the key commit that consolidates the RCU-bh and RCU-sched
> flavors into RCU, however, the RCU-bh and RCU-sched flavors
> still exist independently as well at this point.
>
> 3. Test extended "rcu" read-side critical sections. This commit
> causes rcutorture to test RCU's new-found ability to act as
> the combination of RCU, RCU-bh, and RCU-sched.
>
> 4. Allow processing deferred QSes for exiting RCU-preempt readers.
> This is a optimization.
>
> 5. Remove now-unused ->b.exp_need_qs field from the rcu_special union.
>
> 6. Add warning to detect half-interrupts. Test the claim that
> the Linux kernel no longer does half-interrupts.
>
> 7. Apply RCU-bh QSes to RCU-sched and RCU-preempt when safe, that is,
> make the consolidated RCU inherit RCU-bh's denial-of-service
> avoidance mechanism.
>
> 8. Report expedited grace periods at context-switch time. This is
> an optimization enabled by the RCU flavor consolidation.
>
> 9. Define RCU-bh update API in terms of RCU. This commit gets rid
> of the RCU-bh update mechanism.
>
> 10. Update comments and help text to account for the removal of
> the RCU-bh update mechanism.
>
> 11. Drop "wake" parameter from rcu_report_exp_rdp().
>
> 12. Fix typo in rcu_get_gp_kthreads_prio() header comment.
>
> 13. Define RCU-sched API in terms of RCU for Tree RCU PREEMPT builds.
> Although this commit gets rid of the RCU-sched update mechanism
> from PREEMPT builds, it of course remains as the sole RCU flavor
> for !PREEMPT && !SMP builds.
>
> 14. Express Tiny RCU updates in terms of RCU rather than RCU-sched.
> This will enable additional cleanups and code savings.
>
> 15. Remove RCU_STATE_INITIALIZER() in favor of just using an open-coded
> initializer for the sole remaining rcu_state structure.
>
> 16. Eliminate rcu_state structure's ->call field, as it is now always
> just call_rcu().
>
> 17. Remove rcu_state structure's ->rda field, as there is now only one
> set of per-CPU rcu_data structures.
And last, but perhaps not least:
18. Remove rcu_state_p pointer to default rcu_state structure, now
that there is only one rcu_state structure.
19. Remove rcu_data_p pointer to default rcu_data structure, now that
there is only one set of per-CPU rcu_data structures.
Thanx, Paul
> ------------------------------------------------------------------------
>
> Documentation/RCU/Design/Requirements/Requirements.html | 50 -
> include/linux/rcupdate.h | 48 -
> include/linux/rcupdate_wait.h | 6
> include/linux/rcutiny.h | 61 +
> include/linux/rcutree.h | 31
> include/linux/sched.h | 6
> kernel/rcu/Kconfig | 10
> kernel/rcu/rcutorture.c | 1
> kernel/rcu/tiny.c | 163 +--
> kernel/rcu/tree.c | 655
> +++++-----------
> kernel/rcu/tree.h | 44 -
> kernel/rcu/tree_exp.h | 256 +++---
> kernel/rcu/tree_plugin.h | 523 ++++++------
> kernel/rcu/update.c | 2
> kernel/softirq.c | 3
> 15 files changed, 836 insertions(+), 1023 deletions(-)
