[PATCH RFC tip/core/rcu 0/14] Rework expedited grace periods

Paul E. McKenney
2015-06-30T22:25:39Z

Hello!

This RFC series reworks the handling of expedited grace periods, eliminating
the previous use of try_stop_cpus(), improving scalability, and adding
an RCU CPU stall-warning capability. This series is as follows:

1. Replace try_stop_cpus() with stop_one_cpu(), courtesy of
Peter Zijlstra.

2. Improve counter handling to more efficiently detect that some
other task has already done the required work.

3. Replace synchronize_sched_expedited()'s polling loop with
funnel locking.

4. Replace stop_one_cpu() with stop_one_cpu_nowait() to avoid the
latency hit from #1 above, also courtesy of Peter Zijlstra.

5. Abstract the counter handling.

6. Apply the newly abstracted counter handling to
synchronize_rcu_expedited().

7. Abstract the funnel locking.

8. Fix a stupid type error in synchronize_sched_expedited().

9. Replace synchronize_rcu_expedited()'s polling with the newly
abstracted funnel locking.

10. Apply the abstracted counter handling to _rcu_barrier().

11. Consolidate the last expedited open-coded expedited memory barrier
into the counter handling.

12. Extend the funnel locking to the rcu_data structure in order to
further increase scalability.

13. Add stall warnings to synchronize_sched_expedited().

14. Document the newly added stall warnings.

Thanx, Paul

------------------------------------------------------------------------

b/Documentation/RCU/stallwarn.txt | 17 +
b/include/trace/events/rcu.h | 1
b/kernel/rcu/tree.c | 581 +++++++++++++++++++-------------------
b/kernel/rcu/tree.h | 31 +-
b/kernel/rcu/tree_plugin.h | 53 +--
b/kernel/rcu/tree_trace.c | 25 -
6 files changed, 369 insertions(+), 339 deletions(-)