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Subject[PATCH tip/core/rcu 0/23] Improvements to RT response on big systems and expedited functions

This patch series contains additional improvements to latency for
large systems (beyond those in 3.6), along with improvements to
synchronize_rcu_expedited(). It also fixes one race introduced by the
latency improvements and another that was there to start with (but made
more probable by the latency improvements). These are in a single
series due to conflicts that would otherwise occur. The individual
patches are as follows:

1-6. Move RCU grace-period initialization and cleanup into a kthread:
1. Move RCU grace-period initialization into kthread.
2. Allow RCU grace-period initialization to be preempted.
3. Move RCU grace-period cleanup into kthread.
4. Allow RCU grace-period cleanup to be preempted.
5. Prevent offline CPUs from executing RCU core code.
6. Break up rcu_gp_kthread() into subfunctions.
7. Provide an OOM handler to allow lazy callbacks to be motivated
under memory pressure.
8. Segregate rcu_state fields to improve cache locality
(Courtesy of Dimitri Sivanich).
9-12. Move RCU grace-period forcing into a kthread.
9. Move quiescent-state forcing into kthread.
10. Allow RCU quiescent-state forcing to be preempted.
11. Adjust debugfs tracing for kthread-based quiescent-state
12. Prevent force_quiescent_state() memory contention.
13. Control grace-period duration from sysfs.
14. Remove now-unused rcu_state fields.
15. Make rcutree module parameters visible in sysfs.
16. Prevent initialization-time quiescent-state race.
17. Fix day-zero grace-period initialization/cleanup race.
18. Add random PROVE_RCU_DELAY to provoke initalization races.
19. Adjust for unconditional ->completed assignment.
20. Remove callback acceleration from grace-period initialization
due it no longer being safe.
21. Eliminate signed overflow in synchronize_rcu_expedited().
22. Reduce synchronize_rcu_expedited() latency.
23. Simplify quiescent-state detection.

Thanx, Paul

b/Documentation/RCU/trace.txt | 43 -
b/Documentation/kernel-parameters.txt | 11
b/kernel/rcutree.c | 191 +++++---
b/kernel/rcutree.h | 3
b/kernel/rcutree_plugin.h | 80 +++
b/kernel/rcutree_trace.c | 3
kernel/rcutree.c | 805 +++++++++++++++++-----------------
kernel/rcutree.h | 25 -
kernel/rcutree_plugin.h | 48 +-
kernel/rcutree_trace.c | 12
10 files changed, 690 insertions(+), 531 deletions(-)

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