RFC RCU commits for 3.4

Hello!

This patchset makes RCU more aggressive about entering dyntick-idle mode in order to improve energy efficiency, converts a few more call_rcu()s to kfree_rcu(), applies a number of rcutree fixes and cleanups to rcutiny, removes CONFIG_SMP #ifdef from treercu, allows RCU CPU stall times to be set via sysfs, add CPU-stall capability to rcutorture, adds more RCU-abuse diagnostics, updates documentation, and yet more fixes from the still-ongoing top-to-bottom inspection of RCU with a special focus on the CPU-hotplug code path. The patches are as follows:

1,26,41,40.
Documentation upgrades.
2. Improve synchronize_rcu() diagnostics, courtesy of
Frederic Weisbecker.
3. Add lockdep-RCU checks for simple self deadlock, such as calling
synchronize_rcu() while in an RCU read-side critical section.
4. Add a diagnostic for misaligned rcu_head structures. This is
preparation for a call_rcu_lazy() for added energy efficiency.
5,14,36.
Upgrades to CONFIG_RCU_FAST_NO_HZ.
6. Move CONFIG_RCU_TRACE to lib/Kconfig.debug: not for production use.
7-11. Convert several call_rcu() primitives to kfree_rcu().
12,13,15,16,37-39.
Fixes to and streamlining of CPU-hotplug handling based on review.
17. Remove dubious single-rcu_node optimization from rcu_start_gp().
18-22. Apply prior rcutree fixes to rcutiny.
23. Catch rcu_preempt_needs_cpu()'s name up with 2011.
24. Check for idle-loop entry while in an RCU read-side critical section.
25. Check for sleeping in TREE_RCU read-side critical sections.
27,35. Remove "#ifdef CONFIG_SMP" from treercu, move code accordingly.
28. Allow RCU CPU stall times to be adjusted at runtime via sysfs.
29. Print scheduling-clock timer information on RCU CPU stall warning
messages if requested by CONFIG_RCU_CPU_STALL_INFO config parameter.
30. Allow rcutorture to be told to hold off CPU-hotplug operations during
early boot.
31. Allow rcutorture to generate CPU stalls in order to test RCU CPU
stall warning facility.
33. Silence module-parameter warnings by converting a couple of
rcutorture's module parameters to bool.
34. Check for illegal use of RCU from offlined CPUs.
41. Fix misplaced NULL-pointer check in rcutorture.

For a testing-only version of this patchset from git, please see the following subject-to-rebase branch:

git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git rcu/dev

Thanx, Paul

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

 Documentation/RCU/torture.txt      |   18 
 b/Documentation/RCU/RTFP.txt       | 1910 ++++++++++++++++++++++++++++++++++---
 b/Documentation/RCU/checklist.txt  |   14 
 b/Documentation/RCU/stallwarn.txt  |   85 +
 b/Documentation/RCU/torture.txt    |   15 
 b/Documentation/RCU/trace.txt      |   36 
 b/arch/s390/kernel/irq.c           |    9 
 b/drivers/target/tcm_fc/tfc_sess.c |   12 
 b/include/linux/rcupdate.h         |    2 
 b/include/linux/rcutiny.h          |    6 
 b/include/linux/rcutree.h          |    1 
 b/include/linux/sched.h            |    3 
 b/include/linux/srcu.h             |   11 
 b/include/trace/events/rcu.h       |   63 -
 b/init/Kconfig                     |    9 
 b/kernel/lockdep.c                 |    8 
 b/kernel/rcu.h                     |    4 
 b/kernel/rcupdate.c                |    5 
 b/kernel/rcutiny.c                 |    3 
 b/kernel/rcutiny_plugin.h          |    4 
 b/kernel/rcutorture.c              |    4 
 b/kernel/rcutree.c                 |    6 
 b/kernel/rcutree.h                 |    3 
 b/kernel/rcutree_plugin.h          |    3 
 b/kernel/rcutree_trace.c           |    8 
 b/kernel/srcu.c                    |    4 
 b/lib/Kconfig.debug                |    9 
 b/net/ipv4/cipso_ipv4.c            |   11 
 b/net/ipv4/ip_sockglue.c           |    7 
 b/net/mac80211/mesh_pathtbl.c      |    8 
 include/linux/rcupdate.h           |   40 
 include/linux/rcutiny.h            |    4 
 include/linux/rcutree.h            |   18 
 kernel/rcutiny.c                   |    4 
 kernel/rcutiny_plugin.h            |   72 +
 kernel/rcutorture.c                |   83 +
 kernel/rcutree.c                   |  641 ++++++++----
 kernel/rcutree.h                   |   24 
 kernel/rcutree_plugin.h            |  443 +++++---
 kernel/rcutree_trace.c             |    6 
 kernel/srcu.c                      |   27 
 lib/Kconfig.debug                  |   14 
 42 files changed, 2954 insertions(+), 703 deletions(-)