Preview of yet more RCU changes for 3.3

Hello!

This patchset adds to the pair that were previously posted earlier this month (see https://lkml.org/lkml/2011/11/2/363
and https://lkml.org/lkml/2011/11/15/302). This third set adds more rcutorture capabilities to ease automated testing under KVM (randomized CPU hotplug operations), updates Frederic's user-mode nohz RCU infrastructure, adds tracing for RCU_FAST_NO_HZ, makes a number of improvements to RCU_FAST_NO_HZ suggested by the resulting traces, speeds up TREE_RCU's dyntick-idle identification, and provides documentation updates. The patches are as follows:

1. Add randomized CPU-hotplug capability to rcutorture.
2. Decouple turning off the scheduler tick and informing RCU
of CPU idleness (courtesy of Frederic Weisbecker).
3,4,12. Documentation updates, with the addition of load/store atomicity
guarantees (#3) being of the most widespread interest.
5. Add event tracing for RCU_FAST_NO_HZ.
6,7,8,9,10,11,13.
RCU_FAST_NO_HZ improvements suggested by event-tracing output.

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

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

 b/Documentation/RCU/torture.txt          |    8 +
 b/Documentation/atomic_ops.txt           |   87 +++++++++++++
 b/arch/arm/kernel/process.c              |    6 
 b/arch/avr32/kernel/process.c            |    6 
 b/arch/blackfin/kernel/process.c         |    6 
 b/arch/microblaze/kernel/process.c       |    6 
 b/arch/mips/kernel/process.c             |    6 
 b/arch/openrisc/kernel/idle.c            |    6 
 b/arch/powerpc/kernel/idle.c             |   15 +-
 b/arch/powerpc/platforms/iseries/setup.c |   12 +
 b/arch/s390/kernel/process.c             |    6 
 b/arch/sh/kernel/idle.c                  |    6 
 b/arch/sparc/kernel/process_64.c         |    6 
 b/arch/tile/kernel/process.c             |    6 
 b/arch/um/kernel/process.c               |    6 
 b/arch/unicore32/kernel/process.c        |    6 
 b/arch/x86/kernel/process_32.c           |    6 
 b/include/linux/rcupdate.h               |   15 ++
 b/include/linux/srcu.h                   |    5 
 b/include/linux/tick.h                   |   47 -------
 b/include/trace/events/rcu.h             |   12 +
 b/kernel/rcutorture.c                    |  117 ++++++++++++++++-
 b/kernel/rcutree.c                       |    2 
 b/kernel/rcutree.h                       |    3 
 b/kernel/rcutree_plugin.h                |   18 ++
 b/kernel/time/tick-sched.c               |   15 +-
 include/trace/events/rcu.h               |   41 +++++-
 kernel/rcutree.c                         |   10 +
 kernel/rcutree.h                         |    2 
 kernel/rcutree_plugin.h                  |  205 ++++++++++++++++---------------
 30 files changed, 488 insertions(+), 204 deletions(-)