Pull RCU updates from Paul E. McKenney:

 - Streamline RCU's use of per-CPU variables, shifting from "cpu"
   arguments to functions to "this_"-style per-CPU variable accessors.

 - Signal-handling RCU updates.

 - Real-time updates.

 - Torture-test updates.

 - Miscellaneous fixes.

 - Documentation updates.

Signed-off-by: Ingo Molnar <mingo@kernel.org>

cpu.2014.11.03a: Changes for per-CPU variables.
doc.2014.11.13a: Documentation updates.
fixes.2014.11.13a: Miscellaneous fixes.
signal.2014.10.29a: Signal changes.
rt.2014.10.29a: Real-time changes.
torture.2014.11.03a: torture-test changes.

The comment above rcu_read_unlock() explains the potential deadlock
if the caller holds one of the locks taken by rt_mutex_unlock() paths,
but it is not clear from this documentation that any lock which can
be taken from interrupt can lead to deadlock as well and we need to
take rt_mutex_lock() into account too.

The problem is that rt_mutex_lock() takes wait_lock without disabling
irqs, and thus an interrupt taking some LOCK can obviously race with
rcu_read_unlock_special() called with the same LOCK held.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

The current implementation of cond_resched_rcu_qs() can invoke
rcu_note_voluntary_context_switch() twice in the should_resched()
case, once via the call to __schedule() and once directly.  However, as
noted by Joe Lawrence in a patch to the team subsystem, cond_resched()
returns an indication as to whether or not the call to __schedule()
actually happened.  This commit therefore changes cond_resched_rcu_qs()
so as to invoke rcu_note_voluntary_context_switch() only when __schedule()
was not called.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

Add a sparse check when RCU_INIT_POINTER() is used to assign a non __rcu
annotated pointer.

Signed-off-by: Pranith Kumar <bobby.prani@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

The "cpu" argument to rcu_needs_cpu() is always the current CPU, so drop
it.  This in turn allows the "cpu" argument to rcu_cpu_has_callbacks()
to be removed, which allows the uses of "cpu" in both functions to be
replaced with a this_cpu_ptr().  Again, the anticipated cross-CPU uses
of these functions has been replaced by NO_HZ_FULL.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Pranith Kumar <bobby.prani@gmail.com>

The "cpu" argument was kept around on the off-chance that RCU might
offload scheduler-clock interrupts.  However, this offload approach
has been replaced by NO_HZ_FULL, which offloads -all- RCU processing
from qualifying CPUs.  It is therefore time to remove the "cpu" argument
to rcu_check_callbacks(), which this commit does.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Pranith Kumar <bobby.prani@gmail.com>

PREEMPT_RCU and TREE_PREEMPT_RCU serve the same function after
TINY_PREEMPT_RCU has been removed. This patch removes TREE_PREEMPT_RCU
and uses PREEMPT_RCU config option in its place.

Signed-off-by: Pranith Kumar <bobby.prani@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

Although rcu_dereference() and friends can be used in situations where
object lifetimes are being managed by something other than RCU, the
resulting sparse and lockdep-RCU noise can be annoying.  This commit
therefore supplies a lockless_dereference(), which provides the
protection for dereferences without the RCU-related debugging noise.

Reported-by: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

This commit changes rcutorture_runnable to torture_runnable, which is
consistent with the names of the other parameters and is a bit shorter
as well.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>