Merge branch 'rcu/next' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu into core/rcu

Conflicts:
	arch/x86/kernel/ptrace.c

Pull the latest RCU tree from Paul E. McKenney:

"       The major features of this series are:

  1.	A first version of no-callbacks CPUs.  This version prohibits
  	offlining CPU 0, but only when enabled via CONFIG_RCU_NOCB_CPU=y.
  	Relaxing this constraint is in progress, but not yet ready
  	for prime time.  These commits were posted to LKML at
  	https://lkml.org/lkml/2012/10/30/724, and are at branch rcu/nocb.

  2.	Changes to SRCU that allows statically initialized srcu_struct
  	structures.  These commits were posted to LKML at
  	https://lkml.org/lkml/2012/10/30/296, and are at branch rcu/srcu.

  3.	Restructuring of RCU's debugfs output.  These commits were posted
  	to LKML at https://lkml.org/lkml/2012/10/30/341, and are at
  	branch rcu/tracing.

  4.	Additional CPU-hotplug/RCU improvements, posted to LKML at
  	https://lkml.org/lkml/2012/10/30/327, and are at branch rcu/hotplug.
  	Note that the commit eliminating __stop_machine() was judged to
  	be too-high of risk, so is deferred to 3.9.

  5.	Changes to RCU's idle interface, most notably a new module
  	parameter that redirects normal grace-period operations to
  	their expedited equivalents.  These were posted to LKML at
  	https://lkml.org/lkml/2012/10/30/739, and are at branch rcu/idle.

  6.	Additional diagnostics for RCU's CPU stall warning facility,
  	posted to LKML at https://lkml.org/lkml/2012/10/30/315, and
  	are at branch rcu/stall.  The most notable change reduces the
  	default RCU CPU stall-warning time from 60 seconds to 21 seconds,
  	so that it once again happens sooner than the softlockup timeout.

  7.	Documentation updates, which were posted to LKML at
  	https://lkml.org/lkml/2012/10/30/280, and are at branch rcu/doc.
  	A couple of late-breaking changes were posted at
  	https://lkml.org/lkml/2012/11/16/634 and
  	https://lkml.org/lkml/2012/11/16/547.

  8.	Miscellaneous fixes, which were posted to LKML at
  	https://lkml.org/lkml/2012/10/30/309, along with a late-breaking
  	change posted at Fri, 16 Nov 2012 11:26:25 -0800 with message-ID
  	<20121116192625.GA447@linux.vnet.ibm.com>, but which lkml.org
  	seems to have missed.  These are at branch rcu/fixes.

  9.	Finally, a fix for an lockdep-RCU splat was posted to LKML
  	at https://lkml.org/lkml/2012/11/7/486.  This is at rcu/next. "

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

1 files changed, 44 insertions, 23 deletions

diff --git a/init/Kconfig b/init/Kconfig
index 6fdd6e339326..2054e048bb98 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -486,35 +486,35 @@ config PREEMPT_RCU
           This option enables preemptible-RCU code that is common between
           the TREE_PREEMPT_RCU and TINY_PREEMPT_RCU implementations.
 
+config CONTEXT_TRACKING
+       bool
+
 config RCU_USER_QS
         bool "Consider userspace as in RCU extended quiescent state"
-        depends on HAVE_RCU_USER_QS && SMP
+        depends on HAVE_CONTEXT_TRACKING && SMP
+        select CONTEXT_TRACKING
         help
           This option sets hooks on kernel / userspace boundaries and
           puts RCU in extended quiescent state when the CPU runs in
           userspace. It means that when a CPU runs in userspace, it is
           excluded from the global RCU state machine and thus doesn't
-          to keep the timer tick on for RCU.
+          try to keep the timer tick on for RCU.
 
           Unless you want to hack and help the development of the full
-          tickless feature, you shouldn't enable this option. It adds
-          unnecessary overhead.
+          dynticks mode, you shouldn't enable this option.  It also
+          adds unnecessary overhead.
 
           If unsure say N
 
-config RCU_USER_QS_FORCE
-        bool "Force userspace extended QS by default"
-        depends on RCU_USER_QS
+config CONTEXT_TRACKING_FORCE
+        bool "Force context tracking"
+        depends on CONTEXT_TRACKING
         help
-          Set the hooks in user/kernel boundaries by default in order to
-          test this feature that treats userspace as an extended quiescent
-          state until we have a real user like a full adaptive nohz option.
-
-          Unless you want to hack and help the development of the full
-          tickless feature, you shouldn't enable this option. It adds
-          unnecessary overhead.
-
-          If unsure say N
+          Probe on user/kernel boundaries by default in order to
+          test the features that rely on it such as userspace RCU extended
+          quiescent states.
+          This test is there for debugging until we have a real user like the
+          full dynticks mode.
 
 config RCU_FANOUT
         int "Tree-based hierarchical RCU fanout value"
@@ -582,14 +582,13 @@ config RCU_FAST_NO_HZ
         depends on NO_HZ && SMP
         default n
         help
-          This option causes RCU to attempt to accelerate grace periods
-          in order to allow CPUs to enter dynticks-idle state more
-          quickly.  On the other hand, this option increases the overhead
-          of the dynticks-idle checking, particularly on systems with
-          large numbers of CPUs.
+          This option causes RCU to attempt to accelerate grace periods in
+          order to allow CPUs to enter dynticks-idle state more quickly.
+          On the other hand, this option increases the overhead of the
+          dynticks-idle checking, thus degrading scheduling latency.
 
-          Say Y if energy efficiency is critically important, particularly
-                if you have relatively few CPUs.
+          Say Y if energy efficiency is critically important, and you don't
+                care about real-time response.
 
           Say N if you are unsure.
 
@@ -655,6 +654,28 @@ config RCU_BOOST_DELAY
 
           Accept the default if unsure.
 
+config RCU_NOCB_CPU
+        bool "Offload RCU callback processing from boot-selected CPUs"
+        depends on TREE_RCU || TREE_PREEMPT_RCU
+        default n
+        help
+          Use this option to reduce OS jitter for aggressive HPC or
+          real-time workloads.  It can also be used to offload RCU
+          callback invocation to energy-efficient CPUs in battery-powered
+          asymmetric multiprocessors.
+
+          This option offloads callback invocation from the set of
+          CPUs specified at boot time by the rcu_nocbs parameter.
+          For each such CPU, a kthread ("rcuoN") will be created to
+          invoke callbacks, where the "N" is the CPU being offloaded.
+          Nothing prevents this kthread from running on the specified
+          CPUs, but (1) the kthreads may be preempted between each
+          callback, and (2) affinity or cgroups can be used to force
+          the kthreads to run on whatever set of CPUs is desired.
+
+          Say Y here if you want reduced OS jitter on selected CPUs.
+          Say N here if you are unsure.
+
 endmenu # "RCU Subsystem"
 
 config IKCONFIG