Merge branch 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull RCU changes from Ingo Molnar:

 0. 'idle RCU':

     Adds RCU APIs that allow non-idle tasks to enter RCU idle mode and
     provides x86 code to make use of them, allowing RCU to treat
     user-mode execution as an extended quiescent state when the new
     RCU_USER_QS kernel configuration parameter is specified.  (Work is
     in progress to port this to a few other architectures, but is not
     part of this series.)

 1.  A fix for a latent bug that has been in RCU ever since the addition
     of CPU stall warnings.  This bug results in false-positive stall
     warnings, but thus far only on embedded systems with severely
     cut-down userspace configurations.

 2.  Further reductions in latency spikes for huge systems, along with
     additional boot-time adaptation to the actual hardware.

     This is a large change, as it moves RCU grace-period initialization
     and cleanup, along with quiescent-state forcing, from softirq to a
     kthread.  However, it appears to be in quite good shape (famous
     last words).

 3.  Updates to documentation and rcutorture, the latter category
     including keeping statistics on CPU-hotplug latencies and fixing
     some initialization-time races.

 4.  CPU-hotplug fixes and improvements.

 5.  Idle-loop fixes that were omitted on an earlier submission.

 6.  Miscellaneous fixes and improvements

In certain RCU configurations new kernel threads will show up (rcu_bh,
rcu_sched), showing RCU processing overhead.

* 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (90 commits)
  rcu: Apply micro-optimization and int/bool fixes to RCU's idle handling
  rcu: Userspace RCU extended QS selftest
  x86: Exit RCU extended QS on notify resume
  x86: Use the new schedule_user API on userspace preemption
  rcu: Exit RCU extended QS on user preemption
  rcu: Exit RCU extended QS on kernel preemption after irq/exception
  x86: Exception hooks for userspace RCU extended QS
  x86: Unspaghettize do_general_protection()
  x86: Syscall hooks for userspace RCU extended QS
  rcu: Switch task's syscall hooks on context switch
  rcu: Ignore userspace extended quiescent state by default
  rcu: Allow rcu_user_enter()/exit() to nest
  rcu: Settle config for userspace extended quiescent state
  rcu: Make RCU_FAST_NO_HZ handle adaptive ticks
  rcu: New rcu_user_enter_after_irq() and rcu_user_exit_after_irq() APIs
  rcu: New rcu_user_enter() and rcu_user_exit() APIs
  ia64: Add missing RCU idle APIs on idle loop
  xtensa: Add missing RCU idle APIs on idle loop
  score: Add missing RCU idle APIs on idle loop
  parisc: Add missing RCU idle APIs on idle loop
  ...

1 files changed, 43 insertions, 0 deletions

diff --git a/include/linux/smpboot.h b/include/linux/smpboot.h
new file mode 100644
index 000000000000..e0106d8581d3
--- /dev/null
+++ b/include/linux/smpboot.h
@@ -0,0 +1,43 @@
+#ifndef _LINUX_SMPBOOT_H
+#define _LINUX_SMPBOOT_H
+
+#include <linux/types.h>
+
+struct task_struct;
+/* Cookie handed to the thread_fn*/
+struct smpboot_thread_data;
+
+/**
+ * struct smp_hotplug_thread - CPU hotplug related thread descriptor
+ * @store:              Pointer to per cpu storage for the task pointers
+ * @list:               List head for core management
+ * @thread_should_run:  Check whether the thread should run or not. Called with
+ *                      preemption disabled.
+ * @thread_fn:          The associated thread function
+ * @setup:              Optional setup function, called when the thread gets
+ *                      operational the first time
+ * @cleanup:            Optional cleanup function, called when the thread
+ *                      should stop (module exit)
+ * @park:               Optional park function, called when the thread is
+ *                      parked (cpu offline)
+ * @unpark:             Optional unpark function, called when the thread is
+ *                      unparked (cpu online)
+ * @thread_comm:        The base name of the thread
+ */
+struct smp_hotplug_thread {
+        struct task_struct __percpu     **store;
+        struct list_head                list;
+        int                             (*thread_should_run)(unsigned int cpu);
+        void                            (*thread_fn)(unsigned int cpu);
+        void                            (*setup)(unsigned int cpu);
+        void                            (*cleanup)(unsigned int cpu, bool online);
+        void                            (*park)(unsigned int cpu);
+        void                            (*unpark)(unsigned int cpu);
+        const char                      *thread_comm;
+};
+
+int smpboot_register_percpu_thread(struct smp_hotplug_thread *plug_thread);
+void smpboot_unregister_percpu_thread(struct smp_hotplug_thread *plug_thread);
+int smpboot_thread_schedule(void);
+
+#endif