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
  ...

6 files changed, 98 insertions, 15 deletions

diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h
index c5f856a040b9..5e4e6170f43a 100644
--- a/include/linux/interrupt.h
+++ b/include/linux/interrupt.h
@@ -430,6 +430,8 @@ enum
         NR_SOFTIRQS
 };
 
+#define SOFTIRQ_STOP_IDLE_MASK (~(1 << RCU_SOFTIRQ))
+
 /* map softirq index to softirq name. update 'softirq_to_name' in
  * kernel/softirq.c when adding a new softirq.
  */
diff --git a/include/linux/kthread.h b/include/linux/kthread.h
index 22ccf9dee177..8d816646f766 100644
--- a/include/linux/kthread.h
+++ b/include/linux/kthread.h
@@ -14,6 +14,11 @@ struct task_struct *kthread_create_on_node(int (*threadfn)(void *data),
         kthread_create_on_node(threadfn, data, -1, namefmt, ##arg)
 
 
+struct task_struct *kthread_create_on_cpu(int (*threadfn)(void *data),
+                                          void *data,
+                                          unsigned int cpu,
+                                          const char *namefmt);
+
 /**
  * kthread_run - create and wake a thread.
  * @threadfn: the function to run until signal_pending(current).
@@ -34,9 +39,13 @@ struct task_struct *kthread_create_on_node(int (*threadfn)(void *data),
 
 void kthread_bind(struct task_struct *k, unsigned int cpu);
 int kthread_stop(struct task_struct *k);
-int kthread_should_stop(void);
+bool kthread_should_stop(void);
+bool kthread_should_park(void);
 bool kthread_freezable_should_stop(bool *was_frozen);
 void *kthread_data(struct task_struct *k);
+int kthread_park(struct task_struct *k);
+void kthread_unpark(struct task_struct *k);
+void kthread_parkme(void);
 
 int kthreadd(void *unused);
 extern struct task_struct *kthreadd_task;
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 115ead2b5155..7c968e4f929e 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -191,6 +191,21 @@ extern void rcu_idle_enter(void);
 extern void rcu_idle_exit(void);
 extern void rcu_irq_enter(void);
 extern void rcu_irq_exit(void);
+
+#ifdef CONFIG_RCU_USER_QS
+extern void rcu_user_enter(void);
+extern void rcu_user_exit(void);
+extern void rcu_user_enter_after_irq(void);
+extern void rcu_user_exit_after_irq(void);
+extern void rcu_user_hooks_switch(struct task_struct *prev,
+                                  struct task_struct *next);
+#else
+static inline void rcu_user_enter(void) { }
+static inline void rcu_user_exit(void) { }
+static inline void rcu_user_enter_after_irq(void) { }
+static inline void rcu_user_exit_after_irq(void) { }
+#endif /* CONFIG_RCU_USER_QS */
+
 extern void exit_rcu(void);
 
 /**
@@ -210,14 +225,12 @@ extern void exit_rcu(void);
  * to nest RCU_NONIDLE() wrappers, but the nesting level is currently
  * quite limited.  If deeper nesting is required, it will be necessary
  * to adjust DYNTICK_TASK_NESTING_VALUE accordingly.
- *
- * This macro may be used from process-level code only.
  */
 #define RCU_NONIDLE(a) \
         do { \
-                rcu_idle_exit(); \
+                rcu_irq_enter(); \
                 do { a; } while (0); \
-                rcu_idle_enter(); \
+                rcu_irq_exit(); \
         } while (0)
 
 /*
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 23bddac4bad8..335720a1fc33 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1885,6 +1885,14 @@ static inline void rcu_copy_process(struct task_struct *p)
 
 #endif
 
+static inline void rcu_switch(struct task_struct *prev,
+                              struct task_struct *next)
+{
+#ifdef CONFIG_RCU_USER_QS
+        rcu_user_hooks_switch(prev, next);
+#endif
+}
+
 static inline void tsk_restore_flags(struct task_struct *task,
                                 unsigned long orig_flags, unsigned long flags)
 {
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
diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
index 802de56c41e8..2f322c38bd4d 100644
--- a/include/linux/tracepoint.h
+++ b/include/linux/tracepoint.h
@@ -136,6 +136,22 @@ static inline void tracepoint_synchronize_unregister(void)
                 postrcu;                                                \
         } while (0)
 
+#ifndef MODULE
+#define __DECLARE_TRACE_RCU(name, proto, args, cond, data_proto, data_args)     \
+        static inline void trace_##name##_rcuidle(proto)                \
+        {                                                               \
+                if (static_key_false(&__tracepoint_##name.key))         \
+                        __DO_TRACE(&__tracepoint_##name,                \
+                                TP_PROTO(data_proto),                   \
+                                TP_ARGS(data_args),                     \
+                                TP_CONDITION(cond),                     \
+                                rcu_idle_exit(),                        \
+                                rcu_idle_enter());                      \
+        }
+#else
+#define __DECLARE_TRACE_RCU(name, proto, args, cond, data_proto, data_args)
+#endif
+
 /*
  * Make sure the alignment of the structure in the __tracepoints section will
  * not add unwanted padding between the beginning of the section and the
@@ -151,16 +167,8 @@ static inline void tracepoint_synchronize_unregister(void)
                                 TP_ARGS(data_args),                     \
                                 TP_CONDITION(cond),,);                  \
         }                                                               \
-        static inline void trace_##name##_rcuidle(proto)                \
-        {                                                               \
-                if (static_key_false(&__tracepoint_##name.key))         \
-                        __DO_TRACE(&__tracepoint_##name,                \
-                                TP_PROTO(data_proto),                   \
-                                TP_ARGS(data_args),                     \
-                                TP_CONDITION(cond),                     \
-                                rcu_idle_exit(),                        \
-                                rcu_idle_enter());                      \
-        }                                                               \
+        __DECLARE_TRACE_RCU(name, PARAMS(proto), PARAMS(args),          \
+                PARAMS(cond), PARAMS(data_proto), PARAMS(data_args))    \
         static inline int                                               \
         register_trace_##name(void (*probe)(data_proto), void *data)    \
         {                                                               \