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

Pull RCU updates from Paul E. McKenney.

Major changes:

" 1.	Update RCU documentation.  These were posted to LKML at
	http://article.gmane.org/gmane.linux.kernel/1566994.

  2.	Miscellaneous fixes.  These were posted to LKML at
	http://article.gmane.org/gmane.linux.kernel/1567027.

  3.	Grace-period-related changes, primarily to aid in debugging,
	inspired by a -rt debugging session.  These were posted to
	LKML at http://article.gmane.org/gmane.linux.kernel/1567076.

  4.	Idle entry/exit changes, primarily to address issues located
	by Tibor Billes.  These were posted to LKML at
	http://article.gmane.org/gmane.linux.kernel/1567096.

  5.	Code reorganization moving RCU's source files from kernel
	to kernel/rcu.  This was posted to LKML at
	http://article.gmane.org/gmane.linux.kernel/1577344."

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

4 files changed, 52 insertions, 14 deletions

diff --git a/include/linux/rculist.h b/include/linux/rculist.h
index 4106721c4e5e..45a0a9e81478 100644
--- a/include/linux/rculist.h
+++ b/include/linux/rculist.h
@@ -19,6 +19,21 @@
  */
 
 /*
+ * INIT_LIST_HEAD_RCU - Initialize a list_head visible to RCU readers
+ * @list: list to be initialized
+ *
+ * You should instead use INIT_LIST_HEAD() for normal initialization and
+ * cleanup tasks, when readers have no access to the list being initialized.
+ * However, if the list being initialized is visible to readers, you
+ * need to keep the compiler from being too mischievous.
+ */
+static inline void INIT_LIST_HEAD_RCU(struct list_head *list)
+{
+        ACCESS_ONCE(list->next) = list;
+        ACCESS_ONCE(list->prev) = list;
+}
+
+/*
  * return the ->next pointer of a list_head in an rcu safe
  * way, we must not access it directly
  */
@@ -191,9 +206,13 @@ static inline void list_splice_init_rcu(struct list_head *list,
         if (list_empty(list))
                 return;
 
-        /* "first" and "last" tracking list, so initialize it. */
+        /*
+         * "first" and "last" tracking list, so initialize it.  RCU readers
+         * have access to this list, so we must use INIT_LIST_HEAD_RCU()
+         * instead of INIT_LIST_HEAD().
+         */
 
-        INIT_LIST_HEAD(list);
+        INIT_LIST_HEAD_RCU(list);
 
         /*
          * At this point, the list body still points to the source list.
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index f1f1bc39346b..39cbb889e20d 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -261,6 +261,10 @@ static inline void rcu_user_hooks_switch(struct task_struct *prev,
                 rcu_irq_exit(); \
         } while (0)
 
+#if defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_RCU_TRACE) || defined(CONFIG_SMP)
+extern bool __rcu_is_watching(void);
+#endif /* #if defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_RCU_TRACE) || defined(CONFIG_SMP) */
+
 /*
  * Infrastructure to implement the synchronize_() primitives in
  * TREE_RCU and rcu_barrier_() primitives in TINY_RCU.
@@ -297,10 +301,6 @@ static inline void destroy_rcu_head_on_stack(struct rcu_head *head)
 }
 #endif  /* #else !CONFIG_DEBUG_OBJECTS_RCU_HEAD */
 
-#if defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_SMP)
-extern int rcu_is_cpu_idle(void);
-#endif /* #if defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_SMP) */
-
 #if defined(CONFIG_HOTPLUG_CPU) && defined(CONFIG_PROVE_RCU)
 bool rcu_lockdep_current_cpu_online(void);
 #else /* #if defined(CONFIG_HOTPLUG_CPU) && defined(CONFIG_PROVE_RCU) */
@@ -351,7 +351,7 @@ static inline int rcu_read_lock_held(void)
 {
         if (!debug_lockdep_rcu_enabled())
                 return 1;
-        if (rcu_is_cpu_idle())
+        if (!rcu_is_watching())
                 return 0;
         if (!rcu_lockdep_current_cpu_online())
                 return 0;
@@ -402,7 +402,7 @@ static inline int rcu_read_lock_sched_held(void)
 
         if (!debug_lockdep_rcu_enabled())
                 return 1;
-        if (rcu_is_cpu_idle())
+        if (!rcu_is_watching())
                 return 0;
         if (!rcu_lockdep_current_cpu_online())
                 return 0;
@@ -771,7 +771,7 @@ static inline void rcu_read_lock(void)
         __rcu_read_lock();
         __acquire(RCU);
         rcu_lock_acquire(&rcu_lock_map);
-        rcu_lockdep_assert(!rcu_is_cpu_idle(),
+        rcu_lockdep_assert(rcu_is_watching(),
                            "rcu_read_lock() used illegally while idle");
 }
 
@@ -792,7 +792,7 @@ static inline void rcu_read_lock(void)
  */
 static inline void rcu_read_unlock(void)
 {
-        rcu_lockdep_assert(!rcu_is_cpu_idle(),
+        rcu_lockdep_assert(rcu_is_watching(),
                            "rcu_read_unlock() used illegally while idle");
         rcu_lock_release(&rcu_lock_map);
         __release(RCU);
@@ -821,7 +821,7 @@ static inline void rcu_read_lock_bh(void)
         local_bh_disable();
         __acquire(RCU_BH);
         rcu_lock_acquire(&rcu_bh_lock_map);
-        rcu_lockdep_assert(!rcu_is_cpu_idle(),
+        rcu_lockdep_assert(rcu_is_watching(),
                            "rcu_read_lock_bh() used illegally while idle");
 }
 
@@ -832,7 +832,7 @@ static inline void rcu_read_lock_bh(void)
  */
 static inline void rcu_read_unlock_bh(void)
 {
-        rcu_lockdep_assert(!rcu_is_cpu_idle(),
+        rcu_lockdep_assert(rcu_is_watching(),
                            "rcu_read_unlock_bh() used illegally while idle");
         rcu_lock_release(&rcu_bh_lock_map);
         __release(RCU_BH);
@@ -857,7 +857,7 @@ static inline void rcu_read_lock_sched(void)
         preempt_disable();
         __acquire(RCU_SCHED);
         rcu_lock_acquire(&rcu_sched_lock_map);
-        rcu_lockdep_assert(!rcu_is_cpu_idle(),
+        rcu_lockdep_assert(rcu_is_watching(),
                            "rcu_read_lock_sched() used illegally while idle");
 }
 
@@ -875,7 +875,7 @@ static inline notrace void rcu_read_lock_sched_notrace(void)
  */
 static inline void rcu_read_unlock_sched(void)
 {
-        rcu_lockdep_assert(!rcu_is_cpu_idle(),
+        rcu_lockdep_assert(rcu_is_watching(),
                            "rcu_read_unlock_sched() used illegally while idle");
         rcu_lock_release(&rcu_sched_lock_map);
         __release(RCU_SCHED);
diff --git a/include/linux/rcutiny.h b/include/linux/rcutiny.h
index e31005ee339e..09ebcbe9fd78 100644
--- a/include/linux/rcutiny.h
+++ b/include/linux/rcutiny.h
@@ -132,4 +132,21 @@ static inline void rcu_scheduler_starting(void)
 }
 #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
 
+#if defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_RCU_TRACE)
+
+static inline bool rcu_is_watching(void)
+{
+        return __rcu_is_watching();
+}
+
+#else /* defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_RCU_TRACE) */
+
+static inline bool rcu_is_watching(void)
+{
+        return true;
+}
+
+
+#endif /* #else defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_RCU_TRACE) */
+
 #endif /* __LINUX_RCUTINY_H */
diff --git a/include/linux/rcutree.h b/include/linux/rcutree.h
index 226169d1bd2b..4b9c81548742 100644
--- a/include/linux/rcutree.h
+++ b/include/linux/rcutree.h
@@ -90,4 +90,6 @@ extern void exit_rcu(void);
 extern void rcu_scheduler_starting(void);
 extern int rcu_scheduler_active __read_mostly;
 
+extern bool rcu_is_watching(void);
+
 #endif /* __LINUX_RCUTREE_H */