1 files changed, 73 insertions, 42 deletions

diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 2cf4226ade7e..81c04f4348ec 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -51,6 +51,8 @@ extern int rcutorture_runnable; /* for sysctl */
 #if defined(CONFIG_TREE_RCU) || defined(CONFIG_TREE_PREEMPT_RCU)
 extern void rcutorture_record_test_transition(void);
 extern void rcutorture_record_progress(unsigned long vernum);
+extern void do_trace_rcu_torture_read(char *rcutorturename,
+                                      struct rcu_head *rhp);
 #else
 static inline void rcutorture_record_test_transition(void)
 {
@@ -58,6 +60,12 @@ static inline void rcutorture_record_test_transition(void)
 static inline void rcutorture_record_progress(unsigned long vernum)
 {
 }
+#ifdef CONFIG_RCU_TRACE
+extern void do_trace_rcu_torture_read(char *rcutorturename,
+                                      struct rcu_head *rhp);
+#else
+#define do_trace_rcu_torture_read(rcutorturename, rhp) do { } while (0)
+#endif
 #endif
 
 #define UINT_CMP_GE(a, b)       (UINT_MAX / 2 >= (a) - (b))
@@ -177,23 +185,10 @@ extern void rcu_sched_qs(int cpu);
 extern void rcu_bh_qs(int cpu);
 extern void rcu_check_callbacks(int cpu, int user);
 struct notifier_block;
-
-#ifdef CONFIG_NO_HZ
-
-extern void rcu_enter_nohz(void);
-extern void rcu_exit_nohz(void);
-
-#else /* #ifdef CONFIG_NO_HZ */
-
-static inline void rcu_enter_nohz(void)
-{
-}
-
-static inline void rcu_exit_nohz(void)
-{
-}
-
-#endif /* #else #ifdef CONFIG_NO_HZ */
+extern void rcu_idle_enter(void);
+extern void rcu_idle_exit(void);
+extern void rcu_irq_enter(void);
+extern void rcu_irq_exit(void);
 
 /*
  * Infrastructure to implement the synchronize_() primitives in
@@ -233,22 +228,30 @@ static inline void destroy_rcu_head_on_stack(struct rcu_head *head)
 
 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 
-extern struct lockdep_map rcu_lock_map;
-# define rcu_read_acquire() \
-                lock_acquire(&rcu_lock_map, 0, 0, 2, 1, NULL, _THIS_IP_)
-# define rcu_read_release()     lock_release(&rcu_lock_map, 1, _THIS_IP_)
+#ifdef CONFIG_PROVE_RCU
+extern int rcu_is_cpu_idle(void);
+#else /* !CONFIG_PROVE_RCU */
+static inline int rcu_is_cpu_idle(void)
+{
+        return 0;
+}
+#endif /* else !CONFIG_PROVE_RCU */
 
-extern struct lockdep_map rcu_bh_lock_map;
-# define rcu_read_acquire_bh() \
-                lock_acquire(&rcu_bh_lock_map, 0, 0, 2, 1, NULL, _THIS_IP_)
-# define rcu_read_release_bh()  lock_release(&rcu_bh_lock_map, 1, _THIS_IP_)
+static inline void rcu_lock_acquire(struct lockdep_map *map)
+{
+        WARN_ON_ONCE(rcu_is_cpu_idle());
+        lock_acquire(map, 0, 0, 2, 1, NULL, _THIS_IP_);
+}
 
-extern struct lockdep_map rcu_sched_lock_map;
-# define rcu_read_acquire_sched() \
-                lock_acquire(&rcu_sched_lock_map, 0, 0, 2, 1, NULL, _THIS_IP_)
-# define rcu_read_release_sched() \
-                lock_release(&rcu_sched_lock_map, 1, _THIS_IP_)
+static inline void rcu_lock_release(struct lockdep_map *map)
+{
+        WARN_ON_ONCE(rcu_is_cpu_idle());
+        lock_release(map, 1, _THIS_IP_);
+}
 
+extern struct lockdep_map rcu_lock_map;
+extern struct lockdep_map rcu_bh_lock_map;
+extern struct lockdep_map rcu_sched_lock_map;
 extern int debug_lockdep_rcu_enabled(void);
 
 /**
@@ -262,11 +265,18 @@ extern int debug_lockdep_rcu_enabled(void);
  *
  * Checks debug_lockdep_rcu_enabled() to prevent false positives during boot
  * and while lockdep is disabled.
+ *
+ * Note that rcu_read_lock() and the matching rcu_read_unlock() must
+ * occur in the same context, for example, it is illegal to invoke
+ * rcu_read_unlock() in process context if the matching rcu_read_lock()
+ * was invoked from within an irq handler.
  */
 static inline int rcu_read_lock_held(void)
 {
         if (!debug_lockdep_rcu_enabled())
                 return 1;
+        if (rcu_is_cpu_idle())
+                return 0;
         return lock_is_held(&rcu_lock_map);
 }
 
@@ -290,6 +300,19 @@ extern int rcu_read_lock_bh_held(void);
  *
  * Check debug_lockdep_rcu_enabled() to prevent false positives during boot
  * and while lockdep is disabled.
+ *
+ * Note that if the CPU is in the idle loop from an RCU point of
+ * view (ie: that we are in the section between rcu_idle_enter() and
+ * rcu_idle_exit()) then rcu_read_lock_held() returns false even if the CPU
+ * did an rcu_read_lock().  The reason for this is that RCU ignores CPUs
+ * that are in such a section, considering these as in extended quiescent
+ * state, so such a CPU is effectively never in an RCU read-side critical
+ * section regardless of what RCU primitives it invokes.  This state of
+ * affairs is required --- we need to keep an RCU-free window in idle
+ * where the CPU may possibly enter into low power mode. This way we can
+ * notice an extended quiescent state to other CPUs that started a grace
+ * period. Otherwise we would delay any grace period as long as we run in
+ * the idle task.
  */
 #ifdef CONFIG_PREEMPT_COUNT
 static inline int rcu_read_lock_sched_held(void)
@@ -298,6 +321,8 @@ static inline int rcu_read_lock_sched_held(void)
 
         if (!debug_lockdep_rcu_enabled())
                 return 1;
+        if (rcu_is_cpu_idle())
+                return 0;
         if (debug_locks)
                 lockdep_opinion = lock_is_held(&rcu_sched_lock_map);
         return lockdep_opinion || preempt_count() != 0 || irqs_disabled();
@@ -311,12 +336,8 @@ static inline int rcu_read_lock_sched_held(void)
 
 #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
 
-# define rcu_read_acquire()             do { } while (0)
-# define rcu_read_release()             do { } while (0)
-# define rcu_read_acquire_bh()          do { } while (0)
-# define rcu_read_release_bh()          do { } while (0)
-# define rcu_read_acquire_sched()       do { } while (0)
-# define rcu_read_release_sched()       do { } while (0)
+# define rcu_lock_acquire(a)            do { } while (0)
+# define rcu_lock_release(a)            do { } while (0)
 
 static inline int rcu_read_lock_held(void)
 {
@@ -637,7 +658,7 @@ static inline void rcu_read_lock(void)
 {
         __rcu_read_lock();
         __acquire(RCU);
-        rcu_read_acquire();
+        rcu_lock_acquire(&rcu_lock_map);
 }
 
 /*
@@ -657,7 +678,7 @@ static inline void rcu_read_lock(void)
  */
 static inline void rcu_read_unlock(void)
 {
-        rcu_read_release();
+        rcu_lock_release(&rcu_lock_map);
         __release(RCU);
         __rcu_read_unlock();
 }
@@ -673,12 +694,17 @@ static inline void rcu_read_unlock(void)
  * critical sections in interrupt context can use just rcu_read_lock(),
  * though this should at least be commented to avoid confusing people
  * reading the code.
+ *
+ * Note that rcu_read_lock_bh() and the matching rcu_read_unlock_bh()
+ * must occur in the same context, for example, it is illegal to invoke
+ * rcu_read_unlock_bh() from one task if the matching rcu_read_lock_bh()
+ * was invoked from some other task.
  */
 static inline void rcu_read_lock_bh(void)
 {
         local_bh_disable();
         __acquire(RCU_BH);
-        rcu_read_acquire_bh();
+        rcu_lock_acquire(&rcu_bh_lock_map);
 }
 
 /*
@@ -688,7 +714,7 @@ static inline void rcu_read_lock_bh(void)
  */
 static inline void rcu_read_unlock_bh(void)
 {
-        rcu_read_release_bh();
+        rcu_lock_release(&rcu_bh_lock_map);
         __release(RCU_BH);
         local_bh_enable();
 }
@@ -700,12 +726,17 @@ static inline void rcu_read_unlock_bh(void)
  * are being done using call_rcu_sched() or synchronize_rcu_sched().
  * Read-side critical sections can also be introduced by anything that
  * disables preemption, including local_irq_disable() and friends.
+ *
+ * Note that rcu_read_lock_sched() and the matching rcu_read_unlock_sched()
+ * must occur in the same context, for example, it is illegal to invoke
+ * rcu_read_unlock_sched() from process context if the matching
+ * rcu_read_lock_sched() was invoked from an NMI handler.
  */
 static inline void rcu_read_lock_sched(void)
 {
         preempt_disable();
         __acquire(RCU_SCHED);
-        rcu_read_acquire_sched();
+        rcu_lock_acquire(&rcu_sched_lock_map);
 }
 
 /* Used by lockdep and tracing: cannot be traced, cannot call lockdep. */
@@ -722,7 +753,7 @@ static inline notrace void rcu_read_lock_sched_notrace(void)
  */
 static inline void rcu_read_unlock_sched(void)
 {
-        rcu_read_release_sched();
+        rcu_lock_release(&rcu_sched_lock_map);
         __release(RCU_SCHED);
         preempt_enable();
 }