Check for use of RCU from dyntick-idle mode

index 99f9aa7..0a33075 100644
@@ -179,6 +179,14 @@ static inline void destroy_rcu_head_on_stack(struct rcu_head *head)
 }
 #endif	/* #else !CONFIG_DEBUG_OBJECTS_RCU_HEAD */
 
+
+#if defined(CONFIG_PROVE_RCU) && defined(CONFIG_NO_HZ)
+extern bool rcu_check_extended_qs(void);
+#else
+static inline bool rcu_check_extended_qs(void) { return false; }
+#endif
+
+
 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 
 extern struct lockdep_map rcu_lock_map;

@@ -210,11 +218,25 @@ 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 if the CPU is in an extended quiescent state, for example,
+ * if the CPU is in dyntick-idle mode, 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 extended quiescent states, 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 -- RCU would otherwise need to periodically wake up
+ * dyntick-idle CPUs, which would defeat the whole purpose of dyntick-idle
+ * mode.
  */
 static inline int rcu_read_lock_held(void)
 {
 	if (!debug_lockdep_rcu_enabled())
 		return 1;
+
+	if (rcu_check_extended_qs())
+		return 0;
+
 	return lock_is_held(&rcu_lock_map);
 }
 

@@ -238,6 +260,16 @@ 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 an extended quiescent state, for example,
+ * if the CPU is in dyntick-idle mode, 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 extended quiescent states, 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 -- RCU would otherwise need to periodically wake up
+ * dyntick-idle CPUs, which would defeat the whole purpose of dyntick-idle
+ * mode.
  */
 #ifdef CONFIG_PREEMPT
 static inline int rcu_read_lock_sched_held(void)

@@ -246,6 +278,10 @@ static inline int rcu_read_lock_sched_held(void)
 
 	if (!debug_lockdep_rcu_enabled())
 		return 1;
+
+	if (rcu_check_extended_qs())
+		return 0;
+
 	if (debug_locks)
 		lockdep_opinion = lock_is_held(&rcu_sched_lock_map);
 	return lockdep_opinion || preempt_count() != 0 || irqs_disabled();

index 7784bd2..a0e7e59 100644
@@ -82,12 +82,27 @@ EXPORT_SYMBOL_GPL(debug_lockdep_rcu_enabled);
  * that require that they be called within an RCU read-side critical
  * section.
  *
- * Check debug_lockdep_rcu_enabled() to prevent false positives during boot.
+ * Check debug_lockdep_rcu_enabled() to prevent false positives during boot
+ * and while lockdep is disabled.
+ *
+ * Note that if the CPU is in an extended quiescent state, for example,
+ * if the CPU is in dyntick-idle mode, 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 extended quiescent states, 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 -- RCU would otherwise need to periodically wake up
+ * dyntick-idle CPUs, which would defeat the whole purpose of dyntick-idle
+ * mode.
  */
 int rcu_read_lock_bh_held(void)
 {
 	if (!debug_lockdep_rcu_enabled())
 		return 1;
+
+	if (rcu_check_extended_qs())
+		return 0;
+
 	return in_softirq() || irqs_disabled();
 }
 EXPORT_SYMBOL_GPL(rcu_read_lock_bh_held);

index 7bbac7d..d01d390 100644
@@ -77,6 +77,20 @@ void rcu_exit_nohz(void)
 	rcu_dynticks_nesting++;
 }
 
+
+#ifdef CONFIG_PROVE_RCU
+
+bool rcu_check_extended_qs(void)
+{
+	if (!rcu_dynticks_nesting)
+		return true;
+
+	return false;
+}
+EXPORT_SYMBOL_GPL(rcu_check_extended_qs);
+
+#endif
+
 #endif /* #ifdef CONFIG_NO_HZ */
 
 /*

index 7e59ffb..485cdc9 100644
@@ -438,6 +438,22 @@ void rcu_irq_exit(void)
 	rcu_enter_nohz();
 }
 
+#ifdef CONFIG_PROVE_RCU
+
+bool rcu_check_extended_qs(void)
+{
+	struct rcu_dynticks *rdtp;
+
+	rdtp = &per_cpu(rcu_dynticks, raw_smp_processor_id());
+	if (atomic_read(&rdtp->dynticks) & 0x1)
+		return false;
+
+	return true;
+}
+EXPORT_SYMBOL_GPL(rcu_check_extended_qs);
+
+#endif /* CONFIG_PROVE_RCU */
+
 #ifdef CONFIG_SMP
 
 /*

index 298c927..f2bff04 100644
@@ -3998,6 +3998,26 @@ void lockdep_rcu_dereference(const char *file, const int line)
 			file, line);
 	printk("\nother info that might help us debug this:\n\n");
 	printk("\nrcu_scheduler_active = %d, debug_locks = %d\n", rcu_scheduler_active, debug_locks);
+
+	/*
+	 * If a CPU is in dyntick-idle mode (CONFIG_NO_HZ), then RCU
+	 * considers that CPU to be in an "extended quiescent state",
+	 * which means that RCU will be completely ignoring that CPU.
+	 * Therefore, rcu_read_lock() and friends have absolutely no
+	 * effect on a dyntick-idle CPU.  In other words, even if a
+	 * dyntick-idle CPU has called rcu_read_lock(), RCU might well
+	 * delete data structures out from under it.  RCU really has no
+	 * choice here: if it were to consult the CPU, that would wake
+	 * the CPU up, and the whole point of dyntick-idle mode is to
+	 * allow CPUs to enter extremely deep sleep states.
+	 *
+	 * So complain bitterly if someone does call rcu_read_lock(),
+	 * rcu_read_lock_bh() and so on from extended quiescent states
+	 * such as dyntick-idle mode.
+	 */
+	if (rcu_check_extended_qs())
+		printk("RCU used illegally from extended quiescent state!\n");
+
 	lockdep_print_held_locks(curr);
 	printk("\nstack backtrace:\n");
 	dump_stack();

index 0a33075..bf2c316 100644
@@ -189,21 +189,53 @@ static inline bool rcu_check_extended_qs(void) { return false; }
 
 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 
+static inline void rcu_lock_acquire(struct lockdep_map *map)
+{
+	WARN_ON_ONCE(rcu_check_extended_qs());
+	lock_acquire(map, 0, 0, 2, 1, NULL, _THIS_IP_);
+}
+
+static inline void rcu_lock_release(struct lockdep_map *map)
+{
+	WARN_ON_ONCE(rcu_check_extended_qs());
+	lock_release(map, 1, _THIS_IP_);
+}
+
 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_)
+
+static inline void rcu_read_acquire(void)
+{
+	rcu_lock_acquire(&rcu_lock_map);
+}
+
+static inline void rcu_read_release(void)
+{
+	rcu_lock_release(&rcu_lock_map);
+}
 
 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_read_acquire_bh(void)
+{
+	rcu_lock_acquire(&rcu_bh_lock_map);
+}
+
+static inline void rcu_read_release_bh(void)
+{
+	rcu_lock_release(&rcu_bh_lock_map);
+}
 
 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_read_acquire_sched(void)
+{
+	rcu_lock_acquire(&rcu_sched_lock_map);
+}
+
+static inline void rcu_read_release_sched(void)
+{
+	rcu_lock_release(&rcu_sched_lock_map);
+}
 
 extern int debug_lockdep_rcu_enabled(void);
 

index bf2c316..3fc3aeb 100644
@@ -202,41 +202,8 @@ static inline void rcu_lock_release(struct lockdep_map *map)
 }
 
 extern struct lockdep_map rcu_lock_map;
-
-static inline void rcu_read_acquire(void)
-{
-	rcu_lock_acquire(&rcu_lock_map);
-}
-
-static inline void rcu_read_release(void)
-{
-	rcu_lock_release(&rcu_lock_map);
-}
-
 extern struct lockdep_map rcu_bh_lock_map;
-
-static inline void rcu_read_acquire_bh(void)
-{
-	rcu_lock_acquire(&rcu_bh_lock_map);
-}
-
-static inline void rcu_read_release_bh(void)
-{
-	rcu_lock_release(&rcu_bh_lock_map);
-}
-
 extern struct lockdep_map rcu_sched_lock_map;
-
-static inline void rcu_read_acquire_sched(void)
-{
-	rcu_lock_acquire(&rcu_sched_lock_map);
-}
-
-static inline void rcu_read_release_sched(void)
-{
-	rcu_lock_release(&rcu_sched_lock_map);
-}
-
 extern int debug_lockdep_rcu_enabled(void);
 
 /**

@@ -327,12 +294,8 @@ 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)
 {

@@ -659,7 +622,7 @@ static inline void rcu_read_lock(void)
 {
 	__rcu_read_lock();
 	__acquire(RCU);
-	rcu_read_acquire();
+	rcu_lock_acquire(&rcu_lock_map);
 }
 
 /*

@@ -679,7 +642,7 @@ 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();
 }

@@ -700,7 +663,7 @@ static inline void rcu_read_lock_bh(void)
 {
 	__rcu_read_lock_bh();
 	__acquire(RCU_BH);
-	rcu_read_acquire_bh();
+	rcu_lock_acquire(&rcu_bh_lock_map);
 }
 
 /*

@@ -710,7 +673,7 @@ 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);
 	__rcu_read_unlock_bh();
 }

@@ -727,7 +690,7 @@ 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. */

@@ -744,7 +707,7 @@ 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();
 }

index 58971e8..fcbaee7 100644
@@ -28,6 +28,7 @@
 #define _LINUX_SRCU_H
 
 #include <linux/mutex.h>
+#include <linux/rcupdate.h>
 
 struct srcu_struct_array {
 	int c[2];

@@ -60,18 +61,10 @@ int __init_srcu_struct(struct srcu_struct *sp, const char *name,
 	__init_srcu_struct((sp), #sp, &__srcu_key); \
 })
 
-# define srcu_read_acquire(sp) \
-		lock_acquire(&(sp)->dep_map, 0, 0, 2, 1, NULL, _THIS_IP_)
-# define srcu_read_release(sp) \
-		lock_release(&(sp)->dep_map, 1, _THIS_IP_)
-
 #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
 
 int init_srcu_struct(struct srcu_struct *sp);
 
-# define srcu_read_acquire(sp)  do { } while (0)
-# define srcu_read_release(sp)  do { } while (0)
-
 #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
 
 void cleanup_srcu_struct(struct srcu_struct *sp);

@@ -90,11 +83,23 @@ long srcu_batches_completed(struct srcu_struct *sp);
  * read-side critical section.  In absence of CONFIG_DEBUG_LOCK_ALLOC,
  * this assumes we are in an SRCU read-side critical section unless it can
  * prove otherwise.
+ *
+ * Note that if the CPU is in an extended quiescent state, for example,
+ * if the CPU is in dyntick-idle mode, 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 extended quiescent states, 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 -- RCU would otherwise need to periodically wake up
+ * dyntick-idle CPUs, which would defeat the whole purpose of dyntick-idle
+ * mode.
  */
 static inline int srcu_read_lock_held(struct srcu_struct *sp)
 {
 	if (debug_locks)
 		return lock_is_held(&sp->dep_map);
+	if (rcu_check_extended_qs())
+		return 0;
 	return 1;
 }
 

@@ -150,7 +155,7 @@ static inline int srcu_read_lock(struct srcu_struct *sp) __acquires(sp)
 {
 	int retval = __srcu_read_lock(sp);
 
-	srcu_read_acquire(sp);
+	rcu_lock_acquire(&(sp)->dep_map);
 	return retval;
 }
 

@@ -164,7 +169,7 @@ static inline int srcu_read_lock(struct srcu_struct *sp) __acquires(sp)
 static inline void srcu_read_unlock(struct srcu_struct *sp, int idx)
 	__releases(sp)
 {
-	srcu_read_release(sp);
+	rcu_lock_release(&(sp)->dep_map);
 	__srcu_read_unlock(sp, idx);
 }
 

index fcbaee7..54a70b7 100644
@@ -84,6 +84,9 @@ long srcu_batches_completed(struct srcu_struct *sp);
  * this assumes we are in an SRCU read-side critical section unless it can
  * prove otherwise.
  *
+ * Checks debug_lockdep_rcu_enabled() to prevent false positives during boot
+ * and while lockdep is disabled.
+ *
  * Note that if the CPU is in an extended quiescent state, for example,
  * if the CPU is in dyntick-idle mode, then rcu_read_lock_held() returns
  * false even if the CPU did an rcu_read_lock().  The reason for this is

@@ -96,7 +99,7 @@ long srcu_batches_completed(struct srcu_struct *sp);
  */
 static inline int srcu_read_lock_held(struct srcu_struct *sp)
 {
-	if (debug_locks)
+	if (!debug_lockdep_rcu_enabled())
 		return lock_is_held(&sp->dep_map);
 	if (rcu_check_extended_qs())
 		return 0;