lockdep: annotate rcu_read_{,un}lock{,_bh}

lockdep annotate rcu_read_{,un}lock{,_bh} in order to catch imbalanced
usage.
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

include/linux/lockdep.h

@@ -252,6 +252,13 @@ extern void lockdep_on(void);
 extern void lockdep_init_map(struct lockdep_map *lock, const char *name,
 			     struct lock_class_key *key, int subclass);
 
+/*
+ * To initialize a lockdep_map statically use this macro.
+ * Note that _name must not be NULL.
+ */
+#define STATIC_LOCKDEP_MAP_INIT(_name, _key) \
+	{ .name = (_name), .key = (void *)(_key), }
+
 /*
  * Reinitialize a lock key - for cases where there is special locking or
  * special initialization of locks so that the validator gets the scope

include/linux/rcupdate.h

@@ -41,6 +41,7 @@
 #include <linux/percpu.h>
 #include <linux/cpumask.h>
 #include <linux/seqlock.h>
+#include <linux/lockdep.h>
 
 /**
  * struct rcu_head - callback structure for use with RCU
@@ -133,6 +134,15 @@ static inline void rcu_bh_qsctr_inc(int cpu)
 extern int rcu_pending(int cpu);
 extern int rcu_needs_cpu(int cpu);
 
+#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, _THIS_IP_)
+# define rcu_read_release()	lock_release(&rcu_lock_map, 1, _THIS_IP_)
+#else
+# define rcu_read_acquire()	do { } while (0)
+# define rcu_read_release()	do { } while (0)
+#endif
+
 /**
  * rcu_read_lock - mark the beginning of an RCU read-side critical section.
  *
@@ -166,6 +176,7 @@ extern int rcu_needs_cpu(int cpu);
 	do { \
 		preempt_disable(); \
 		__acquire(RCU); \
+		rcu_read_acquire(); \
 	} while(0)
 
 /**
@@ -175,6 +186,7 @@ extern int rcu_needs_cpu(int cpu);
  */
 #define rcu_read_unlock() \
 	do { \
+		rcu_read_release(); \
 		__release(RCU); \
 		preempt_enable(); \
 	} while(0)
@@ -204,6 +216,7 @@ extern int rcu_needs_cpu(int cpu);
 	do { \
 		local_bh_disable(); \
 		__acquire(RCU_BH); \
+		rcu_read_acquire(); \
 	} while(0)
 
 /*
@@ -213,6 +226,7 @@ extern int rcu_needs_cpu(int cpu);
  */
 #define rcu_read_unlock_bh() \
 	do { \
+		rcu_read_release(); \
 		__release(RCU_BH); \
 		local_bh_enable(); \
 	} while(0)

kernel/rcupdate.c

@@ -49,6 +49,14 @@
 #include <linux/cpu.h>
 #include <linux/mutex.h>
 
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+static struct lock_class_key rcu_lock_key;
+struct lockdep_map rcu_lock_map =
+	STATIC_LOCKDEP_MAP_INIT("rcu_read_lock", &rcu_lock_key);
+
+EXPORT_SYMBOL_GPL(rcu_lock_map);
+#endif
+
 /* Definition for rcupdate control block. */
 static struct rcu_ctrlblk rcu_ctrlblk = {
 	.cur = -300,