7 files changed, 267 insertions, 31 deletions

diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 24440f4bf476..e3d37efe2703 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -78,14 +78,120 @@ extern void rcu_init(void);
 } while (0)
 
 #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_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_)
-#else
-# define rcu_read_acquire()     do { } while (0)
-# define rcu_read_release()     do { } while (0)
-#endif
+
+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_)
+
+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_)
+
+/**
+ * rcu_read_lock_held - might we be in RCU read-side critical section?
+ *
+ * If CONFIG_PROVE_LOCKING is selected and enabled, returns nonzero iff in
+ * an RCU read-side critical section.  In absence of CONFIG_PROVE_LOCKING,
+ * this assumes we are in an RCU read-side critical section unless it can
+ * prove otherwise.
+ */
+static inline int rcu_read_lock_held(void)
+{
+        if (debug_locks)
+                return lock_is_held(&rcu_lock_map);
+        return 1;
+}
+
+/**
+ * rcu_read_lock_bh_held - might we be in RCU-bh read-side critical section?
+ *
+ * If CONFIG_PROVE_LOCKING is selected and enabled, returns nonzero iff in
+ * an RCU-bh read-side critical section.  In absence of CONFIG_PROVE_LOCKING,
+ * this assumes we are in an RCU-bh read-side critical section unless it can
+ * prove otherwise.
+ */
+static inline int rcu_read_lock_bh_held(void)
+{
+        if (debug_locks)
+                return lock_is_held(&rcu_bh_lock_map);
+        return 1;
+}
+
+/**
+ * rcu_read_lock_sched_held - might we be in RCU-sched read-side critical section?
+ *
+ * If CONFIG_PROVE_LOCKING is selected and enabled, returns nonzero iff in an
+ * RCU-sched read-side critical section.  In absence of CONFIG_PROVE_LOCKING,
+ * this assumes we are in an RCU-sched read-side critical section unless it
+ * can prove otherwise.  Note that disabling of preemption (including
+ * disabling irqs) counts as an RCU-sched read-side critical section.
+ */
+static inline int rcu_read_lock_sched_held(void)
+{
+        int lockdep_opinion = 0;
+
+        if (debug_locks)
+                lockdep_opinion = lock_is_held(&rcu_sched_lock_map);
+        return lockdep_opinion || preempt_count() != 0;
+}
+
+#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)
+
+static inline int rcu_read_lock_held(void)
+{
+        return 1;
+}
+
+static inline int rcu_read_lock_bh_held(void)
+{
+        return 1;
+}
+
+static inline int rcu_read_lock_sched_held(void)
+{
+        return preempt_count() != 0;
+}
+
+#endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
+
+#ifdef CONFIG_PROVE_RCU
+
+/**
+ * rcu_dereference_check - rcu_dereference with debug checking
+ *
+ * Do an rcu_dereference(), but check that the context is correct.
+ * For example, rcu_dereference_check(gp, rcu_read_lock_held()) to
+ * ensure that the rcu_dereference_check() executes within an RCU
+ * read-side critical section.  It is also possible to check for
+ * locks being held, for example, by using lockdep_is_held().
+ */
+#define rcu_dereference_check(p, c) \
+        ({ \
+                if (debug_locks) \
+                        WARN_ON_ONCE(!(c)); \
+                rcu_dereference(p); \
+        })
+
+#else /* #ifdef CONFIG_PROVE_RCU */
+
+#define rcu_dereference_check(p, c)     rcu_dereference(p)
+
+#endif /* #else #ifdef CONFIG_PROVE_RCU */
 
 /**
  * rcu_read_lock - mark the beginning of an RCU read-side critical section.
@@ -160,7 +266,7 @@ static inline void rcu_read_lock_bh(void)
 {
         __rcu_read_lock_bh();
         __acquire(RCU_BH);
-        rcu_read_acquire();
+        rcu_read_acquire_bh();
 }
 
 /*
@@ -170,7 +276,7 @@ static inline void rcu_read_lock_bh(void)
  */
 static inline void rcu_read_unlock_bh(void)
 {
-        rcu_read_release();
+        rcu_read_release_bh();
         __release(RCU_BH);
         __rcu_read_unlock_bh();
 }
@@ -188,7 +294,7 @@ static inline void rcu_read_lock_sched(void)
 {
         preempt_disable();
         __acquire(RCU_SCHED);
-        rcu_read_acquire();
+        rcu_read_acquire_sched();
 }
 
 /* Used by lockdep and tracing: cannot be traced, cannot call lockdep. */
@@ -205,7 +311,7 @@ static inline notrace void rcu_read_lock_sched_notrace(void)
  */
 static inline void rcu_read_unlock_sched(void)
 {
-        rcu_read_release();
+        rcu_read_release_sched();
         __release(RCU_SCHED);
         preempt_enable();
 }
diff --git a/include/linux/srcu.h b/include/linux/srcu.h
index 4765d97dcafb..adbe1670b366 100644
--- a/include/linux/srcu.h
+++ b/include/linux/srcu.h
@@ -35,6 +35,9 @@ struct srcu_struct {
         int completed;
         struct srcu_struct_array *per_cpu_ref;
         struct mutex mutex;
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+        struct lockdep_map dep_map;
+#endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
 };
 
 #ifndef CONFIG_PREEMPT
@@ -43,12 +46,92 @@ struct srcu_struct {
 #define srcu_barrier()
 #endif /* #else #ifndef CONFIG_PREEMPT */
 
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+
+int __init_srcu_struct(struct srcu_struct *sp, const char *name,
+                       struct lock_class_key *key);
+
+#define init_srcu_struct(sp) \
+({ \
+        static struct lock_class_key __srcu_key; \
+        \
+        __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);
-int srcu_read_lock(struct srcu_struct *sp) __acquires(sp);
-void srcu_read_unlock(struct srcu_struct *sp, int idx) __releases(sp);
+int __srcu_read_lock(struct srcu_struct *sp) __acquires(sp);
+void __srcu_read_unlock(struct srcu_struct *sp, int idx) __releases(sp);
 void synchronize_srcu(struct srcu_struct *sp);
 void synchronize_srcu_expedited(struct srcu_struct *sp);
 long srcu_batches_completed(struct srcu_struct *sp);
 
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+
+/**
+ * srcu_read_lock_held - might we be in SRCU read-side critical section?
+ *
+ * If CONFIG_PROVE_LOCKING is selected and enabled, returns nonzero iff in
+ * an SRCU read-side critical section.  In absence of CONFIG_PROVE_LOCKING,
+ * this assumes we are in an SRCU read-side critical section unless it can
+ * prove otherwise.
+ */
+static inline int srcu_read_lock_held(struct srcu_struct *sp)
+{
+        if (debug_locks)
+                return lock_is_held(&sp->dep_map);
+        return 1;
+}
+
+#else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
+
+static inline int srcu_read_lock_held(struct srcu_struct *sp)
+{
+        return 1;
+}
+
+#endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
+
+/**
+ * srcu_read_lock - register a new reader for an SRCU-protected structure.
+ * @sp: srcu_struct in which to register the new reader.
+ *
+ * Enter an SRCU read-side critical section.  Note that SRCU read-side
+ * critical sections may be nested.
+ */
+static inline int srcu_read_lock(struct srcu_struct *sp) __acquires(sp)
+{
+        int retval = __srcu_read_lock(sp);
+
+        srcu_read_acquire(sp);
+        return retval;
+}
+
+/**
+ * srcu_read_unlock - unregister a old reader from an SRCU-protected structure.
+ * @sp: srcu_struct in which to unregister the old reader.
+ * @idx: return value from corresponding srcu_read_lock().
+ *
+ * Exit an SRCU read-side critical section.
+ */
+static inline void srcu_read_unlock(struct srcu_struct *sp, int idx)
+        __releases(sp)
+{
+        srcu_read_release(sp);
+        __srcu_read_unlock(sp, idx);
+}
+
 #endif
diff --git a/kernel/rcupdate.c b/kernel/rcupdate.c
index 9b7fd4723878..033cb55c26df 100644
--- a/kernel/rcupdate.c
+++ b/kernel/rcupdate.c
@@ -50,6 +50,16 @@ 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);
+
+static struct lock_class_key rcu_bh_lock_key;
+struct lockdep_map rcu_bh_lock_map =
+        STATIC_LOCKDEP_MAP_INIT("rcu_read_lock_bh", &rcu_bh_lock_key);
+EXPORT_SYMBOL_GPL(rcu_bh_lock_map);
+
+static struct lock_class_key rcu_sched_lock_key;
+struct lockdep_map rcu_sched_lock_map =
+        STATIC_LOCKDEP_MAP_INIT("rcu_read_lock_sched", &rcu_sched_lock_key);
+EXPORT_SYMBOL_GPL(rcu_sched_lock_map);
 #endif
 
 /*
diff --git a/kernel/rcutorture.c b/kernel/rcutorture.c
index adda92bfafac..5f43f30fcd1d 100644
--- a/kernel/rcutorture.c
+++ b/kernel/rcutorture.c
@@ -796,7 +796,11 @@ static void rcu_torture_timer(unsigned long unused)
 
         idx = cur_ops->readlock();
         completed = cur_ops->completed();
-        p = rcu_dereference(rcu_torture_current);
+        p = rcu_dereference_check(rcu_torture_current,
+                                  rcu_read_lock_held() ||
+                                  rcu_read_lock_bh_held() ||
+                                  rcu_read_lock_sched_held() ||
+                                  srcu_read_lock_held(&srcu_ctl));
         if (p == NULL) {
                 /* Leave because rcu_torture_writer is not yet underway */
                 cur_ops->readunlock(idx);
@@ -853,7 +857,11 @@ rcu_torture_reader(void *arg)
                 }
                 idx = cur_ops->readlock();
                 completed = cur_ops->completed();
-                p = rcu_dereference(rcu_torture_current);
+                p = rcu_dereference_check(rcu_torture_current,
+                                          rcu_read_lock_held() ||
+                                          rcu_read_lock_bh_held() ||
+                                          rcu_read_lock_sched_held() ||
+                                          srcu_read_lock_held(&srcu_ctl));
                 if (p == NULL) {
                         /* Wait for rcu_torture_writer to get underway */
                         cur_ops->readunlock(idx);
diff --git a/kernel/srcu.c b/kernel/srcu.c
index 31b275b9c112..bde4295774c8 100644
--- a/kernel/srcu.c
+++ b/kernel/srcu.c
@@ -34,6 +34,30 @@
 #include <linux/smp.h>
 #include <linux/srcu.h>
 
+static int init_srcu_struct_fields(struct srcu_struct *sp)
+{
+        sp->completed = 0;
+        mutex_init(&sp->mutex);
+        sp->per_cpu_ref = alloc_percpu(struct srcu_struct_array);
+        return sp->per_cpu_ref ? 0 : -ENOMEM;
+}
+
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+
+int __init_srcu_struct(struct srcu_struct *sp, const char *name,
+                       struct lock_class_key *key)
+{
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+        /* Don't re-initialize a lock while it is held. */
+        debug_check_no_locks_freed((void *)sp, sizeof(*sp));
+        lockdep_init_map(&sp->dep_map, name, key, 0);
+#endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
+        return init_srcu_struct_fields(sp);
+}
+EXPORT_SYMBOL_GPL(__init_srcu_struct);
+
+#else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
+
 /**
  * init_srcu_struct - initialize a sleep-RCU structure
  * @sp: structure to initialize.
@@ -44,13 +68,12 @@
  */
 int init_srcu_struct(struct srcu_struct *sp)
 {
-        sp->completed = 0;
-        mutex_init(&sp->mutex);
-        sp->per_cpu_ref = alloc_percpu(struct srcu_struct_array);
-        return (sp->per_cpu_ref ? 0 : -ENOMEM);
+        return init_srcu_struct_fields(sp);
 }
 EXPORT_SYMBOL_GPL(init_srcu_struct);
 
+#endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
+
 /*
  * srcu_readers_active_idx -- returns approximate number of readers
  *      active on the specified rank of per-CPU counters.
@@ -100,15 +123,12 @@ void cleanup_srcu_struct(struct srcu_struct *sp)
 }
 EXPORT_SYMBOL_GPL(cleanup_srcu_struct);
 
-/**
- * srcu_read_lock - register a new reader for an SRCU-protected structure.
- * @sp: srcu_struct in which to register the new reader.
- *
+/*
  * Counts the new reader in the appropriate per-CPU element of the
  * srcu_struct.  Must be called from process context.
  * Returns an index that must be passed to the matching srcu_read_unlock().
  */
-int srcu_read_lock(struct srcu_struct *sp)
+int __srcu_read_lock(struct srcu_struct *sp)
 {
         int idx;
 
@@ -120,26 +140,22 @@ int srcu_read_lock(struct srcu_struct *sp)
         preempt_enable();
         return idx;
 }
-EXPORT_SYMBOL_GPL(srcu_read_lock);
+EXPORT_SYMBOL_GPL(__srcu_read_lock);
 
-/**
- * srcu_read_unlock - unregister a old reader from an SRCU-protected structure.
- * @sp: srcu_struct in which to unregister the old reader.
- * @idx: return value from corresponding srcu_read_lock().
- *
+/*
  * Removes the count for the old reader from the appropriate per-CPU
  * element of the srcu_struct.  Note that this may well be a different
  * CPU than that which was incremented by the corresponding srcu_read_lock().
  * Must be called from process context.
  */
-void srcu_read_unlock(struct srcu_struct *sp, int idx)
+void __srcu_read_unlock(struct srcu_struct *sp, int idx)
 {
         preempt_disable();
         srcu_barrier();  /* ensure compiler won't misorder critical section. */
         per_cpu_ptr(sp->per_cpu_ref, smp_processor_id())->c[idx]--;
         preempt_enable();
 }
-EXPORT_SYMBOL_GPL(srcu_read_unlock);
+EXPORT_SYMBOL_GPL(__srcu_read_unlock);
 
 /*
  * Helper function for synchronize_srcu() and synchronize_srcu_expedited().
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 6bf97d176326..6af20a8a0a54 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -499,6 +499,18 @@ config PROVE_LOCKING
 
          For more details, see Documentation/lockdep-design.txt.
 
+config PROVE_RCU
+        bool "RCU debugging: prove RCU correctness"
+        depends on PROVE_LOCKING
+        default n
+        help
+         This feature enables lockdep extensions that check for correct
+         use of RCU APIs.  This is currently under development.  Say Y
+         if you want to debug RCU usage or help work on the PROVE_RCU
+         feature.
+
+         Say N if you are unsure.
+
 config LOCKDEP
         bool
         depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
diff --git a/lib/debug_locks.c b/lib/debug_locks.c
index bc3b11731b9c..5bf0020b9248 100644
--- a/lib/debug_locks.c
+++ b/lib/debug_locks.c
@@ -23,6 +23,7 @@
  * shut up after that.
  */
 int debug_locks = 1;
+EXPORT_SYMBOL_GPL(debug_locks);
 
 /*
  * The locking-testsuite uses <debug_locks_silent> to get a