1 files changed, 93 insertions, 24 deletions

diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index c84373626336..db266bbed23f 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -41,6 +41,10 @@
 #include <linux/lockdep.h>
 #include <linux/completion.h>
 
+#ifdef CONFIG_RCU_TORTURE_TEST
+extern int rcutorture_runnable; /* for sysctl */
+#endif /* #ifdef CONFIG_RCU_TORTURE_TEST */
+
 /**
  * struct rcu_head - callback structure for use with RCU
  * @next: next update requests in a list
@@ -97,6 +101,8 @@ extern struct lockdep_map rcu_sched_lock_map;
 # define rcu_read_release_sched() \
                 lock_release(&rcu_sched_lock_map, 1, _THIS_IP_)
 
+extern int debug_lockdep_rcu_enabled(void);
+
 /**
  * rcu_read_lock_held - might we be in RCU read-side critical section?
  *
@@ -104,28 +110,21 @@ extern struct lockdep_map rcu_sched_lock_map;
  * 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.
+ *
+ * Check rcu_scheduler_active to prevent false positives during boot.
  */
 static inline int rcu_read_lock_held(void)
 {
-        if (debug_locks)
-                return lock_is_held(&rcu_lock_map);
-        return 1;
+        if (!debug_lockdep_rcu_enabled())
+                return 1;
+        return lock_is_held(&rcu_lock_map);
 }
 
-/**
- * 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.
+/*
+ * rcu_read_lock_bh_held() is defined out of line to avoid #include-file
+ * hell.
  */
-static inline int rcu_read_lock_bh_held(void)
-{
-        if (debug_locks)
-                return lock_is_held(&rcu_bh_lock_map);
-        return 1;
-}
+extern int rcu_read_lock_bh_held(void);
 
 /**
  * rcu_read_lock_sched_held - might we be in RCU-sched read-side critical section?
@@ -135,15 +134,26 @@ static inline int rcu_read_lock_bh_held(void)
  * 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.
+ *
+ * Check rcu_scheduler_active to prevent false positives during boot.
  */
+#ifdef CONFIG_PREEMPT
 static inline int rcu_read_lock_sched_held(void)
 {
         int lockdep_opinion = 0;
 
+        if (!debug_lockdep_rcu_enabled())
+                return 1;
         if (debug_locks)
                 lockdep_opinion = lock_is_held(&rcu_sched_lock_map);
-        return lockdep_opinion || preempt_count() != 0 || !rcu_scheduler_active;
+        return lockdep_opinion || preempt_count() != 0 || irqs_disabled();
 }
+#else /* #ifdef CONFIG_PREEMPT */
+static inline int rcu_read_lock_sched_held(void)
+{
+        return 1;
+}
+#endif /* #else #ifdef CONFIG_PREEMPT */
 
 #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
 
@@ -164,38 +174,97 @@ static inline int rcu_read_lock_bh_held(void)
         return 1;
 }
 
+#ifdef CONFIG_PREEMPT
 static inline int rcu_read_lock_sched_held(void)
 {
-        return preempt_count() != 0 || !rcu_scheduler_active;
+        return !rcu_scheduler_active || preempt_count() != 0 || irqs_disabled();
 }
+#else /* #ifdef CONFIG_PREEMPT */
+static inline int rcu_read_lock_sched_held(void)
+{
+        return 1;
+}
+#endif /* #else #ifdef CONFIG_PREEMPT */
 
 #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
 
 #ifdef CONFIG_PROVE_RCU
 
+extern int rcu_my_thread_group_empty(void);
+
 /**
  * rcu_dereference_check - rcu_dereference with debug checking
+ * @p: The pointer to read, prior to dereferencing
+ * @c: The conditions under which the dereference will take place
+ *
+ * Do an rcu_dereference(), but check that the conditions under which the
+ * dereference will take place are correct.  Typically the conditions indicate
+ * the various locking conditions that should be held at that point.  The check
+ * should return true if the conditions are satisfied.
  *
- * 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().
+ * For example:
+ *
+ *      bar = rcu_dereference_check(foo->bar, rcu_read_lock_held() ||
+ *                                            lockdep_is_held(&foo->lock));
+ *
+ * could be used to indicate to lockdep that foo->bar may only be dereferenced
+ * if either the RCU read lock is held, or that the lock required to replace
+ * the bar struct at foo->bar is held.
+ *
+ * Note that the list of conditions may also include indications of when a lock
+ * need not be held, for example during initialisation or destruction of the
+ * target struct:
+ *
+ *      bar = rcu_dereference_check(foo->bar, rcu_read_lock_held() ||
+ *                                            lockdep_is_held(&foo->lock) ||
+ *                                            atomic_read(&foo->usage) == 0);
  */
 #define rcu_dereference_check(p, c) \
         ({ \
-                if (debug_locks && !(c)) \
+                if (debug_lockdep_rcu_enabled() && !(c)) \
                         lockdep_rcu_dereference(__FILE__, __LINE__); \
                 rcu_dereference_raw(p); \
         })
 
+/**
+ * rcu_dereference_protected - fetch RCU pointer when updates prevented
+ *
+ * Return the value of the specified RCU-protected pointer, but omit
+ * both the smp_read_barrier_depends() and the ACCESS_ONCE().  This
+ * is useful in cases where update-side locks prevent the value of the
+ * pointer from changing.  Please note that this primitive does -not-
+ * prevent the compiler from repeating this reference or combining it
+ * with other references, so it should not be used without protection
+ * of appropriate locks.
+ */
+#define rcu_dereference_protected(p, c) \
+        ({ \
+                if (debug_lockdep_rcu_enabled() && !(c)) \
+                        lockdep_rcu_dereference(__FILE__, __LINE__); \
+                (p); \
+        })
+
 #else /* #ifdef CONFIG_PROVE_RCU */
 
 #define rcu_dereference_check(p, c)     rcu_dereference_raw(p)
+#define rcu_dereference_protected(p, c) (p)
 
 #endif /* #else #ifdef CONFIG_PROVE_RCU */
 
 /**
+ * rcu_access_pointer - fetch RCU pointer with no dereferencing
+ *
+ * Return the value of the specified RCU-protected pointer, but omit the
+ * smp_read_barrier_depends() and keep the ACCESS_ONCE().  This is useful
+ * when the value of this pointer is accessed, but the pointer is not
+ * dereferenced, for example, when testing an RCU-protected pointer against
+ * NULL.  This may also be used in cases where update-side locks prevent
+ * the value of the pointer from changing, but rcu_dereference_protected()
+ * is a lighter-weight primitive for this use case.
+ */
+#define rcu_access_pointer(p)   ACCESS_ONCE(p)
+
+/**
  * rcu_read_lock - mark the beginning of an RCU read-side critical section.
  *
  * When synchronize_rcu() is invoked on one CPU while other CPUs