Merge branch 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip

* 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  Revert "net: Make accesses to ->br_port safe for sparse RCU"
  mce: convert to rcu_dereference_index_check()
  net: Make accesses to ->br_port safe for sparse RCU
  vfs: add fs.h to define struct file
  lockdep: Add an in_workqueue_context() lockdep-based test function
  rcu: add __rcu API for later sparse checking
  rcu: add an rcu_dereference_index_check()
  tree/tiny rcu: Add debug RCU head objects
  mm: remove all rcu head initializations
  fs: remove all rcu head initializations, except on_stack initializations
  powerpc: remove all rcu head initializations

1 files changed, 82 insertions, 0 deletions

diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index b653b4aaa8a6..9fbc54a2585d 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -40,6 +40,7 @@
 #include <linux/seqlock.h>
 #include <linux/lockdep.h>
 #include <linux/completion.h>
+#include <linux/debugobjects.h>
 
 #ifdef CONFIG_RCU_TORTURE_TEST
 extern int rcutorture_runnable; /* for sysctl */
@@ -79,6 +80,16 @@ extern void rcu_init(void);
        (ptr)->next = NULL; (ptr)->func = NULL; \
 } while (0)
 
+/*
+ * init_rcu_head_on_stack()/destroy_rcu_head_on_stack() are needed for dynamic
+ * initialization and destruction of rcu_head on the stack. rcu_head structures
+ * allocated dynamically in the heap or defined statically don't need any
+ * initialization.
+ */
+#ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
+extern void init_rcu_head_on_stack(struct rcu_head *head);
+extern void destroy_rcu_head_on_stack(struct rcu_head *head);
+#else /* !CONFIG_DEBUG_OBJECTS_RCU_HEAD */
 static inline void init_rcu_head_on_stack(struct rcu_head *head)
 {
 }
@@ -86,6 +97,7 @@ static inline void init_rcu_head_on_stack(struct rcu_head *head)
 static inline void destroy_rcu_head_on_stack(struct rcu_head *head)
 {
 }
+#endif  /* #else !CONFIG_DEBUG_OBJECTS_RCU_HEAD */
 
 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 
@@ -517,4 +529,74 @@ extern void call_rcu(struct rcu_head *head,
 extern void call_rcu_bh(struct rcu_head *head,
                         void (*func)(struct rcu_head *head));
 
+/*
+ * debug_rcu_head_queue()/debug_rcu_head_unqueue() are used internally
+ * by call_rcu() and rcu callback execution, and are therefore not part of the
+ * RCU API. Leaving in rcupdate.h because they are used by all RCU flavors.
+ */
+
+#ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
+# define STATE_RCU_HEAD_READY   0
+# define STATE_RCU_HEAD_QUEUED  1
+
+extern struct debug_obj_descr rcuhead_debug_descr;
+
+static inline void debug_rcu_head_queue(struct rcu_head *head)
+{
+        debug_object_activate(head, &rcuhead_debug_descr);
+        debug_object_active_state(head, &rcuhead_debug_descr,
+                                  STATE_RCU_HEAD_READY,
+                                  STATE_RCU_HEAD_QUEUED);
+}
+
+static inline void debug_rcu_head_unqueue(struct rcu_head *head)
+{
+        debug_object_active_state(head, &rcuhead_debug_descr,
+                                  STATE_RCU_HEAD_QUEUED,
+                                  STATE_RCU_HEAD_READY);
+        debug_object_deactivate(head, &rcuhead_debug_descr);
+}
+#else   /* !CONFIG_DEBUG_OBJECTS_RCU_HEAD */
+static inline void debug_rcu_head_queue(struct rcu_head *head)
+{
+}
+
+static inline void debug_rcu_head_unqueue(struct rcu_head *head)
+{
+}
+#endif  /* #else !CONFIG_DEBUG_OBJECTS_RCU_HEAD */
+
+#ifndef CONFIG_PROVE_RCU
+#define __do_rcu_dereference_check(c) do { } while (0)
+#endif /* #ifdef CONFIG_PROVE_RCU */
+
+#define __rcu_dereference_index_check(p, c) \
+        ({ \
+                typeof(p) _________p1 = ACCESS_ONCE(p); \
+                __do_rcu_dereference_check(c); \
+                smp_read_barrier_depends(); \
+                (_________p1); \
+        })
+
+/**
+ * rcu_dereference_index_check() - rcu_dereference for indices with debug checking
+ * @p: The pointer to read, prior to dereferencing
+ * @c: The conditions under which the dereference will take place
+ *
+ * Similar to rcu_dereference_check(), but omits the sparse checking.
+ * This allows rcu_dereference_index_check() to be used on integers,
+ * which can then be used as array indices.  Attempting to use
+ * rcu_dereference_check() on an integer will give compiler warnings
+ * because the sparse address-space mechanism relies on dereferencing
+ * the RCU-protected pointer.  Dereferencing integers is not something
+ * that even gcc will put up with.
+ *
+ * Note that this function does not implicitly check for RCU read-side
+ * critical sections.  If this function gains lots of uses, it might
+ * make sense to provide versions for each flavor of RCU, but it does
+ * not make sense as of early 2010.
+ */
+#define rcu_dereference_index_check(p, c) \
+        __rcu_dereference_index_check((p), (c))
+
 #endif /* __LINUX_RCUPDATE_H */