Merge branch 'x86/entry' into ras/core

to fixup conflicts in arch/x86/kernel/cpu/mce/core.c so MCE specific follow
up patches can be applied without creating a horrible merge conflict
afterwards.

1 files changed, 26 insertions, 6 deletions

diff --git a/include/linux/rcuwait.h b/include/linux/rcuwait.h
index 2ffe1ee6d482..61c56cca95c4 100644
--- a/include/linux/rcuwait.h
+++ b/include/linux/rcuwait.h
@@ -25,16 +25,38 @@ static inline void rcuwait_init(struct rcuwait *w)
 	w->task = NULL;
 }
 
-extern void rcuwait_wake_up(struct rcuwait *w);
+/*
+ * Note: this provides no serialization and, just as with waitqueues,
+ * requires care to estimate as to whether or not the wait is active.
+ */
+static inline int rcuwait_active(struct rcuwait *w)
+{
+	return !!rcu_access_pointer(w->task);
+}
+
+extern int rcuwait_wake_up(struct rcuwait *w);
 
 /*
  * The caller is responsible for locking around rcuwait_wait_event(),
- * such that writes to @task are properly serialized.
+ * and [prepare_to/finish]_rcuwait() such that writes to @task are
+ * properly serialized.
  */
+
+static inline void prepare_to_rcuwait(struct rcuwait *w)
+{
+	rcu_assign_pointer(w->task, current);
+}
+
+static inline void finish_rcuwait(struct rcuwait *w)
+{
+        rcu_assign_pointer(w->task, NULL);
+	__set_current_state(TASK_RUNNING);
+}
+
 #define rcuwait_wait_event(w, condition, state)				\
 ({									\
 	int __ret = 0;							\
-	rcu_assign_pointer((w)->task, current);				\
+	prepare_to_rcuwait(w);						\
 	for (;;) {							\
 		/*							\
 		 * Implicit barrier (A) pairs with (B) in		\
@@ -51,9 +73,7 @@ extern void rcuwait_wake_up(struct rcuwait *w);
 									\
 		schedule();						\
 	}								\
-									\
-	WRITE_ONCE((w)->task, NULL);					\
-	__set_current_state(TASK_RUNNING);				\
+	finish_rcuwait(w);						\
 	__ret;								\
 })