block: add QUEUE_FLAG_NOWAIT

[linux-2.6-microblaze.git] / include / linux / rcuwait.h

diff --git a/include/linux/rcuwait.h b/include/linux/rcuwait.h
index 2ffe1ee..61c56cc 100644 (file)
--- 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;                                                          \
 })