rcuwait: Introduce rcuwait_active()
This call is lockless and thus should not be trusted blindly.
For example, the return value of rcuwait_wakeup() should be used to
track whether a process was woken up.
Signed-off-by: Davidlohr Bueso <[email protected]>
Message-Id: <[email protected]>
Acked-by: Peter Zijlstra (Intel) <[email protected]>
Signed-off-by: Paolo Bonzini <[email protected]>
diff --git a/include/linux/rcuwait.h b/include/linux/rcuwait.h
index 45bc660..c1414ce 100644
--- a/include/linux/rcuwait.h
+++ b/include/linux/rcuwait.h
@@ -25,6 +25,15 @@ static inline void rcuwait_init(struct rcuwait *w)
w->task = NULL;
}
+/*
+ * 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_dereference(w->task);
+}
+
extern int rcuwait_wake_up(struct rcuwait *w);
/*
