1 files changed, 21 insertions, 0 deletions

diff --git a/include/linux/wait.h b/include/linux/wait.h
index 1e1bf9f963a9..6aa09a875fbd 100644
--- a/include/linux/wait.h
+++ b/include/linux/wait.h
@@ -107,6 +107,27 @@ static inline int waitqueue_active(wait_queue_head_t *q)
         return !list_empty(&q->task_list);
 }
 
+/**
+ * wq_has_sleeper - check if there are any waiting processes
+ * @wq: wait queue head
+ *
+ * Returns true if wq has waiting processes
+ *
+ * Please refer to the comment for waitqueue_active.
+ */
+static inline bool wq_has_sleeper(wait_queue_head_t *wq)
+{
+        /*
+         * We need to be sure we are in sync with the
+         * add_wait_queue modifications to the wait queue.
+         *
+         * This memory barrier should be paired with one on the
+         * waiting side.
+         */
+        smp_mb();
+        return waitqueue_active(wq);
+}
+
 extern void add_wait_queue(wait_queue_head_t *q, wait_queue_t *wait);
 extern void add_wait_queue_exclusive(wait_queue_head_t *q, wait_queue_t *wait);
 extern void remove_wait_queue(wait_queue_head_t *q, wait_queue_t *wait);