Merge tag 'gfs2-v5.3-rc3.fixes' of git://git.kernel.org/pub/scm/linux/kernel/git...

[linux.git] / include / linux / wait.h

diff --git a/include/linux/wait.h b/include/linux/wait.h
index 5f3efabc36f4bb27af254bd7533e6c869bb68aaa..30c515520fb28c69873aad6d0b498a59679f46ab 100644 (file)
--- a/include/linux/wait.h
+++ b/include/linux/wait.h
@@ -101,7 +101,7 @@ init_waitqueue_func_entry(struct wait_queue_entry *wq_entry, wait_queue_func_t f
  * lead to sporadic and non-obvious failure.
  *
  * Use either while holding wait_queue_head::lock or when used for wakeups
- * with an extra smp_mb() like:
+ * with an extra smp_mb() like::
  *
  *      CPU0 - waker                    CPU1 - waiter
  *
@@ -126,6 +126,19 @@ static inline int waitqueue_active(struct wait_queue_head *wq_head)
        return !list_empty(&wq_head->head);
 }
 
+/**
+ * wq_has_single_sleeper - check if there is only one sleeper
+ * @wq_head: wait queue head
+ *
+ * Returns true of wq_head has only one sleeper on the list.
+ *
+ * Please refer to the comment for waitqueue_active.
+ */
+static inline bool wq_has_single_sleeper(struct wait_queue_head *wq_head)
+{
+       return list_is_singular(&wq_head->head);
+}
+
 /**
  * wq_has_sleeper - check if there are any waiting processes
  * @wq_head: wait queue head