diff --git a/tokio/src/task/yield_now.rs b/tokio/src/task/yield_now.rs
index a58e85ee7..ea09804ad 100644
--- a/tokio/src/task/yield_now.rs
+++ b/tokio/src/task/yield_now.rs
@@ -46,6 +46,12 @@ pub async fn yield_now() {
 
         yielded = true;
 
+        // Don't wake the task immediately, as that would push it right back
+        // onto the run queue and it could be polled again before other tasks
+        // or the IO/timer driver get a chance to run. Instead, hand the waker
+        // to the scheduler, which wakes deferred tasks only after it has run
+        // out of ready tasks and polled the driver. When polled from outside
+        // a Tokio runtime, the waker is woken immediately.
         context::defer(cx.waker());
 
         Poll::Pending