Change task_num to len based on the annotation

tokio/src/runtime/scheduler/multi_thread/queue.rs

@@ -106,11 +106,8 @@ pub(crate) fn local<T: 'static>() -> (Steal<T>, Local<T>) {
 
 impl<T> Local<T> {
     /// Returns the number of entries in the queue
-    pub(crate) fn tasks_num(&self) -> (usize /* stealable */, usize /* total */) {
-        let n = self.inner.len() as usize;
-        // I'm not sure if it's really necessary to return a tuple, but based on has_tasks's comments,
-        // it seems that there may be tasks in queue that cannot be stolen?
-        (n, n)
+    pub(crate) fn len(&self) -> usize {
+        self.inner.len() as usize
     }
 
     /// How many tasks can be pushed into the queue

tokio/src/runtime/scheduler/multi_thread/worker.rs

@@ -854,11 +854,7 @@ impl Core {
         if self.is_searching {
             return false;
         }
-        let (stealable_tasks, total_tasks) = self.run_queue.tasks_num();
-        if stealable_tasks == 0 {
-            return false;
-        }
-        self.lifo_slot.is_some() as usize + (total_tasks - stealable_tasks) > 0
+        self.lifo_slot.is_some() as usize + self.run_queue.len() > 1
     }
 
     /// Prepares the worker state for parking.