rt: fix potential leak during runtime shutdown (#2649)

JoinHandle of threads created by the pool are now tracked and properly joined at
shutdown. If the thread does not return within the timeout, then it's not joined and
left to the OS for cleanup.

Also, break a cycle between wakers held by the timer and the runtime.

Fixes #2641, #2535 

1 files changed, 12 insertions, 0 deletions

diff --git a/tokio/src/runtime/park.rs b/tokio/src/runtime/park.rs
index ee437d1d..1dcf65af 100644
--- a/tokio/src/runtime/park.rs
+++ b/tokio/src/runtime/park.rs
@@ -104,6 +104,10 @@ impl Park for Parker {
             Ok(())
         }
     }
+
+    fn shutdown(&mut self) {
+        self.inner.shutdown();
+    }
 }
 
 impl Unpark for Unparker {
@@ -242,4 +246,12 @@ impl Inner {
     fn unpark_driver(&self) {
         self.shared.handle.unpark();
     }
+
+    fn shutdown(&self) {
+        if let Some(mut driver) = self.shared.driver.try_lock() {
+            driver.shutdown();
+        }
+
+        self.condvar.notify_all();
+    }
 }