3 files changed, 106 insertions, 7 deletions

diff --git a/js/net_test.ts b/js/net_test.ts
index 6ba36547f..be415f19c 100644
--- a/js/net_test.ts
+++ b/js/net_test.ts
@@ -8,6 +8,42 @@ testPerm({ net: true }, function netListenClose() {
   listener.close();
 });
 
+testPerm({ net: true }, async function netCloseWhileAccept() {
+  const listener = deno.listen("tcp", ":4501");
+  const p = listener.accept();
+  listener.close();
+  let err;
+  try {
+    await p;
+  } catch (e) {
+    err = e;
+  }
+  assert(!!err);
+  assertEqual(err.kind, deno.ErrorKind.Other);
+  assertEqual(err.message, "Listener has been closed");
+});
+
+testPerm({ net: true }, async function netConcurrentAccept() {
+  const listener = deno.listen("tcp", ":4502");
+  let err;
+  // Consume this accept error
+  // (since it would still be waiting when listener.close is called)
+  listener.accept().catch(e => {
+    assertEqual(e.kind, deno.ErrorKind.Other);
+    assertEqual(e.message, "Listener has been closed");
+  });
+  const p1 = listener.accept();
+  try {
+    await p1;
+  } catch (e) {
+    err = e;
+  }
+  assert(!!err);
+  assertEqual(err.kind, deno.ErrorKind.Other);
+  assertEqual(err.message, "Another accept task is ongoing");
+  listener.close();
+});
+
 testPerm({ net: true }, async function netDialListen() {
   const listener = deno.listen("tcp", ":4500");
   listener.accept().then(async conn => {
diff --git a/src/resources.rs b/src/resources.rs
index 55e1a9f64..1f5a121de 100644
--- a/src/resources.rs
+++ b/src/resources.rs
@@ -87,7 +87,12 @@ enum Repr {
   Stdout(tokio::fs::File),
   Stderr(tokio::io::Stderr),
   FsFile(tokio::fs::File),
-  TcpListener(tokio::net::TcpListener),
+  // Since TcpListener might be closed while there is a pending accept task,
+  // we need to track the task so that when the listener is closed,
+  // this pending task could be notified and die.
+  // Currently TcpListener itself does not take care of this issue.
+  // See: https://github.com/tokio-rs/tokio/issues/846
+  TcpListener(tokio::net::TcpListener, Option<futures::task::Task>),
   TcpStream(tokio::net::TcpStream),
   HttpBody(HttpBody),
   Repl(Repl),
@@ -132,7 +137,7 @@ fn inspect_repr(repr: &Repr) -> String {
     Repr::Stdout(_) => "stdout",
     Repr::Stderr(_) => "stderr",
     Repr::FsFile(_) => "fsFile",
-    Repr::TcpListener(_) => "tcpListener",
+    Repr::TcpListener(_, _) => "tcpListener",
     Repr::TcpStream(_) => "tcpStream",
     Repr::HttpBody(_) => "httpBody",
     Repr::Repl(_) => "repl",
@@ -159,20 +164,60 @@ impl Resource {
     let mut table = RESOURCE_TABLE.lock().unwrap();
     let maybe_repr = table.get_mut(&self.rid);
     match maybe_repr {
-      None => panic!("bad rid"),
+      None => Err(std::io::Error::new(
+        std::io::ErrorKind::Other,
+        "Listener has been closed",
+      )),
       Some(repr) => match repr {
-        Repr::TcpListener(ref mut s) => s.poll_accept(),
+        Repr::TcpListener(ref mut s, _) => s.poll_accept(),
         _ => panic!("Cannot accept"),
       },
     }
   }
 
+  /// Track the current task (for TcpListener resource).
+  /// Throws an error if another task is already tracked.
+  pub fn track_task(&mut self) -> Result<(), std::io::Error> {
+    let mut table = RESOURCE_TABLE.lock().unwrap();
+    // Only track if is TcpListener.
+    if let Some(Repr::TcpListener(_, t)) = table.get_mut(&self.rid) {
+      // Currently, we only allow tracking a single accept task for a listener.
+      // This might be changed in the future with multiple workers.
+      // Caveat: TcpListener by itself also only tracks an accept task at a time.
+      // See https://github.com/tokio-rs/tokio/issues/846#issuecomment-454208883
+      if t.is_some() {
+        return Err(std::io::Error::new(
+          std::io::ErrorKind::Other,
+          "Another accept task is ongoing",
+        ));
+      }
+      t.replace(futures::task::current());
+    }
+    Ok(())
+  }
+
+  /// Stop tracking a task (for TcpListener resource).
+  /// Happens when the task is done and thus no further tracking is needed.
+  pub fn untrack_task(&mut self) {
+    let mut table = RESOURCE_TABLE.lock().unwrap();
+    // Only untrack if is TcpListener.
+    if let Some(Repr::TcpListener(_, t)) = table.get_mut(&self.rid) {
+      assert!(t.is_some());
+      t.take();
+    }
+  }
+
   // close(2) is done by dropping the value. Therefore we just need to remove
   // the resource from the RESOURCE_TABLE.
   pub fn close(&self) {
     let mut table = RESOURCE_TABLE.lock().unwrap();
     let r = table.remove(&self.rid);
     assert!(r.is_some());
+    // If TcpListener, we must kill all pending accepts!
+    if let Repr::TcpListener(_, Some(t)) = r.unwrap() {
+      // Call notify on the tracked task, so that they would error out.
+      t.notify();
+    }
   }
 
   pub fn shutdown(&mut self, how: Shutdown) -> Result<(), DenoError> {
@@ -264,7 +309,7 @@ pub fn add_fs_file(fs_file: tokio::fs::File) -> Resource {
 pub fn add_tcp_listener(listener: tokio::net::TcpListener) -> Resource {
   let rid = new_rid();
   let mut tg = RESOURCE_TABLE.lock().unwrap();
-  let r = tg.insert(rid, Repr::TcpListener(listener));
+  let r = tg.insert(rid, Repr::TcpListener(listener, None));
   assert!(r.is_none());
   Resource { rid }
 }
@@ -515,7 +560,7 @@ pub fn eager_accept(resource: Resource) -> EagerAccept {
   match maybe_repr {
     None => panic!("bad rid"),
     Some(repr) => match repr {
-      Repr::TcpListener(ref mut tcp_listener) => {
+      Repr::TcpListener(ref mut tcp_listener, _) => {
         eager::tcp_accept(tcp_listener, resource)
       }
       _ => Either::A(tokio_util::accept(resource)),
diff --git a/src/tokio_util.rs b/src/tokio_util.rs
index 32542aa43..2eb0211db 100644
--- a/src/tokio_util.rs
+++ b/src/tokio_util.rs
@@ -63,7 +63,25 @@ impl Future for Accept {
 
   fn poll(&mut self) -> Poll<Self::Item, Self::Error> {
     let (stream, addr) = match self.state {
-      AcceptState::Pending(ref mut r) => try_ready!(r.poll_accept()),
+      // Similar to try_ready!, but also track/untrack accept task
+      // in TcpListener resource.
+      // In this way, when the listener is closed, the task can be
+      // notified to error out (instead of stuck forever).
+      AcceptState::Pending(ref mut r) => match r.poll_accept() {
+        Ok(futures::prelude::Async::Ready(t)) => {
+          r.untrack_task();
+          t
+        }
+        Ok(futures::prelude::Async::NotReady) => {
+          // Would error out if another accept task is being tracked.
+          r.track_task()?;
+          return Ok(futures::prelude::Async::NotReady);
+        }
+        Err(e) => {
+          r.untrack_task();
+          return Err(From::from(e));
+        }
+      },
       AcceptState::Empty => panic!("poll Accept after it's done"),
     };