Uses an open thread handle as the ThreadJoinId on Windows.

runtime/vm/thread_pool.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/thread_pool.h"
 
 #include "vm/dart.h"
 #include "vm/flags.h"
 #include "vm/lockers.h"
 
@@ skipping 194 matching lines @@
       current->all_next_ = worker->all_next_;
       worker->all_next_ = NULL;
       worker->owned_ = false;
       return true;
     }
   }
   return false;
 }
 
 
+void ThreadPool::SetIdleLocked(Worker* worker) {

[siva, 2016/05/16 17:59:27]

ASSERT(mutex_.IsOwnedByCurrentThread());

[zra, 2016/05/16 20:32:55]

Done.

+  ASSERT(worker->owned_ && !IsIdle(worker));
+  worker->idle_next_ = idle_workers_;
+  idle_workers_ = worker;
+  count_idle_++;
+  count_running_--;
+}
+
+
 void ThreadPool::SetIdleAndReapExited(Worker* worker) {
   JoinList* list = NULL;
   {
     MutexLocker ml(&mutex_);
     if (shutting_down_) {
       return;
     }
-    ASSERT(worker->owned_ && !IsIdle(worker));
-    worker->idle_next_ = idle_workers_;
-    idle_workers_ = worker;
-    count_idle_++;
-    count_running_--;
-
-    // While we have the lock, opportunistically grab and clear the join_list_.
+    if (join_list_ == NULL) {
+      // Nothing to join, add to the idle list and return.
+      SetIdleLocked(worker);
+      return;
+    }
+    // There is something to join. Grab the join list, drop the lock, do the
+    // join, then grab the lock again and add to the idle list.
     list = join_list_;
     join_list_ = NULL;
   }
   JoinList::Join(&list);
+
+  {
+    MutexLocker ml(&mutex_);
+    if (shutting_down_) {
+      return;
+    }
+    SetIdleLocked(worker);
+  }
 }
 
 
 bool ThreadPool::ReleaseIdleWorker(Worker* worker) {
   MutexLocker ml(&mutex_);
   if (shutting_down_) {
     return false;
   }
   // Remove from idle list.
   if (!RemoveWorkerFromIdleList(worker)) {
@@ skipping 243 matching lines @@
   }
 
   // Call the thread exit hook here to notify the embedder that the
   // thread pool thread is exiting.
   if (Dart::thread_exit_callback() != NULL) {
     (*Dart::thread_exit_callback())();
   }
 }
 
 }  // namespace dart