Avoid race in isolate shutdown; add assertions, error messages

runtime/vm/thread_registry.h

 // Copyright (c) 2015, 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.
 
 #ifndef VM_THREAD_REGISTRY_H_
 #define VM_THREAD_REGISTRY_H_
 
 #include "vm/globals.h"
 #include "vm/growable_array.h"
 #include "vm/isolate.h"
@@ skipping 45 matching lines @@
     ASSERT(entry->scheduled);
     entry->scheduled = false;
     entry->state = state;
   }
 
   bool Contains(Thread* thread) {
     MutexLocker ml(mutex_);
     return (FindEntry(thread) != NULL);
   }
 
+  void CheckNotScheduled(Isolate* isolate) {
+    MutexLocker ml(mutex_);
+    for (int i = 0; i < entries_.length(); ++i) {
+      const Entry& entry = entries_[i];
+      if (entry.scheduled) {
+        FATAL3("Isolate %p still scheduled on %p (whose isolate_ is %p)\n",
+               isolate,
+               entry.thread,
+               entry.thread->isolate());
+      }
+    }
+  }
+
   void VisitObjectPointers(ObjectPointerVisitor* visitor) {
     MutexLocker ml(mutex_);
     for (int i = 0; i < entries_.length(); ++i) {
       const Entry& entry = entries_[i];
       Zone* zone = entry.scheduled ? entry.thread->zone() : entry.state.zone;
       if (zone != NULL) {
         zone->VisitObjectPointers(visitor);
       }
     }
   }
@@ skipping 20 matching lines @@
   Mutex* mutex_;
   MallocGrowableArray<Entry> entries_;
 
 
   DISALLOW_COPY_AND_ASSIGN(ThreadRegistry);
 };
 
 }  // namespace dart
 
 #endif  // VM_THREAD_REGISTRY_H_