Avoid race in isolate shutdown; add assertions, error messages

runtime/vm/isolate.cc

 // Copyright (c) 2013, 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/isolate.h"
 
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "platform/json.h"
 #include "vm/code_observers.h"
@@ skipping 1414 matching lines @@
 
 void Isolate::Shutdown() {
   ASSERT(this == Isolate::Current());
   ASSERT(top_resource() == NULL);
 #if defined(DEBUG)
   if (heap_ != NULL) {
     // The VM isolate keeps all objects marked.
     heap_->Verify(this == Dart::vm_isolate() ? kRequireMarked : kForbidMarked);
   }
 #endif  // DEBUG
+  if (heap_ != NULL) {
+    // Wait for any concurrent GC tasks to finish before shutting down.
+    PageSpace* old_space = heap_->old_space();
+    MonitorLocker ml(old_space->tasks_lock());
+    while (old_space->tasks() > 0) {
+      ml.Wait();
+    }
+  }

[siva, 2015/07/13 23:37:00]

I am wondering if we should do this wait after removing the isolate from the
list of isolates.

[koda, 2015/07/14 00:41:40]

Done.

 
   // Remove this isolate from the list *before* we start tearing it down, to
   // avoid exposing it in a state of decay.
   RemoveIsolateFromList(this);
 
   // Create an area where we do have a zone and a handle scope so that we can
   // call VM functions while tearing this isolate down.
   {
     StackZone stack_zone(this);
     HandleScope handle_scope(this);
@@ skipping 38 matching lines @@
 
     if ((timeline_event_recorder_ != NULL) &&
         (FLAG_timeline_trace_dir != NULL)) {
       timeline_event_recorder_->WriteTo(FLAG_timeline_trace_dir);
     }
   }
 
   // TODO(5411455): For now just make sure there are no current isolates
   // as we are shutting down the isolate.
   Thread::ExitIsolate();
+  // All threads should have exited by now.
+  thread_registry()->CheckNotScheduled(this);
   Profiler::ShutdownProfilingForIsolate(this);
 }
 
 
 Dart_IsolateCreateCallback Isolate::create_callback_ = NULL;
 Dart_IsolateInterruptCallback Isolate::interrupt_callback_ = NULL;
 Dart_IsolateUnhandledExceptionCallback
     Isolate::unhandled_exception_callback_ = NULL;
 Dart_IsolateShutdownCallback Isolate::shutdown_callback_ = NULL;
 Dart_FileOpenCallback Isolate::file_open_callback_ = NULL;
@@ skipping 584 matching lines @@
                            serialized_message_, serialized_message_len_);
 }
 
 
 void IsolateSpawnState::Cleanup() {
   SwitchIsolateScope switch_scope(I);
   Dart::ShutdownIsolate();
 }
 
 }  // namespace dart