Support wedging isolates before startup or before exit.

runtime/vm/message_handler.cc

 // Copyright (c) 2011, 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/message_handler.h"
 #include "vm/port.h"
 #include "vm/dart.h"
 
 namespace dart {
 
@@ skipping 16 matching lines @@
 
   DISALLOW_COPY_AND_ASSIGN(MessageHandlerTask);
 };
 
 
 MessageHandler::MessageHandler()
     : queue_(new MessageQueue()),
       oob_queue_(new MessageQueue()),
       control_ports_(0),
       live_ports_(0),
+      pause_on_start_(false),
+      pause_on_exit_(false),
+      paused_on_exit_(false),
       pool_(NULL),
       task_(NULL),
       start_callback_(NULL),
       end_callback_(NULL),
       callback_data_(0) {
   ASSERT(queue_ != NULL);
   ASSERT(oob_queue_ != NULL);
 }
 
 
@@ skipping 143 matching lines @@
 
 void MessageHandler::TaskCallback() {
   ASSERT(Isolate::Current() == NULL);
   bool ok = true;
   bool run_end_callback = false;
   {
     MonitorLocker ml(&monitor_);
     // Initialize the message handler by running its start function,
     // if we have one.  For an isolate, this will run the isolate's
     // main() function.
+    if (pause_on_start()) {
+      HandleMessages(false, false);
+      if (pause_on_start()) {
+        // Still paused.
+        task_ = NULL;  // No task in queue.
+        return;
+      }
+    }
+
     if (start_callback_) {
       monitor_.Exit();
       ok = start_callback_(callback_data_);
       ASSERT(Isolate::Current() == NULL);
       start_callback_ = NULL;
       monitor_.Enter();
     }
 
     // Handle any pending messages for this message handler.
     if (ok) {
       ok = HandleMessages(true, true);
     }
     task_ = NULL;  // No task in queue.
 
     if (!ok || !HasLivePorts()) {
-      if (FLAG_trace_isolates) {
+      if (pause_on_exit()) {
+        paused_on_exit_ = true;
+      } else {
+        if (FLAG_trace_isolates) {
         OS::Print("[-] Stopping message handler (%s):\n"
                   "\thandler:    %s\n",
                   (ok ? "no live ports" : "error"),
                   name());
+        }
+        pool_ = NULL;
+        run_end_callback = true;
+        paused_on_exit_ = false;
       }
-      pool_ = NULL;
-      run_end_callback = true;
     }
   }
   if (run_end_callback && end_callback_ != NULL) {
     end_callback_(callback_data_);
     // The handler may have been deleted after this point.
   }
 }
 
 
 void MessageHandler::ClosePort(Dart_Port port) {
@@ skipping 48 matching lines @@
 
 void MessageHandler::decrement_control_ports() {
   MonitorLocker ml(&monitor_);
 #if defined(DEBUG)
   CheckAccess();
 #endif
   control_ports_--;
 }
 
 }  // namespace dart