Fix for issue 10488 standalone/basic_debugger_test flaky

runtime/bin/dbg_connection.cc

Index: runtime/bin/dbg_connection.cc
===================================================================
--- runtime/bin/dbg_connection.cc	(revision 22486)
+++ runtime/bin/dbg_connection.cc	(working copy)
@@ -22,7 +22,7 @@
 namespace bin {
 
 int DebuggerConnectionHandler::listener_fd_ = -1;
-dart::Monitor DebuggerConnectionHandler::handler_lock_;
+dart::Monitor* DebuggerConnectionHandler::handler_lock_ = NULL;
 
 // TODO(asiva): Remove this once we have support for multiple debugger
 // connections. For now we just store the single debugger connection
@@ -280,7 +280,10 @@
 
 void DebuggerConnectionHandler::StartHandler(const char* address,
                                              int port_number) {
-  MonitorLocker ml(&handler_lock_);
+  handler_lock_ = new dart::Monitor();

[hausner, 2013/05/08 15:26:48]

What if two threads call this function by accident? Then there will be two
locks, and one thread may have lock 1 while the second one grabs lock 2.

Not entirely safe, but maybe good enough: ASSERT(handler_lock_ == NULL) before
allocating the lock.

[siva, 2013/05/08 20:48:12]

I changed the initialization of handler_lock_ into a static initialization, that
should protect against multiple invocations of StartHandler.

On 2013/05/08 15:26:48, hausner wrote:

+  ASSERT(handler_lock_ != NULL);
+
+  MonitorLocker ml(handler_lock_);
   if (listener_fd_ != -1) {
     return;  // The debugger connection handler was already started.
   }
@@ -307,7 +310,8 @@
 
 
 void DebuggerConnectionHandler::WaitForConnection() {
-  MonitorLocker ml(&handler_lock_);
+  ASSERT(handler_lock_ != NULL);
+  MonitorLocker ml(handler_lock_);
   while (!IsConnected()) {
     dart::Monitor::WaitResult res = ml.Wait();
     ASSERT(res == dart::Monitor::kNotified);
@@ -316,13 +320,15 @@
 
 
 void DebuggerConnectionHandler::SendMsg(int debug_fd, dart::TextBuffer* msg) {
-  MonitorLocker ml(&handler_lock_);
+  ASSERT(handler_lock_ != NULL);
+  MonitorLocker ml(handler_lock_);
   SendMsgHelper(debug_fd, msg);
 }
 
 
 void DebuggerConnectionHandler::BroadcastMsg(dart::TextBuffer* msg) {
-  MonitorLocker ml(&handler_lock_);
+  ASSERT(handler_lock_ != NULL);
+  MonitorLocker ml(handler_lock_);
   // TODO(asiva): Once we support connection to multiple debuggers
   // we need to send the message to all of them.
   ASSERT(singleton_handler != NULL);
@@ -371,7 +377,8 @@
 void DebuggerConnectionHandler::AcceptDbgConnection(int debug_fd) {
   AddNewDebuggerConnection(debug_fd);
   {
-    MonitorLocker ml(&handler_lock_);
+    ASSERT(handler_lock_ != NULL);
+    MonitorLocker ml(handler_lock_);
     ml.NotifyAll();
   }
   // TODO(asiva): Once we implement support for multiple connections