Wait for the GDB server to be listening before doing anything else

We were trying to connect the GDB client even before we got the
listening event. The debugger server thread is now looping forever.

Signed-off-by: Louis-Francis Ratté-Boulianne <lfrb@collabora.com>
Reviewed-by: Sjoerd Simons <sjoerd.simons@collabora.co.uk>
Differential Revision: https://phabricator.apertis.org/D5327

tools/ade

@@ -177,19 +177,39 @@ class TargetTriplet:
 
 class DebuggerServerThread(threading.Thread):
 
-    def __init__(self, target, port, app, *args):
+    def __init__(self, cond, target, port, app, *args):
         super().__init__()
         self.target = target
         self.port = port
         self.app = app
         self.args = args
 
+        self._cond = cond
+        self._exception = None
+        self._listening = False
+
     def run(self):
-        self._data = self.target.start_gdbserver(self.port, self.app, *self.args)
+        try:
+            self._data = self.target.start_gdbserver(self.port, self.app, *self.args)
+            with self._cond:
+                self._listening = True
+                self._cond.notify()
+            while True:
+                pass
+        except Exception as e:
+            with self._cond:
+                self._exception = e
+                self._cond.notify()
 
     def stop(self):
         self.target.stop_gdbserver(self._data)
 
+    def is_listening(self):
+        return self._listening
+
+    def get_exception(self):
+        return self._exception
+
 
 class DebuggerServer:
 
@@ -201,8 +221,14 @@ class DebuggerServer:
         self._thread = None
 
     def __enter__(self):
-        self._thread = DebuggerServerThread(self.target, self.port, self.app, *self.args)
+        cond = threading.Condition()
+        self._thread = DebuggerServerThread(cond, self.target, self.port, self.app, *self.args)
         self._thread.start()
+        with cond:
+            while not self._thread.is_listening() and not self._thread.get_exception():
+                cond.wait()
+        if self._thread.get_exception():
+            raise self._thread.get_exception()
         return self
 
     def __exit__(self, et, ev, tb):