add thread enforcement decorators

This adds a couple of decorators that can be used to
mark functions as needing to be run in the gdb thread
or in the gtk thread.

This found at least one bug.

gui/commands.py

@@ -1,4 +1,4 @@
-# Copyright (C) 2012 Tom Tromey <tom@tromey.com>
+# Copyright (C) 2012, 2013 Tom Tromey <tom@tromey.com>
 
 # This program is free software; you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -21,6 +21,7 @@ import gui.toplevel
 import gui.dprintf
 import gui.events
 import re
+from gui.startup import in_gtk_thread
 
 class GuiCommand(gdb.Command):
     def __init__(self):

gui/dprintf.py

@@ -17,13 +17,16 @@
 
 import gdb
 import gui.logwindow
+from gui.startup import in_gdb_thread
 
 class DPrintfBreakpoint(gdb.Breakpoint):
+    @in_gdb_thread
     def __init__(self, spec, window, arg):
         super(DPrintfBreakpoint, self).__init__(spec, gdb.BP_BREAKPOINT)
         self.window = window
         self.command = 'printf ' + arg
 
+    @in_gdb_thread
     def stop(self):
         window = self.window
         if window is not None:

gui/invoker.py

@@ -14,6 +14,7 @@
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 import gdb
+from gui.startup import in_gdb_thread
 
 class Invoker(object):
     """A simple class that can invoke a gdb command.
@@ -23,9 +24,11 @@ class Invoker(object):
         self.cmd = cmd
 
     # This is invoked in the gdb thread to run the command.
+    @in_gdb_thread
     def do_call(self):
         gdb.execute(self.cmd, from_tty = True, to_string = True)
 
-    # The object itself is the Gtk event handler.
+    # The object itself is the Gtk event handler -- though really this
+    # can be run in any thread.
     def __call__(self, *args):
         gdb.post_event(self.do_call)

gui/source.py

@@ -19,6 +19,7 @@ import gdb
 from gui.invoker import Invoker
 from gui.toplevel import Toplevel
 import gui.startup
+from gui.startup import in_gdb_thread, in_gtk_thread
 import gui.toplevel
 import gui.events
 
@@ -55,6 +56,7 @@ buffer_manager = BufferManager()
 # Return (FILE, LINE) for the selected frame, or, if there is no
 # frame, for "main".  If there is no symbol file, return (None, None)
 # instead.
+@in_gdb_thread
 def get_current_location():
     try:
         frame = gdb.selected_frame()
@@ -80,10 +82,7 @@ class LRUHandler:
     def __init__(self):
         self.windows = []
 
-    #
-    # These functions must run in the gdb thread.
-    #
-
+    @in_gdb_thread
     def on_event(self, *args):
         (frame, filename, lineno) = get_current_location()
         if filename is not None:
@@ -91,6 +90,7 @@ class LRUHandler:
                                                              filename,
                                                              lineno))
 
+    @in_gdb_thread
     def _connect_events(self):
         # FIXME - we need an event for "selected frame changed".
         # ... and thread-changed
@@ -98,14 +98,12 @@ class LRUHandler:
         gdb.events.stop.connect(self.on_event)
         gui.events.frame_changed.connect(self.on_event)
 
+    @in_gdb_thread
     def _disconnect_events(self):
         gdb.events.stop.disconnect(self.on_event)
         gui.event.frame_changed.disconnect(self.on_event)
 
-    #
-    # These functions must run in the Gtk thread.
-    #
-
+    @in_gtk_thread
     def pick_window(self, frame):
         # If a window is showing FRAME, use it.
         # Otherwise, if a window has no frame, use that.
@@ -123,6 +121,7 @@ class LRUHandler:
             return no_frame
         return self.windows[0]
 
+    @in_gtk_thread
     def show_source(self, frame, srcfile, srcline):
         w = self.pick_window(frame)
         # LRU policy.
@@ -131,17 +130,19 @@ class LRUHandler:
         w.frame = frame
         w.show_source(srcfile, srcline)
 
+    @in_gtk_thread
     def remove(self, window):
         self.windows.remove(window)
         if len(self.windows) == 0:
             gui.startup.send_to_gtk(self._disconnect_events)
 
+    @in_gtk_thread
     def add(self, window):
         self.windows.insert(0, window)
         if len(self.windows) == 1:
-            gui.startup.send_to_gtk(self._connect_events)
+            gdb.post_event(self._connect_events)
         # Show something.
-        gui.startup.send_to_gtk(lambda: self.on_event(None))
+        gdb.post_event(lambda: self.on_event(None))
 
 lru_handler = LRUHandler()
 

gui/startup.py

@@ -47,13 +47,16 @@ class _GtkThread(threading.Thread):
         GObject.type_register(GtkSource.View)
         Gtk.main()
 
+_gdb_thread = None
 _t = None
 
 def start_gtk():
     global _t
+    global _gdb_thread
     if _t is None:
         GObject.threads_init()
         Gdk.threads_init()
+        _gdb_thread = threading.current_thread()
         _t = _GtkThread()
         _t.setDaemon(True)
         _t.start()
@@ -64,3 +67,16 @@ def create_builder(filename):
     builder.add_from_file(os.path.join(gui.self_dir, filename))
     return builder
 
+def in_gdb_thread(func):
+    def ensure_gdb_thread(*args, **kwargs):
+        if threading.current_thread() is not _gdb_thread:
+            raise RuntimeError("must run '%s' in gdb thread" % repr(func))
+        return func(*args, **kwargs)
+    return ensure_gdb_thread
+
+def in_gtk_thread(func):
+    def ensure_gtk_thread(*args, **kwargs):
+        if threading.current_thread() is not _t:
+            raise RuntimeError("must run '%s' in Gtk thread" % repr(func))
+        return func(*args, **kwargs)
+    return ensure_gtk_thread