2010-08-11 Tom Tromey <tromey@redhat.com>

Phil Muldoon  <pmuldoon@redhat.com>

	* python/python.c (gdbpy_run_events): New function.
	(gdbpy_post_event): Likewise.
	(gdbpy_initialize_events): Likewise.
	(_initialize_python): Call gdbpy_initialize_events.


2010-08-11  Tom Tromey  <tromey@redhat.com>
            Phil Muldoon <pmuldoon@redhat.com>

	* gdb.texinfo (Basic Python): Describe post_event API.

2010-08-11  Phil Muldoon  <pmuldoon@redhat.com>

	* gdb.python/python.exp (gdb_py_test_multiple): Add gdb.post_event
	tests.

gdb/python/python.c

@@ -28,6 +28,7 @@
 #include "value.h"
 #include "language.h"
 #include "exceptions.h"
+#include "event-loop.h"
 
 #include <ctype.h>
 
@@ -548,6 +549,114 @@ source_python_script (FILE *stream, const char *file)
 
 
 
+/* Posting and handling events.  */
+
+/* A single event.  */
+struct gdbpy_event
+{
+  /* The Python event.  This is just a callable object.  */
+  PyObject *event;
+  /* The next event.  */
+  struct gdbpy_event *next;
+};
+
+/* All pending events.  */
+static struct gdbpy_event *gdbpy_event_list;
+/* The final link of the event list.  */
+static struct gdbpy_event **gdbpy_event_list_end;
+
+/* We use a file handler, and not an async handler, so that we can
+   wake up the main thread even when it is blocked in poll().  */
+static int gdbpy_event_fds[2];
+
+/* The file handler callback.  This reads from the internal pipe, and
+   then processes the Python event queue.  This will always be run in
+   the main gdb thread.  */
+static void
+gdbpy_run_events (int err, gdb_client_data ignore)
+{
+  struct cleanup *cleanup;
+  char buffer[100];
+  int r;
+
+  cleanup = ensure_python_env (get_current_arch (), current_language);
+
+  /* Just read whatever is available on the fd.  It is relatively
+     harmless if there are any bytes left over.  */
+  r = read (gdbpy_event_fds[0], buffer, sizeof (buffer));
+
+  while (gdbpy_event_list)
+    {
+      /* Dispatching the event might push a new element onto the event
+	 loop, so we update here "atomically enough".  */
+      struct gdbpy_event *item = gdbpy_event_list;
+      gdbpy_event_list = gdbpy_event_list->next;
+      if (gdbpy_event_list == NULL)
+	gdbpy_event_list_end = &gdbpy_event_list;
+
+      /* Ignore errors.  */
+      if (PyObject_CallObject (item->event, NULL) == NULL)
+	PyErr_Clear ();
+
+      Py_DECREF (item->event);
+      xfree (item);
+    }
+
+  do_cleanups (cleanup);
+}
+
+/* Submit an event to the gdb thread.  */
+static PyObject *
+gdbpy_post_event (PyObject *self, PyObject *args)
+{
+  struct gdbpy_event *event;
+  PyObject *func;
+  int wakeup;
+
+  if (!PyArg_ParseTuple (args, "O", &func))
+    return NULL;
+
+  if (!PyCallable_Check (func))
+    {
+      PyErr_SetString (PyExc_RuntimeError, 
+		       _("Posted event is not callable"));
+      return NULL;
+    }
+
+  Py_INCREF (func);
+
+  /* From here until the end of the function, we have the GIL, so we
+     can operate on our global data structures without worrying.  */
+  wakeup = gdbpy_event_list == NULL;
+
+  event = XNEW (struct gdbpy_event);
+  event->event = func;
+  event->next = NULL;
+  *gdbpy_event_list_end = event;
+  gdbpy_event_list_end = &event->next;
+
+  /* Wake up gdb when needed.  */
+  if (wakeup)
+    {
+      char c = 'q';		/* Anything. */
+      if (write (gdbpy_event_fds[1], &c, 1) != 1)
+        return PyErr_SetFromErrno (PyExc_IOError);
+    }
+
+  Py_RETURN_NONE;
+}
+
+/* Initialize the Python event handler.  */
+static void
+gdbpy_initialize_events (void)
+{
+  if (!pipe (gdbpy_event_fds))
+    {
+      gdbpy_event_list_end = &gdbpy_event_list;
+      add_file_handler (gdbpy_event_fds[0], gdbpy_run_events, NULL);
+    }
+}
+
 /* Printing.  */
 
 /* A python function to write a single string using gdb's filtered
@@ -854,6 +963,7 @@ Enables or disables printing of Python stack traces."),
   gdbpy_initialize_lazy_string ();
   gdbpy_initialize_thread ();
   gdbpy_initialize_inferior ();
+  gdbpy_initialize_events ();
 
   PyRun_SimpleString ("import gdb");
   PyRun_SimpleString ("gdb.pretty_printers = []");
@@ -974,6 +1084,9 @@ gdb.Symtab_and_line objects (or None)."},
 Parse String as an expression, evaluate it, and return the result as a Value."
   },
 
+  { "post_event", gdbpy_post_event, METH_VARARGS,
+    "Post an event into gdb's event loop." },
+
   { "target_charset", gdbpy_target_charset, METH_NOARGS,
     "target_charset () -> string.\n\
 Return the name of the current target charset." },