* python/python-internal.h (PyGILState_Ensure): New define.

(PyGILState_Release): Likewise.
	(PyEval_InitThreads): Likewise.
	(PyThreadState_Swap): Likewise.
	(PyEval_InitThreads): Likewise.
	* python/python.c (_initialize_python): Initialize threads.
	Release GIL.
	(eval_python_from_control_command): Acquire GIL.
	(python_command): Likewise.
	* python/python-internal.h (make_cleanup_py_restore_gil):
	Declare.
	* python/python-utils.c (py_gil_restore): New function.
	(make_cleanup_py_restore_gil): Likewise.

gdb/ChangeLog

@@ -1,3 +1,19 @@
+2008-11-21  Tom Tromey  <tromey@redhat.com>
+
+	* python/python-internal.h (PyGILState_Ensure): New define.
+	(PyGILState_Release): Likewise.
+	(PyEval_InitThreads): Likewise.
+	(PyThreadState_Swap): Likewise.
+	(PyEval_InitThreads): Likewise.
+	* python/python.c (_initialize_python): Initialize threads.
+	Release GIL.
+	(eval_python_from_control_command): Acquire GIL.
+	(python_command): Likewise.
+	* python/python-internal.h (make_cleanup_py_restore_gil):
+	Declare.
+	* python/python-utils.c (py_gil_restore): New function.
+	(make_cleanup_py_restore_gil): Likewise.
+
 2008-11-20  Doug Evans  <dje@google.com>
 
 	* frame.c (frame_debug_got_null_frame): Remove file arg.

gdb/python/python-internal.h

@@ -43,6 +43,17 @@ typedef Py_intptr_t Py_ssize_t;
 #error "Unable to find usable Python.h"
 #endif
 
+/* If Python.h does not define WITH_THREAD, then the various
+   GIL-related functions will not be defined.  However,
+   PyGILState_STATE will be.  */
+#ifndef WITH_THREAD
+#define PyGILState_Ensure() ((PyGILState_STATE) 0)
+#define PyGILState_Release(ARG) (ARG)
+#define PyEval_InitThreads() 0
+#define PyThreadState_Swap(ARG) (ARG)
+#define PyEval_InitThreads() 0
+#endif
+
 struct value;
 
 extern PyObject *gdb_module;
@@ -57,6 +68,7 @@ struct value *convert_value_from_python (PyObject *obj);
 void gdbpy_initialize_values (void);
 
 struct cleanup *make_cleanup_py_decref (PyObject *py);
+struct cleanup *make_cleanup_py_restore_gil (PyGILState_STATE *state);
 
 /* Use this after a TRY_EXCEPT to throw the appropriate Python
    exception.  */

gdb/python/python-utils.c

@@ -46,6 +46,23 @@ make_cleanup_py_decref (PyObject *py)
   return make_cleanup (py_decref, (void *) py);
 }
 
+/* A cleanup function to restore the thread state.  */
+
+static void
+py_gil_restore (void *p)
+{
+  PyGILState_STATE *state = p;
+  PyGILState_Release (*state);
+}
+
+/* Return a new cleanup which will restore the Python GIL state.  */
+
+struct cleanup *
+make_cleanup_py_restore_gil (PyGILState_STATE *state)
+{
+  return make_cleanup (py_gil_restore, state);
+}
+
 /* Converts a Python 8-bit string to a unicode string object.  Assumes the
    8-bit string is in the host charset.  If an error occurs during conversion,
    returns NULL with a python exception set.

gdb/python/python.c

@@ -103,10 +103,15 @@ void
 eval_python_from_control_command (struct command_line *cmd)
 {
   char *script;
+  struct cleanup *cleanup;
+  PyGILState_STATE state;
 
   if (cmd->body_count != 1)
     error (_("Invalid \"python\" block structure."));
 
+  state = PyGILState_Ensure ();
+  cleanup = make_cleanup_py_restore_gil (&state);
+
   script = compute_python_string (cmd->body_list[0]);
   PyRun_SimpleString (script);
   xfree (script);
@@ -115,6 +120,8 @@ eval_python_from_control_command (struct command_line *cmd)
       gdbpy_print_stack ();
       error (_("error while executing Python code"));
     }
+
+  do_cleanups (cleanup);
 }
 
 /* Implementation of the gdb "python" command.  */
@@ -122,6 +129,12 @@ eval_python_from_control_command (struct command_line *cmd)
 static void
 python_command (char *arg, int from_tty)
 {
+  struct cleanup *cleanup;
+  PyGILState_STATE state;
+
+  state = PyGILState_Ensure ();
+  cleanup = make_cleanup_py_restore_gil (&state);
+
   while (arg && *arg && isspace (*arg))
     ++arg;
   if (arg && *arg)
@@ -136,10 +149,11 @@ python_command (char *arg, int from_tty)
   else
     {
       struct command_line *l = get_command_line (python_control, "");
-      struct cleanup *cleanups = make_cleanup_free_command_lines (&l);
+      make_cleanup_free_command_lines (&l);
       execute_control_command_untraced (l);
-      do_cleanups (cleanups);
     }
+
+  do_cleanups (cleanup);
 }
 
 
@@ -392,6 +406,7 @@ Enables or disables printing of Python stack traces."),
 
 #ifdef HAVE_PYTHON
   Py_Initialize ();
+  PyEval_InitThreads ();
 
   gdb_module = Py_InitModule ("gdb", GdbMethods);
 
@@ -429,5 +444,10 @@ class GdbOutputFile:\n\
 sys.stderr = GdbOutputFile()\n\
 sys.stdout = GdbOutputFile()\n\
 ");
+
+  /* Release the GIL while gdb runs.  */
+  PyThreadState_Swap (NULL);
+  PyEval_ReleaseLock ();
+
 #endif /* HAVE_PYTHON */
 }