scripts/gdb: add cache for type objects

Type lookups are very slow in gdb-python which is often noticeable when
iterating over a number of objects.  Introduce the helper class CachedType
that keeps a reference to a gdb.Type object but also refreshes it after an
object file has been loaded.
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Jason Wessel <jason.wessel@windriver.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Ben Widawsky <ben@bwidawsk.net>
Cc: Borislav Petkov <bp@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

scripts/gdb/linux/utils.py

+#
+# gdb helper commands and functions for Linux kernel debugging
+#
+#  common utilities
+#
+# Copyright (c) Siemens AG, 2011-2013
+#
+# Authors:
+#  Jan Kiszka <jan.kiszka@siemens.com>
+#
+# This work is licensed under the terms of the GNU GPL version 2.
+#
+
+import gdb
+
+
+class CachedType:
+    def __init__(self, name):
+        self._type = None
+        self._name = name
+
+    def _new_objfile_handler(self, event):
+        self._type = None
+        gdb.events.new_objfile.disconnect(self._new_objfile_handler)
+
+    def get_type(self):
+        if self._type is None:
+            self._type = gdb.lookup_type(self._name)
+            if self._type is None:
+                raise gdb.GdbError(
+                    "cannot resolve type '{0}'".format(self._name))
+            if hasattr(gdb, 'events') and hasattr(gdb.events, 'new_objfile'):
+                gdb.events.new_objfile.connect(self._new_objfile_handler)
+        return self._type