scripts/gdb: add task iteration class

This class allows to iterate over all tasks of the target.
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/tasks.py

+#
+# gdb helper commands and functions for Linux kernel debugging
+#
+#  task & thread tools
+#
+# 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
+
+from linux import utils
+
+
+task_type = utils.CachedType("struct task_struct")
+
+
+class TaskList:
+    def __init__(self):
+        global task_type
+        self.task_ptr_type = task_type.get_type().pointer()
+        self.init_task = gdb.parse_and_eval("init_task")
+        self.curr_group = self.init_task.address
+        self.curr_task = None
+
+    def __iter__(self):
+        return self
+
+    def next(self):
+        t = self.curr_task
+        if not t or t == self.curr_group:
+            self.curr_group = \
+                utils.container_of(self.curr_group['tasks']['next'],
+                                   self.task_ptr_type, "tasks")
+            if self.curr_group == self.init_task.address:
+                raise StopIteration
+            t = self.curr_task = self.curr_group
+        else:
+            self.curr_task = \
+                utils.container_of(t['thread_group']['next'],
+                                   self.task_ptr_type, "thread_group")
+        return t