scripts/qemu-gdb: add simple tcg lock status helper

Add a simple helper to dump lock state.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

scripts/qemugdb/tcg.py

@@ -0,0 +1,46 @@
+#!/usr/bin/python
+# -*- coding: utf-8 -*-
+#
+# GDB debugging support, TCG status
+#
+# Copyright 2016 Linaro Ltd
+#
+# Authors:
+#  Alex Bennée <alex.bennee@linaro.org>
+#
+# This work is licensed under the terms of the GNU GPL, version 2.  See
+# the COPYING file in the top-level directory.
+#
+# Contributions after 2012-01-13 are licensed under the terms of the
+# GNU GPL, version 2 or (at your option) any later version.
+
+# 'qemu tcg-lock-status' -- display the TCG lock status across threads
+
+import gdb
+
+class TCGLockStatusCommand(gdb.Command):
+    '''Display TCG Execution Status'''
+    def __init__(self):
+        gdb.Command.__init__(self, 'qemu tcg-lock-status', gdb.COMMAND_DATA,
+                             gdb.COMPLETE_NONE)
+
+    def invoke(self, arg, from_tty):
+        gdb.write("Thread, BQL (iothread_mutex), Replay, Blocked?\n")
+        for thread in gdb.inferiors()[0].threads():
+            thread.switch()
+
+            iothread = gdb.parse_and_eval("iothread_locked")
+            replay = gdb.parse_and_eval("replay_locked")
+
+            frame = gdb.selected_frame()
+            if frame.name() == "__lll_lock_wait":
+                frame.older().select()
+                mutex = gdb.parse_and_eval("mutex")
+                owner = gdb.parse_and_eval("mutex->__data.__owner")
+                blocked = ("__lll_lock_wait waiting on %s from %d" %
+                           (mutex, owner))
+            else:
+                blocked = "not blocked"
+
+            gdb.write("%d/%d, %s, %s, %s\n" % (thread.num, thread.ptid[1],
+                                               iothread, replay, blocked))