From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner+w=401wt.eu-S1422653AbXDCS5v@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1422653AbXDCS5v (ORCPT <rfc822;w@1wt.eu>);
	Tue, 3 Apr 2007 14:57:51 -0400
Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1422651AbXDCS5v
	(ORCPT <rfc822;linux-kernel-outgoing>);
	Tue, 3 Apr 2007 14:57:51 -0400
Received: from gateway-1237.mvista.com ([63.81.120.158]:65318 "EHLO
	gateway-1237.mvista.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1422654AbXDCS5u (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Tue, 3 Apr 2007 14:57:50 -0400
Subject: real time hang w/ latency tracing
From: Daniel Walker <dwalker@mvista.com>
To: mingo@elte.hu
Cc: linux-kernel@vger.kernel.org
Content-Type: text/plain
Date: Tue, 03 Apr 2007 11:57:05 -0700
Message-Id: <1175626625.10738.21.camel@imap.mvista.com>
Mime-Version: 1.0
X-Mailer: Evolution 2.8.2.1 (2.8.2.1-3.fc6) 
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
X-Mailing-List: linux-kernel@vger.kernel.org


With 2.6.21-rc5-rt8 / i386 . If I disable wakeup timing , and enable
interrupt off timing with latency tracing I can cause,

BUG: scheduling with irqs disabled: IRQ-16/0x00000000/909
caller is rt_spin_lock_slowlock+0x94/0x190
 [<c010577a>] show_trace_log_lvl+0x3a/0x60
 [<c0105fdd>] show_trace+0x2d/0x30
 [<c01060c7>] dump_stack+0x27/0x30
 [<c03f52db>] schedule+0x12b/0x130
 [<c03f6314>] rt_spin_lock_slowlock+0x94/0x190
 [<c03f6b35>] rt_spin_lock+0x25/0x30
 [<c02f19bf>] serial8250_console_write+0x16f/0x190
 [<c012b3aa>] __call_console_drivers+0x7a/0xa0
 [<c012b427>] _call_console_drivers+0x57/0xa0
 [<c012b58d>] release_console_sem+0xdd/0x1e0
 [<c012bd46>] vprintk+0x226/0x3b0
 [<c012bef0>] printk+0x20/0x30
 [<c0158d29>] print_traces+0x49/0x100
 [<c0105792>] show_trace_log_lvl+0x52/0x60
 [<c0105fdd>] show_trace+0x2d/0x30
 [<c01060c7>] dump_stack+0x27/0x30
 [<c0158481>] check_critical_timing+0x2b1/0x380
 [<c01585f6>] trace_hardirqs_on+0xa6/0xc0
 [<c01046e5>] restore_nocheck+0x12/0x15
 =======================

I do this by running,

echo 1 > /proc/sys/kernel/preempt_thresh

which clearly causes loads of output .. Then while the output is
screaming along I hold down the left arrow key and eventually the
message above starts to appear often .. Then the system hangs.

Also I'm using an NFS root which might help to bring out the error ..

Daniel