From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754143Ab2HVBDi (ORCPT ); Tue, 21 Aug 2012 21:03:38 -0400 Received: from mga11.intel.com ([192.55.52.93]:5644 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751539Ab2HVBDf (ORCPT ); Tue, 21 Aug 2012 21:03:35 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.77,806,1336374000"; d="scan'208";a="207988957" Date: Wed, 22 Aug 2012 09:03:32 +0800 From: Fengguang Wu To: "Paul E. McKenney" Cc: Thomas Gleixner , Steven Rostedt , linux-kernel@vger.kernel.org Subject: Re: lockdep warning on rt_mutex_lock() Message-ID: <20120822010332.GA417@localhost> References: <20120817100635.GA30765@localhost> <20120817134328.GB2872@linux.vnet.ibm.com> <20120817140240.GB539@localhost> <20120817144437.GC2872@linux.vnet.ibm.com> <20120818045908.GA7503@localhost> <20120821192149.GM2456@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120821192149.GM2456@linux.vnet.ibm.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Aug 21, 2012 at 12:21:49PM -0700, Paul E. McKenney wrote: > On Sat, Aug 18, 2012 at 12:59:08PM +0800, Fengguang Wu wrote: > > On Fri, Aug 17, 2012 at 07:44:37AM -0700, Paul E. McKenney wrote: > > > On Fri, Aug 17, 2012 at 10:02:40PM +0800, Fengguang Wu wrote: > > > > On Fri, Aug 17, 2012 at 06:43:28AM -0700, Paul E. McKenney wrote: > > > > > On Fri, Aug 17, 2012 at 06:06:35PM +0800, Fengguang Wu wrote: > > > > > > Greetings, > > > > > > > > > > > > FYI, a lockdep warning: > > > > > > > > > > Certainly looks problematic! > > > > > > > > > > Any hint as to what version of the kernel produced this splat? > > > > > (Yes, lazy of me to ask, I know, but I am not seeing it in my testing.) > > > > > > > > It happens on both 3.5.0 and 3.6-rc1. Will bisect (try older kernels) help? > > > > Bisect is handy for me :) > > > > > > Bisection would be very welcome!!! ;-) > > > > The bisect result is... > > Hmmm... This patch is a bit of a blast from the past. > > > commit 9e571a82f0cb205a65a0ea41657f19f22b7fabb8 > > Author: Paul E. McKenney > > Date: Thu Sep 30 21:26:52 2010 -0700 > > > > rcu: add tracing for TINY_RCU and TINY_PREEMPT_RCU > > > > Add tracing for the tiny RCU implementations, including statistics on > > boosting in the case of TINY_PREEMPT_RCU and RCU_BOOST. > > > > Signed-off-by: Paul E. McKenney > > Signed-off-by: Paul E. McKenney > > So the lockdep complaint indicates that lockdep and the actual hardware > had different opinions about whether or not interrupts were enabled. > One way that can happen is through use of raw_local_irq_save(). And this > commit did add a raw_local_irq_save(). > > So maybe converting to local_irq_save() will make things work better. > > Fengguang, could you please try out the following patch? It reliably fixed the warnings. Thank you very much! Tested-by: Fengguang Wu