From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754186Ab1APAPV (ORCPT ); Sat, 15 Jan 2011 19:15:21 -0500 Received: from e1.ny.us.ibm.com ([32.97.182.141]:52700 "EHLO e1.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752889Ab1APAPT (ORCPT ); Sat, 15 Jan 2011 19:15:19 -0500 Date: Sat, 15 Jan 2011 16:15:16 -0800 From: "Paul E. McKenney" To: Ingo Molnar Cc: linux-kernel@vger.kernel.org, mingo@redhat.com, hpa@zytor.com, paul.mckenney@linaro.org, rmk+kernel@arm.linux.org.uk, weber@corscience.de, tglx@linutronix.de, linux-tip-commits@vger.kernel.org Subject: Re: [tip:core/urgent] rcu: avoid pointless blocked-task warnings Message-ID: <20110116001516.GB2229@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20110115142857.GA8610@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110115142857.GA8610@elte.hu> User-Agent: Mutt/1.5.20 (2009-06-14) X-Content-Scanned: Fidelis XPS MAILER Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Jan 15, 2011 at 03:28:57PM +0100, Ingo Molnar wrote: > > * tip-bot for Paul E. McKenney wrote: > > > Commit-ID: b24efdfdf679cf9b05947c531971905fc727dd40 > > Gitweb: http://git.kernel.org/tip/b24efdfdf679cf9b05947c531971905fc727dd40 > > Author: Paul E. McKenney > > AuthorDate: Wed, 12 Jan 2011 14:18:11 -0800 > > Committer: Paul E. McKenney > > CommitDate: Fri, 14 Jan 2011 04:58:08 -0800 > > > > rcu: avoid pointless blocked-task warnings > > > > If the RCU callback-processing kthread has nothing to do, it parks in > > a wait_event(). If RCU remains idle for more than two minutes, the > > kernel complains about this. This commit changes from wait_event() > > to wait_event_interruptible() to prevent the kernel from complaining > > just because RCU is idle. > > Btw., a sidenote, it's not just about the blocked-tasks lockup detector warning, > uninterruptible sleeps will also artificially inflate the load average of the box, > +1.0 per such task. So it's definitely a bug to sleep for a very long time > uninterruptible. Good point, and I have made the corresponding change in the in-progress TREE_PREEMPT_RCU variant of RCU priority boosting. Some thought will be required when merging SRCU into the Tiny and Tree RCU implementations. ;-) Thanx, Paul