From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Paul E. McKenney" Subject: Re: [next-20120823] NOHZ: local_softirq_pending 200 on s/r Date: Fri, 24 Aug 2012 07:52:47 -0700 Message-ID: <20120824145247.GB2472@linux.vnet.ibm.com> References: <1345793168.4331.64.camel@marge.simpson.net> Reply-To: paulmck@linux.vnet.ibm.com Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from e33.co.us.ibm.com ([32.97.110.151]:46171 "EHLO e33.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754458Ab2HXOxP (ORCPT ); Fri, 24 Aug 2012 10:53:15 -0400 Received: from /spool/local by e33.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Fri, 24 Aug 2012 08:53:14 -0600 Content-Disposition: inline In-Reply-To: <1345793168.4331.64.camel@marge.simpson.net> Sender: linux-next-owner@vger.kernel.org List-ID: To: Mike Galbraith Cc: sedat.dilek@gmail.com, Paul McKenney , LKML , Thomas Gleixner , x86@kernel.org, linux-next On Fri, Aug 24, 2012 at 09:26:08AM +0200, Mike Galbraith wrote: > On Thu, 2012-08-23 at 12:04 +0200, Sedat Dilek wrote: > > > Jack Winter confirmed to see similiar NOHZ messages also on > > v3.4.9-rt17 kernel (CPU: Core2Duo when no suspend performed): > > > > [15223.171585] NOHZ: local_softirq_pending 08 > > These can be caused by blocking while holding local_softirq_lock. > > Even with per softirq threads, and then (yet more overhead) splitting > the lock to make sure one softirq type can't block another, _and_ only > griping if the lock for the pending softirq is _not_ held, seems the > little bugger can still be triggered very rarely by syn flood induced > handler bail/raise. Annoying little gripe :) Hmmm... Now that you mention it, if I understand correctly, the conversion of spinlocks to sleeplocks in -rt would seem to invalidate this particular diagnostic completely. So, what am I missing? Thanx, Paul