From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757225Ab2IFO5c (ORCPT ); Thu, 6 Sep 2012 10:57:32 -0400 Received: from casper.infradead.org ([85.118.1.10]:46078 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757094Ab2IFO53 convert rfc822-to-8bit (ORCPT ); Thu, 6 Sep 2012 10:57:29 -0400 Message-ID: <1346943414.18408.31.camel@twins> Subject: Re: [PATCH tip/core/rcu 11/15] rcu: Avoid spurious RCU CPU stall warnings From: Peter Zijlstra To: "Paul E. McKenney" Cc: linux-kernel@vger.kernel.org, mingo@elte.hu, laijs@cn.fujitsu.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@polymtl.ca, josh@joshtriplett.org, niv@us.ibm.com, tglx@linutronix.de, rostedt@goodmis.org, Valdis.Kletnieks@vt.edu, dhowells@redhat.com, eric.dumazet@gmail.com, darren@dvhart.com, fweisbec@gmail.com, sbw@mit.edu, patches@linaro.org, "Paul E. McKenney" Date: Thu, 06 Sep 2012 16:56:54 +0200 In-Reply-To: <1346352988-32444-11-git-send-email-paulmck@linux.vnet.ibm.com> References: <20120830185607.GA32148@linux.vnet.ibm.com> <1346352988-32444-1-git-send-email-paulmck@linux.vnet.ibm.com> <1346352988-32444-11-git-send-email-paulmck@linux.vnet.ibm.com> Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7BIT X-Mailer: Evolution 3.2.2- Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2012-08-30 at 11:56 -0700, Paul E. McKenney wrote: > > If a given CPU avoids the idle loop but also avoids starting a new > RCU grace period for a full minute, RCU can issue spurious RCU CPU > stall warnings. This commit fixes this issue by adding a check for > ongoing grace period to avoid these spurious stall warnings. How would it avoid starting a new period for over a minute? fqs should happen, right? And holding rcu_read_lock() for over a minute surely is a bug.