From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755255AbZEROkx (ORCPT ); Mon, 18 May 2009 10:40:53 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751961AbZEROkm (ORCPT ); Mon, 18 May 2009 10:40:42 -0400 Received: from e6.ny.us.ibm.com ([32.97.182.146]:58824 "EHLO e6.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751090AbZEROkl (ORCPT ); Mon, 18 May 2009 10:40:41 -0400 Date: Mon, 18 May 2009 07:40:39 -0700 From: "Paul E. McKenney" To: Lai Jiangshan Cc: linux-kernel@vger.kernel.org, netdev@vger.kernel.org, netfilter-devel@vger.kernel.org, mingo@elte.hu, akpm@linux-foundation.org, torvalds@linux-foundation.org, davem@davemloft.net, dada1@cosmosbay.com, zbr@ioremap.net, jeff.chua.linux@gmail.com, paulus@samba.org, jengelh@medozas.de, r000n@r000n.net, benh@kernel.crashing.org, mathieu.desnoyers@polymtl.ca Subject: Re: [PATCH RFC] v5 expedited "big hammer" RCU grace periods Message-ID: <20090518144039.GA6768@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20090517191141.GA25915@linux.vnet.ibm.com> <4A110768.2040707@cn.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4A110768.2040707@cn.fujitsu.com> User-Agent: Mutt/1.5.15+20070412 (2007-04-11) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, May 18, 2009 at 02:59:52PM +0800, Lai Jiangshan wrote: > Paul E. McKenney wrote: > > +void sched_expedited_wake(void *unused) > > +{ > > + mutex_lock(&__get_cpu_var(sched_expedited_done_mutex)); > > + if (__get_cpu_var(sched_expedited_done_qs) == > > + SCHED_EXPEDITED_QS_DONE_QS) { > > + __get_cpu_var(sched_expedited_done_qs) = > > + SCHED_EXPEDITED_QS_NEED_QS; > > + wake_up(&__get_cpu_var(sched_expedited_qs_wq)); > > + } > > + mutex_unlock(&__get_cpu_var(sched_expedited_done_mutex)); > > +} > > [...] > > > + get_online_cpus(); > > + preempt_disable(); > > + mycpu = smp_processor_id(); > > + smp_call_function(sched_expedited_wake, NULL, 1); > > sched_expedited_wake() calls mutex_lock() which may sleep? Good eyes! Fixing this and the failure to release this lock in krcu_sched_expedited_percpu() allows it to survive 10 hours of rcutorture running in parallel with onlining/offlining random CPUs. > And I think you have re-implement workqueue. Hmmm... I suppose I could use schedule_work(), though I am concerned about interference from other work. But I will give this some thought. Thanx, Paul