From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752756AbaHDMhg (ORCPT ); Mon, 4 Aug 2014 08:37:36 -0400 Received: from e32.co.us.ibm.com ([32.97.110.150]:44226 "EHLO e32.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751117AbaHDMhe (ORCPT ); Mon, 4 Aug 2014 08:37:34 -0400 Date: Mon, 4 Aug 2014 05:37:27 -0700 From: "Paul E. McKenney" To: Peter Zijlstra Cc: Lai Jiangshan , linux-kernel@vger.kernel.org, mingo@kernel.org, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, josh@joshtriplett.org, tglx@linutronix.de, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, dvhart@linux.intel.com, fweisbec@gmail.com, oleg@redhat.com, bobby.prani@gmail.com Subject: Re: [PATCH v3 tip/core/rcu 1/9] rcu: Add call_rcu_tasks() Message-ID: <20140804123727.GJ8101@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20140731215445.GA21933@linux.vnet.ibm.com> <1406843709-23396-1-git-send-email-paulmck@linux.vnet.ibm.com> <53DEE1CD.4000705@cn.fujitsu.com> <20140804074620.GH9918@twins.programming.kicks-ass.net> <53DF41ED.2020508@cn.fujitsu.com> <20140804115043.GA31903@linux.vnet.ibm.com> <20140804122515.GR19379@twins.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140804122515.GR19379@twins.programming.kicks-ass.net> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 14080412-0928-0000-0000-000003DD0AB5 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Aug 04, 2014 at 02:25:15PM +0200, Peter Zijlstra wrote: > On Mon, Aug 04, 2014 at 04:50:44AM -0700, Paul E. McKenney wrote: > > OK, I will bite... > > > > What kinds of tasks are on a runqueue, but neither ->on_cpu nor > > PREEMPT_ACTIVE? > > Userspace tasks, they don't necessarily get PREEMPT_ACTIVE when > preempted. Now obviously you're not _that_ interested in userspace tasks > for this, so that might be ok. Right, I detect userspace tasks using RCU's scheduling-clock handler. (And code to handle the NO_HZ_FULL case is under construction.) > But the main point was, you cannot use ->on_cpu or PREEMPT_ACTIVE > without holding rq->lock. OK, got it. Thanx, Paul