Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932092Ab1FGR3c (ORCPT ); Tue, 7 Jun 2011 13:29:32 -0400 Received: from casper.infradead.org ([85.118.1.10]:55047 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755722Ab1FGR3b convert rfc822-to-8bit (ORCPT ); Tue, 7 Jun 2011 13:29:31 -0400 Subject: Re: [PATCH] sched: remove rcu_read_lock from wake_affine From: Peter Zijlstra To: paulmck@linux.vnet.ibm.com Cc: "Nikunj A. Dadhania" , mingo@elte.hu, linux-kernel@vger.kernel.org In-Reply-To: <20110607172606.GA2286@linux.vnet.ibm.com> References: <20110607101251.777.34547.stgit@IBM-009124035060.in.ibm.com> <1307442411.2322.246.camel@twins> <20110607172606.GA2286@linux.vnet.ibm.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8BIT Date: Tue, 07 Jun 2011 19:29:23 +0200 Message-ID: <1307467763.2322.282.camel@twins> Mime-Version: 1.0 X-Mailer: Evolution 2.30.3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1196 Lines: 29 On Tue, 2011-06-07 at 10:26 -0700, Paul E. McKenney wrote: > > Nikunj, one such approach is is "WARN_ON_ONCE(!rcu_read_lock_held())". > > This will complain if this function is called without an rcu_read_lock() > in effect, but only if CONFIG_PROVE_RCU=y. rcu_lockdep_assert(rcu_read_lock_held()) would be nicer, however, since the below: > > > static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync) > > > { > > > s64 this_load, load; > > > @@ -1481,7 +1482,6 @@ static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync) > > > * effect of the currently running task from the load > > > * of the current CPU: > > > */ > > > - rcu_read_lock(); > > > if (sync) { > > > tg = task_group(current); > > > weight = current->se.load.weight; task_group() has an rcu_dereference_check() in, its really not needed, the thing will yell if we get this wrong. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/