Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758384Ab0FBO45 (ORCPT ); Wed, 2 Jun 2010 10:56:57 -0400 Received: from e9.ny.us.ibm.com ([32.97.182.139]:51800 "EHLO e9.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754564Ab0FBO4z (ORCPT ); Wed, 2 Jun 2010 10:56:55 -0400 Date: Wed, 2 Jun 2010 07:56:53 -0700 From: "Paul E. McKenney" To: Daniel J Blueman Cc: Linux Kernel Subject: Re: [PATCH] RCU: don't turn off lockdep when find suspicious rcu_dereference_check() usage Message-ID: <20100602145653.GA2385@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3201 Lines: 96 On Tue, Jun 01, 2010 at 02:06:13PM +0100, Daniel J Blueman wrote: > Hi Paul, > > With 2.6.35-rc1 and your patch in the context below, we still see > "include/linux/cgroup.h:534 invoked rcu_dereference_check() without > protection!", so need this additional patch: > > Acquire read-side RCU lock around task_group() calls, addressing > "include/linux/cgroup.h:534 invoked rcu_dereference_check() without > protection!" warning. > > Signed-off-by: Daniel J Blueman Thank you, Daniel! I have queued this for 2.6.35. I had to apply the patch by hand due to line wrapping. Could you please check your email-agent settings? This simple patch was no problem to hand apply, but for a larger patch this process would be both tedious and error prone. Thanx, Paul > diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c > index 217e4a9..50ec9ea 100644 > --- a/kernel/sched_fair.c > +++ b/kernel/sched_fair.c > @@ -1241,6 +1241,7 @@ 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; > @@ -1250,6 +1251,7 @@ static int wake_affine(struct sched_domain *sd, > struct task_struct *p, int sync) > } > > tg = task_group(p); > + rcu_read_unlock(); > weight = p->se.load.weight; > > imbalance = 100 + (sd->imbalance_pct - 100) / 2; > > --- > > On Wed, Apr 21, 2010 at 02:35:43PM -0700, Paul E. McKenney wrote: > On Tue, Apr 20, 2010 at 11:38:28AM -0400, Miles Lane wrote: > Excellent. Here are the results on my machine. .config appended. > First, thank you very much for testing this, Miles! > > And as Tetsuo Handa pointed out privately, my patch was way broken. > > Here is an updated version. > > Thanx, Paul > > commit b15e561ed91b7a366c3cc635026f3b9ce6483070 > Author: Paul E. McKenney > Date: Wed Apr 21 14:04:56 2010 -0700 > > sched: protect __sched_setscheduler() access to cgroups > > A given task's cgroups structures must remain while that task is running > due to reference counting, so this is presumably a false positive. > Updated to reflect feedback from Tetsuo Handa. > > Signed-off-by: Paul E. McKenney > > diff --git a/kernel/sched.c b/kernel/sched.c > index 14c44ec..f425a2b 100644 > --- a/kernel/sched.c > +++ b/kernel/sched.c > @@ -4575,9 +4575,13 @@ recheck: > * Do not allow realtime tasks into groups that have no runtime > * assigned. > */ > + rcu_read_lock(); > if (rt_bandwidth_enabled() && rt_policy(policy) && > - task_group(p)->rt_bandwidth.rt_runtime == 0) > + task_group(p)->rt_bandwidth.rt_runtime == 0) { > + rcu_read_unlock(); > return -EPERM; > + } > + rcu_read_unlock(); > #endif > > retval = security_task_setscheduler(p, policy, param); > -- > Daniel J Blueman -- 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/