Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756250Ab0FANGQ (ORCPT ); Tue, 1 Jun 2010 09:06:16 -0400 Received: from mail-gy0-f174.google.com ([209.85.160.174]:50827 "EHLO mail-gy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756045Ab0FANGO (ORCPT ); Tue, 1 Jun 2010 09:06:14 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:date:message-id:subject:from:to:content-type; b=YBVaCqACG1p1yykM8+hCu5KvWvA4/LmX4H6/MwVEQYrjkPFXDqZT0DnvdyyxNpOIuL Ew1VbE5cSPhykVMawn0eQrl/B9m+gFXPBr4wMoQn9hXWxFkCZM1qkY3CrwdqmhGbjhKV xv6dGe1/sqvrurbbopbPQ+cXPIi10th+nRk7w= MIME-Version: 1.0 Date: Tue, 1 Jun 2010 14:06:13 +0100 Message-ID: Subject: Re: [PATCH] RCU: don't turn off lockdep when find suspicious rcu_dereference_check() usage From: Daniel J Blueman To: paulmck@linux.vnet.ibm.com, Linux Kernel Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2672 Lines: 86 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 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/