From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Paul E. McKenney" Subject: Re: [PATCH] cgroup: Check task_lock in task_subsys_state() Date: Thu, 22 Apr 2010 21:10:03 -0700 Message-ID: <20100423041003.GC2619@linux.vnet.ibm.com> References: <4BD10788.8060006@cn.fujitsu.com> Reply-To: paulmck@linux.vnet.ibm.com Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <4BD10788.8060006@cn.fujitsu.com> Sender: linux-kernel-owner@vger.kernel.org To: Li Zefan Cc: Peter Zijlstra , Lai JIangshan , Paul Menage , Matt Helsley , Cedric Le Goater , LKML , "containers@lists.osdl.org" , Andrew Morton List-Id: containers.vger.kernel.org On Fri, Apr 23, 2010 at 10:35:52AM +0800, Li Zefan wrote: > task_subsys_state() is safe under task_lock(). See > Documentation/cgroups/cgroups.txt for locking rule. > > This fixes an RCU warning when resume from suspend. The > warning comes from freezer cgroup in cgroup_freezing_or_frozen(). > > Signed-off-by: Li Zefan > --- > > I'm not sure which is preferable - access ->alloc_lock directly > like this patch or add task_lock_is_held() in sched.h This is for the maintainers to decide, either way works from my viewpoint. I have queued it as is with Matt's Acked-by, and am testing it. Thank you!!! Thanx, Paul > --- > include/linux/cgroup.h | 1 + > 1 files changed, 1 insertions(+), 0 deletions(-) > > diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h > index b8ad1ea..8f78073 100644 > --- a/include/linux/cgroup.h > +++ b/include/linux/cgroup.h > @@ -530,6 +530,7 @@ static inline struct cgroup_subsys_state *task_subsys_state( > { > return rcu_dereference_check(task->cgroups->subsys[subsys_id], > rcu_read_lock_held() || > + lockdep_is_held(&task->alloc_lock) || > cgroup_lock_is_held()); > } > > -- > 1.6.3