linux-kernel - Re: [cgroup/task_lock] INFO: suspicious RCU usage.

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Message-ID: <20140225150636.GF26788@htj.dyndns.org>
Date:	Tue, 25 Feb 2014 10:06:36 -0500
From:	Tejun Heo <tj@...nel.org>
To:	Li Zefan <lizefan@...wei.com>
Cc:	Fengguang Wu <fengguang.wu@...el.com>, cgroups@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [cgroup/task_lock] INFO: suspicious RCU usage.

Hello, Li.

On Tue, Feb 25, 2014 at 08:01:25PM +0800, Li Zefan wrote:
...
> >> So, this is from removing task_lock from task_css_set_check() and
> >> adding rcu_read_lock() in cpuset_cpus_allowed() should fix it.
> > 
> > Yeah, rcu_read_lock() should be sufficient.
> > 
> >> I'm
> >> not sure how much of task_lock() locking we currently have in cpuset
> >> is actually necessary tho.  Shouldn't we be able to do most with just
> >> callback_mutex, if not cpuset_mutex?  Li, any ideas?
> >>
> > 
> > task_lock() is also used to protect task->mems_allowed. I'll see if we
> > can get rid of most (if not all) task_lock() lockings in cpuset.
> > 
> 
> After a quick lock, I think except the one in cpuset_change_task_nodemask(), all
> other task_lock() lockings can be replace by rcu_readlock().

I committed the original series as-is.  Can you please post follow-up
patches to update cpuset locking?

Thanks.

-- 
tejun
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