From: David Miller <davem@davemloft.net>
To: peterz@infradead.org
Cc: lizf@cn.fujitsu.com, herbert@gondor.hengli.com.au,
davej@redhat.com, netdev@vger.kernel.org,
linux-kernel@vger.kernel.org, paulmck@linux.vnet.ibm.com
Subject: Re: [PATCH] cls_cgroup: Fix rcu lockdep warning
Date: Thu, 02 Sep 2010 10:05:51 -0700 (PDT) [thread overview]
Message-ID: <20100902.100551.115929058.davem@davemloft.net> (raw)
In-Reply-To: <1283423916.2059.1847.camel@laptop>
From: Peter Zijlstra <peterz@infradead.org>
Date: Thu, 02 Sep 2010 12:38:36 +0200
> On Thu, 2010-09-02 at 14:30 +0800, Li Zefan wrote:
>> Calling task_subsys_state() without holding rcu_read_lock or
>> cgroup_mutex can cause lockdep warning.
>>
>
> That is not a suitable changelog.
>
> Was the warning correct? Is your patch correct? What does RCU protect
> here and why can we use classid after dropping it.
>
> Simply frobbing code to make the warning go away is not good.
In fact shouldn't this be a rcu_dereference() or similar?
next prev parent reply other threads:[~2010-09-02 17:05 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-09-02 6:30 Li Zefan
2010-09-02 10:38 ` Peter Zijlstra
2010-09-02 17:05 ` David Miller [this message]
2010-09-02 17:16 ` Paul E. McKenney
2010-09-03 1:10 ` Li Zefan
2010-09-03 4:52 ` Herbert Xu
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