linux-kernel - Re: 2.6.34-rc1: rcu lockdep bug?

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Message-ID: <2375c9f91003150312u37dfd70fk55a4b8820e13590e@mail.gmail.com>
Date:	Mon, 15 Mar 2010 18:12:29 +0800
From:	Américo Wang <xiyou.wangcong@...il.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	David Miller <davem@...emloft.net>, peterz@...radead.org,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: 2.6.34-rc1: rcu lockdep bug?

On Mon, Mar 15, 2010 at 6:04 PM, Eric Dumazet <eric.dumazet@...il.com> wrote:
> Le lundi 15 mars 2010 à 17:39 +0800, Américo Wang a écrit :
>
>>
>> Ok, I think I found what lockdep really complains about, it is that we took
>> spin_lock in netpoll_poll_lock() which is in hardirq-enabled environment,
>> later, we took another spin_lock with spin_lock_irqsave() in netpoll_rx(),
>> so lockdep thought we broke the locking rule.
>>
>> I don't know why netpoll_rx() needs irq disabled, it looks like that no one
>> takes rx_lock in hardirq context. So can we use spin_lock(&rx_lock)
>> instead? Or am I missing something here? Eric? David?
>
> I am a bit lost.
>
> Could you give the complete picture, because I cannot find it in my
> netdev archives.
>

Sure, sorry for this.

Here is the whole thread:

http://lkml.org/lkml/2010/3/11/100
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