netdev - Re: [PATCH] net/802/mrp: fix lockdep splat

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Date:	Mon, 13 May 2013 18:30:34 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Cong Wang <amwang@...hat.com>
Cc:	Denys Fedoryshchenko <denys@...p.net.lb>,
	David Ward <david.ward@...mit.edu>,
	hayeswang <hayeswang@...ltek.com>,
	Francois Romieu <romieu@...zoreil.com>, netdev@...r.kernel.org
Subject: Re: [PATCH] net/802/mrp: fix lockdep splat

On Tue, 2013-05-14 at 09:12 +0800, Cong Wang wrote:
> On Mon, 2013-05-13 at 05:24 -0700, Eric Dumazet wrote:
> >         del_timer_sync(&app->join_timer);
> >  
> > -       spin_lock(&app->lock);
> > +       spin_lock_bh(&app->lock); 
> 
> But we just have removed the join timer before taking this spin lock, so
> it is not possible to race with timer, but we still have race condition
> with mrp_rcv() which is called in BH context too. However, this is not
> what Denys reported, so I have no idea on this.
> 

Thats a lockdep splat.

lockdep cannot know join timer wont fire again.



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