From mboxrd@z Thu Jan  1 00:00:00 1970
From: Roland Dreier <rdreier@cisco.com>
Subject: [ofa-general] Re: [PATCH] IB/ipoib: Do not turn on carrier to a non
	active port
Date: Thu, 17 Sep 2009 08:50:18 -0700
Message-ID: <adamy4td0zp.fsf@cisco.com>
References: <4AB20C6C.9090005@Voltaire.COM>
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In-Reply-To: <4AB20C6C.9090005@Voltaire.COM> (Moni Shoua's message of "Thu, 17
	Sep 2009 13:16:12 +0300")
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To: Moni Shoua <monis@Voltaire.COM>
Cc: linux-rdma <linux-rdma@vger.kernel.org>, OpenFabrics General <general@lists.openfabrics.org>
List-Id: linux-rdma@vger.kernel.org

And by the way, this current patch has a deadlock I think:

 > @@ -724,6 +724,8 @@ int ipoib_ib_dev_down(struct net_device *dev, int flush)
 >  	ipoib_dbg(priv, "downing ib_dev\n");
 >  
 >  	clear_bit(IPOIB_FLAG_OPER_UP, &priv->flags);
 > +	cancel_delayed_work(&priv->carrier_on_task);

ipoib_ib_dev_down() is called with rtnl held but carrier_on_task() does
rtn_lock().  So if carrier_on_task() is running but about to take the
rtnl when we try to do cancel_delayed_work() here, then it will wait
forever.

I think using lockdep on a new enough kernel (2.6.30 or maybe 2.6.31)
will report workqueue / timer vs. lock deadlocks.

 - R.