netdev - Re: [Patch net-next] vxlan: fix a soft lockup in vxlan module removal

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Message-Id: <20130809.114245.1171395854188554598.davem@davemloft.net>
Date:	Fri, 09 Aug 2013 11:42:45 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	amwang@...hat.com
Cc:	netdev@...r.kernel.org, stephen@...workplumber.org
Subject: Re: [Patch net-next] vxlan: fix a soft lockup in vxlan module
 removal

From: Cong Wang <amwang@...hat.com>
Date: Wed,  7 Aug 2013 16:43:22 +0800

> From: Cong Wang <amwang@...hat.com>
> 
> This is a regression introduced by:
> 
> 	commit fe5c3561e6f0ac7c9546209f01351113c1b77ec8
> 	Author: stephen hemminger <stephen@...workplumber.org>
> 	Date:   Sat Jul 13 10:18:18 2013 -0700
> 
> 	    vxlan: add necessary locking on device removal
> 
> The problem is that vxlan_dellink(), which is called with RTNL lock
> held, tries to flush the workqueue synchronously, but apparently
> igmp_join and igmp_leave work need to hold RTNL lock too, therefore we
> have a soft lockup! 
> 
> As suggested by Stephen, probably the flush_workqueue can just be
> removed and let the normal refcounting work. The workqueue has a
> reference to device and socket, therefore the cleanups should work
> correctly.
> 
> Suggested-by: Stephen Hemminger <stephen@...workplumber.org>
> Cc: Stephen Hemminger <stephen@...workplumber.org>
> Cc: David S. Miller <davem@...emloft.net>
> Tested-by: Cong Wang <amwang@...hat.com>
> Signed-off-by: Cong Wang <amwang@...hat.com>

Applied.
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