Re: [PATCH] tipc: fix deadlock during socket release

[David Miller <davem@davemloft.net>]

From: Ying Xue <ying.xue@windriver.com>
Date: Fri, 27 Dec 2013 10:18:28 +0800

> A deadlock might occur if name table is withdrawn in socket release
> routine, and while packets are still being received from bearer.
> 
>        CPU0                       CPU1
> T0:   recv_msg()               release()
> T1:   tipc_recv_msg()          tipc_withdraw()
> T2:   [grab node lock]         [grab port lock]
> T3:   tipc_link_wakeup_ports() tipc_nametbl_withdraw()
> T4:   [grab port lock]*        named_cluster_distribute()
> T5:   wakeupdispatch()         tipc_link_send()
> T6:                            [grab node lock]*
> 
> The opposite order of holding port lock and node lock on above two
> different paths may result in a deadlock. If socket lock instead of
> port lock is used to protect port instance in tipc_withdraw(), the
> reverse order of holding port lock and node lock will be eliminated,
> as a result, the deadlock is killed as well.
> 
> Reported-by: Lars Everbrand <lars.everbrand@ericsson.com>
> Reviewed-by: Erik Hugne <erik.hugne@ericsson.com>
> Signed-off-by: Ying Xue <ying.xue@windriver.com>

Applied, thanks.