PROBLEM: (84401, MGO35023A, 78934, 79892) (PATCH ID: OSF510-139)
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This patch corrects a hang that can be seen on multi-cpu systems
using NFS-over-TCP.  THE SMP race is seen between the
'nfs_tcp_input' and the 'nfs_tcp_thread' functions.
The stack of the netisr_thread may look like:

        (kdbx) tset 0xfffffc003cf38e00
         (kdbx) t
         >  0 thread_block
            1 lock_wait
            2 lock_write
            3 solock
            4 soclose
            5 tsp_unref
            6 nfs_tcp_input 
            7 sbwakeup
            8 sowakeup
            9 tcp_close
           10 tcp_input_common 
           11 tcp_input
           12 ipintr
           13 netisr_thread