(!sk->sk_forward_alloc) assertation failure in 2.6.25.6

dmesg excerpt:

nfsd: last server has exited
nfsd: unexporting all filesystems
KERNEL: assertion (!sk->sk_forward_alloc) failed at net/ipv4/af_inet.c (157)
NFSD: Using /var/lib/nfs/v4recovery as the NFSv4 state recovery directory
NFSD: starting 90-second grace period
nfsd: last server has exited
nfsd: unexporting all filesystems
NFSD: Using /var/lib/nfs/v4recovery as the NFSv4 state recovery directory
NFSD: starting 90-second grace period

As reported in:

  http://kerneltrap.org/mailarchive/linux-netdev/2008/6/21/2189804 

the NFS server was restarting when the error occurred.

Phil.