Its waiting for a bh to clear for the synchronize_bh in timer.c
because the other CPU has deadlocked in an IRQ or BH. How many
processors does this machine have.
I can see this deadlock for 2 or more CPUs in the sunrpc code
Its
CPU #0
nfs->sunrpc->udp_sendmsg->lock_sock->copying
irq,bh
net_bh->udp_recv->rpc callback->sk_recv_datagram-lock_sock => Deadlock
CPU #1
spots it
That means someone has to fix the UDP callback cases for the NFS sockets.
Im not sure why it should occur SMP only or if its the one you see, but that
does look like a deadlock to me. The lock_sock code also claims its
'a very broken bottom half synchronization mechanism' which worries me
even more.
Also that bug has been there for a lot longer than the past 2 or 3 kernels
Alan
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