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    SubjectRe: Linux 2.1.118 SMP problem
    Date
    > On the serial console we get the message
    >
    > wait_on_bh, CPU 0:
    > irq: 1 [0 1]
    > bh: 1 [0 1]
    > <[c0113c4f]> <[c0175342]> <[c0175424]> <[c0148761]>
    >
    > repeating every few seconds.
    >
    > System.map says:
    >
    > del_timer __rpc_wake_up rpc_wake_up_task nfs_updatepage

    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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