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  • Neil Horman's avatar
    bonding: Fix deadlock in bonding driver resulting from internal locking when using netpoll · e843fa50
    Neil Horman authored
    The monitoring paths in the bonding driver take write locks that are shared by
    the tx path.  If netconsole is in use, these paths can call printk which puts us
    in the netpoll tx path, which, if netconsole is attached to the bonding driver,
    result in deadlock (the xmit_lock guards are useless in netpoll_send_skb, as the
    monitor paths in the bonding driver don't claim the xmit_lock, nor should they).
    The solution is to use a per cpu flag internal to the driver to indicate when a
    cpu is holding the lock in a path that might recusrse into the tx path for the
    driver via netconsole.  By checking this flag on transmit, we can defer the
    sending of the netconsole frames until a later time using the retransmit feature
    of netpoll_send_skb that is triggered on the return code NETDEV_TX_BUSY.  I've
    tested this and am able to transmit via netconsole while causing failover
    conditions on the bond slave links.
    Signed-off-by: default avatarNeil Horman <>
    Signed-off-by: default avatarDavid S. Miller <>