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    SubjectRe: [PATCH 2/5] rcu: don't check ->donelist in __rcu_pending()
    On Sun, Jan 08, 2006 at 10:19:24PM +0300, Oleg Nesterov wrote:
    > ->donelist becomes != NULL only in rcu_process_callbacks().
    >
    > rcu_process_callbacks() always calls rcu_do_batch() when
    > ->donelist != NULL.
    >
    > rcu_do_batch() schedules rcu_process_callbacks() again if
    > ->donelist was not flushed entirely.
    >
    > So ->donelist != NULL means that rcu_tasklet is either
    > TASKLET_STATE_SCHED or TASKLET_STATE_RUN, we don't need to
    > check it in __rcu_pending().

    Do I smell a bug wrt CPU Hotplug here? Basically, I see that we do
    a rcu_move_batch of ->curlist and ->nxtlist of the dead CPU. Why not
    ->donelist? If we have to do a rcu_move_batch of ->donelist also,
    then perhaps the ->donelist != NULL check is required in
    rcu_pending? This is considering that the RCU tasklet of the dead
    CPU is killed (rather than moved over to a different CPU).


    --


    Thanks and Regards,
    Srivatsa Vaddagiri,
    Linux Technology Center,
    IBM Software Labs,
    Bangalore, INDIA - 560017
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