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    SubjectRe: Is adding requeue_delayed_work() a good idea

    > > In my particular case it doesn't really matter. In the queued case it
    > > could leave it to run whenever it gets to the head of the workqueue. In
    > > the already running case then I think the timer should be reset. The
    > > main point is that if I do requeue_delayed_work() I want to make sure
    > > the work runs all the way through from the beginning at some point in
    > > the future. The pattern I have in mind is something like:
    > >
    > > spin_lock_irqsave(&mydata_lock);
    > > new_timeout = add_item_to_timeout_list();
    > > requeue_delayed_work(wq, &process_timeout_list_work, new_timeout);
    > > spin_unlock_irqsave(&mydata_lock);
    > >
    > > so if the process_timeout_list_work runs early or twice it doesn't
    > > matter; I just want to make sure that the work runs from the beginning
    > > and sees the new item I added to the list at some point after the
    > > requeue.
    > Hmm. But, asuming that process_timeout_list_work->func() takes mydata_lock
    > too, you can just use queue_delayed_work() ?
    > process_timeout_list_work can't miss new items, queue_delayed_work()
    > can only fail if dwork is pending and its ->func has not started yet.

    Maybe I misunderstand the code or misunderstand you, but looking at it:

    int queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
    struct delayed_work *dwork, unsigned long delay)
    int ret = 0;
    struct timer_list *timer = &dwork->timer;
    struct work_struct *work = &dwork->work;

    if (!test_and_set_bit(WORK_STRUCT_PENDING, work_data_bits(work))) {
    return ret;

    if I have dwork already queued and try to requeue it for earlier it
    seems that this will just silently return with the later expiration
    still in effect.

    Maybe I wasn't totally clear on what I want to happen; an example would
    be if, say, I have delayed work queued with timer set to expire in 100
    seconds and then a new piece of work is added that needs to expire in 1
    second. So I want to requeue delayed work to run in 1 second, not wait
    the 100 seconds for the original timeout work.

    > I think we need requeue_xxx helper(s), but the exact semantics is not
    > clear to me.

    Not clear to me either unfortunately.

    - R.

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      Last update: 2009-08-24 23:13    [W:0.022 / U:239.192 seconds]
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