Messages in this thread | | | From | Roland Dreier <> | Subject | Re: Is adding requeue_delayed_work() a good idea | Date | Mon, 24 Aug 2009 14:11:00 -0700 |
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> > 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))) { BUG_ON(timer_pending(timer)); BUG_ON(!list_empty(&work->entry)); //... } 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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