On Thu, Apr 26, 2007 at 08:34:06PM +0400, Oleg Nesterov wrote:
> On 04/26, Jarek Poplawski wrote:
> >
> > > void cancel_rearming_delayed_work(struct delayed_work *dwork)
> > > {
> > > struct work_struct *work = &dwork->work;
> > > struct cpu_workqueue_struct *cwq = get_wq_data(work);
> > > int done;
> >
> > I don't understand, why you think cwq cannot be NULL here.
>
> sure it can, this is just a template.
>
> > >
> > > do {
> > > done = 1;
> > > spin_lock_irq(&cwq->lock);
> > >
> > > if (!list_empty(&work->entry))
> > > list_del_init(&work->entry);
> >
> > BTW, isn't needs_a_good_name needles after this and after del_timer positive?
>
> no, we still need it. work->func() may be running on another CPU as well.
>
> >
> > > else if (test_and_set_bit(WORK_STRUCT_PENDING, work_data_bits(work)))
> > > done = del_timer(&dwork->timer)
> >
> > If this runs while a work function is fired in run_workqueue,
> > it sets _PENDING bit, but if the work skips rearming, we have probably
> > endless loop, again.
>
> No, if the work skips rearming (or didn't yet), we set WORK_STRUCT_PENDING
> successfully.
Sorry! Should be:
"If this runs while a work function is fired in run_workqueue,
it sets _PENDING bit, but if the work skips rearming, I have probably
endless loop, again."
>
> > It is something alike to the current
> > way, with some added measures: you try to shoot a work on the run,
> > while queued or timer_pending, plus the _PENDING flag set, so it seems,
> > there is some risk of longer than planed looping.
>
> Sorry, can't understand. done == 0 means that the queueing in progress,
> this work should be placed on cwq->worklist very soon, most probably
> right after we drop cwq->lock.
I think, theoretically, probably, maybe, there is possible some strange
case, this function gets spin_lock only when: list_empty(&work->entry) == 1
&& _PENDING == 1 && del_timer(&dwork->timer) == 0.
>
> > I have to look at this more, at home and, if something new, I'll write
> > tomorrow. So, the good news, is you should have enough sleep this time!
>
> Thanks for review!
OK. Here is the review:
It looks great!!! I cannot believe, it could be so "easy"!
Regards,
Jarek P.
PS: probably unusable, but for my own satisfaction:
Acked-by: Jarek Poplawski <[email protected]
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