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    SubjectRe: [PATCH 6/8] PM: Add suspend blocking work.
    Date
    On Wednesday 28 April 2010, Oleg Nesterov wrote:
    > On 04/27, Arve Hjønnevåg wrote:
    > >
    > > Allow work to be queued that will block suspend while it is pending
    > > or executing. To get the same functionality in the calling code often
    > > requires a separate suspend_blocker for pending and executing work, or
    > > additional state and locking. This implementation does add additional
    > > state and locking, but this can be removed later if we add support for
    > > suspend blocking work to the core workqueue code.
    >
    > I think this patch is fine.
    >
    > Just one silly question,
    >
    > > +int queue_suspend_blocking_work(struct workqueue_struct *wq,
    > > + struct suspend_blocking_work *work)
    > > +{
    > > + int ret;
    > > + unsigned long flags;
    > > +
    > > + spin_lock_irqsave(&work->lock, flags);
    > > + suspend_block(&work->suspend_blocker);
    > > + ret = queue_work(wq, &work->work);
    > > + if (ret)
    > > + work->active++;
    >
    > why not
    >
    > ret = queue_work(wq, &work->work);
    > if (ret) {
    > suspend_block(&work->suspend_blocker);
    > work->active++;
    > }
    >
    > ?
    >
    > Afaics, we can't race with work->func() doing unblock, we hold work-lock.
    > And this way the code looks more clear.

    Agreed. Arve, any objections to doing that?

    > Sorry, I had no chance to read the previous patches. After the quick look
    > at 1/8 I think it is OK to call suspend_block() twice, but still...

    It is.

    > Or I missed something? Just curious.
    >
    >
    > Hmm... actually, queue_work() can also fail if we race with cancel_ which
    > temporary sets WORK_STRUCT_PENDING. In that case suspend_block() won't
    > be paired by unblock ?
    >
    >
    > > +int schedule_suspend_blocking_work(struct suspend_blocking_work *work)
    > > +{
    > > ...
    > > + ret = schedule_work(&work->work);
    >
    > Off-topic. We should probably export keventd_wq to avoid the duplications
    > like this.

    Please see my reply to Tejun. :-)

    Rafael
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