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    SubjectRe: [PATCH] RT: Add priority-queuing and priority-inheritance to workqueue infrastructure
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    On Thu, 2007-08-02 at 00:18 +0400, Oleg Nesterov wrote:
    > On 08/01, Daniel Walker wrote:
    > >
    > > On Wed, 2007-08-01 at 22:12 +0400, Oleg Nesterov wrote:
    > >
    > > > And I personally think it is not very useful, even if it was correct.
    > > > You can create your own workqueue and change the priority of cwq->thread.
    > >
    > > This change is more dynamic than than just setting a single priority ..
    > > There was some other work going on around this, so it's not totally
    > > clear what the benefits are ..
    >
    > Yes, I see. But still I think the whole idea is broken, not just the
    > implementation.

    It's translating priorities through the work queues, which doesn't seem
    to happen with the current implementation. A high priority, say
    SCHED_FIFO priority 99, task may have to wait for a nice -5 work queue
    to finish.. You can set the priority of your work queue, but you never
    know what the priority of the tasks are that use the work queue ..

    > What about delayed_work? insert_work() will use ->normal_prio of
    > the random interrupted process, while queue_work() uses current.

    Actually it would be the priority of the timer softirq .. I think what
    is desired here would be saving the priority of the task calling
    delayed_work then using that..

    > What if a niced thread queues the work? This work may have no chance
    > to run if workqueue is actively used.

    Yes , if it actively used by higher priority threads .. We could
    restrict it to SCHED_FIFO/SCHED_RR tho ..

    > > As the topic suggests , it's a Real Time kernel .. I can give you a link
    > > where to download it if you want.
    >
    > Ok, thanks, I'll take a look. Still, we can't use raw_smp_processor_id()
    > unless we disabled cpu-hotplug.

    I didn't touch this particular piece of code, but I'm assuming the
    raw_smp_processor_id() is safe giving the rest of the code in -rt ..

    Daniel

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