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    SubjectRe: linux-next: workqueues tree build failure
    At Thu, 26 Nov 2009 18:12:26 +0900,
    Tejun Heo wrote:
    > Hello,
    > 11/26/2009 05:16 PM, Peter Ujfalusi wrote:
    > >> Takashi, RT workqueue is going away. Do you really need it?
    > >
    > > What can be used instead of RT workqueue?
    > > The tlv320dac33 needs RT workqueue because I need to send the I2C
    > > command with minimum delay to the codec. If this can not be done
    > > (the workqueue is delayed), and the codec does not receive the
    > > command in time, it will literally die. What are the options to
    > > replace the RT workqueue?
    > The problem with RT workqueue is that RT and queue don't really mix
    > well. To act in real time, it requires all the resource pre-allocated
    > and dedicated to it making queueing or pooling meaningless. The
    > original workqueue code created dedicated pool of threads for each
    > workqueue so it could be used for RT but new implementation uses
    > shared worker pool, so it can't be used as an interface to dedicated
    > threads.
    > I haven't read the code but,
    > * If you need to respond fast, wouldn't you be doing that from IRQ
    > handler or softirq? Do you need task context?
    > * Or is it that it's not triggered by IRQ but once the transfer
    > started it can't be interrupted? But in this case preempt_disable()
    > or local_irq_disable() should suffice.

    The relevant code uses the workqueue as a sort of BH, just triggers
    from the hard irq handler. If any, we may use a threaded handler or



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