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    SubjectRe: new IRQ scalability changes in 2.3.48
    Andrea Arcangeli wrote:
    > >Note: In many cases, spinlock_irqsave doesn't need to do the
    > >spinlock_depth thing on UP. [..]
    > It doesn't need that in SMP either.

    An interrupt on another process can wake up a task and set
    current->need_resched on this processor.

    > >[..] However, not all cases: the code in the
    > >lock region might wake up another task.
    > If you wakeup another task you don't risk to get rescheduled before you
    > drop the lock.

    Waking up another task may set current->need_resched. But it can't
    actually reschedule until reaching the spin_unlock_irqsave. At that
    point or some low-latency time later, you need to reschedule to get low

    -- Jamie

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