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    SubjectRe: [BUG] "sched: Remove rq->lock from the first half of ttwu()" locks up on ARM

    * Russell King - ARM Linux <linux@arm.linux.org.uk> wrote:

    > On Thu, May 26, 2011 at 02:26:23PM +0200, Ingo Molnar wrote:
    > >
    > > * Peter Zijlstra <peterz@infradead.org> wrote:
    > >
    > > > Sort this by reverting to the old behaviour for this situation
    > > > and perform a full remote wake-up.
    > >
    > > Btw., ARM should consider switching most of its subarchitectures
    > > to !__ARCH_WANT_INTERRUPTS_ON_CTXSW - enabling irqs during
    > > context switches is silly and now expensive as well.
    >
    > Not going to happen. The reason we do it is because most of the
    > CPUs have to (slowly) flush their caches during switch_mm(), and to
    > have IRQs off over the cache flush means that we lose IRQs.

    How much time does that take on contemporary ARM hardware, typically
    (and worst-case)?

    Thanks,

    Ingo


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