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    SubjectRe: [PATCH RFC tip/core/rcu 09/16] rcu-tasks: Add an RCU-tasks rude variant
    On Sun, 10 May 2020 17:59:27 +0800
    Lai Jiangshan <jiangshanlai@gmail.com> wrote:

    > I think adding a small number of instructions to preempt_schedule_irq()
    > is sufficient to create the needed protected region between the start
    > of a function and the trampoline body.
    >
    > preempt_schedule_irq() {
    > + if (unlikely(is_trampoline_page(page_of(interrupted_ip)))) {
    > + return; // don't do preempt schedule
    > +
    > + }
    > preempt_schedule_irq() original body
    > }

    First, this would never be accepted due to the overhead it would cause,
    next, the interrupt instruction pointer could be the call to the
    trampoline itself. It would be hard to guarantee that we are not on the way
    to the trampoline in question.

    -- Steve

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