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    SubjectRe: start_kernel(): bug: interrupts were enabled early

    On Thu, 1 Apr 2010, Andrew Morton wrote:
    > > So making the slow-path do the spin_[un]lock_irq{save,restore}() versions
    > > sounds like the right thing. It won't be a performance issue: it _is_ the
    > > slow-path, and we're already doing the expensive part (the spinlock itself
    > > and the irq thing).
    > It's actually on the fastpath for lib/rwsem-spinlock.c.

    Ahh, yes. In this case, that doesn't likely change anything. The
    save/restore versions of the irq-safe locks shouldn't be appreciably more
    expensive than the non-saving ones. And architectures that really care
    should have done their own per-arch optimized version anyway.

    Maybe we should even document that - so that nobody else makes the mistake
    x86-64 did of thinking that the "generic spinlock" version of the rwsem's
    is anything but a hacky and bad fallback case.


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