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    SubjectRe: linux-next ppc64: RCU mods cause __might_sleep BUGs
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    On Wed, 2012-05-02 at 13:25 -0700, Hugh Dickins wrote:
    > Got it at last. Embarrassingly obvious. __rcu_read_lock() and
    > __rcu_read_unlock() are not safe to be using __this_cpu operations,
    > the cpu may change in between the rmw's read and write: they should
    > be using this_cpu operations (or, I put preempt_disable/enable in the
    > __rcu_read_unlock below). __this_cpus there work out fine on x86,
    > which was given good instructions to use; but not so well on PowerPC.
    >
    > I've been running successfully for an hour now with the patch below;
    > but I expect you'll want to consider the tradeoffs, and may choose a
    > different solution.

    Didn't Linus recently rant about these __this_cpu vs this_cpu nonsense ?

    I thought that was going out..

    Cheers,
    Ben.




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