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    SubjectRe: [PATCH 1/3] futex: do not pagefault_disable in futex_atomic_cmpxchg_inatomic()
    On Sun, 2011-03-13 at 17:55 -0700, Darren Hart wrote:
    > I wondered about the preempt vs pagefault disable

    In current mainline they happen to be the same, but for -rt they're not.

    Its also conceptually different, with preempt disable we dis-allow any
    scheduling, which thus also precludes most fault handlers.

    Disabling pagefault can be done without also disabling preemption (as is
    done in -rt) and simply means that we'll never try to handle the fault
    and fallback to the exception table or give up and segfault the kernel.

    Its not dis-similar to the whole rcu_read_lock() vs preempt_disable()
    stuff, for a while one implied the other.

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