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    SubjectRe: [PATCH 2/2] ptrace: fix set_task_blockstep()->update_debugctlmsr() logic
    On 08/03/2012 07:38 PM, Oleg Nesterov wrote:
    >>> update_debugctlmsr(debugctl);
    >>> + local_irq_enable();
    >>
    >> wouldn't preempt_disable() be enough?
    >
    > preempt_disable() can't help if interrupt handler changes
    > other bits in between?

    So perf() uses this register as well. Since perf() uses the raw
    primitives (raw_spin_lock()) shouldn't you do the same? If I recall
    correctly (but it is Friday and late) local_irq_enable() wouldn't
    disable irqs on RT and perf takes the raw lock so the irqs there should
    be really disabled.

    >
    > Oleg.

    Sebastian


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