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    SubjectRe: [PATCH RFC v1 1/3] ARM: Add irq disabled version of soft_restart.
    On 02/25/2014 02:27 AM, Thomas Gleixner wrote:
    > On Mon, 24 Feb 2014, Russ Dill wrote:
    >> On 02/24/2014 03:13 PM, Sebastian Capella wrote:
    >>> Quoting Russell King - ARM Linux (2014-02-22 02:26:17)
    >>>> On Tue, Feb 18, 2014 at 05:52:07PM -0800, Sebastian Capella
    >>>> wrote:
    >>>>> From: Russ Dill <Russ.Dill@ti.com>
    >>>>>
    >>>>> This adds the ability to run soft_restart with
    >>>>> local_irq/fiq_disable already called. This is helpful for
    >>>>> the hibernation code paths.
    >>>>
    >>>> I'd rather keep this simple. There's no problem with calling
    >>>> soft_restart with interrupts already disabled.
    >>>> local_irq_disable()/local_fiq_disable() there should be
    >>>> harmless.
    >>>
    >>> Hi Russell,
    >>>
    >>> I'm observing a data abort loop when I replace this call:
    >>>
    >>> In the local_irq_disable, it ends up calling
    >>> trace_hardirqs_off (CONFIG_TRACE_IRQFLAGS_SUPPORT is enabled),
    >>> which calls trace_hardirqs_off_caller which checks
    >>> lockdep_recursion in the current task, but we've switched to a
    >>> temporary stack with the call_with_stack, and get_current is
    >>> returning NULL. This triggers a data abort, which calls
    >>> trace_hardirqs_off again and so on.
    >>>
    >>> Do you have any suggestions here?
    >>>
    >>> Thanks,
    >>>
    >>> Sebastian
    >>>
    >>
    >> So the alternative is to have a version of the call that calls a
    >> special no trace version of
    >> local_irq_disable()/local_fiq_disable(). Which would be
    >> preferable? Having a noirq version of soft_restart seems much
    >> simpler to me.
    >
    > If you want escape the tracer and in that case you really want it
    > being on a different stack, use raw_local_irq_* which are not
    > traced.

    So it might make sense to change soft_restart to use the
    raw_local_irq_* calls.


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