Nathan Lynch <[email protected]> wrote:
>
> Andrew Morton wrote:
> > Ingo Molnar <[email protected]> wrote:
> > > - so buggy early bootup code which relies on interrupts being
> > > off might be surprised by it.
> >
> > I don't think it's necessarily buggy that bootup code needs interrupts
> > disabled. It _is_ buggy that bootup code which needs interrupts disabled
> > is calling lock_cpu_hotplug().
>
> I guess I don't understand -- why is it wrong for code that runs only
> in early early bootup, when there is only one process context, to use
> common code to e.g. register a hotplug cpu notifier?
OK, it's not wrong I guess - we're running code which requires
local_irq_disable() and that code is calling functions which do
local_irq_enable() but we know that those functions won't do that because
there cannot be any lock contention.
So it works, and will continue to work, but it's all rather unpleasant, IMO.
> Should the
> powerpc numa code be made to wait to register its notifier until
> initcall time or something?
I think the powerpc code is busted, really - it shouldn't be keeling over
like that if someone enables local interrupts. That being said, it's a
good way of detecting accidental interrupt-enablings.
> Yes, which would be why this code never triggered a warning when
> cpucontrol was a semaphore.
Yup. Perhaps a sane fix which preserves the unpleasant semantics is to do
irqsave in the mutex debug code.
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