On Sat, 2013-06-22 at 17:42 +0000, Seiji Aguchi wrote:
> > +static inline void load_current_idt(void)
> > +{
> > + unsigned long flags;
> > +
> > + local_irq_save(flags);
> > + if (is_debug_idt_enabled())
> > + load_debug_idt();
> > + else
> > + load_idt((const struct desc_ptr *)&idt_descr);
> > + local_irq_restore(flags);
> > +}
> >
> > It's not safe to call local_irq_save() here. From entry_64.S:
> >
> > .macro TRACE_IRQS_OFF_DEBUG
> > call debug_stack_set_zero
> > TRACE_IRQS_OFF
> > call debug_stack_reset
> > .endm
> >
> > We must change the idt before we can trace irqs being disabled. The
> > local_irq_save() here is going to be traced by lockdep. Why do we need
> > to disable interrupts? It's pretty pointless since this same code can be
> > called by NMIs.
>
> OK, I agree to remove the local_irq_save().
>
> I thought it is safe to disable interrupt to avoid potential races,
> because the load_current_id() is a common function and someone else may use
> it near future.
It should not be that common of a function. Not many should use it.
I'm testing a patch now and should post it in a few hours.
-- Steve
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