Question:add Iirq mask method in irq disable call.

[tglx@linutronix.de (Thomas Gleixner)]

On Fri, 11 Jan 2013, steve.zhan wrote:
> Resend Email because MUTT email send error.
> 
> 2013/1/11 Steve zhan <zhanzhenbo@gmail.com>:
> > All:
> >         I have find that arm gic driver have not register irq_disable
> > method, as below:
> > static struct irq_chip gic_chip = {
> >         .name                   = "GIC",
> >         .irq_mask               = gic_mask_irq,
> >         .irq_unmask             = gic_unmask_irq,
> >         .irq_eoi                = gic_eoi_irq,
> >         .irq_set_type           = gic_set_type,
> >         .irq_retrigger          = gic_retrigger,
> > #ifdef CONFIG_SMP
> >         .irq_set_affinity       = gic_set_affinity,
> > #endif
> >         .irq_set_wake           = gic_set_wake,
> > };
> >
> > Question is:
> >         When some drivers want to disable irq, maybe it will call
> > linux standard inerface: irq_disable() that defined in include\
> > linux\interrupt.h, this function will call
> > void irq_disable(struct irq_desc *desc)
> > {
> >         irq_state_set_disabled(desc);
> >         if (desc->irq_data.chip->irq_disable) {
> >                 desc->irq_data.chip->irq_disable(&desc->irq_data);
> >                 irq_state_set_masked(desc);
> >         }
> > }
> >
> > Because gic have not register irq_diable method, so the interrupt can
> > not disable immediately, it is enable until the interrupt come next time,
> > then disalbed by mask because irq_state_set_disable(desc);
> >
> > I have checked irq_enable method:
> > void irq_enable(struct irq_desc *desc)
> > {
> >         irq_state_clr_disabled(desc);
> >         if (desc->irq_data.chip->irq_enable)
> >                 desc->irq_data.chip->irq_enable(&desc->irq_data);
> >         else
> >                 desc->irq_data.chip->irq_unmask(&desc->irq_data);
> >         irq_state_clr_masked(desc);
> > }
> > This method have do unmask when irq_enable method is not exist.
> >
> > Is it a good idea to add irq_mask call in irq_disable()?

No. It's a very bad idea. We intentionally disable interrupts lazy.

Thanks,

	tglx