Subject: Re: linux-next: User Mode Linux broken

From: Thomas Gleixner <[email-masked]>
Date: Thu, 21 Oct 2010 21:45:35 +0200 (CEST)

On Thu, 21 Oct 2010, Richard Weinberger wrote:
> Am Donnerstag 21 Oktober 2010, 18:09:22 schrieb Thomas Gleixner:
> > On Thu, 21 Oct 2010, Richard Weinberger wrote:
> > > Thomas,
> > > 
> > > Your commit c5f7563 ("genirq: Provide compat handling for
> > > chip->enable()") breaks UML.
> > > It does not start anymore.
> > > 
> > > When I apply this patch it works fine again.
> > > http://userweb.kernel.org/~akpm/mmotm/broken-out/um-migrate-from-__do_irq
> > > -to- generic_handle_irq.patch
> > > 
> > > Maybe your patch breaks all users of __do_IRQ()?
> > 
> > Not intentionally :)
> > 
> > The irq_chip of um has it's own dummy enable function, so the compat
> > code uses it.
> > 
> > +static void compat_irq_enable(struct irq_data *data)
> > +{
> > +	data->chip->enable(data->irq);
> > +}
> > +
> > 
> > ...
> > 
> > +	if (chip->enable)
> > +		chip->irq_enable = compat_irq_enable;
> > +
> > +	/*
> > +	 * The real defaults
> > +	 */
> > +	if (!chip->irq_enable)
> > +		chip->irq_enable = default_enable;
> > 
> > So I really can't see how's that supposed to break UM
> > 
> 
> This patch solves the issue for me.
> What do you think?
> 
> Thanks,
> //richard
> 
> diff --git a/kernel/irq/resend.c b/kernel/irq/resend.c
> index 891115a..1fb4012 100644
> --- a/kernel/irq/resend.c
> +++ b/kernel/irq/resend.c
> @@ -60,8 +60,11 @@ void check_irq_resend(struct irq_desc *desc, unsigned int 
> irq)
>         /*
>          * Make sure the interrupt is enabled, before resending it:
>          */
> +#ifndef CONFIG_GENERIC_HARDIRQS_NO_DEPRECATED
> +       desc->irq_data.chip->enable(irq);
> +#elif
>         desc->irq_data.chip->irq_enable(&desc->irq_data);
> -
> +#endif
>         /*
>          * We do not resend level type interrupts. Level type
>          * interrupts are resent by hardware when they are still

Why shold it solve it ? irq_enable is set to compat_irq_enable which
in turn calls chip->enable.

So how's that different ?

Thanks,

	tglx