Re: [patch 3/8] x86/apic: Provide apic_ack_irq()

[Song Liu]

On Mon, Jun 4, 2018 at 8:33 AM, Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote:
> apic_ack_edge() is explicitely for handling interrupt affinity cleanup when
> interrupt remapping is not available or disable.
>
> Remapped interrupts and also some of the platform specific special
> interrupts, e.g. UV, invoke ack_APIC_irq() directly.
>
> To address the issue of failing an affinity update with -EBUSY the delayed
> affinity mechanism can be reused, but ack_APIC_irq() does not handle
> that. Adding this to ack_APIC_irq() is not possible, because that function
> is also used for exceptions and directly handled interrupts like IPIs.
>
> Create a new function, which just contains the conditional invocation of
> irq_move_irq() and the final ack_APIC_irq(). Making the invocation of
> irq_move_irq() conditional avoids the out of line call if the pending bit
> is not set.
>
> Reuse the new function in apic_ack_edge().
>
> Preparatory change for the real fix
>
> Fixes: dccfe3147b42 ("x86/vector: Simplify vector move cleanup")
> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx

Tested-by: Song Liu <songliubraving@xxxxxx>

> ---
>  arch/x86/include/asm/apic.h   |    2 ++
>  arch/x86/kernel/apic/vector.c |   10 ++++++++--
>  2 files changed, 10 insertions(+), 2 deletions(-)
>
> --- a/arch/x86/include/asm/apic.h
> +++ b/arch/x86/include/asm/apic.h
> @@ -436,6 +436,8 @@ static inline void apic_set_eoi_write(vo
>
>  #endif /* CONFIG_X86_LOCAL_APIC */
>
> +extern void apic_ack_irq(struct irq_data *data);
> +
>  static inline void ack_APIC_irq(void)
>  {
>         /*
> --- a/arch/x86/kernel/apic/vector.c
> +++ b/arch/x86/kernel/apic/vector.c
> @@ -809,11 +809,17 @@ static int apic_retrigger_irq(struct irq
>         return 1;
>  }
>
> +void apic_ack_irq(struct irq_data *irqd)
> +{
> +       if (unlikely(irqd_is_setaffinity_pending(irqd)))
> +               irq_move_irq(irqd);
> +       ack_APIC_irq();
> +}
> +
>  void apic_ack_edge(struct irq_data *irqd)
>  {
>         irq_complete_move(irqd_cfg(irqd));
> -       irq_move_irq(irqd);
> -       ack_APIC_irq();
> +       apic_ack_irq(irqd);
>  }
>
>  static struct irq_chip lapic_controller = {
>
>