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

From: Dou Liyang
Date: Tue Jun 05 2018 - 07:31:23 EST


Hi Thomas,

At 06/04/2018 11:33 PM, Thomas Gleixner 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
---
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)))

Affinity pending is also judged in

+ irq_move_irq(irqd);

If we can remove the if(...) statement here

Thanks,
dou

+ 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 = {