[PATCH] ARM: perf-events: request PMU interrupts with IRQF_NOBALANCING

[PATCH] ARM: perf-events: request PMU interrupts with IRQF_NOBALANCING

[Will Deacon]

If IRQ balancing is used on a multicore ARM system, PMU interrupt
lines may be relocated onto CPUs other than the one causing the
counter overflow. This can result in misattribution of events to
the wrong core and, in the case that the CPU handling the interrupt
has not experience counter overflow, the interrupt can be disabled
because the handler returns IRQ_NONE.

This patch adds the IRQF_NOBALANCING flag to the request_irq call
in perf_events.c.

Cc: Jamie Iles <jamie.iles@picochip.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
---
 arch/arm/kernel/perf_event.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/arch/arm/kernel/perf_event.c b/arch/arm/kernel/perf_event.c
index c54ceb3..b44d159 100644
--- a/arch/arm/kernel/perf_event.c
+++ b/arch/arm/kernel/perf_event.c
@@ -332,7 +332,8 @@ armpmu_reserve_hardware(void)
 
 	for (i = 0; i < pmu_irqs->num_irqs; ++i) {
 		err = request_irq(pmu_irqs->irqs[i], armpmu->handle_irq,
-				  IRQF_DISABLED, "armpmu", NULL);
+				  IRQF_DISABLED | IRQF_NOBALANCING,
+				  "armpmu", NULL);
 		if (err) {
 			pr_warning("unable to request IRQ%d for ARM "
 				   "perf counters\n", pmu_irqs->irqs[i]);
-- 
1.6.3.3

[PATCH] ARM: perf-events: request PMU interrupts with IRQF_NOBALANCING

[Jamie Iles]

On Thu, Feb 25, 2010 at 12:12:18PM +0000, Will Deacon wrote:
> If IRQ balancing is used on a multicore ARM system, PMU interrupt
> lines may be relocated onto CPUs other than the one causing the
> counter overflow. This can result in misattribution of events to
> the wrong core and, in the case that the CPU handling the interrupt
> has not experience counter overflow, the interrupt can be disabled
> because the handler returns IRQ_NONE.
> 
> This patch adds the IRQF_NOBALANCING flag to the request_irq call
> in perf_events.c.
> 
> Cc: Jamie Iles <jamie.iles@picochip.com>
> Signed-off-by: Will Deacon <will.deacon@arm.com>
> ---
>  arch/arm/kernel/perf_event.c |    3 ++-
>  1 files changed, 2 insertions(+), 1 deletions(-)
> 
> diff --git a/arch/arm/kernel/perf_event.c b/arch/arm/kernel/perf_event.c
> index c54ceb3..b44d159 100644
> --- a/arch/arm/kernel/perf_event.c
> +++ b/arch/arm/kernel/perf_event.c
> @@ -332,7 +332,8 @@ armpmu_reserve_hardware(void)
>  
>  	for (i = 0; i < pmu_irqs->num_irqs; ++i) {
>  		err = request_irq(pmu_irqs->irqs[i], armpmu->handle_irq,
> -				  IRQF_DISABLED, "armpmu", NULL);
> +				  IRQF_DISABLED | IRQF_NOBALANCING,
> +				  "armpmu", NULL);
>  		if (err) {
>  			pr_warning("unable to request IRQ%d for ARM "
>  				   "perf counters\n", pmu_irqs->irqs[i]);
> -- 
> 1.6.3.3
Hi Will,

Looks good to me.

Acked-by: Jamie Iles <jamie.iles@picochip.com>

Jamie