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SubjectRe: [RFC PATCH 5/5] arm: perf: Use FIQ to handle PMU events.
Date
On Tuesday, January 13, 2015 04:35:31 PM Daniel Thompson wrote:
> Using FIQ (if it is available) gives perf a better insight into the
> system by allowing code run with interrupts disabled to be profiled.
>
> Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
> ---
> arch/arm/include/asm/pmu.h | 4 ++++
> arch/arm/kernel/perf_event.c | 2 +-
> arch/arm/kernel/perf_event_cpu.c | 35 ++++++++++++++++++++++++++++++++---
> arch/arm/kernel/traps.c | 3 ++-
> 4 files changed, 39 insertions(+), 5 deletions(-)
>
> diff --git a/arch/arm/include/asm/pmu.h b/arch/arm/include/asm/pmu.h
> index b1596bd59129..2a7ea97a4a14 100644
> --- a/arch/arm/include/asm/pmu.h
> +++ b/arch/arm/include/asm/pmu.h
> @@ -123,6 +123,8 @@ struct arm_pmu {
>
> extern const struct dev_pm_ops armpmu_dev_pm_ops;
>
> +irqreturn_t armpmu_dispatch_irq(int irq, void *dev);
> +
> int armpmu_register(struct arm_pmu *armpmu, int type);
>
> u64 armpmu_event_update(struct perf_event *event);
> @@ -136,6 +138,8 @@ int armpmu_map_event(struct perf_event *event,
> [PERF_COUNT_HW_CACHE_RESULT_MAX],
> u32 raw_event_mask);
>
> +void cpu_pmu_handle_fiq(int irq);
> +
> struct pmu_probe_info {
> unsigned int cpuid;
> unsigned int mask;
> diff --git a/arch/arm/kernel/perf_event.c b/arch/arm/kernel/perf_event.c
> index f7c65adaa428..5ae9adf7f18e 100644
> --- a/arch/arm/kernel/perf_event.c
> +++ b/arch/arm/kernel/perf_event.c
> @@ -296,7 +296,7 @@ validate_group(struct perf_event *event)
> return 0;
> }
>
> -static irqreturn_t armpmu_dispatch_irq(int irq, void *dev)
> +irqreturn_t armpmu_dispatch_irq(int irq, void *dev)
> {
> struct arm_pmu *armpmu;
> struct platform_device *plat_device;
> diff --git a/arch/arm/kernel/perf_event_cpu.c
> b/arch/arm/kernel/perf_event_cpu.c index a80309087a7b..5c4e9ce23389 100644
> --- a/arch/arm/kernel/perf_event_cpu.c
> +++ b/arch/arm/kernel/perf_event_cpu.c
> @@ -36,6 +36,9 @@
> /* Set at runtime when we know what CPU type we are. */
> static struct arm_pmu *cpu_pmu;
>
> +/* Allows us to find out if an IRQ is for us (mostly used from NMI context)
> */ +static DEFINE_PER_CPU(int, cpu_pmu_irqs);
> +
> /*
> * Despite the names, these two functions are CPU-specific and are used
> * by the OProfile/perf code.
> @@ -127,6 +130,24 @@ static void cpu_pmu_free_irq(struct arm_pmu *cpu_pmu)
> }
> }
>
> +/*
> + * This handler is called *unconditionally* from the default NMI/FIQ
> + * handler. The irq may not be anything to do with us so the main
> + * job of this function is to figure out if the irq passed in is ours
> + * or not.
> + */

This comment is an indicator that all the code in cpu_pmu_handle_fiq is
in the wrong place.
It (or something like it) belongs at the level of the default
FIQ handler, and not in perf_event_cpu.c

> +void cpu_pmu_handle_fiq(int irq)
> +{
> + int cpu = smp_processor_id();
> +
> + if (irq != get_cpu_var(cpu_pmu_irqs))
> + return;
> +
> + (void)armpmu_dispatch_irq(irq,
> + get_cpu_ptr(&cpu_pmu->hw_events->percpu_pmu));
> +}
> +
> +
> static int cpu_pmu_request_irq(struct arm_pmu *cpu_pmu, irq_handler_t
> handler) {
> int i, err, irq, irqs;
> @@ -170,9 +191,16 @@ static int cpu_pmu_request_irq(struct arm_pmu *cpu_pmu,
> irq_handler_t handler) continue;
> }
>
> - err = request_irq(irq, handler,
> - IRQF_NOBALANCING | IRQF_NO_THREAD, "arm-pmu",
> - per_cpu_ptr(&hw_events->percpu_pmu, i));
> + err = request_nmi_irq(
> + irq, IRQF_NOBALANCING, "arm-pmu",
> + per_cpu_ptr(&hw_events->percpu_pmu, i));
> + if (err) {
> + err = request_irq(
> + irq, handler,
> + IRQF_NOBALANCING | IRQF_NO_THREAD,
> + "arm-pmu",
> + per_cpu_ptr(&hw_events->percpu_pmu, i));
> + }
> if (err) {
> pr_err("unable to request IRQ%d for ARM PMU counters\n",
> irq);
> @@ -180,6 +208,7 @@ static int cpu_pmu_request_irq(struct arm_pmu *cpu_pmu,
> irq_handler_t handler) }
>
> cpumask_set_cpu(i, &cpu_pmu->active_irqs);
> + per_cpu(cpu_pmu_irqs, i) = irq;
> }
> }
>
> diff --git a/arch/arm/kernel/traps.c b/arch/arm/kernel/traps.c
> index 74c752b9db68..c581e07517ff 100644
> --- a/arch/arm/kernel/traps.c
> +++ b/arch/arm/kernel/traps.c
> @@ -38,6 +38,7 @@
> #include <asm/tls.h>
> #include <asm/system_misc.h>
> #include <asm/opcodes.h>
> +#include <asm/pmu.h>
>
>
> static const char *handler[]= {
> @@ -485,7 +486,7 @@ asmlinkage void __exception_irq_entry
> handle_fiq_as_nmi(struct pt_regs *regs) irq = gic_ack_fiq();
>
> if (irq) {
> - /* empty - no SPI handlers (yet) */
> + cpu_pmu_handle_fiq(irq);
> } else {
> #ifdef CONFIG_SMP
> ipi_cpu_backtrace(regs);
> --
> 1.9.3
>
>
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

--
Joshua Clayton
Software Engineer
UniWest
122 S. 4th Avenue
Pasco, WA 99301
Ph: (509) 544-0720
Fx: (509) 544-0868


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