On Mon, Nov 18, 2013 at 7:16 PM, Marc Zyngier [off-list ref] wrote:

Vinayak,


On 2013-11-18 13:22, Vinayak Kale wrote:

quoted

Add support for irq registration when pmu interrupt is percpu.

Signed-off-by: Vinayak Kale <redacted>
Signed-off-by: Tuan Phan <redacted>
---
 arch/arm64/kernel/perf_event.c |  102
+++++++++++++++++++++++++++++-----------
 1 file changed, 74 insertions(+), 28 deletions(-)

diff --git a/arch/arm64/kernel/perf_event.c

b/arch/arm64/kernel/perf_event.c
index cea1594..23475f6 100644

--- a/arch/arm64/kernel/perf_event.c
+++ b/arch/arm64/kernel/perf_event.c

@@ -22,6 +22,7 @@

 #include <linux/bitmap.h>
 #include <linux/interrupt.h>
+#include <linux/irq.h>
 #include <linux/kernel.h>
 #include <linux/export.h>
 #include <linux/perf_event.h>

@@ -363,22 +364,51 @@ validate_group(struct perf_event *event)
 }

 static void
+armpmu_disable_percpu_irq(void *data)
+{
+       struct arm_pmu *armpmu = data;
+       struct platform_device *pmu_device = armpmu->plat_device;
+       int irq = platform_get_irq(pmu_device, 0);
+
+       cpumask_test_and_clear_cpu(smp_processor_id(),

&armpmu->active_irqs);
+       disable_percpu_irq(irq);
+}
+
+static void
 armpmu_release_hardware(struct arm_pmu *armpmu)
 {
        int i, irq, irqs;
        struct platform_device *pmu_device = armpmu->plat_device;

-       irqs = min(pmu_device->num_resources, num_possible_cpus());
+       irq = platform_get_irq(pmu_device, 0);

-       for (i = 0; i < irqs; ++i) {
-               if (!cpumask_test_and_clear_cpu(i, &armpmu->active_irqs))
-                       continue;
-               irq = platform_get_irq(pmu_device, i);
-               if (irq >= 0)
-                       free_irq(irq, armpmu);
+       if (irq_to_desc(irq) && irq_is_percpu(irq)) {

Why do you need to check the irq_desc here? It really looks like a misuse of
the API.

I don't think it's being misused. In case of invalid irq number, the
API would return null.

Instead, you should check the value of irq itself (it should be strictly
positive).

quoted

+               on_each_cpu(armpmu_disable_percpu_irq, armpmu, 1);
+               free_percpu_irq(irq, &cpu_hw_events);
+       } else {
+               irqs = min(pmu_device->num_resources,
num_possible_cpus());
+
+               for (i = 0; i < irqs; ++i) {
+                       if (!cpumask_test_and_clear_cpu(i,
&armpmu->active_irqs))
+                               continue;
+                       irq = platform_get_irq(pmu_device, i);
+                       if (irq >= 0)

irq == 0 means "no-irq". You should handle it as an error case.

This part of the code (for non-percpu irq) was already present in driver as is.
Will was Okay with it as per his review on V1 here:
http://lists.infradead.org/pipermail/linux-arm-kernel/2013-November/210102.html

quoted

+                               free_irq(irq, armpmu);
+               }
        }
 }

+static void
+armpmu_enable_percpu_irq(void *data)
+{
+       struct arm_pmu *armpmu = data;
+       struct platform_device *pmu_device = armpmu->plat_device;
+       int irq = platform_get_irq(pmu_device, 0);
+
+       enable_percpu_irq(irq, 0);
+       cpumask_set_cpu(smp_processor_id(), &armpmu->active_irqs);
+}
+
 static int
 armpmu_reserve_hardware(struct arm_pmu *armpmu)
 {

@@ -396,34 +426,50 @@ armpmu_reserve_hardware(struct arm_pmu *armpmu)
                return -ENODEV;
        }

-       for (i = 0; i < irqs; ++i) {
-               err = 0;
-               irq = platform_get_irq(pmu_device, i);
-               if (irq < 0)
-                       continue;
+       irq = platform_get_irq(pmu_device, 0);

-               /*
-                * If we have a single PMU interrupt that we can't shift,
-                * assume that we're running on a uniprocessor machine and
-                * continue. Otherwise, continue without this interrupt.
-                */
-               if (irq_set_affinity(irq, cpumask_of(i)) && irqs > 1) {
-                       pr_warning("unable to set irq affinity (irq=%d,

cpu=%u)\n",
-                                   irq, i);
-                       continue;
-               }
+       if (irq_to_desc(irq) && irq_is_percpu(irq)) {

Same comment about irq_to_desc.

quoted

+               err = request_percpu_irq(irq, armpmu->handle_irq,
+                               "arm-pmu", &cpu_hw_events);

-               err = request_irq(irq, armpmu->handle_irq,
-                                 IRQF_NOBALANCING,
-                                 "arm-pmu", armpmu);
                if (err) {
-                       pr_err("unable to request IRQ%d for ARM PMU
counters\n",
-                               irq);
+                       pr_err("unable to request percpu IRQ%d for ARM PMU
counters\n",
+                                       irq);
                        armpmu_release_hardware(armpmu);
                        return err;
                }

-               cpumask_set_cpu(i, &armpmu->active_irqs);
+               on_each_cpu(armpmu_enable_percpu_irq, armpmu, 1);
+       } else {
+               for (i = 0; i < irqs; ++i) {
+                       err = 0;
+                       irq = platform_get_irq(pmu_device, i);
+                       if (irq < 0)

Same comment about irq == 0.

This part of the code (for non-percpu irq) was already present in driver as is.
Will was Okay with it as per his review on V1 here:
http://lists.infradead.org/pipermail/linux-arm-kernel/2013-November/210102.html

quoted

+                               continue;
+
+                       /*
+                        * If we have a single PMU interrupt that we can't
shift,
+                        * assume that we're running on a uniprocessor
machine and
+                        * continue. Otherwise, continue without this
interrupt.
+                        */
+                       if (irq_set_affinity(irq, cpumask_of(i)) && irqs >
1) {
+                               pr_warning("unable to set irq affinity
(irq=%d, cpu=%u)\n",
+                                               irq, i);
+                               continue;
+                       }
+
+                       err = request_irq(irq, armpmu->handle_irq,
+                                       IRQF_NOBALANCING,
+                                       "arm-pmu", armpmu);
+                       if (err) {
+                               pr_err("unable to request IRQ%d for ARM
PMU counters\n",
+                                               irq);
+                               armpmu_release_hardware(armpmu);
+                               return err;
+                       }
+
+                       cpumask_set_cpu(i, &armpmu->active_irqs);
+               }
        }

        return 0;

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