ARM: perf: use cpumask_t to record active IRQs

Commit 5dfc54e0 ("ARM: GIC: avoid routing interrupts to offline CPUs")
prevents the GIC from setting the affinity of an IRQ to a CPU with
id >= nr_cpu_ids. This was previously abused by perf on some platforms
where more IRQs were registered than possible CPUs.

This patch fixes the problem by using a cpumask_t to keep track of the
active (requested) interrupts in perf. The same effect could be achieved
by limiting the number of IRQs to the number of CPUs, but using a mask
instead will be useful for adding extended CPU hotplug support in the
future.

Acked-by: Jamie Iles <jamie@jamieiles.com>
Reviewed-by: Jean Pihet <j-pihet@ti.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

diff --git a/arch/arm/kernel/perf_event.c b/arch/arm/kernel/perf_event.c
index 8514855ffc2e203f7b2f66db8869d60f11b3c70d..d507fe148e00f3054e44616d6798eb3c261102db 100644 (file)
--- a/arch/arm/kernel/perf_event.c
+++ b/arch/arm/kernel/perf_event.c
@@ -69,6 +69,7 @@ static DEFINE_PER_CPU(struct cpu_hw_events, cpu_hw_events);
 
 struct arm_pmu {
        enum arm_perf_pmu_ids id;
+       cpumask_t       active_irqs;
        const char      *name;
        irqreturn_t     (*handle_irq)(int irq_num, void *dev);
        void            (*enable)(struct hw_perf_event *evt, int idx);
@@ -388,6 +389,25 @@ static irqreturn_t armpmu_platform_irq(int irq, void *dev)
        return plat->handle_irq(irq, dev, armpmu->handle_irq);
 }
 
+static void
+armpmu_release_hardware(void)
+{
+       int i, irq, irqs;
+
+       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)
+                       free_irq(irq, NULL);
+       }
+
+       armpmu->stop();
+       release_pmu(ARM_PMU_DEVICE_CPU);
+}
+
 static int
 armpmu_reserve_hardware(void)
 {
@@ -401,20 +421,20 @@ armpmu_reserve_hardware(void)
                return err;
        }
 
-       irqs = pmu_device->num_resources;
-
        plat = dev_get_platdata(&pmu_device->dev);
        if (plat && plat->handle_irq)
                handle_irq = armpmu_platform_irq;
        else
                handle_irq = armpmu->handle_irq;
 
+       irqs = min(pmu_device->num_resources, num_possible_cpus());
        if (irqs < 1) {
                pr_err("no irqs for PMUs defined\n");
                return -ENODEV;
        }
 
        for (i = 0; i < irqs; ++i) {
+               err = 0;
                irq = platform_get_irq(pmu_device, i);
                if (irq < 0)
                        continue;
@@ -422,13 +442,12 @@ armpmu_reserve_hardware(void)
                /*
                 * If we have a single PMU interrupt that we can't shift,
                 * assume that we're running on a uniprocessor machine and
-                * continue.
+                * continue. Otherwise, continue without this interrupt.
                 */
-               err = irq_set_affinity(irq, cpumask_of(i));
-               if (err && irqs > 1) {
-                       pr_err("unable to set irq affinity (irq=%d, cpu=%u)\n",
-                               irq, i);
-                       break;
+               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, handle_irq,
@@ -437,35 +456,14 @@ armpmu_reserve_hardware(void)
                if (err) {
                        pr_err("unable to request IRQ%d for ARM PMU counters\n",
                                irq);
-                       break;
+                       armpmu_release_hardware();
+                       return err;
                }
-       }
 
-       if (err) {
-               for (i = i - 1; i >= 0; --i) {
-                       irq = platform_get_irq(pmu_device, i);
-                       if (irq >= 0)
-                               free_irq(irq, NULL);
-               }
-               release_pmu(ARM_PMU_DEVICE_CPU);
+               cpumask_set_cpu(i, &armpmu->active_irqs);
        }
 
-       return err;
-}
-
-static void
-armpmu_release_hardware(void)
-{
-       int i, irq;
-
-       for (i = pmu_device->num_resources - 1; i >= 0; --i) {
-               irq = platform_get_irq(pmu_device, i);
-               if (irq >= 0)
-                       free_irq(irq, NULL);
-       }
-       armpmu->stop();
-
-       release_pmu(ARM_PMU_DEVICE_CPU);
+       return 0;
 }
 
 static atomic_t active_events = ATOMIC_INIT(0);