[PATCH] drivers/perf: arm_pmu: Request PMU SPIs with IRQF_PER

Mark Rutland

2017-07-25 16:26:25 UTC

Post by Will Deacon
Since the PMU register interface is banked per CPU, CPU PMU interrrupts
cannot be handled by a CPU other than the one with the PMU asserting the
interrupt. This means that migrating PMU SPIs, as we do during a CPU
hotplug operation doesn't make any sense and can lead to the IRQ being
disabled entirely if we route a spurious IRQ to the new affinity target.
This has been observed in practice on AMD Seattle, where CPUs on the
non-boot cluster appear to take a spurious PMU IRQ when coming online,
which is routed to CPU0 where it cannot be handled.
This patch passes IRQF_PERCPU for PMU SPIs and forcefullt sets their

forcefully

Post by Will Deacon
affinity prior to requesting them, ensuring that they cannot
be migrated during hotplug events.
Fixes: 3cf7ee98b848 ("drivers/perf: arm_pmu: move irq request/free into probe")

The patch itself looks good to me.

Acked-by: Mark Rutland <***@arm.com>

Mark.

Post by Will Deacon
---
drivers/perf/arm_pmu.c | 30 +++++++++++++++++-------------
1 file changed, 17 insertions(+), 13 deletions(-)
diff --git a/drivers/perf/arm_pmu.c b/drivers/perf/arm_pmu.c
index dc459eb1246b..fa18e4858141 100644
--- a/drivers/perf/arm_pmu.c
+++ b/drivers/perf/arm_pmu.c
@@ -569,22 +569,32 @@ int armpmu_request_irq(struct arm_pmu *armpmu, int cpu)
if (irq != other_irq) {
pr_warn("mismatched PPIs detected.\n");
err = -EINVAL;
+ goto err_out;
}
} else {
+ err = irq_force_affinity(irq, cpumask_of(cpu));
+
+ if (err && num_possible_cpus() > 1) {
+ pr_warn("unable to set irq affinity (irq=%d, cpu=%u)\n",
+ irq, cpu);
+ goto err_out;
+ }
+
err = request_irq(irq, handler,
- IRQF_NOBALANCING | IRQF_NO_THREAD, "arm-pmu",
+ IRQF_PERCPU | IRQF_NOBALANCING | IRQF_NO_THREAD,
+ "arm-pmu",
per_cpu_ptr(&hw_events->percpu_pmu, cpu));
}
- if (err) {
- pr_err("unable to request IRQ%d for ARM PMU counters\n",
- irq);
- return err;
- }
+ if (err)
+ goto err_out;
cpumask_set_cpu(cpu, &armpmu->active_irqs);
-
return 0;
+
+ pr_err("unable to request IRQ%d for ARM PMU counters\n", irq);
+ return err;
}
int armpmu_request_irqs(struct arm_pmu *armpmu)
@@ -628,12 +638,6 @@ static int arm_perf_starting_cpu(unsigned int cpu, struct hlist_node *node)
enable_percpu_irq(irq, IRQ_TYPE_NONE);
return 0;
}
-
- if (irq_force_affinity(irq, cpumask_of(cpu)) &&
- num_possible_cpus() > 1) {
- pr_warn("unable to set irq affinity (irq=%d, cpu=%u)\n",
- irq, cpu);
- }
}
return 0;
--
2.1.4