[PATCH 4.9 046/148] bus: arm-cci: Fix use of smp_processor_id() in preemptible context

[Greg Kroah-Hartman]

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Marc Zyngier <marc.zyngier@xxxxxxx>

commit 4608af8aa53e7f3922ddee695d023b7bcd5cb35b upstream.

The ARM CCI driver seem to be using smp_processor_id() in a
preemptible context, which is likely to make a DEBUG_PREMPT
kernel scream at boot time.

Turn this into a get_cpu()/put_cpu() that extends over the CPU
hotplug registration, making sure that we don't race against
a CPU down operation.

Signed-off-by: Marc Zyngier <marc.zyngier@xxxxxxx>
Acked-by: Mark Rutland <mark.rutland@xxxxxxx>
Signed-off-by: Pawel Moll <pawel.moll@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/bus/arm-cci.c |    7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

--- a/drivers/bus/arm-cci.c
+++ b/drivers/bus/arm-cci.c
@@ -1755,14 +1755,17 @@ static int cci_pmu_probe(struct platform
 	raw_spin_lock_init(&cci_pmu->hw_events.pmu_lock);
 	mutex_init(&cci_pmu->reserve_mutex);
 	atomic_set(&cci_pmu->active_events, 0);
-	cpumask_set_cpu(smp_processor_id(), &cci_pmu->cpus);
+	cpumask_set_cpu(get_cpu(), &cci_pmu->cpus);
 
 	ret = cci_pmu_init(cci_pmu, pdev);
-	if (ret)
+	if (ret) {
+		put_cpu();
 		return ret;
+	}
 
 	cpuhp_state_add_instance_nocalls(CPUHP_AP_PERF_ARM_CCI_ONLINE,
 					 &cci_pmu->node);
+	put_cpu();
 	pr_info("ARM %s PMU driver probed", cci_pmu->model->name);
 	return 0;
 }