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Subject[PATCH 4.9 046/148] bus: arm-cci: Fix use of smp_processor_id() in preemptible context
Date
4.9-stable review patch.  If anyone has any objections, please let me know.

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

From: Marc Zyngier <marc.zyngier@arm.com>

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@arm.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Pawel Moll <pawel.moll@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
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;
}

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