linux-kernel - [PATCH v2 2/2] bus: arm-cci: Fix use of smp_processor

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Message-Id: <20171003171413.18592-3-marc.zyngier@arm.com>
Date:   Tue,  3 Oct 2017 18:14:13 +0100
From:   Marc Zyngier <marc.zyngier@....com>
To:     Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Pawel Moll <pawel.moll@....com>,
        Mark Rutland <mark.rutland@....com>
Cc:     linux-kernel@...r.kernel.org
Subject: [PATCH v2 2/2] bus: arm-cci: Fix use of smp_processor_id() in preemptible context

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

diff --git a/drivers/bus/arm-cci.c b/drivers/bus/arm-cci.c
index c49da15d9790..d1aa11c083f9 100644
--- a/drivers/bus/arm-cci.c
+++ b/drivers/bus/arm-cci.c
@@ -1755,14 +1755,17 @@ static int cci_pmu_probe(struct platform_device *pdev)
 	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;
 }
-- 
2.11.0