@@ -419,13 +419,16 @@ static irqreturn_t dmc620_pmu_handle_irq(int irq_num, void *data)
}
static struct dmc620_pmu_irq *__dmc620_pmu_get_irq(int irq_num)
+ __releases(&dmc620_pmu_irqs_lock)
{
struct dmc620_pmu_irq *irq;
int ret;
list_for_each_entry(irq, &dmc620_pmu_irqs, irqs_node)
if (irq->irq_num == irq_num && refcount_inc_not_zero(&irq->refcount))
- return irq;
+ goto out_unlock;
+
+ mutex_unlock(&dmc620_pmu_irqs_lock);
irq = kzalloc(sizeof(*irq), GFP_KERNEL);
if (!irq)
@@ -452,8 +455,12 @@ static struct dmc620_pmu_irq *__dmc620_pmu_get_irq(int irq_num)
goto out_free_irq;
irq->irq_num = irq_num;
+
+ mutex_lock(&dmc620_pmu_irqs_lock);
list_add(&irq->irqs_node, &dmc620_pmu_irqs);
+out_unlock:
+ mutex_unlock(&dmc620_pmu_irqs_lock);
return irq;
out_free_irq:
@@ -469,7 +476,7 @@ static int dmc620_pmu_get_irq(struct dmc620_pmu *dmc620_pmu, int irq_num)
mutex_lock(&dmc620_pmu_irqs_lock);
irq = __dmc620_pmu_get_irq(irq_num);
- mutex_unlock(&dmc620_pmu_irqs_lock);
+ /* mutex_unlock() called inside __dmc620_pmu_get_irq() */
if (IS_ERR(irq))
return PTR_ERR(irq);
The following circular locking dependency was reported when running cpus online/offline test on an arm64 system. [ 84.195923] Chain exists of: dmc620_pmu_irqs_lock --> cpu_hotplug_lock --> cpuhp_state-down [ 84.207305] Possible unsafe locking scenario: [ 84.213212] CPU0 CPU1 [ 84.217729] ---- ---- [ 84.222247] lock(cpuhp_state-down); [ 84.225899] lock(cpu_hotplug_lock); [ 84.232068] lock(cpuhp_state-down); [ 84.238237] lock(dmc620_pmu_irqs_lock); [ 84.242236] *** DEADLOCK *** The problematic locking order seems to be lock(dmc620_pmu_irqs_lock) --> lock(cpu_hotplug_lock) This locking order happens when dmc620_pmu_get_irq() is called from dmc620_pmu_device_probe(). Since dmc620_pmu_irqs_lock is used for protecting the dmc620_pmu_irqs structure only, we don't actually need to hold the lock when adding a new instance to the CPU hotplug subsystem. Fix this possible deadlock scenario by releasing the lock when a new dmc620_pmu_irq needs to be created and reacquring it again when the new irq is inserted into dmc620_pmu_irqs. Suggested-by: Robin Murphy <robin.murphy@arm.com> Signed-off-by: Waiman Long <longman@redhat.com> --- drivers/perf/arm_dmc620_pmu.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-)