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perf/arm-dmc620: Fix dmc620_pmu_irqs_lock/cpu_hotplug_lock circular lock dependency

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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 following locking order happens when dmc620_pmu_get_irq() calls
cpuhp_state_add_instance_nocalls().

	lock(dmc620_pmu_irqs_lock) --> lock(cpu_hotplug_lock)

On the other hand, the calling sequence

  cpuhp_thread_fun()
    => cpuhp_invoke_callback()
      => dmc620_pmu_cpu_teardown()

leads to the locking sequence

	lock(cpuhp_state-down) => lock(dmc620_pmu_irqs_lock)

Here dmc620_pmu_irqs_lock protects both the dmc620_pmu_irqs and the
pmus_node lists in various dmc620_pmu instances. dmc620_pmu_get_irq()
requires protected access to dmc620_pmu_irqs whereas
dmc620_pmu_cpu_teardown() needs protection to the pmus_node lists.
Break this circular locking dependency by using two separate locks to
protect dmc620_pmu_irqs list and the pmus_node lists respectively.

Suggested-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Waiman Long <longman@redhat.com>
Link: https://lore.kernel.org/r/20230812235549.494174-1-longman@redhat.com
Signed-off-by: Will Deacon <will@kernel.org>
This commit is contained in:
Waiman Long 2023-08-12 19:55:49 -04:00 committed by Will Deacon
parent 1b0e3ea930
commit 4c1d2f56d6
1 changed files with 13 additions and 6 deletions
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19
drivers/perf/arm_dmc620_pmu.c
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@ -66,8 +66,13 @@
#define DMC620_PMU_COUNTERn_OFFSET(n) \
(DMC620_PMU_COUNTERS_BASE + 0x28 * (n))
static LIST_HEAD(dmc620_pmu_irqs);
/*
* dmc620_pmu_irqs_lock: protects dmc620_pmu_irqs list
* dmc620_pmu_node_lock: protects pmus_node lists in all dmc620_pmu instances
*/
static DEFINE_MUTEX(dmc620_pmu_irqs_lock);
static DEFINE_MUTEX(dmc620_pmu_node_lock);
static LIST_HEAD(dmc620_pmu_irqs);
struct dmc620_pmu_irq {
struct hlist_node node;
@ -475,9 +480,9 @@ static int dmc620_pmu_get_irq(struct dmc620_pmu *dmc620_pmu, int irq_num)
return PTR_ERR(irq);
dmc620_pmu->irq = irq;
mutex_lock(&dmc620_pmu_irqs_lock);
mutex_lock(&dmc620_pmu_node_lock);
list_add_rcu(&dmc620_pmu->pmus_node, &irq->pmus_node);
mutex_unlock(&dmc620_pmu_irqs_lock);
mutex_unlock(&dmc620_pmu_node_lock);
return 0;
}
@ -486,9 +491,11 @@ static void dmc620_pmu_put_irq(struct dmc620_pmu *dmc620_pmu)
{
struct dmc620_pmu_irq *irq = dmc620_pmu->irq;
mutex_lock(&dmc620_pmu_irqs_lock);
mutex_lock(&dmc620_pmu_node_lock);
list_del_rcu(&dmc620_pmu->pmus_node);
mutex_unlock(&dmc620_pmu_node_lock);
mutex_lock(&dmc620_pmu_irqs_lock);
if (!refcount_dec_and_test(&irq->refcount)) {
mutex_unlock(&dmc620_pmu_irqs_lock);
return;
@ -638,10 +645,10 @@ static int dmc620_pmu_cpu_teardown(unsigned int cpu,
return 0;
/* We're only reading, but this isn't the place to be involving RCU */
mutex_lock(&dmc620_pmu_irqs_lock);
mutex_lock(&dmc620_pmu_node_lock);
list_for_each_entry(dmc620_pmu, &irq->pmus_node, pmus_node)
perf_pmu_migrate_context(&dmc620_pmu->pmu, irq->cpu, target);
mutex_unlock(&dmc620_pmu_irqs_lock);
mutex_unlock(&dmc620_pmu_node_lock);
WARN_ON(irq_set_affinity(irq->irq_num, cpumask_of(target)));
irq->cpu = target;