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authorWaiman Long <longman@redhat.com>2023-08-12 19:55:49 -0400
committerWill Deacon <will@kernel.org>2023-08-16 14:16:03 +0100
commit4c1d2f56d685406fc6b452ca5f797bda62a06609 (patch)
tree3205645f5ef1c130a76a414e1c609f12920d98e3 /drivers/perf
parent1b0e3ea9301a422003d385cda8f8dee6c878ad05 (diff)
perf/arm-dmc620: Fix dmc620_pmu_irqs_lock/cpu_hotplug_lock circular lock dependency
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>
Diffstat (limited to 'drivers/perf')
-rw-r--r--drivers/perf/arm_dmc620_pmu.c19
1 files changed, 13 insertions, 6 deletions
diff --git a/drivers/perf/arm_dmc620_pmu.c b/drivers/perf/arm_dmc620_pmu.c
index 9d0f01c4455a..30cea6859574 100644
--- a/drivers/perf/arm_dmc620_pmu.c
+++ b/drivers/perf/arm_dmc620_pmu.c
@@ -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;