[PATCH v7 06/20] ACPI: CPPC: Release CPC descriptors through kobject
From: Christian Loehle
Date: Wed Sep 16 2026 - 12:37:52 EST
The CPC descriptor embeds the kobject used for its sysfs directory, but
it has no release callback and processor exit frees the descriptor
immediately after kobject_put(). It also unmaps register resources and
releases PCC state before sysfs removal has drained active attribute
callbacks.
Provide a release callback which unmaps and frees the descriptor, and use
the same cleanup helper before kobject initialization. Once initialized,
let kobject_put() own descriptor cleanup so its error path cannot free the
object twice.
On processor exit, first unpublish the per-CPU descriptor and remove its
sysfs directory, then release PCC state and drop the kobject reference.
This keeps all resources valid while sysfs callbacks are active and also
works with delayed kobject release.
The frequency-invariance teardown can run after processor removal has
unpublished a descriptor. Remember which PCC work items were initialized
so policy exit drains them without looking up that descriptor. Also make
the counter-transport query tolerate a missing descriptor.
Fixes: 158c998ea44b ("ACPI / CPPC: add sysfs support to compute delivered performance")
Reported-by: Sashiko <sashiko-bot@xxxxxxxxxx>
Link: https://sashiko.dev/#/patchset/20260724134251.1632824-1-christian.loehle%40arm.com
Signed-off-by: Christian Loehle <christian.loehle@xxxxxxx>
---
drivers/acpi/cppc_acpi.c | 52 +++++++++++++++++++++-------------
drivers/cpufreq/cppc_cpufreq.c | 15 +++++-----
2 files changed, 39 insertions(+), 28 deletions(-)
diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c
index 2198376a6a9c..0f0cce383007 100644
--- a/drivers/acpi/cppc_acpi.c
+++ b/drivers/acpi/cppc_acpi.c
@@ -373,7 +373,27 @@ static struct attribute *cppc_attrs[] = {
};
ATTRIBUTE_GROUPS(cppc);
+static void cppc_free_desc(struct cpc_desc *cpc_ptr)
+{
+ unsigned int i;
+
+ for (i = 2; i < cpc_ptr->num_entries; i++) {
+ void __iomem *addr = cpc_ptr->cpc_regs[i - 2].sys_mem_vaddr;
+
+ if (addr)
+ iounmap(addr);
+ }
+
+ kfree(cpc_ptr);
+}
+
+static void cppc_kobj_release(struct kobject *kobj)
+{
+ cppc_free_desc(to_cpc_desc(kobj));
+}
+
static const struct kobj_type cppc_ktype = {
+ .release = cppc_kobj_release,
.sysfs_ops = &kobj_sysfs_ops,
.default_groups = cppc_groups,
};
@@ -1178,21 +1198,14 @@ int acpi_cppc_processor_probe(struct acpi_processor *pr)
if (ret) {
per_cpu(cpc_desc_ptr, pr->id) = NULL;
kobject_put(&cpc_ptr->kobj);
- goto out_free;
+ goto out_buf_free;
}
kfree(output.pointer);
return 0;
out_free:
- /* Free all the mapped sys mem areas for this CPU */
- for (i = 2; i < cpc_ptr->num_entries; i++) {
- void __iomem *addr = cpc_ptr->cpc_regs[i-2].sys_mem_vaddr;
-
- if (addr)
- iounmap(addr);
- }
- kfree(cpc_ptr);
+ cppc_free_desc(cpc_ptr);
out_buf_free:
if (cpc_present)
@@ -1211,10 +1224,14 @@ EXPORT_SYMBOL_GPL(acpi_cppc_processor_probe);
void acpi_cppc_processor_exit(struct acpi_processor *pr)
{
struct cpc_desc *cpc_ptr;
- unsigned int i;
- void __iomem *addr;
int pcc_ss_id = per_cpu(cpu_pcc_subspace_idx, pr->id);
+ cpc_ptr = per_cpu(cpc_desc_ptr, pr->id);
+ if (cpc_ptr) {
+ per_cpu(cpc_desc_ptr, pr->id) = NULL;
+ kobject_del(&cpc_ptr->kobj);
+ }
+
if (pcc_ss_id >= 0 && pcc_data[pcc_ss_id]) {
if (pcc_data[pcc_ss_id]->pcc_channel_acquired) {
pcc_data[pcc_ss_id]->refcount--;
@@ -1225,20 +1242,12 @@ void acpi_cppc_processor_exit(struct acpi_processor *pr)
}
}
}
+ per_cpu(cpu_pcc_subspace_idx, pr->id) = -1;
- cpc_ptr = per_cpu(cpc_desc_ptr, pr->id);
if (!cpc_ptr)
return;
- /* Free all the mapped sys mem areas for this CPU */
- for (i = 2; i < cpc_ptr->num_entries; i++) {
- addr = cpc_ptr->cpc_regs[i-2].sys_mem_vaddr;
- if (addr)
- iounmap(addr);
- }
-
kobject_put(&cpc_ptr->kobj);
- kfree(cpc_ptr);
}
EXPORT_SYMBOL_GPL(acpi_cppc_processor_exit);
@@ -1822,6 +1831,9 @@ bool cppc_perf_ctrs_in_pcc_cpu(unsigned int cpu)
{
struct cpc_desc *cpc_desc = per_cpu(cpc_desc_ptr, cpu);
+ if (!cpc_desc)
+ return false;
+
return CPC_IN_PCC(&cpc_desc->cpc_regs[DELIVERED_CTR]) ||
CPC_IN_PCC(&cpc_desc->cpc_regs[REFERENCE_CTR]) ||
CPC_IN_PCC(&cpc_desc->cpc_regs[CTR_WRAP_TIME]);
diff --git a/drivers/cpufreq/cppc_cpufreq.c b/drivers/cpufreq/cppc_cpufreq.c
index 80893844353c..af46f913e907 100644
--- a/drivers/cpufreq/cppc_cpufreq.c
+++ b/drivers/cpufreq/cppc_cpufreq.c
@@ -41,6 +41,7 @@ MODULE_PARM_DESC(fie_disabled, "Disable Frequency Invariance Engine (FIE)");
/* Frequency invariance support */
struct cppc_freq_invariance {
int cpu;
+ bool pcc_work_initialized;
struct irq_work irq_work;
struct kthread_work work;
struct cppc_perf_fb_ctrs prev_perf_fb_ctrs;
@@ -163,6 +164,7 @@ static void cppc_cpufreq_cpu_fie_init(struct cpufreq_policy *policy)
if (cppc_perf_ctrs_in_pcc_cpu(cpu)) {
kthread_init_work(&cppc_fi->work, cppc_scale_freq_workfn);
init_irq_work(&cppc_fi->irq_work, cppc_irq_work);
+ cppc_fi->pcc_work_initialized = true;
sftd = &cppc_sftd_pcc;
}
@@ -184,12 +186,8 @@ static void cppc_cpufreq_cpu_fie_init(struct cpufreq_policy *policy)
}
/*
- * We free all the resources on policy's removal and not on CPU removal as the
- * irq-work are per-cpu and the hotplug core takes care of flushing the pending
- * irq-works (hint: smpcfd_dying_cpu()) on CPU hotplug. Even if the kthread-work
- * fires on another CPU after the concerned CPU is removed, it won't harm.
- *
- * We just need to make sure to remove them all on policy->exit().
+ * Drain work initialized by this policy even if processor removal has
+ * already unpublished the CPU's CPC descriptor.
*/
static void cppc_cpufreq_cpu_fie_exit(struct cpufreq_policy *policy)
{
@@ -203,11 +201,12 @@ static void cppc_cpufreq_cpu_fie_exit(struct cpufreq_policy *policy)
topology_clear_scale_freq_source(SCALE_FREQ_SOURCE_CPPC, policy->related_cpus);
for_each_cpu(cpu, policy->related_cpus) {
- if (!cppc_perf_ctrs_in_pcc_cpu(cpu))
- continue;
cppc_fi = &per_cpu(cppc_freq_inv, cpu);
+ if (!cppc_fi->pcc_work_initialized)
+ continue;
irq_work_sync(&cppc_fi->irq_work);
kthread_cancel_work_sync(&cppc_fi->work);
+ cppc_fi->pcc_work_initialized = false;
}
}
--
2.34.1