On Fri, Nov 05, 2021 at 06:33:10PM -0700, Ricardo Neri wrote:

  +	raw_spinlock_t		interrupt_lock;

	// this here uses ->event_lock to serialize against the
	// interrupt below changing the data...

+}
+
+void intel_hfi_process_event(__u64 pkg_therm_status_msr_val)
+{
+	struct hfi_instance *hfi_instance;
+	int cpu = smp_processor_id();
+	struct hfi_cpu_info *info;
+	unsigned long flags;
+	u64 timestamp;
+
+	if (!pkg_therm_status_msr_val)
+		return;
+
+	info = &per_cpu(hfi_cpu_info, cpu);
+	if (!info)
+		return;
+
+	/*
+	 * It is possible that we get an HFI thermal interrupt on this CPU
+	 * before its HFI instance is initialized. This is not a problem. The
+	 * CPU that enabled the interrupt for this package will also get the
+	 * interrupt and is fully initialized.
+	 */
+	hfi_instance = info->hfi_instance;
+	if (!hfi_instance)
+		return;
+

	/*
	 * If someone is already handling the interrupt, we shouldn't be
	 * burning time waiting for them to then do more nothing.
	 */
	if (!raw_spin_trylock(&hfi_instance->interrupt_lock))
		return;

+	raw_spin_lock_irqsave(&hfi_instance->event_lock, flags);
+
+	/*
+	 * On most systems, all CPUs in the package receive a package-level
+	 * thermal interrupt when there is an HFI update. Since they all are
+	 * dealing with the same update (as indicated by the update timestamp),
+	 * it is sufficient to let a single CPU to acknowledge the update and
+	 * schedule work to process it.
+	 */
+	timestamp = *(u64 *)hfi_instance->hw_table;
+	if (hfi_instance->timestamp >= timestamp)
+		goto unlock_spinlock;

This can go the way of the dodo.

+
+	hfi_instance->timestamp = timestamp;
+
+	memcpy(hfi_instance->table_base, hfi_instance->hw_table,
+	       hfi_features.nr_table_pages << PAGE_SHIFT);
+	/*
+	 * Let hardware and other CPUs know that we are done reading the HFI
+	 * table and it is free to update it again.
+	 */
+	pkg_therm_status_msr_val &= THERM_STATUS_CLEAR_PKG_MASK &
+				    ~PACKAGE_THERM_STATUS_HFI_UPDATED;
+	wrmsrl(MSR_IA32_PACKAGE_THERM_STATUS, pkg_therm_status_msr_val);
+	schedule_delayed_work(&hfi_instance->update_work, HFI_UPDATE_INTERVAL);
+
+unlock_spinlock:
+	raw_spin_unlock_irqrestore(&hfi_instance->event_lock, flags);

	raw_spin_unlock(&hfi_instance->interrupt_lock);

+}