[PATCH] thermal/intel_powerclamp: Convert to CPU hotplug state

[Sebastian Andrzej Siewior]

This is a conversation to the new hotplug state machine with
the difference that CPU_DEAD becomes CPU_PREDOWN.

At the same time it makes the handling of the two states symmetrical.
stop_power_clamp_worker() is called unconditionally and the controversial
error message is removed.

Finally, the hotplug state callbacks are removed after the powerclamping
is stopped to avoid a potential race.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
[pmladek@xxxxxxxx: Fixed the possible race in powerclamp_exit()]
Signed-off-by: Petr Mladek <pmladek@xxxxxxxx>
---
 drivers/thermal/intel_powerclamp.c | 70 ++++++++++++++++++++------------------
 1 file changed, 36 insertions(+), 34 deletions(-)

diff --git a/drivers/thermal/intel_powerclamp.c b/drivers/thermal/intel_powerclamp.c
index 0244805b7b86..4ebfea3f0f1e 100644
--- a/drivers/thermal/intel_powerclamp.c
+++ b/drivers/thermal/intel_powerclamp.c
@@ -572,45 +572,38 @@ static void end_power_clamp(void)
 	}
 }
 
-static int powerclamp_cpu_callback(struct notifier_block *nfb,
-				unsigned long action, void *hcpu)
+static int powerclamp_cpu_online(unsigned int cpu)
+{
+	if (clamping == false)
+		return 0;
+	start_power_clamp_thread(cpu);
+	/* prefer BSP as controlling CPU */
+	if (cpu == 0) {
+		control_cpu = 0;
+		smp_mb();
+	}
+	return 0;
+}
+
+static int powerclamp_cpu_predown(unsigned int cpu)
 {
-	unsigned long cpu = (unsigned long)hcpu;
 	struct task_struct **percpu_thread =
 		per_cpu_ptr(powerclamp_thread, cpu);
 
-	if (false == clamping)
-		goto exit_ok;
+	if (clamping == false)
+		return 0;
 
-	switch (action) {
-	case CPU_ONLINE:
-		start_power_clamp_thread(cpu);
-		/* prefer BSP as controlling CPU */
-		if (cpu == 0) {
-			control_cpu = 0;
-			smp_mb();
-		}
-		break;
-	case CPU_DEAD:
-		if (test_bit(cpu, cpu_clamping_mask)) {
-			pr_err("cpu %lu dead but powerclamping thread is not\n",
-				cpu);
-			kthread_stop(*percpu_thread);
-		}
-		if (cpu == control_cpu) {
-			control_cpu = smp_processor_id();
-			smp_mb();
-		}
-	}
+	kthread_stop(*percpu_thread);
+	if (cpu != control_cpu)
+		return 0;
 
-exit_ok:
-	return NOTIFY_OK;
+	control_cpu = cpumask_first(cpu_online_mask);
+	if (control_cpu == cpu)
+		control_cpu = cpumask_next(cpu, cpu_online_mask);
+	smp_mb();
+	return 0;
 }
 
-static struct notifier_block powerclamp_cpu_notifier = {
-	.notifier_call = powerclamp_cpu_callback,
-};
-
 static int powerclamp_get_max_state(struct thermal_cooling_device *cdev,
 				 unsigned long *state)
 {
@@ -730,6 +723,8 @@ static inline void powerclamp_create_debug_files(void)
 	debugfs_remove_recursive(debug_dir);
 }
 
+static enum cpuhp_state hp_state;
+
 static int __init powerclamp_init(void)
 {
 	int retval;
@@ -747,7 +742,14 @@ static int __init powerclamp_init(void)
 
 	/* set default limit, maybe adjusted during runtime based on feedback */
 	window_size = 2;
-	register_hotcpu_notifier(&powerclamp_cpu_notifier);
+	retval = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN,
+					   "thermal/intel_powerclamp:online",
+					   powerclamp_cpu_online,
+					   powerclamp_cpu_predown);
+	if (retval < 0)
+		goto exit_free;
+
+	hp_state = retval;
 
 	powerclamp_thread = alloc_percpu(struct task_struct *);
 	if (!powerclamp_thread) {
@@ -772,7 +774,7 @@ static int __init powerclamp_init(void)
 exit_free_thread:
 	free_percpu(powerclamp_thread);
 exit_unregister:
-	unregister_hotcpu_notifier(&powerclamp_cpu_notifier);
+	cpuhp_remove_state_nocalls(hp_state);
 exit_free:
 	kfree(cpu_clamping_mask);
 	return retval;
@@ -781,8 +783,8 @@ static int __init powerclamp_init(void)
 
 static void __exit powerclamp_exit(void)
 {
-	unregister_hotcpu_notifier(&powerclamp_cpu_notifier);
 	end_power_clamp();
+	cpuhp_remove_state_nocalls(hp_state);
 	free_percpu(powerclamp_thread);
 	thermal_cooling_device_unregister(cooling_dev);
 	kfree(cpu_clamping_mask);
-- 
1.8.5.6