[PATCH 3/3] thermal/intel_powerclamp: Convert to CPU hotplug state

From: Petr Mladek
Date: Mon Oct 17 2016 - 08:34:08 EST


From: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>

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 | 69 +++++++++++++++++++-------------------
1 file changed, 35 insertions(+), 34 deletions(-)

diff --git a/drivers/thermal/intel_powerclamp.c b/drivers/thermal/intel_powerclamp.c
index a94f7c849a4e..390e50b97324 100644
--- a/drivers/thermal/intel_powerclamp.c
+++ b/drivers/thermal/intel_powerclamp.c
@@ -622,43 +622,35 @@ 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)
{
- unsigned long cpu = (unsigned long)hcpu;
+ if (clamping == false)
+ return 0;
+ start_power_clamp_worker(cpu);
+ /* prefer BSP as controlling CPU */
+ if (cpu == 0) {
+ control_cpu = 0;
+ smp_mb();
+ }
+ return 0;
+}

- if (false == clamping)
- goto exit_ok;
+static int powerclamp_cpu_predown(unsigned int cpu)
+{
+ if (clamping == false)
+ return 0;

- switch (action) {
- case CPU_ONLINE:
- start_power_clamp_worker(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);
- stop_power_clamp_worker(cpu);
- }
- if (cpu == control_cpu) {
- control_cpu = smp_processor_id();
- smp_mb();
- }
- }
+ stop_power_clamp_worker(cpu);
+ 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)
{
@@ -788,6 +780,8 @@ 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;
@@ -805,7 +799,14 @@ 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;

worker_data = alloc_percpu(struct powerclamp_worker_data);
if (!worker_data) {
@@ -830,7 +831,7 @@ static int __init powerclamp_init(void)
exit_free_thread:
free_percpu(worker_data);
exit_unregister:
- unregister_hotcpu_notifier(&powerclamp_cpu_notifier);
+ cpuhp_remove_state_nocalls(hp_state);
exit_free:
kfree(cpu_clamping_mask);
return retval;
@@ -839,8 +840,8 @@ 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(worker_data);
thermal_cooling_device_unregister(cooling_dev);
kfree(cpu_clamping_mask);
--
1.8.5.6