[patch V2 26/67] perf/x86/amd/power: Convert the hotplug notifier to state machine

[Anna-Maria Gleixner]

From: Anna-Maria Gleixner <anna-maria@xxxxxxxxxxxxx>

Install the callbacks via the state machine.

Signed-off-by: Anna-Maria Gleixner <anna-maria@xxxxxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxx>
Cc: Huang Rui <ray.huang@xxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
---
 arch/x86/events/amd/power.c | 58 +++++++++------------------------------------
 include/linux/cpuhotplug.h  |  1 +
 2 files changed, 12 insertions(+), 47 deletions(-)

diff --git a/arch/x86/events/amd/power.c b/arch/x86/events/amd/power.c
index 204df18..9842270 100644
--- a/arch/x86/events/amd/power.c
+++ b/arch/x86/events/amd/power.c
@@ -228,12 +228,12 @@ static struct pmu pmu_class = {
 	.read		= pmu_event_read,
 };
 
-static void power_cpu_exit(int cpu)
+static int power_cpu_exit(unsigned int cpu)
 {
 	int target;
 
 	if (!cpumask_test_and_clear_cpu(cpu, &cpu_mask))
-		return;
+		return 0;
 
 	/*
 	 * Find a new CPU on the same compute unit, if was set in cpumask
@@ -245,9 +245,10 @@ static void power_cpu_exit(int cpu)
 		cpumask_set_cpu(target, &cpu_mask);
 		perf_pmu_migrate_context(&pmu_class, cpu, target);
 	}
+	return 0;
 }
 
-static void power_cpu_init(int cpu)
+static int power_cpu_init(unsigned int cpu)
 {
 	int target;
 
@@ -263,33 +264,9 @@ static void power_cpu_init(int cpu)
 	target = cpumask_any_but(topology_sibling_cpumask(cpu), cpu);
 	if (target >= nr_cpumask_bits)
 		cpumask_set_cpu(cpu, &cpu_mask);
+	return 0;
 }
 
-static int
-power_cpu_notifier(struct notifier_block *self, unsigned long action, void *hcpu)
-{
-	unsigned int cpu = (long)hcpu;
-
-	switch (action & ~CPU_TASKS_FROZEN) {
-	case CPU_DOWN_FAILED:
-	case CPU_ONLINE:
-		power_cpu_init(cpu);
-		break;
-	case CPU_DOWN_PREPARE:
-		power_cpu_exit(cpu);
-		break;
-	default:
-		break;
-	}
-
-	return NOTIFY_OK;
-}
-
-static struct notifier_block power_cpu_notifier_nb = {
-	.notifier_call = power_cpu_notifier,
-	.priority = CPU_PRI_PERF,
-};
-
 static const struct x86_cpu_id cpu_match[] = {
 	{ .vendor = X86_VENDOR_AMD, .family = 0x15 },
 	{},
@@ -297,7 +274,7 @@ static const struct x86_cpu_id cpu_match[] = {
 
 static int __init amd_power_pmu_init(void)
 {
-	int cpu, target, ret;
+	int ret;
 
 	if (!x86_match_cpu(cpu_match))
 		return 0;
@@ -312,38 +289,25 @@ static int __init amd_power_pmu_init(void)
 		return -ENODEV;
 	}
 
-	cpu_notifier_register_begin();
 
-	/* Choose one online core of each compute unit. */
-	for_each_online_cpu(cpu) {
-		target = cpumask_first(topology_sibling_cpumask(cpu));
-		if (!cpumask_test_cpu(target, &cpu_mask))
-			cpumask_set_cpu(target, &cpu_mask);
-	}
+	cpuhp_setup_state(CPUHP_AP_PERF_X86_AMD_POWER_ONLINE,
+			  "AP_PERF_X86_AMD_POWER_ONLINE",
+			  power_cpu_init, power_cpu_exit);
 
 	ret = perf_pmu_register(&pmu_class, "power", -1);
 	if (WARN_ON(ret)) {
 		pr_warn("AMD Power PMU registration failed\n");
-		goto out;
+		return ret;
 	}
 
-	__register_cpu_notifier(&power_cpu_notifier_nb);
-
 	pr_info("AMD Power PMU detected\n");
-
-out:
-	cpu_notifier_register_done();
-
 	return ret;
 }
 module_init(amd_power_pmu_init);
 
 static void __exit amd_power_pmu_exit(void)
 {
-	cpu_notifier_register_begin();
-	__unregister_cpu_notifier(&power_cpu_notifier_nb);
-	cpu_notifier_register_done();
-
+	cpuhp_remove_state_nocalls(CPUHP_AP_PERF_X86_AMD_POWER_ONLINE);
 	perf_pmu_unregister(&pmu_class);
 }
 module_exit(amd_power_pmu_exit);
diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
index f187c46..acfeda1 100644
--- a/include/linux/cpuhotplug.h
+++ b/include/linux/cpuhotplug.h
@@ -41,6 +41,7 @@ enum cpuhp_state {
 	CPUHP_AP_PERF_X86_ONLINE,
 	CPUHP_AP_PERF_X86_UNCORE_ONLINE,
 	CPUHP_AP_PERF_X86_AMD_UNCORE_ONLINE,
+	CPUHP_AP_PERF_X86_AMD_POWER_ONLINE,
 	CPUHP_AP_PERF_X86_RAPL_ONLINE,
 	CPUHP_AP_PERF_X86_CQM_ONLINE,
 	CPUHP_AP_PERF_X86_CSTATE_ONLINE,
-- 
2.8.1