[PATCH v2] arm/perf: Convert to hotplug state machine

[Sebastian Andrzej Siewior <bigeasy@linutronix.de>]

From: Thomas Gleixner <tglx@linutronix.de>

Straight forward conversion w/o bells and whistles.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Anna-Maria Gleixner <anna-maria@linutronix.de>
Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: rt@linutronix.de
[bigeasy: use arm_pmu_list to handle multiple  PMUs in the system]
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 drivers/perf/arm_pmu.c       | 59 +++++++++++++++++++++++++++-----------------
 include/linux/cpuhotplug.h   |  1 +
 include/linux/perf/arm_pmu.h |  2 +-
 3 files changed, 39 insertions(+), 23 deletions(-)

diff --git a/drivers/perf/arm_pmu.c b/drivers/perf/arm_pmu.c
index 140436a046c0..b7a64c0ec673 100644
--- a/drivers/perf/arm_pmu.c
+++ b/drivers/perf/arm_pmu.c
@@ -685,30 +685,29 @@ static int cpu_pmu_request_irq(struct arm_pmu *cpu_pmu, irq_handler_t handler)
 	return 0;
 }
 
+static DEFINE_MUTEX(arm_pmu_mutex);
+static LIST_HEAD(arm_pmu_list);
+
 /*
  * PMU hardware loses all context when a CPU goes offline.
  * When a CPU is hotplugged back in, since some hardware registers are
  * UNKNOWN at reset, the PMU must be explicitly reset to avoid reading
  * junk values out of them.
  */
-static int cpu_pmu_notify(struct notifier_block *b, unsigned long action,
-			  void *hcpu)
+static int arm_perf_starting_cpu(unsigned int cpu)
 {
-	int cpu = (unsigned long)hcpu;
-	struct arm_pmu *pmu = container_of(b, struct arm_pmu, hotplug_nb);
+	struct arm_pmu *pmu;
 
-	if ((action & ~CPU_TASKS_FROZEN) != CPU_STARTING)
-		return NOTIFY_DONE;
+	mutex_lock(&arm_pmu_mutex);
+	list_for_each_entry(pmu, &arm_pmu_list, entry) {
 
-	if (!cpumask_test_cpu(cpu, &pmu->supported_cpus))
-		return NOTIFY_DONE;
-
-	if (pmu->reset)
-		pmu->reset(pmu);
-	else
-		return NOTIFY_DONE;
-
-	return NOTIFY_OK;
+		if (!cpumask_test_cpu(cpu, &pmu->supported_cpus))
+			continue;
+		if (pmu->reset)
+			pmu->reset(pmu);
+	}
+	mutex_unlock(&arm_pmu_mutex);
+	return 0;
 }
 
 #ifdef CONFIG_CPU_PM
@@ -819,10 +818,9 @@ static int cpu_pmu_init(struct arm_pmu *cpu_pmu)
 	if (!cpu_hw_events)
 		return -ENOMEM;
 
-	cpu_pmu->hotplug_nb.notifier_call = cpu_pmu_notify;
-	err = register_cpu_notifier(&cpu_pmu->hotplug_nb);
-	if (err)
-		goto out_hw_events;
+	mutex_lock(&arm_pmu_mutex);
+	list_add_tail(&cpu_pmu->entry, &arm_pmu_list);
+	mutex_unlock(&arm_pmu_mutex);
 
 	err = cpu_pm_pmu_register(cpu_pmu);
 	if (err)
@@ -858,8 +856,9 @@ static int cpu_pmu_init(struct arm_pmu *cpu_pmu)
 	return 0;
 
 out_unregister:
-	unregister_cpu_notifier(&cpu_pmu->hotplug_nb);
-out_hw_events:
+	mutex_lock(&arm_pmu_mutex);
+	list_del(&cpu_pmu->entry);
+	mutex_unlock(&arm_pmu_mutex);
 	free_percpu(cpu_hw_events);
 	return err;
 }
@@ -867,7 +866,9 @@ static int cpu_pmu_init(struct arm_pmu *cpu_pmu)
 static void cpu_pmu_destroy(struct arm_pmu *cpu_pmu)
 {
 	cpu_pm_pmu_unregister(cpu_pmu);
-	unregister_cpu_notifier(&cpu_pmu->hotplug_nb);
+	mutex_lock(&arm_pmu_mutex);
+	list_del(&cpu_pmu->entry);
+	mutex_unlock(&arm_pmu_mutex);
 	free_percpu(cpu_pmu->hw_events);
 }
 
@@ -1044,3 +1045,17 @@ int arm_pmu_device_probe(struct platform_device *pdev,
 	kfree(pmu);
 	return ret;
 }
+
+static int arm_pmu_hp_init(void)
+{
+	int ret;
+
+	ret = cpuhp_setup_state_nocalls(CPUHP_AP_PERF_ARM_STARTING,
+					"AP_PERF_ARM_STARTING",
+					arm_perf_starting_cpu, NULL);
+	if (ret)
+		pr_err("CPU hotplug notifier for ARM PMU could not be "
+		       "registered: %d\n", ret);
+	return ret;
+}
+subsys_initcall(arm_pmu_hp_init);
diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
index 4c63cb30aee6..a5b6a6526af8 100644
--- a/include/linux/cpuhotplug.h
+++ b/include/linux/cpuhotplug.h
@@ -35,6 +35,7 @@ enum cpuhp_state {
 	CPUHP_AP_PERF_X86_CSTATE_STARTING,
 	CPUHP_AP_PERF_XTENSA_STARTING,
 	CPUHP_AP_ARM_VFP_STARTING,
+	CPUHP_AP_PERF_ARM_STARTING,
 	CPUHP_AP_NOTIFY_STARTING,
 	CPUHP_AP_ONLINE,
 	CPUHP_TEARDOWN_CPU,
diff --git a/include/linux/perf/arm_pmu.h b/include/linux/perf/arm_pmu.h
index d28ac05c7f92..e18843809eec 100644
--- a/include/linux/perf/arm_pmu.h
+++ b/include/linux/perf/arm_pmu.h
@@ -109,7 +109,7 @@ struct arm_pmu {
 	DECLARE_BITMAP(pmceid_bitmap, ARMV8_PMUV3_MAX_COMMON_EVENTS);
 	struct platform_device	*plat_device;
 	struct pmu_hw_events	__percpu *hw_events;
-	struct notifier_block	hotplug_nb;
+	struct list_head	entry;
 	struct notifier_block	cpu_pm_nb;
 };
 
-- 
2.8.1