[PATCH] drivers: base: update cpu offline info when do hotplug

[Neil Zhang <zhangwm@marvell.com>]

The current per-cpu offline info won't be updated if it is
hotplugged in/out by a kernel governer.
Let's update it via cpu notifier.

Signed-off-by: Neil Zhang <zhangwm@marvell.com>
---
 drivers/base/cpu.c |   25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c
index 006b1bc..9d61824 100644
--- a/drivers/base/cpu.c
+++ b/drivers/base/cpu.c
@@ -418,10 +418,35 @@ static void __init cpu_dev_register_generic(void)
 #endif
 }
 
+static int device_hotplug_notifier(struct notifier_block *nfb,
+				      unsigned long action, void *hcpu)
+{
+	unsigned int cpu = (unsigned long)hcpu;
+	struct device *dev = get_cpu_device(cpu);
+	int ret;
+
+	switch (action & ~CPU_TASKS_FROZEN) {
+	case CPU_ONLINE:
+		dev->offline = false;
+		ret = NOTIFY_OK;
+		break;
+	case CPU_DYING:
+		dev->offline = true;
+		ret = NOTIFY_OK;
+		break;
+	default:
+		ret = NOTIFY_DONE;
+		break;
+	}
+
+	return ret;
+}
+
 void __init cpu_dev_init(void)
 {
 	if (subsys_system_register(&cpu_subsys, cpu_root_attr_groups))
 		panic("Failed to register CPU subsystem");
 
 	cpu_dev_register_generic();
+	cpu_notifier(device_hotplug_notifier, 0);
 }
-- 
1.7.9.5