x86/msr: Convert to hotplug state machine

Install the callbacks via the state machine and let the core invoke
the callbacks on the already online CPUs.

Move the callbacks to online/offline as there is no point in having the
files around before the cpu is online and until its completely gone.

[ tglx: Move the callbacks to online/offline ]

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: rt@linuxtronix.de
Link: http://lkml.kernel.org/r/20161117183541.8588-4-bigeasy@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

diff --git a/arch/x86/kernel/msr.c b/arch/x86/kernel/msr.c
index 7f3550acde1b8ce604f4b5cc8b53c232450c524f..f5e3ff835cc8a318c12c3decc8532cc9df411b69 100644 (file)
--- a/arch/x86/kernel/msr.c
+++ b/arch/x86/kernel/msr.c
@@ -44,6 +44,7 @@
 #include <asm/msr.h>
 
 static struct class *msr_class;
+static enum cpuhp_state cpuhp_msr_state;
 
 static ssize_t msr_read(struct file *file, char __user *buf,
                        size_t count, loff_t *ppos)
@@ -180,7 +181,7 @@ static const struct file_operations msr_fops = {
        .compat_ioctl = msr_ioctl,
 };
 
-static int msr_device_create(int cpu)
+static int msr_device_create(unsigned int cpu)
 {
        struct device *dev;
 
@@ -189,34 +190,12 @@ static int msr_device_create(int cpu)
        return PTR_ERR_OR_ZERO(dev);
 }
 
-static void msr_device_destroy(int cpu)
+static int msr_device_destroy(unsigned int cpu)
 {
        device_destroy(msr_class, MKDEV(MSR_MAJOR, cpu));
+       return 0;
 }
 
-static int msr_class_cpu_callback(struct notifier_block *nfb,
-                                 unsigned long action, void *hcpu)
-{
-       unsigned int cpu = (unsigned long)hcpu;
-       int err = 0;
-
-       switch (action) {
-       case CPU_UP_PREPARE:
-               err = msr_device_create(cpu);
-               break;
-       case CPU_UP_CANCELED:
-       case CPU_UP_CANCELED_FROZEN:
-       case CPU_DEAD:
-               msr_device_destroy(cpu);
-               break;
-       }
-       return notifier_from_errno(err);
-}
-
-static struct notifier_block __refdata msr_class_cpu_notifier = {
-       .notifier_call = msr_class_cpu_callback,
-};
-
 static char *msr_devnode(struct device *dev, umode_t *mode)
 {
        return kasprintf(GFP_KERNEL, "cpu/%u/msr", MINOR(dev->devt));
@@ -224,13 +203,11 @@ static char *msr_devnode(struct device *dev, umode_t *mode)
 
 static int __init msr_init(void)
 {
-       int i, err = 0;
-       i = 0;
+       int err;
 
        if (__register_chrdev(MSR_MAJOR, 0, NR_CPUS, "cpu/msr", &msr_fops)) {
                pr_err("unable to get major %d for msr\n", MSR_MAJOR);
-               err = -EBUSY;
-               goto out;
+               return -EBUSY;
        }
        msr_class = class_create(THIS_MODULE, "msr");
        if (IS_ERR(msr_class)) {
@@ -239,44 +216,28 @@ static int __init msr_init(void)
        }
        msr_class->devnode = msr_devnode;
 
-       cpu_notifier_register_begin();
-       for_each_online_cpu(i) {
-               err = msr_device_create(i);
-               if (err != 0)
-                       goto out_class;
-       }
-       __register_hotcpu_notifier(&msr_class_cpu_notifier);
-       cpu_notifier_register_done();
-
-       err = 0;
-       goto out;
+       err  = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "x86/msr:online",
+                                msr_device_create, msr_device_destroy);
+       if (err < 0)
+               goto out_class;
+       cpuhp_msr_state = err;
+       return 0;
 
 out_class:
-       i = 0;
-       for_each_online_cpu(i)
-               msr_device_destroy(i);
-       cpu_notifier_register_done();
+       cpuhp_remove_state(cpuhp_msr_state);
        class_destroy(msr_class);
 out_chrdev:
        __unregister_chrdev(MSR_MAJOR, 0, NR_CPUS, "cpu/msr");
-out:
        return err;
 }
+module_init(msr_init);
 
 static void __exit msr_exit(void)
 {
-       int cpu = 0;
-
-       cpu_notifier_register_begin();
-       for_each_online_cpu(cpu)
-               msr_device_destroy(cpu);
+       cpuhp_remove_state(cpuhp_msr_state);
        class_destroy(msr_class);
        __unregister_chrdev(MSR_MAJOR, 0, NR_CPUS, "cpu/msr");
-       __unregister_hotcpu_notifier(&msr_class_cpu_notifier);
-       cpu_notifier_register_done();
 }
-
-module_init(msr_init);
 module_exit(msr_exit)
 
 MODULE_AUTHOR("H. Peter Anvin <hpa@zytor.com>");