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Commit 8fba38c9 authored by Sebastian Andrzej Siewior's avatar Sebastian Andrzej Siewior Committed by Thomas Gleixner
Browse files

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: default avatarSebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: rt@linuxtronix.de
Link: http://lkml.kernel.org/r/20161117183541.8588-4-bigeasy@linutronix.de


Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent ee92be9b

arch/x86/kernel/msr.c

+15 −54
Original line number Diff line number Diff line
@@ -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)

	err  = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "x86/msr:online",

				 msr_device_create, msr_device_destroy);

	if (err < 0)

		goto out_class;

	}

	__register_hotcpu_notifier(&msr_class_cpu_notifier);

	cpu_notifier_register_done();



	err = 0;

	goto out;

	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>");